%% This Source Code Form is subject to the terms of the Mozilla Public
%% License, v. 2.0. If a copy of the MPL was not distributed with this
%% file, You can obtain one at https://mozilla.org/MPL/2.0/.
%%
%% Copyright (c) 2007-2020 VMware, Inc. or its affiliates.  All rights reserved.
%%

-module(rabbit_channel).

%% Transitional step until we can require Erlang/OTP 21 and
%% use the now recommended try/catch syntax for obtaining the stack trace.
-compile(nowarn_deprecated_function).

%% rabbit_channel processes represent an AMQP 0-9-1 channels.
%%
%% Connections parse protocol frames coming from clients and
%% dispatch them to channel processes.
%% Channels are responsible for implementing the logic behind
%% the various protocol methods, involving other processes as
%% needed:
%%
%%  * Routing messages (using functions in various exchange type
%%    modules) to queue processes.
%%  * Managing queues, exchanges, and bindings.
%%  * Keeping track of consumers
%%  * Keeping track of unacknowledged deliveries to consumers
%%  * Keeping track of publisher confirms
%%  * Transaction management
%%  * Authorisation (enforcing permissions)
%%  * Publishing trace events if tracing is enabled
%%
%% Every channel has a number of dependent processes:
%%
%%  * A writer which is responsible for sending frames to clients.
%%  * A limiter which controls how many messages can be delivered
%%    to consumers according to active QoS prefetch and internal
%%    flow control logic.
%%
%% Channels are also aware of their connection's queue collector.
%% When a queue is declared as exclusive on a channel, the channel
%% will notify queue collector of that queue.

-include_lib("rabbit_common/include/rabbit_framing.hrl").
-include_lib("rabbit_common/include/rabbit.hrl").
-include_lib("rabbit_common/include/rabbit_misc.hrl").

-include("amqqueue.hrl").

-behaviour(gen_server2).

-export([start_link/11, start_link/12, do/2, do/3, do_flow/3, flush/1, shutdown/1]).
-export([send_command/2, deliver/4, deliver_reply/2,
         send_credit_reply/2, send_drained/2]).
-export([list/0, info_keys/0, info/1, info/2, info_all/0, info_all/1,
         emit_info_all/4, info_local/1]).
-export([refresh_config_local/0, ready_for_close/1]).
-export([refresh_interceptors/0]).
-export([force_event_refresh/1]).
-export([update_user_state/2]).

-export([init/1, terminate/2, code_change/3, handle_call/3, handle_cast/2,
         handle_info/2, handle_pre_hibernate/1, handle_post_hibernate/1,
         prioritise_call/4, prioritise_cast/3, prioritise_info/3,
         format_message_queue/2]).

%% Internal
-export([list_local/0, emit_info_local/3, deliver_reply_local/3]).
-export([get_vhost/1, get_user/1]).
%% For testing
-export([build_topic_variable_map/3]).
-export([list_queue_states/1, get_max_message_size/0]).

%% Mgmt HTTP API refactor
-export([handle_method/6]).

-record(conf, {
          %% starting | running | flow | closing
          state,
          %% same as reader's protocol. Used when instantiating
          %% (protocol) exceptions.
          protocol,
          %% channel number
          channel,
          %% reader process
          reader_pid,
          %% writer process
          writer_pid,
          %%
          conn_pid,
          %% same as reader's name, see #v1.name
          %% in rabbit_reader
          conn_name,
          %% channel's originating source e.g. rabbit_reader | rabbit_direct | undefined
          %% or any other channel creating/spawning entity
          source,
          %% same as #v1.user in the reader, used in
          %% authorisation checks
          user,
          %% same as #v1.user in the reader
          virtual_host,
          %% when queue.bind's queue field is empty,
          %% this name will be used instead
          most_recently_declared_queue,
          %% when a queue is declared as exclusive, queue
          %% collector must be notified.
          %% see rabbit_queue_collector for more info.
          queue_collector_pid,

          %% same as capabilities in the reader
          capabilities,
          %% tracing exchange resource if tracing is enabled,
          %% 'none' otherwise
          trace_state,
          consumer_prefetch,
          %% Message content size limit
          max_message_size,
          consumer_timeout,
          authz_context,
          %% defines how ofter gc will be executed
          writer_gc_threshold
         }).

-record(ch, {cfg :: #conf{},
             %% limiter state, see rabbit_limiter
             limiter,
             %% none | {Msgs, Acks} | committing | failed |
             tx,
             %% (consumer) delivery tag sequence
             next_tag,
             %% messages pending consumer acknowledgement
             unacked_message_q,
             %% a map of queue ref to queue name
             queue_names,
             %% queue processes are monitored to update
             %% queue names
             queue_monitors,
             %% a map of consumer tags to
             %% consumer details: #amqqueue record, acknowledgement mode,
             %% consumer exclusivity, etc
             consumer_mapping,
             %% a map of queue pids to consumer tag lists
             queue_consumers,
             %% a set of pids of queues that have unacknowledged
             %% deliveries
             delivering_queues,
             %% timer used to emit statistics
             stats_timer,
             %% are publisher confirms enabled for this channel?
             confirm_enabled,
             %% publisher confirm delivery tag sequence
             publish_seqno,
             %% an unconfirmed_messages data structure used to track unconfirmed
             %% (to publishers) messages
             unconfirmed,
             %% a list of tags for published messages that were
             %% delivered but are yet to be confirmed to the client
             confirmed,
             %% a list of tags for published messages that were
             %% rejected but are yet to be sent to the client
             rejected,
             %% used by "one shot RPC" (amq.
             reply_consumer,
             %% flow | noflow, see rabbitmq-server#114
             delivery_flow,
             interceptor_state,
             queue_states,
             tick_timer
            }).

-define(QUEUE, lqueue).

-define(MAX_PERMISSION_CACHE_SIZE, 12).

-define(REFRESH_TIMEOUT, 15000).

-define(STATISTICS_KEYS,
        [reductions,
         pid,
         transactional,
         confirm,
         consumer_count,
         messages_unacknowledged,
         messages_unconfirmed,
         messages_uncommitted,
         acks_uncommitted,
         pending_raft_commands,
         prefetch_count,
         global_prefetch_count,
         state,
         garbage_collection]).

-define(CREATION_EVENT_KEYS,
        [pid,
         name,
         connection,
         number,
         user,
         vhost,
         user_who_performed_action]).

-define(INFO_KEYS, ?CREATION_EVENT_KEYS ++ ?STATISTICS_KEYS -- [pid]).

-define(INCR_STATS(Type, Key, Inc, Measure, State),
        case rabbit_event:stats_level(State, #ch.stats_timer) of
            fine ->
                rabbit_core_metrics:channel_stats(Type, Measure, {self(), Key}, Inc),
                %% Keys in the process dictionary are used to clean up the core metrics
                put({Type, Key}, none);
            _ ->
                ok
        end).

-define(INCR_STATS(Type, Key, Inc, Measure),
        begin
            rabbit_core_metrics:channel_stats(Type, Measure, {self(), Key}, Inc),
            %% Keys in the process dictionary are used to clean up the core metrics
            put({Type, Key}, none)
        end).

-define(IS_CLASSIC(QPid), is_pid(QPid)).
-define(IS_QUORUM(QPid), is_tuple(QPid)).

%%----------------------------------------------------------------------------

-export_type([channel_number/0]).

-type channel_number() :: non_neg_integer().

-export_type([channel/0]).

-type channel() :: #ch{}.

%%----------------------------------------------------------------------------

-spec start_link
        (channel_number(), pid(), pid(), pid(), string(), rabbit_types:protocol(),
         rabbit_types:user(), rabbit_types:vhost(), rabbit_framing:amqp_table(),
         pid(), pid()) ->
            rabbit_types:ok_pid_or_error().

start_link(Channel, ReaderPid, WriterPid, ConnPid, ConnName, Protocol, User,
           VHost, Capabilities, CollectorPid, Limiter) ->
    start_link(Channel, ReaderPid, WriterPid, ConnPid, ConnName, Protocol, User,
           VHost, Capabilities, CollectorPid, Limiter, undefined).

-spec start_link
        (channel_number(), pid(), pid(), pid(), string(), rabbit_types:protocol(),
         rabbit_types:user(), rabbit_types:vhost(), rabbit_framing:amqp_table(),
         pid(), pid(), any()) ->
            rabbit_types:ok_pid_or_error().

start_link(Channel, ReaderPid, WriterPid, ConnPid, ConnName, Protocol, User,
           VHost, Capabilities, CollectorPid, Limiter, AmqpParams) ->
    gen_server2:start_link(
      ?MODULE, [Channel, ReaderPid, WriterPid, ConnPid, ConnName, Protocol,
                User, VHost, Capabilities, CollectorPid, Limiter, AmqpParams], []).

-spec do(pid(), rabbit_framing:amqp_method_record()) -> 'ok'.

do(Pid, Method) ->
    rabbit_channel_common:do(Pid, Method).

-spec do
        (pid(), rabbit_framing:amqp_method_record(),
         rabbit_types:maybe(rabbit_types:content())) ->
            'ok'.

do(Pid, Method, Content) ->
    rabbit_channel_common:do(Pid, Method, Content).

-spec do_flow
        (pid(), rabbit_framing:amqp_method_record(),
         rabbit_types:maybe(rabbit_types:content())) ->
            'ok'.

do_flow(Pid, Method, Content) ->
    rabbit_channel_common:do_flow(Pid, Method, Content).

-spec flush(pid()) -> 'ok'.

flush(Pid) ->
    gen_server2:call(Pid, flush, infinity).

-spec shutdown(pid()) -> 'ok'.

shutdown(Pid) ->
    gen_server2:cast(Pid, terminate).

-spec send_command(pid(), rabbit_framing:amqp_method_record()) -> 'ok'.

send_command(Pid, Msg) ->
    gen_server2:cast(Pid,  {command, Msg}).

-spec deliver
        (pid(), rabbit_types:ctag(), boolean(), rabbit_amqqueue:qmsg()) -> 'ok'.

deliver(Pid, ConsumerTag, AckRequired, Msg) ->
    gen_server2:cast(Pid, {deliver, ConsumerTag, AckRequired, Msg}).

-spec deliver_reply(binary(), rabbit_types:delivery()) -> 'ok'.

deliver_reply(<<"amq.rabbitmq.reply-to.", Rest/binary>>, Delivery) ->
    case decode_fast_reply_to(Rest) of
        {ok, Pid, Key} ->
            delegate:invoke_no_result(
              Pid, {?MODULE, deliver_reply_local, [Key, Delivery]});
        error ->
            ok
    end.

%% We want to ensure people can't use this mechanism to send a message
%% to an arbitrary process and kill it!

-spec deliver_reply_local(pid(), binary(), rabbit_types:delivery()) -> 'ok'.

deliver_reply_local(Pid, Key, Delivery) ->
    case pg_local:in_group(rabbit_channels, Pid) of
        true  -> gen_server2:cast(Pid, {deliver_reply, Key, Delivery});
        false -> ok
    end.

declare_fast_reply_to(<<"amq.rabbitmq.reply-to">>) ->
    exists;
declare_fast_reply_to(<<"amq.rabbitmq.reply-to.", Rest/binary>>) ->
    case decode_fast_reply_to(Rest) of
        {ok, Pid, Key} ->
            Msg = {declare_fast_reply_to, Key},
            rabbit_misc:with_exit_handler(
              rabbit_misc:const(not_found),
              fun() -> gen_server2:call(Pid, Msg, infinity) end);
        error ->
            not_found
    end;
declare_fast_reply_to(_) ->
    not_found.

decode_fast_reply_to(Rest) ->
    case string:tokens(binary_to_list(Rest), ".") of
        [PidEnc, Key] -> Pid = binary_to_term(base64:decode(PidEnc)),
                         {ok, Pid, Key};
        _             -> error
    end.

-spec send_credit_reply(pid(), non_neg_integer()) -> 'ok'.

send_credit_reply(Pid, Len) ->
    gen_server2:cast(Pid, {send_credit_reply, Len}).

-spec send_drained(pid(), [{rabbit_types:ctag(), non_neg_integer()}]) -> 'ok'.

send_drained(Pid, CTagCredit) ->
    gen_server2:cast(Pid, {send_drained, CTagCredit}).

-spec list() -> [pid()].

list() ->
    Nodes = rabbit_nodes:all_running(),
    rabbit_misc:append_rpc_all_nodes(Nodes, rabbit_channel, list_local, [], ?RPC_TIMEOUT).

-spec list_local() -> [pid()].

list_local() ->
    pg_local:get_members(rabbit_channels).

-spec info_keys() -> rabbit_types:info_keys().

info_keys() -> ?INFO_KEYS.

-spec info(pid()) -> rabbit_types:infos().

info(Pid) ->
    {Timeout, Deadline} = get_operation_timeout_and_deadline(),
    try
        case gen_server2:call(Pid, {info, Deadline}, Timeout) of
            {ok, Res}      -> Res;
            {error, Error} -> throw(Error)
        end
    catch
        exit:{timeout, _} ->
            rabbit_log:error("Timed out getting channel ~p info", [Pid]),
            throw(timeout)
    end.

-spec info(pid(), rabbit_types:info_keys()) -> rabbit_types:infos().

info(Pid, Items) ->
    {Timeout, Deadline} = get_operation_timeout_and_deadline(),
    try
        case gen_server2:call(Pid, {{info, Items}, Deadline}, Timeout) of
            {ok, Res}      -> Res;
            {error, Error} -> throw(Error)
        end
    catch
        exit:{timeout, _} ->
            rabbit_log:error("Timed out getting channel ~p info", [Pid]),
            throw(timeout)
    end.

-spec info_all() -> [rabbit_types:infos()].

info_all() ->
    rabbit_misc:filter_exit_map(fun (C) -> info(C) end, list()).

-spec info_all(rabbit_types:info_keys()) -> [rabbit_types:infos()].

info_all(Items) ->
    rabbit_misc:filter_exit_map(fun (C) -> info(C, Items) end, list()).

info_local(Items) ->
    rabbit_misc:filter_exit_map(fun (C) -> info(C, Items) end, list_local()).

emit_info_all(Nodes, Items, Ref, AggregatorPid) ->
    Pids = [ spawn_link(Node, rabbit_channel, emit_info_local, [Items, Ref, AggregatorPid]) || Node <- Nodes ],
    rabbit_control_misc:await_emitters_termination(Pids).

emit_info_local(Items, Ref, AggregatorPid) ->
    emit_info(list_local(), Items, Ref, AggregatorPid).

emit_info(PidList, InfoItems, Ref, AggregatorPid) ->
    rabbit_control_misc:emitting_map_with_exit_handler(
      AggregatorPid, Ref, fun(C) -> info(C, InfoItems) end, PidList).

-spec refresh_config_local() -> 'ok'.

refresh_config_local() ->
    rabbit_misc:upmap(
      fun (C) ->
        try
          gen_server2:call(C, refresh_config, infinity)
        catch _:Reason ->
          rabbit_log:error("Failed to refresh channel config "
                           "for channel ~p. Reason ~p",
                           [C, Reason])
        end
      end,
      list_local()),
    ok.

refresh_interceptors() ->
    rabbit_misc:upmap(
      fun (C) ->
        try
          gen_server2:call(C, refresh_interceptors, ?REFRESH_TIMEOUT)
        catch _:Reason ->
          rabbit_log:error("Failed to refresh channel interceptors "
                           "for channel ~p. Reason ~p",
                           [C, Reason])
        end
      end,
      list_local()),
    ok.

-spec ready_for_close(pid()) -> 'ok'.

ready_for_close(Pid) ->
    rabbit_channel_common:ready_for_close(Pid).

-spec force_event_refresh(reference()) -> 'ok'.

% Note: https://www.pivotaltracker.com/story/show/166962656
% This event is necessary for the stats timer to be initialized with
% the correct values once the management agent has started
force_event_refresh(Ref) ->
    [gen_server2:cast(C, {force_event_refresh, Ref}) || C <- list()],
    ok.

list_queue_states(Pid) ->
    gen_server2:call(Pid, list_queue_states).

-spec update_user_state(pid(), rabbit_types:auth_user()) -> 'ok' | {error, channel_terminated}.

update_user_state(Pid, UserState) when is_pid(Pid) ->
    case erlang:is_process_alive(Pid) of
        true  -> Pid ! {update_user_state, UserState},
                 ok;
        false -> {error, channel_terminated}
    end.

%%---------------------------------------------------------------------------

init([Channel, ReaderPid, WriterPid, ConnPid, ConnName, Protocol, User, VHost,
      Capabilities, CollectorPid, LimiterPid, AmqpParams]) ->
    process_flag(trap_exit, true),
    ?LG_PROCESS_TYPE(channel),
    ?store_proc_name({ConnName, Channel}),
    ok = pg_local:join(rabbit_channels, self()),
    Flow = case rabbit_misc:get_env(rabbit, mirroring_flow_control, true) of
             true   -> flow;
             false  -> noflow
           end,
    {ok, {Global, Prefetch}} = application:get_env(rabbit, default_consumer_prefetch),
    Limiter0 = rabbit_limiter:new(LimiterPid),
    Limiter = case {Global, Prefetch} of
                  {true, 0} ->
                      rabbit_limiter:unlimit_prefetch(Limiter0);
                  {true, _} ->
                      rabbit_limiter:limit_prefetch(Limiter0, Prefetch, 0);
                  _ ->
                      Limiter0
              end,
    %% Process dictionary is used here because permission cache already uses it. MK.
    put(permission_cache_can_expire, rabbit_access_control:permission_cache_can_expire(User)),
    MaxMessageSize = get_max_message_size(),
    ConsumerTimeout = get_consumer_timeout(),
    OptionalVariables = extract_variable_map_from_amqp_params(AmqpParams),
    {ok, GCThreshold} = application:get_env(rabbit, writer_gc_threshold),
    State = #ch{cfg = #conf{state = starting,
                            protocol = Protocol,
                            channel = Channel,
                            reader_pid = ReaderPid,
                            writer_pid = WriterPid,
                            conn_pid = ConnPid,
                            conn_name = ConnName,
                            user = User,
                            virtual_host = VHost,
                            most_recently_declared_queue = <<>>,
                            queue_collector_pid = CollectorPid,
                            capabilities = Capabilities,
                            trace_state = rabbit_trace:init(VHost),
                            consumer_prefetch = Prefetch,
                            max_message_size = MaxMessageSize,
                            consumer_timeout = ConsumerTimeout,
                            authz_context = OptionalVariables,
                            writer_gc_threshold = GCThreshold
                           },
                limiter = Limiter,
                tx                      = none,
                next_tag                = 1,
                unacked_message_q       = ?QUEUE:new(),
                queue_names             = #{},
                queue_monitors          = pmon:new(),
                consumer_mapping        = #{},
                queue_consumers         = #{},
                delivering_queues       = sets:new(),
                confirm_enabled         = false,
                publish_seqno           = 1,
                unconfirmed             = unconfirmed_messages:new(),
                rejected                = [],
                confirmed               = [],
                reply_consumer          = none,
                delivery_flow           = Flow,
                interceptor_state       = undefined,
                queue_states            = #{}
               },
    State1 = State#ch{
               interceptor_state = rabbit_channel_interceptor:init(State)},
    State2 = rabbit_event:init_stats_timer(State1, #ch.stats_timer),
    Infos = infos(?CREATION_EVENT_KEYS, State2),
    rabbit_core_metrics:channel_created(self(), Infos),
    rabbit_event:notify(channel_created, Infos),
    rabbit_event:if_enabled(State2, #ch.stats_timer,
                            fun() -> emit_stats(State2) end),
    put_operation_timeout(),
    State3 = init_tick_timer(State2),
    {ok, State3, hibernate,
     {backoff, ?HIBERNATE_AFTER_MIN, ?HIBERNATE_AFTER_MIN, ?DESIRED_HIBERNATE}}.

prioritise_call(Msg, _From, _Len, _State) ->
    case Msg of
        info           -> 9;
        {info, _Items} -> 9;
        _              -> 0
    end.

prioritise_cast(Msg, _Len, _State) ->
    case Msg of
        {confirm,            _MsgSeqNos, _QPid} -> 5;
        {reject_publish,     _MsgSeqNos, _QPid} -> 5;
        _                                       -> 0
    end.

prioritise_info(Msg, _Len, _State) ->
    case Msg of
        emit_stats                   -> 7;
        _                            -> 0
    end.

handle_call(flush, _From, State) ->
    reply(ok, State);

handle_call({info, Deadline}, _From, State) ->
    try
        reply({ok, infos(?INFO_KEYS, Deadline, State)}, State)
    catch
        Error ->
            reply({error, Error}, State)
    end;

handle_call({{info, Items}, Deadline}, _From, State) ->
    try
        reply({ok, infos(Items, Deadline, State)}, State)
    catch
        Error ->
            reply({error, Error}, State)
    end;

handle_call(refresh_config, _From,
            State = #ch{cfg = #conf{virtual_host = VHost} = Cfg}) ->
    reply(ok, State#ch{cfg = Cfg#conf{trace_state = rabbit_trace:init(VHost)}});

handle_call(refresh_interceptors, _From, State) ->
    IState = rabbit_channel_interceptor:init(State),
    reply(ok, State#ch{interceptor_state = IState});

handle_call({declare_fast_reply_to, Key}, _From,
            State = #ch{reply_consumer = Consumer}) ->
    reply(case Consumer of
              {_, _, Key} -> exists;
              _           -> not_found
          end, State);

handle_call(list_queue_states, _From, State = #ch{queue_states = QueueStates}) ->
    %% For testing of cleanup only
    {reply, maps:keys(QueueStates), State};

handle_call(_Request, _From, State) ->
    noreply(State).

handle_cast({method, Method, Content, Flow},
            State = #ch{cfg = #conf{reader_pid = Reader},
                        interceptor_state = IState}) ->
    case Flow of
        %% We are going to process a message from the rabbit_reader
        %% process, so here we ack it. In this case we are accessing
        %% the rabbit_channel process dictionary.
        flow   -> credit_flow:ack(Reader);
        noflow -> ok
    end,
    try handle_method(rabbit_channel_interceptor:intercept_in(
                        expand_shortcuts(Method, State), Content, IState),
                      State) of
        {reply, Reply, NewState} ->
            ok = send(Reply, NewState),
            noreply(NewState);
        {noreply, NewState} ->
            noreply(NewState);
        stop ->
            {stop, normal, State}
    catch
        exit:Reason = #amqp_error{} ->
            MethodName = rabbit_misc:method_record_type(Method),
            handle_exception(Reason#amqp_error{method = MethodName}, State);
        _:Reason:Stacktrace ->
            {stop, {Reason, Stacktrace}, State}
    end;

handle_cast(ready_for_close,
            State = #ch{cfg = #conf{state = closing,
                                    writer_pid = WriterPid}}) ->
    ok = rabbit_writer:send_command_sync(WriterPid, #'channel.close_ok'{}),
    {stop, normal, State};

handle_cast(terminate, State = #ch{cfg = #conf{writer_pid = WriterPid}}) ->
    ok = rabbit_writer:flush(WriterPid),
    {stop, normal, State};

handle_cast({command, #'basic.consume_ok'{consumer_tag = CTag} = Msg}, State) ->
    ok = send(Msg, State),
    noreply(consumer_monitor(CTag, State));

handle_cast({command, Msg}, State) ->
    ok = send(Msg, State),
    noreply(State);

handle_cast({deliver, _CTag, _AckReq, _Msg},
            State = #ch{cfg = #conf{state = closing}}) ->
    noreply(State);
handle_cast({deliver, ConsumerTag, AckRequired, Msg}, State) ->
    noreply(handle_deliver(ConsumerTag, AckRequired, Msg, State));

handle_cast({deliver_reply, _K, _Del},
            State = #ch{cfg = #conf{state = closing}}) ->
    noreply(State);
handle_cast({deliver_reply, _K, _Del}, State = #ch{reply_consumer = none}) ->
    noreply(State);
handle_cast({deliver_reply, Key, #delivery{message =
                    #basic_message{exchange_name = ExchangeName,
                                   routing_keys  = [RoutingKey | _CcRoutes],
                                   content       = Content}}},
            State = #ch{cfg = #conf{writer_pid = WriterPid},
                        next_tag = DeliveryTag,
                        reply_consumer = {ConsumerTag, _Suffix, Key}}) ->
    ok = rabbit_writer:send_command(
           WriterPid,
           #'basic.deliver'{consumer_tag = ConsumerTag,
                            delivery_tag = DeliveryTag,
                            redelivered  = false,
                            exchange     = ExchangeName#resource.name,
                            routing_key  = RoutingKey},
           Content),
    noreply(State);
handle_cast({deliver_reply, _K1, _}, State=#ch{reply_consumer = {_, _, _K2}}) ->
    noreply(State);

handle_cast({send_credit_reply, Len},
            State = #ch{cfg = #conf{writer_pid = WriterPid}}) ->
    ok = rabbit_writer:send_command(
           WriterPid, #'basic.credit_ok'{available = Len}),
    noreply(State);

handle_cast({send_drained, CTagCredit},
            State = #ch{cfg = #conf{writer_pid = WriterPid}}) ->
    [ok = rabbit_writer:send_command(
            WriterPid, #'basic.credit_drained'{consumer_tag   = ConsumerTag,
                                               credit_drained = CreditDrained})
     || {ConsumerTag, CreditDrained} <- CTagCredit],
    noreply(State);

% Note: https://www.pivotaltracker.com/story/show/166962656
% This event is necessary for the stats timer to be initialized with
% the correct values once the management agent has started
handle_cast({force_event_refresh, Ref}, State) ->
    rabbit_event:notify(channel_created, infos(?CREATION_EVENT_KEYS, State),
                        Ref),
    noreply(rabbit_event:init_stats_timer(State, #ch.stats_timer));

handle_cast({mandatory_received, _MsgSeqNo}, State) ->
    %% This feature was used by `rabbit_amqqueue_process` and
    %% `rabbit_mirror_queue_slave` up-to and including RabbitMQ 3.7.x.
    %% It is unused in 3.8.x and thus deprecated. We keep it to support
    %% in-place upgrades to 3.8.x (i.e. mixed-version clusters), but it
    %% is a no-op starting with that version.
    %%
    %% NB: don't call noreply/1 since we don't want to send confirms.
    noreply_coalesce(State);

handle_cast({reject_publish, MsgSeqNo, _QPid}, State = #ch{unconfirmed = UC}) ->
    %% It does not matter which queue rejected the message,
    %% if any queue did, it should not be confirmed.
    {MaybeRejected, UC1} = unconfirmed_messages:reject_msg(MsgSeqNo, UC),
    %% NB: don't call noreply/1 since we don't want to send confirms.
    case MaybeRejected of
        not_confirmed ->
            noreply_coalesce(State#ch{unconfirmed = UC1});
        {rejected, MX} ->
            noreply_coalesce(record_rejects([MX], State#ch{unconfirmed = UC1}))
    end;

handle_cast({confirm, MsgSeqNos, QPid}, State) ->
    noreply_coalesce(confirm(MsgSeqNos, QPid, State));

handle_cast({queue_event, _, {{_, _} = From, {applied, _} = Evt}}, State) ->
    %% Forward compatibility with queue types, it might be needed during
    %% upgrades in mixed-version clusters
    handle_info({ra_event, From, Evt}, State);

handle_cast({queue_event, _, {{_, _} = From, {rejected, _} = Evt}}, State) ->
    %% Forward compatibility with queue types, it might be needed during
    %% upgrades in mixed-version clusters
    handle_info({ra_event, From, Evt}, State);

handle_cast({queue_event, _, {{_, _} = From, {machine, _} = Evt}}, State) ->
    %% Forward compatibility with queue types, it might be needed during
    %% upgrades in mixed-version clusters
    handle_info({ra_event, From, Evt}, State);

handle_cast({queue_event, _, Evt}, State) ->
    %% Forward compatibility with queue types, it might be needed during
    %% upgrades in mixed-version clusters
    handle_cast(Evt, State).

handle_info({ra_event, {Name, _} = From, _} = Evt,
            #ch{queue_states = QueueStates,
                queue_names = QNames,
                consumer_mapping = ConsumerMapping} = State0) ->
    case QueueStates of
        #{Name := QState0} ->
            QName = rabbit_quorum_queue:queue_name(QState0),
            case rabbit_quorum_queue:handle_event(Evt, QState0) of
                {{delivery, CTag, Msgs}, QState1} ->
                    AckRequired = case maps:find(CTag, ConsumerMapping) of
                                      error ->
                                          true;
                                      {ok, {_, {NoAck, _, _, _}}} ->
                                          not NoAck
                                  end,
                    QState2 = case AckRequired of
                                  false ->
                                      {MsgIds, _} = lists:unzip(Msgs),
                                      {ok, FS} = rabbit_quorum_queue:ack(CTag, MsgIds, QState1),
                                      FS;
                                  true ->
                                      QState1
                              end,
                    State = lists:foldl(
                              fun({MsgId, {MsgHeader, Msg}}, Acc) ->
                                      IsDelivered = case MsgHeader of
                                                        #{delivery_count := _} ->
                                                            true;
                                                        _ ->
                                                            false
                                                    end,
                                      Msg1 = add_delivery_count_header(MsgHeader, Msg),
                                      handle_deliver(CTag, AckRequired,
                                                     {QName, From, MsgId, IsDelivered, Msg1},
                                                     Acc)
                              end, State0#ch{queue_states = maps:put(Name, QState2, QueueStates)}, Msgs),
                    noreply(State);
                {internal, MsgSeqNos, Actions, QState1} ->
                    State = State0#ch{queue_states = maps:put(Name, QState1, QueueStates)},
                    %% execute actions
                    WriterPid = State#ch.cfg#conf.writer_pid,
                    lists:foreach(fun ({send_credit_reply, Avail}) ->
                                          ok = rabbit_writer:send_command(
                                                 WriterPid,
                                                 #'basic.credit_ok'{available =
                                                                    Avail});
                                      ({send_drained, {CTag, Credit}}) ->
                                          ok = rabbit_writer:send_command(
                                                 WriterPid,
                                                 #'basic.credit_drained'{consumer_tag   = CTag,
                                                                         credit_drained = Credit})
                                  end, Actions),
                    noreply_coalesce(confirm(MsgSeqNos, Name, State));
                eol ->
                    State1 = handle_consuming_queue_down_or_eol(Name, State0),
                    State2 = handle_delivering_queue_down(Name, State1),
                    {ConfirmMXs, RejectMXs, UC1} =
                        unconfirmed_messages:forget_ref(Name, State2#ch.unconfirmed),
                    %% Deleted queue is a special case.
                    %% Do not nack the "rejected" messages.
                    State3 = record_confirms(ConfirmMXs ++ RejectMXs,
                                             State2#ch{unconfirmed = UC1}),
                    erase_queue_stats(QName),
                    noreply_coalesce(
                      State3#ch{queue_states = maps:remove(Name, QueueStates),
                                queue_names = maps:remove(Name, QNames)})
            end;
        _ ->
            %% the assumption here is that the queue state has been cleaned up and
            %% this is a residual Ra notification
            noreply_coalesce(State0)
    end;

handle_info({bump_credit, Msg}, State) ->
    %% A rabbit_amqqueue_process is granting credit to our channel. If
    %% our channel was being blocked by this process, and no other
    %% process is blocking our channel, then this channel will be
    %% unblocked. This means that any credit that was deferred will be
    %% sent to rabbit_reader processs that might be blocked by this
    %% particular channel.
    credit_flow:handle_bump_msg(Msg),
    noreply(State);

handle_info(timeout, State) ->
    noreply(State);

handle_info(emit_stats, State) ->
    emit_stats(State),
    State1 = rabbit_event:reset_stats_timer(State, #ch.stats_timer),
    %% NB: don't call noreply/1 since we don't want to kick off the
    %% stats timer.
    {noreply, send_confirms_and_nacks(State1), hibernate};

handle_info({'DOWN', _MRef, process, QPid, Reason}, State) ->
    State1 = handle_publishing_queue_down(QPid, Reason, State),
    State3 = handle_consuming_queue_down_or_eol(QPid, State1),
    State4 = handle_delivering_queue_down(QPid, State3),
    %% A rabbit_amqqueue_process has died. If our channel was being
    %% blocked by this process, and no other process is blocking our
    %% channel, then this channel will be unblocked. This means that
    %% any credit that was deferred will be sent to the rabbit_reader
    %% processs that might be blocked by this particular channel.
    credit_flow:peer_down(QPid),
    #ch{queue_names = QNames, queue_monitors = QMons} = State4,
    case maps:find(QPid, QNames) of
        {ok, QName} -> erase_queue_stats(QName);
        error       -> ok
    end,
    noreply(State4#ch{queue_names    = maps:remove(QPid, QNames),
                      queue_monitors = pmon:erase(QPid, QMons)});

handle_info({'EXIT', _Pid, Reason}, State) ->
    {stop, Reason, State};

handle_info({{Ref, Node}, LateAnswer},
            State = #ch{cfg = #conf{channel = Channel}})
  when is_reference(Ref) ->
    rabbit_log_channel:warning("Channel ~p ignoring late answer ~p from ~p",
        [Channel, LateAnswer, Node]),
    noreply(State);

handle_info(tick, State0 = #ch{queue_states = QueueStates0}) ->
    case get(permission_cache_can_expire) of
      true  -> ok = clear_permission_cache();
      _     -> ok
    end,
    QueueStates1 =
        maps:filter(fun(_, QS) ->
                            QName = rabbit_quorum_queue:queue_name(QS),
                            [] /= rabbit_amqqueue:lookup([QName])
                    end, QueueStates0),
    case evaluate_consumer_timeout(State0#ch{queue_states = QueueStates1}) of
        {noreply, State} ->
            noreply(init_tick_timer(reset_tick_timer(State)));
        Return ->
            Return
    end;
handle_info({update_user_state, User}, State = #ch{cfg = Cfg}) ->
    noreply(State#ch{cfg = Cfg#conf{user = User}}).


handle_pre_hibernate(State0) ->
    ok = clear_permission_cache(),
    State = maybe_cancel_tick_timer(State0),
    rabbit_event:if_enabled(
      State, #ch.stats_timer,
      fun () -> emit_stats(State,
                           [{idle_since,
                             os:system_time(milli_seconds)}])
      end),
    {hibernate, rabbit_event:stop_stats_timer(State, #ch.stats_timer)}.

handle_post_hibernate(State0) ->
    State = init_tick_timer(State0),
    {noreply, State}.

terminate(_Reason,
          State = #ch{cfg = #conf{user = #user{username = Username}}}) ->
    {_Res, _State1} = notify_queues(State),
    pg_local:leave(rabbit_channels, self()),
    rabbit_event:if_enabled(State, #ch.stats_timer,
                            fun() -> emit_stats(State) end),
    [delete_stats(Tag) || {Tag, _} <- get()],
    rabbit_core_metrics:channel_closed(self()),
    rabbit_event:notify(channel_closed, [{pid, self()},
                                         {user_who_performed_action, Username}]).

code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

format_message_queue(Opt, MQ) -> rabbit_misc:format_message_queue(Opt, MQ).

-spec get_max_message_size() -> non_neg_integer().

get_max_message_size() ->
    case application:get_env(rabbit, max_message_size) of
        {ok, MS} when is_integer(MS) ->
            erlang:min(MS, ?MAX_MSG_SIZE);
        _ ->
            ?MAX_MSG_SIZE
    end.

get_consumer_timeout() ->
    case application:get_env(rabbit, consumer_timeout) of
        {ok, MS} when is_integer(MS) ->
            MS;
        _ ->
            undefined
    end.
%%---------------------------------------------------------------------------

reply(Reply, NewState) -> {reply, Reply, next_state(NewState), hibernate}.

noreply(NewState) -> {noreply, next_state(NewState), hibernate}.

next_state(State) -> ensure_stats_timer(send_confirms_and_nacks(State)).

noreply_coalesce(State = #ch{confirmed = C, rejected = R}) ->
    Timeout = case {C, R} of {[], []} -> hibernate; _ -> 0 end,
    {noreply, ensure_stats_timer(State), Timeout}.

ensure_stats_timer(State) ->
    rabbit_event:ensure_stats_timer(State, #ch.stats_timer, emit_stats).

return_ok(State, true, _Msg)  -> {noreply, State};
return_ok(State, false, Msg)  -> {reply, Msg, State}.

ok_msg(true, _Msg) -> undefined;
ok_msg(false, Msg) -> Msg.

send(_Command, #ch{cfg = #conf{state = closing}}) ->
    ok;
send(Command, #ch{cfg = #conf{writer_pid = WriterPid}}) ->
    ok = rabbit_writer:send_command(WriterPid, Command).

format_soft_error(#amqp_error{name = N, explanation = E, method = M}) ->
    io_lib:format("operation ~s caused a channel exception ~s: ~ts", [M, N, E]).

handle_exception(Reason, State = #ch{cfg = #conf{protocol = Protocol,
                                                 channel = Channel,
                                                 writer_pid = WriterPid,
                                                 reader_pid = ReaderPid,
                                                 conn_pid = ConnPid,
                                                 conn_name = ConnName,
                                                 virtual_host = VHost,
                                                 user = User
                                                }}) ->
    %% something bad's happened: notify_queues may not be 'ok'
    {_Result, State1} = notify_queues(State),
    case rabbit_binary_generator:map_exception(Channel, Reason, Protocol) of
        {Channel, CloseMethod} ->
            rabbit_log_channel:error(
                "Channel error on connection ~p (~s, vhost: '~s',"
                " user: '~s'), channel ~p:~n~s~n",
                [ConnPid, ConnName, VHost, User#user.username,
                 Channel, format_soft_error(Reason)]),
            ok = rabbit_writer:send_command(WriterPid, CloseMethod),
            {noreply, State1};
        {0, _} ->
            ReaderPid ! {channel_exit, Channel, Reason},
            {stop, normal, State1}
    end.

-spec precondition_failed(string()) -> no_return().

precondition_failed(Format) -> precondition_failed(Format, []).

-spec precondition_failed(string(), [any()]) -> no_return().

precondition_failed(Format, Params) ->
    rabbit_misc:protocol_error(precondition_failed, Format, Params).

return_queue_declare_ok(#resource{name = ActualName},
                        NoWait, MessageCount, ConsumerCount,
                        #ch{cfg = Cfg} = State) ->
    return_ok(State#ch{cfg = Cfg#conf{most_recently_declared_queue = ActualName}},
              NoWait, #'queue.declare_ok'{queue          = ActualName,
                                          message_count  = MessageCount,
                                          consumer_count = ConsumerCount}).

check_resource_access(User, Resource, Perm, Context) ->
    V = {Resource, Context, Perm},

    Cache = case get(permission_cache) of
                undefined -> [];
                Other     -> Other
            end,
    case lists:member(V, Cache) of
        true  -> ok;
        false -> ok = rabbit_access_control:check_resource_access(
                        User, Resource, Perm, Context),
                 CacheTail = lists:sublist(Cache, ?MAX_PERMISSION_CACHE_SIZE-1),
                 put(permission_cache, [V | CacheTail])
    end.

clear_permission_cache() -> erase(permission_cache),
                            erase(topic_permission_cache),
                            ok.

check_configure_permitted(Resource, User, Context) ->
    check_resource_access(User, Resource, configure, Context).

check_write_permitted(Resource, User, Context) ->
    check_resource_access(User, Resource, write, Context).

check_read_permitted(Resource, User, Context) ->
    check_resource_access(User, Resource, read, Context).

check_write_permitted_on_topic(Resource, User, RoutingKey, AuthzContext) ->
    check_topic_authorisation(Resource, User, RoutingKey, AuthzContext, write).

check_read_permitted_on_topic(Resource, User, RoutingKey, AuthzContext) ->
    check_topic_authorisation(Resource, User, RoutingKey, AuthzContext, read).

check_user_id_header(#'P_basic'{user_id = undefined}, _) ->
    ok;
check_user_id_header(#'P_basic'{user_id = Username},
                     #ch{cfg = #conf{user = #user{username = Username}}}) ->
    ok;
check_user_id_header(
  #'P_basic'{}, #ch{cfg = #conf{user = #user{authz_backends =
                                 [{rabbit_auth_backend_dummy, _}]}}}) ->
    ok;
check_user_id_header(#'P_basic'{user_id = Claimed},
                     #ch{cfg = #conf{user = #user{username = Actual,
                                                  tags     = Tags}}}) ->
    case lists:member(impersonator, Tags) of
        true  -> ok;
        false -> precondition_failed(
                   "user_id property set to '~s' but authenticated user was "
                   "'~s'", [Claimed, Actual])
    end.

check_expiration_header(Props) ->
    case rabbit_basic:parse_expiration(Props) of
        {ok, _}    -> ok;
        {error, E} -> precondition_failed("invalid expiration '~s': ~p",
                                          [Props#'P_basic'.expiration, E])
    end.

check_internal_exchange(#exchange{name = Name, internal = true}) ->
    rabbit_misc:protocol_error(access_refused,
                               "cannot publish to internal ~s",
                               [rabbit_misc:rs(Name)]);
check_internal_exchange(_) ->
    ok.

check_topic_authorisation(#exchange{name = Name = #resource{virtual_host = VHost}, type = topic},
                             User = #user{username = Username},
                          RoutingKey, AuthzContext, Permission) ->
    Resource = Name#resource{kind = topic},
    VariableMap = build_topic_variable_map(AuthzContext, VHost, Username),
    Context = #{routing_key  => RoutingKey,
                variable_map => VariableMap},
    Cache = case get(topic_permission_cache) of
                undefined -> [];
                Other     -> Other
            end,
    case lists:member({Resource, Context, Permission}, Cache) of
        true  -> ok;
        false -> ok = rabbit_access_control:check_topic_access(
            User, Resource, Permission, Context),
            CacheTail = lists:sublist(Cache, ?MAX_PERMISSION_CACHE_SIZE-1),
            put(topic_permission_cache, [{Resource, Context, Permission} | CacheTail])
    end;
check_topic_authorisation(_, _, _, _, _) ->
    ok.


build_topic_variable_map(AuthzContext, VHost, Username) when is_map(AuthzContext) ->
    maps:merge(AuthzContext, #{<<"vhost">> => VHost, <<"username">> => Username});
build_topic_variable_map(AuthzContext, VHost, Username) ->
    maps:merge(extract_variable_map_from_amqp_params(AuthzContext), #{<<"vhost">> => VHost, <<"username">> => Username}).

%% Use tuple representation of amqp_params to avoid a dependency on amqp_client.
%% Extracts variable map only from amqp_params_direct, not amqp_params_network.
%% amqp_params_direct records are usually used by plugins (e.g. MQTT, STOMP)
extract_variable_map_from_amqp_params({amqp_params, {amqp_params_direct, _, _, _, _,
                                                        {amqp_adapter_info, _,_,_,_,_,_,AdditionalInfo}, _}}) ->
    proplists:get_value(variable_map, AdditionalInfo, #{});
extract_variable_map_from_amqp_params({amqp_params_direct, _, _, _, _,
                                             {amqp_adapter_info, _,_,_,_,_,_,AdditionalInfo}, _}) ->
    proplists:get_value(variable_map, AdditionalInfo, #{});
extract_variable_map_from_amqp_params([Value]) ->
    extract_variable_map_from_amqp_params(Value);
extract_variable_map_from_amqp_params(_) ->
    #{}.

check_msg_size(Content, MaxMessageSize, GCThreshold) ->
    Size = rabbit_basic:maybe_gc_large_msg(Content, GCThreshold),
    case Size of
        S when S > MaxMessageSize ->
            ErrorMessage = case MaxMessageSize of
                ?MAX_MSG_SIZE ->
                    "message size ~B is larger than max size ~B";
                _ ->
                    "message size ~B is larger than configured max size ~B"
            end,
            precondition_failed(ErrorMessage,
                                [Size, MaxMessageSize]);
        _ -> ok
    end.

check_vhost_queue_limit(#resource{name = QueueName}, VHost) ->
  case rabbit_vhost_limit:is_over_queue_limit(VHost) of
    false         -> ok;
    {true, Limit} -> precondition_failed("cannot declare queue '~s': "
                               "queue limit in vhost '~s' (~p) is reached",
                               [QueueName, VHost, Limit])

  end.

qbin_to_resource(QueueNameBin, VHostPath) ->
    name_to_resource(queue, QueueNameBin, VHostPath).

name_to_resource(Type, NameBin, VHostPath) ->
    rabbit_misc:r(VHostPath, Type, NameBin).

expand_queue_name_shortcut(<<>>, #ch{cfg = #conf{most_recently_declared_queue = <<>>}}) ->
    rabbit_misc:protocol_error(not_found, "no previously declared queue", []);
expand_queue_name_shortcut(<<>>, #ch{cfg = #conf{most_recently_declared_queue = MRDQ}}) ->
    MRDQ;
expand_queue_name_shortcut(QueueNameBin, _) ->
    QueueNameBin.

expand_routing_key_shortcut(<<>>, <<>>,
                            #ch{cfg = #conf{most_recently_declared_queue = <<>>}}) ->
    rabbit_misc:protocol_error(not_found, "no previously declared queue", []);
expand_routing_key_shortcut(<<>>, <<>>,
                            #ch{cfg = #conf{most_recently_declared_queue = MRDQ}}) ->
    MRDQ;
expand_routing_key_shortcut(_QueueNameBin, RoutingKey, _State) ->
    RoutingKey.

expand_shortcuts(#'basic.get'    {queue = Q} = M, State) ->
    M#'basic.get'    {queue = expand_queue_name_shortcut(Q, State)};
expand_shortcuts(#'basic.consume'{queue = Q} = M, State) ->
    M#'basic.consume'{queue = expand_queue_name_shortcut(Q, State)};
expand_shortcuts(#'queue.delete' {queue = Q} = M, State) ->
    M#'queue.delete' {queue = expand_queue_name_shortcut(Q, State)};
expand_shortcuts(#'queue.purge'  {queue = Q} = M, State) ->
    M#'queue.purge'  {queue = expand_queue_name_shortcut(Q, State)};
expand_shortcuts(#'queue.bind'   {queue = Q, routing_key = K} = M, State) ->
    M#'queue.bind'   {queue       = expand_queue_name_shortcut(Q, State),
                      routing_key = expand_routing_key_shortcut(Q, K, State)};
expand_shortcuts(#'queue.unbind' {queue = Q, routing_key = K} = M, State) ->
    M#'queue.unbind' {queue       = expand_queue_name_shortcut(Q, State),
                      routing_key = expand_routing_key_shortcut(Q, K, State)};
expand_shortcuts(M, _State) ->
    M.

check_not_default_exchange(#resource{kind = exchange, name = <<"">>}) ->
    rabbit_misc:protocol_error(
      access_refused, "operation not permitted on the default exchange", []);
check_not_default_exchange(_) ->
    ok.

check_exchange_deletion(XName = #resource{name = <<"amq.", _/binary>>,
                                          kind = exchange}) ->
    rabbit_misc:protocol_error(
      access_refused, "deletion of system ~s not allowed",
      [rabbit_misc:rs(XName)]);
check_exchange_deletion(_) ->
    ok.

%% check that an exchange/queue name does not contain the reserved
%% "amq."  prefix.
%%
%% As per the AMQP 0-9-1 spec, the exclusion of "amq." prefixed names
%% only applies on actual creation, and not in the cases where the
%% entity already exists or passive=true.
%%
%% NB: We deliberately do not enforce the other constraints on names
%% required by the spec.
check_name(Kind, NameBin = <<"amq.", _/binary>>) ->
    rabbit_misc:protocol_error(
      access_refused,
      "~s name '~s' contains reserved prefix 'amq.*'",[Kind, NameBin]);
check_name(_Kind, NameBin) ->
    NameBin.

strip_cr_lf(NameBin) ->
  binary:replace(NameBin, [<<"\n">>, <<"\r">>], <<"">>, [global]).


maybe_set_fast_reply_to(
  C = #content{properties = P = #'P_basic'{reply_to =
                                               <<"amq.rabbitmq.reply-to">>}},
  #ch{reply_consumer = ReplyConsumer}) ->
    case ReplyConsumer of
        none         -> rabbit_misc:protocol_error(
                          precondition_failed,
                          "fast reply consumer does not exist", []);
        {_, Suf, _K} -> Rep = <<"amq.rabbitmq.reply-to.", Suf/binary>>,
                        rabbit_binary_generator:clear_encoded_content(
                          C#content{properties = P#'P_basic'{reply_to = Rep}})
    end;
maybe_set_fast_reply_to(C, _State) ->
    C.

record_rejects([], State) ->
    State;
record_rejects(MXs, State = #ch{rejected = R, tx = Tx}) ->
    Tx1 = case Tx of
        none -> none;
        _    -> failed
    end,
    State#ch{rejected = [MXs | R], tx = Tx1}.

record_confirms([], State) ->
    State;
record_confirms(MXs, State = #ch{confirmed = C}) ->
    State#ch{confirmed = [MXs | C]}.

handle_method({Method, Content}, State) ->
    handle_method(Method, Content, State).

handle_method(#'channel.open'{}, _,
              State = #ch{cfg = #conf{state = starting} = Cfg}) ->
    %% Don't leave "starting" as the state for 5s. TODO is this TRTTD?
    State1 = State#ch{cfg = Cfg#conf{state = running}},
    rabbit_event:if_enabled(State1, #ch.stats_timer,
                            fun() -> emit_stats(State1) end),
    {reply, #'channel.open_ok'{}, State1};

handle_method(#'channel.open'{}, _, _State) ->
    rabbit_misc:protocol_error(
      channel_error, "second 'channel.open' seen", []);

handle_method(_Method, _, #ch{cfg = #conf{state = starting}}) ->
    rabbit_misc:protocol_error(channel_error, "expected 'channel.open'", []);

handle_method(#'channel.close_ok'{}, _, #ch{cfg = #conf{state = closing}}) ->
    stop;

handle_method(#'channel.close'{}, _,
              State = #ch{cfg = #conf{state = closing,
                                      writer_pid = WriterPid}}) ->
    ok = rabbit_writer:send_command(WriterPid, #'channel.close_ok'{}),
    {noreply, State};

handle_method(_Method, _, State = #ch{cfg = #conf{state = closing}}) ->
    {noreply, State};

handle_method(#'channel.close'{}, _,
              State = #ch{cfg = #conf{reader_pid = ReaderPid}}) ->
    {_Result, State1} = notify_queues(State),
    %% We issue the channel.close_ok response after a handshake with
    %% the reader, the other half of which is ready_for_close. That
    %% way the reader forgets about the channel before we send the
    %% response (and this channel process terminates). If we didn't do
    %% that, a channel.open for the same channel number, which a
    %% client is entitled to send as soon as it has received the
    %% close_ok, might be received by the reader before it has seen
    %% the termination and hence be sent to the old, now dead/dying
    %% channel process, instead of a new process, and thus lost.
    ReaderPid ! {channel_closing, self()},
    {noreply, State1};

%% Even though the spec prohibits the client from sending commands
%% while waiting for the reply to a synchronous command, we generally
%% do allow this...except in the case of a pending tx.commit, where
%% it could wreak havoc.
handle_method(_Method, _, #ch{tx = Tx})
  when Tx =:= committing orelse Tx =:= failed ->
    rabbit_misc:protocol_error(
      channel_error, "unexpected command while processing 'tx.commit'", []);

handle_method(#'access.request'{},_, State) ->
    {reply, #'access.request_ok'{ticket = 1}, State};

handle_method(#'basic.publish'{immediate = true}, _Content, _State) ->
    rabbit_misc:protocol_error(not_implemented, "immediate=true", []);

handle_method(#'basic.publish'{exchange    = ExchangeNameBin,
                               routing_key = RoutingKey,
                               mandatory   = Mandatory},
              Content, State = #ch{cfg = #conf{channel = ChannelNum,
                                               conn_name = ConnName,
                                               virtual_host = VHostPath,
                                               user = #user{username = Username} = User,
                                               trace_state = TraceState,
                                               max_message_size = MaxMessageSize,
                                               authz_context = AuthzContext,
                                               writer_gc_threshold = GCThreshold
                                              },
                                   tx               = Tx,
                                   confirm_enabled  = ConfirmEnabled,
                                   delivery_flow    = Flow
                                   }) ->
    check_msg_size(Content, MaxMessageSize, GCThreshold),
    ExchangeName = rabbit_misc:r(VHostPath, exchange, ExchangeNameBin),
    check_write_permitted(ExchangeName, User, AuthzContext),
    Exchange = rabbit_exchange:lookup_or_die(ExchangeName),
    check_internal_exchange(Exchange),
    check_write_permitted_on_topic(Exchange, User, RoutingKey, AuthzContext),
    %% We decode the content's properties here because we're almost
    %% certain to want to look at delivery-mode and priority.
    DecodedContent = #content {properties = Props} =
        maybe_set_fast_reply_to(
          rabbit_binary_parser:ensure_content_decoded(Content), State),
    check_user_id_header(Props, State),
    check_expiration_header(Props),
    DoConfirm = Tx =/= none orelse ConfirmEnabled,
    {MsgSeqNo, State1} =
        case DoConfirm orelse Mandatory of
            false -> {undefined, State};
            true  -> SeqNo = State#ch.publish_seqno,
                     {SeqNo, State#ch{publish_seqno = SeqNo + 1}}
        end,
    case rabbit_basic:message(ExchangeName, RoutingKey, DecodedContent) of
        {ok, Message} ->
            Delivery = rabbit_basic:delivery(
                         Mandatory, DoConfirm, Message, MsgSeqNo),
            QNames = rabbit_exchange:route(Exchange, Delivery),
            rabbit_trace:tap_in(Message, QNames, ConnName, ChannelNum,
                                Username, TraceState),
            DQ = {Delivery#delivery{flow = Flow}, QNames},
            {noreply, case Tx of
                          none         -> deliver_to_queues(DQ, State1);
                          {Msgs, Acks} -> Msgs1 = ?QUEUE:in(DQ, Msgs),
                                          State1#ch{tx = {Msgs1, Acks}}
                      end};
        {error, Reason} ->
            precondition_failed("invalid message: ~p", [Reason])
    end;

handle_method(#'basic.nack'{delivery_tag = DeliveryTag,
                            multiple     = Multiple,
                            requeue      = Requeue}, _, State) ->
    reject(DeliveryTag, Requeue, Multiple, State);

handle_method(#'basic.ack'{delivery_tag = DeliveryTag,
                           multiple     = Multiple},
              _, State = #ch{unacked_message_q = UAMQ, tx = Tx}) ->
    {Acked, Remaining} = collect_acks(UAMQ, DeliveryTag, Multiple),
    State1 = State#ch{unacked_message_q = Remaining},
    {noreply, case Tx of
                  none         -> ack(Acked, State1);
                  {Msgs, Acks} -> Acks1 = ack_cons(ack, Acked, Acks),
                                  State1#ch{tx = {Msgs, Acks1}}
              end};

handle_method(#'basic.get'{queue = QueueNameBin, no_ack = NoAck},
              _, State = #ch{cfg = #conf{writer_pid = WriterPid,
                                         conn_pid = ConnPid,
                                         user = User,
                                         virtual_host = VHostPath,
                                         authz_context = AuthzContext
                                        },
                             limiter = Limiter,
                             next_tag   = DeliveryTag,
                             queue_states = QueueStates0}) ->
    QueueName = qbin_to_resource(QueueNameBin, VHostPath),
    check_read_permitted(QueueName, User, AuthzContext),
    case rabbit_amqqueue:with_exclusive_access_or_die(
           QueueName, ConnPid,
           %% Use the delivery tag as consumer tag for quorum queues
           fun (Q) -> rabbit_amqqueue:basic_get(
                        Q, self(), NoAck, rabbit_limiter:pid(Limiter),
                        DeliveryTag, QueueStates0)
           end) of
        {ok, MessageCount, Msg} ->
            handle_basic_get(WriterPid, DeliveryTag, NoAck, MessageCount, Msg, State);
        {ok, MessageCount, Msg, QueueStates} ->
            handle_basic_get(WriterPid, DeliveryTag, NoAck, MessageCount, Msg,
                             State#ch{queue_states = QueueStates});
        {empty, QueueStates} ->
            ?INCR_STATS(queue_stats, QueueName, 1, get_empty, State),
            {reply, #'basic.get_empty'{}, State#ch{queue_states = QueueStates}};
        empty ->
            ?INCR_STATS(queue_stats, QueueName, 1, get_empty, State),
            {reply, #'basic.get_empty'{}, State}
    end;

handle_method(#'basic.consume'{queue        = <<"amq.rabbitmq.reply-to">>,
                               consumer_tag = CTag0,
                               no_ack       = NoAck,
                               nowait       = NoWait},
              _, State = #ch{reply_consumer   = ReplyConsumer,
                             consumer_mapping = ConsumerMapping}) ->
    case maps:find(CTag0, ConsumerMapping) of
        error ->
            case {ReplyConsumer, NoAck} of
                {none, true} ->
                    CTag = case CTag0 of
                               <<>>  -> rabbit_guid:binary(
                                          rabbit_guid:gen_secure(), "amq.ctag");
                               Other -> Other
                           end,
                    %% Precalculate both suffix and key; base64 encoding is
                    %% expensive
                    Key = base64:encode(rabbit_guid:gen_secure()),
                    PidEnc = base64:encode(term_to_binary(self())),
                    Suffix = <<PidEnc/binary, ".", Key/binary>>,
                    Consumer = {CTag, Suffix, binary_to_list(Key)},
                    State1 = State#ch{reply_consumer = Consumer},
                    case NoWait of
                        true  -> {noreply, State1};
                        false -> Rep = #'basic.consume_ok'{consumer_tag = CTag},
                                 {reply, Rep, State1}
                    end;
                {_, false} ->
                    rabbit_misc:protocol_error(
                      precondition_failed,
                      "reply consumer cannot acknowledge", []);
                _ ->
                    rabbit_misc:protocol_error(
                      precondition_failed, "reply consumer already set", [])
            end;
        {ok, _} ->
            %% Attempted reuse of consumer tag.
            rabbit_misc:protocol_error(
              not_allowed, "attempt to reuse consumer tag '~s'", [CTag0])
    end;

handle_method(#'basic.cancel'{consumer_tag = ConsumerTag, nowait = NoWait},
              _, State = #ch{reply_consumer = {ConsumerTag, _, _}}) ->
    State1 = State#ch{reply_consumer = none},
    case NoWait of
        true  -> {noreply, State1};
        false -> Rep = #'basic.cancel_ok'{consumer_tag = ConsumerTag},
                 {reply, Rep, State1}
    end;

handle_method(#'basic.consume'{queue        = QueueNameBin,
                               consumer_tag = ConsumerTag,
                               no_local     = _, % FIXME: implement
                               no_ack       = NoAck,
                               exclusive    = ExclusiveConsume,
                               nowait       = NoWait,
                               arguments    = Args},
              _, State = #ch{cfg = #conf{consumer_prefetch = ConsumerPrefetch,
                                         user = User,
                                         virtual_host = VHostPath,
                                         authz_context = AuthzContext},
                             consumer_mapping  = ConsumerMapping
                            }) ->
    case maps:find(ConsumerTag, ConsumerMapping) of
        error ->
            QueueName = qbin_to_resource(QueueNameBin, VHostPath),
            check_read_permitted(QueueName, User, AuthzContext),
            ActualConsumerTag =
                case ConsumerTag of
                    <<>>  -> rabbit_guid:binary(rabbit_guid:gen_secure(),
                                                "amq.ctag");
                    Other -> Other
                end,
            case basic_consume(
                   QueueName, NoAck, ConsumerPrefetch, ActualConsumerTag,
                   ExclusiveConsume, Args, NoWait, State) of
                {ok, State1} ->
                    {noreply, State1};
                {error, exclusive_consume_unavailable} ->
                    rabbit_misc:protocol_error(
                      access_refused, "~s in exclusive use",
                      [rabbit_misc:rs(QueueName)]);
                {error, global_qos_not_supported_for_queue_type} ->
                    rabbit_misc:protocol_error(
                      not_implemented, "~s does not support global qos",
                      [rabbit_misc:rs(QueueName)])
            end;
        {ok, _} ->
            %% Attempted reuse of consumer tag.
            rabbit_misc:protocol_error(
              not_allowed, "attempt to reuse consumer tag '~s'", [ConsumerTag])
    end;

handle_method(#'basic.cancel'{consumer_tag = ConsumerTag, nowait = NoWait},
              _, State = #ch{cfg = #conf{user = #user{username = Username}},
                             consumer_mapping = ConsumerMapping,
                             queue_consumers  = QCons,
                             queue_states     = QueueStates0}) ->
    OkMsg = #'basic.cancel_ok'{consumer_tag = ConsumerTag},
    case maps:find(ConsumerTag, ConsumerMapping) of
        error ->
            %% Spec requires we ignore this situation.
            return_ok(State, NoWait, OkMsg);
        {ok, {Q, _CParams}} when ?is_amqqueue(Q) ->
            QPid = amqqueue:get_pid(Q),
            ConsumerMapping1 = maps:remove(ConsumerTag, ConsumerMapping),
            QRef = qpid_to_ref(QPid),
            QCons1 =
                case maps:find(QRef, QCons) of
                    error       -> QCons;
                    {ok, CTags} -> CTags1 = gb_sets:delete(ConsumerTag, CTags),
                                   case gb_sets:is_empty(CTags1) of
                                       true  -> maps:remove(QRef, QCons);
                                       false -> maps:put(QRef, CTags1, QCons)
                                   end
                end,
            NewState = State#ch{consumer_mapping = ConsumerMapping1,
                                queue_consumers  = QCons1},
            %% In order to ensure that no more messages are sent to
            %% the consumer after the cancel_ok has been sent, we get
            %% the queue process to send the cancel_ok on our
            %% behalf. If we were sending the cancel_ok ourselves it
            %% might overtake a message sent previously by the queue.
            case rabbit_misc:with_exit_handler(
                   fun () -> {error, not_found} end,
                   fun () ->
                           rabbit_amqqueue:basic_cancel(
                             Q, self(), ConsumerTag, ok_msg(NoWait, OkMsg),
                             Username, QueueStates0)
                   end) of
                {ok, QueueStates} ->
                    {noreply, NewState#ch{queue_states = QueueStates}};
                {error, not_found} ->
                    %% Spec requires we ignore this situation.
                    return_ok(NewState, NoWait, OkMsg)
            end
    end;

handle_method(#'basic.qos'{prefetch_size = Size}, _, _State) when Size /= 0 ->
    rabbit_misc:protocol_error(not_implemented,
                               "prefetch_size!=0 (~w)", [Size]);

handle_method(#'basic.qos'{global         = false,
                           prefetch_count = PrefetchCount},
              _, State = #ch{cfg = Cfg,
                             limiter = Limiter}) ->
    %% Ensures that if default was set, it's overridden
    Limiter1 = rabbit_limiter:unlimit_prefetch(Limiter),
    {reply, #'basic.qos_ok'{}, State#ch{cfg = Cfg#conf{consumer_prefetch = PrefetchCount},
                                        limiter = Limiter1}};

handle_method(#'basic.qos'{global         = true,
                           prefetch_count = 0},
              _, State = #ch{limiter = Limiter}) ->
    Limiter1 = rabbit_limiter:unlimit_prefetch(Limiter),
    {reply, #'basic.qos_ok'{}, State#ch{limiter = Limiter1}};

handle_method(#'basic.qos'{global         = true,
                           prefetch_count = PrefetchCount},
              _, State = #ch{limiter = Limiter, unacked_message_q = UAMQ}) ->
    %% TODO ?QUEUE:len(UAMQ) is not strictly right since that counts
    %% unacked messages from basic.get too. Pretty obscure though.
    Limiter1 = rabbit_limiter:limit_prefetch(Limiter,
                                             PrefetchCount, ?QUEUE:len(UAMQ)),
    case ((not rabbit_limiter:is_active(Limiter)) andalso
          rabbit_limiter:is_active(Limiter1)) of
        true  -> rabbit_amqqueue:activate_limit_all(
                   consumer_queue_refs(State#ch.consumer_mapping), self());
        false -> ok
    end,
    {reply, #'basic.qos_ok'{}, State#ch{limiter = Limiter1}};

handle_method(#'basic.recover_async'{requeue = true},
              _, State = #ch{unacked_message_q = UAMQ, limiter = Limiter,
                             queue_states = QueueStates0}) ->
    OkFun = fun () -> ok end,
    UAMQL = ?QUEUE:to_list(UAMQ),
    QueueStates =
        foreach_per_queue(
          fun ({QPid, CTag}, MsgIds, Acc0) ->
                  rabbit_misc:with_exit_handler(
                    OkFun,
                    fun () ->
                            rabbit_amqqueue:requeue(QPid, {CTag, MsgIds},
                                                    self(), Acc0)
                    end)
          end, lists:reverse(UAMQL), QueueStates0),
    ok = notify_limiter(Limiter, UAMQL),
    %% No answer required - basic.recover is the newer, synchronous
    %% variant of this method
    {noreply, State#ch{unacked_message_q = ?QUEUE:new(),
                       queue_states = QueueStates}};

handle_method(#'basic.recover_async'{requeue = false}, _, _State) ->
    rabbit_misc:protocol_error(not_implemented, "requeue=false", []);

handle_method(#'basic.recover'{requeue = Requeue}, Content, State) ->
    {noreply, State1} = handle_method(#'basic.recover_async'{requeue = Requeue},
                                      Content, State),
    {reply, #'basic.recover_ok'{}, State1};

handle_method(#'basic.reject'{delivery_tag = DeliveryTag, requeue = Requeue},
              _, State) ->
    reject(DeliveryTag, Requeue, false, State);

handle_method(#'exchange.declare'{nowait = NoWait} = Method,
              _, State = #ch{cfg = #conf{virtual_host = VHostPath,
                                         user = User,
                                         queue_collector_pid = CollectorPid,
                                         conn_pid = ConnPid,
                                         authz_context = AuthzContext}}) ->
    handle_method(Method, ConnPid, AuthzContext, CollectorPid, VHostPath, User),
    return_ok(State, NoWait, #'exchange.declare_ok'{});

handle_method(#'exchange.delete'{nowait = NoWait} = Method,
              _, State = #ch{cfg = #conf{conn_pid = ConnPid,
                                         authz_context = AuthzContext,
                                         virtual_host = VHostPath,
                                         queue_collector_pid = CollectorPid,
                                         user = User}}) ->
    handle_method(Method, ConnPid, AuthzContext, CollectorPid, VHostPath, User),
    return_ok(State, NoWait,  #'exchange.delete_ok'{});

handle_method(#'exchange.bind'{nowait = NoWait} = Method,
              _, State = #ch{cfg = #conf{virtual_host = VHostPath,
                                         conn_pid = ConnPid,
                                         authz_context = AuthzContext,
                                         queue_collector_pid = CollectorPid,
                                         user = User}}) ->
    handle_method(Method, ConnPid, AuthzContext, CollectorPid, VHostPath, User),
    return_ok(State, NoWait, #'exchange.bind_ok'{});

handle_method(#'exchange.unbind'{nowait = NoWait} = Method,
              _, State = #ch{cfg = #conf{virtual_host = VHostPath,
                                         conn_pid = ConnPid,
                                         authz_context = AuthzContext,
                                         queue_collector_pid = CollectorPid,
                                         user = User}}) ->
    handle_method(Method, ConnPid, AuthzContext, CollectorPid, VHostPath, User),
    return_ok(State, NoWait, #'exchange.unbind_ok'{});

handle_method(#'queue.declare'{nowait = NoWait} = Method,
              _, State = #ch{cfg = #conf{virtual_host = VHostPath,
                                         conn_pid = ConnPid,
                                         authz_context = AuthzContext,
                                         queue_collector_pid = CollectorPid,
                                         user = User}}) ->
    {ok, QueueName, MessageCount, ConsumerCount} =
        handle_method(Method, ConnPid, AuthzContext, CollectorPid, VHostPath, User),
    return_queue_declare_ok(QueueName, NoWait, MessageCount,
                            ConsumerCount, State);

handle_method(#'queue.delete'{nowait = NoWait} = Method, _,
              State = #ch{cfg = #conf{conn_pid = ConnPid,
                                      authz_context = AuthzContext,
                                      virtual_host = VHostPath,
                                      queue_collector_pid = CollectorPid,
                                      user = User}}) ->
    {ok, PurgedMessageCount} =
        handle_method(Method, ConnPid, AuthzContext, CollectorPid, VHostPath, User),
    return_ok(State, NoWait,
              #'queue.delete_ok'{message_count = PurgedMessageCount});

handle_method(#'queue.bind'{nowait = NoWait} = Method, _,
              State = #ch{cfg = #conf{conn_pid = ConnPid,
                                      authz_context = AuthzContext,
                                      user = User,
                                      queue_collector_pid = CollectorPid,
                                      virtual_host = VHostPath}}) ->
    handle_method(Method, ConnPid, AuthzContext, CollectorPid, VHostPath, User),
    return_ok(State, NoWait, #'queue.bind_ok'{});

handle_method(#'queue.unbind'{} = Method, _,
              State = #ch{cfg = #conf{conn_pid = ConnPid,
                                      authz_context = AuthzContext,
                                      user = User,
                                      queue_collector_pid = CollectorPid,
                                      virtual_host = VHostPath}}) ->
    handle_method(Method, ConnPid, AuthzContext, CollectorPid, VHostPath, User),
    return_ok(State, false, #'queue.unbind_ok'{});

handle_method(#'queue.purge'{nowait = NoWait} = Method,
              _, State = #ch{cfg = #conf{conn_pid = ConnPid,
                                         authz_context = AuthzContext,
                                         user = User,
                                         queue_collector_pid = CollectorPid,
                                         virtual_host = VHostPath}}) ->
    case handle_method(Method, ConnPid, AuthzContext, CollectorPid,
                       VHostPath, User) of
        {ok, PurgedMessageCount} ->
            return_ok(State, NoWait,
                      #'queue.purge_ok'{message_count = PurgedMessageCount})
    end;

handle_method(#'tx.select'{}, _, #ch{confirm_enabled = true}) ->
    precondition_failed("cannot switch from confirm to tx mode");

handle_method(#'tx.select'{}, _, State = #ch{tx = none}) ->
    {reply, #'tx.select_ok'{}, State#ch{tx = new_tx()}};

handle_method(#'tx.select'{}, _, State) ->
    {reply, #'tx.select_ok'{}, State};

handle_method(#'tx.commit'{}, _, #ch{tx = none}) ->
    precondition_failed("channel is not transactional");

handle_method(#'tx.commit'{}, _, State = #ch{tx      = {Msgs, Acks},
                                             limiter = Limiter}) ->
    State1 = queue_fold(fun deliver_to_queues/2, State, Msgs),
    Rev = fun (X) -> lists:reverse(lists:sort(X)) end,
    State2 = lists:foldl(fun ({ack,     A}, Acc) ->
                                 ack(Rev(A), Acc);
                             ({Requeue, A}, Acc) ->
                                 internal_reject(Requeue, Rev(A), Limiter, Acc)
                         end, State1, lists:reverse(Acks)),
    {noreply, maybe_complete_tx(State2#ch{tx = committing})};

handle_method(#'tx.rollback'{}, _, #ch{tx = none}) ->
    precondition_failed("channel is not transactional");

handle_method(#'tx.rollback'{}, _, State = #ch{unacked_message_q = UAMQ,
                                               tx = {_Msgs, Acks}}) ->
    AcksL = lists:append(lists:reverse([lists:reverse(L) || {_, L} <- Acks])),
    UAMQ1 = ?QUEUE:from_list(lists:usort(AcksL ++ ?QUEUE:to_list(UAMQ))),
    {reply, #'tx.rollback_ok'{}, State#ch{unacked_message_q = UAMQ1,
                                          tx                = new_tx()}};

handle_method(#'confirm.select'{}, _, #ch{tx = {_, _}}) ->
    precondition_failed("cannot switch from tx to confirm mode");

handle_method(#'confirm.select'{nowait = NoWait}, _, State) ->
    return_ok(State#ch{confirm_enabled = true},
              NoWait, #'confirm.select_ok'{});

handle_method(#'channel.flow'{active = true}, _, State) ->
    {reply, #'channel.flow_ok'{active = true}, State};

handle_method(#'channel.flow'{active = false}, _, _State) ->
    rabbit_misc:protocol_error(not_implemented, "active=false", []);

handle_method(#'basic.credit'{consumer_tag = CTag,
                              credit       = Credit,
                              drain        = Drain},
              _, State = #ch{consumer_mapping = Consumers,
                             queue_states = QStates0}) ->
    case maps:find(CTag, Consumers) of
        {ok, {Q, _CParams}} ->
            {ok, QStates} = rabbit_amqqueue:credit(
                              Q, self(), CTag, Credit, Drain, QStates0),
            {noreply, State#ch{queue_states = QStates}};
        error -> precondition_failed(
                   "unknown consumer tag '~s'", [CTag])
    end;

handle_method(_MethodRecord, _Content, _State) ->
    rabbit_misc:protocol_error(
      command_invalid, "unimplemented method", []).

%%----------------------------------------------------------------------------

%% We get the queue process to send the consume_ok on our behalf. This
%% is for symmetry with basic.cancel - see the comment in that method
%% for why.
basic_consume(QueueName, NoAck, ConsumerPrefetch, ActualConsumerTag,
              ExclusiveConsume, Args, NoWait,
              State = #ch{cfg = #conf{conn_pid = ConnPid,
                                      user = #user{username = Username}},
                          limiter = Limiter,
                          consumer_mapping  = ConsumerMapping,
                          queue_states = QueueStates0}) ->
    case rabbit_amqqueue:with_exclusive_access_or_die(
           QueueName, ConnPid,
           fun (Q) ->
                   {rabbit_amqqueue:basic_consume(
                      Q, NoAck, self(),
                      rabbit_limiter:pid(Limiter),
                      rabbit_limiter:is_active(Limiter),
                      ConsumerPrefetch, ActualConsumerTag,
                      ExclusiveConsume, Args,
                      ok_msg(NoWait, #'basic.consume_ok'{
                               consumer_tag = ActualConsumerTag}),
                      Username, QueueStates0),
                    Q}
           end) of
        {{ok, QueueStates}, Q} when ?is_amqqueue(Q) ->
            QPid = amqqueue:get_pid(Q),
            QName = amqqueue:get_name(Q),
            CM1 = maps:put(
                    ActualConsumerTag,
                    {Q, {NoAck, ConsumerPrefetch, ExclusiveConsume, Args}},
                    ConsumerMapping),
            State1 = track_delivering_queue(
                       NoAck, QPid, QName,
                       State#ch{consumer_mapping = CM1,
                                queue_states = QueueStates}),
            {ok, case NoWait of
                     true  -> consumer_monitor(ActualConsumerTag, State1);
                     false -> State1
                 end};
        {ok, Q} when ?is_amqqueue(Q) ->
            QPid = amqqueue:get_pid(Q),
            QName = amqqueue:get_name(Q),
            CM1 = maps:put(
                    ActualConsumerTag,
                    {Q, {NoAck, ConsumerPrefetch, ExclusiveConsume, Args}},
                    ConsumerMapping),
            State1 = track_delivering_queue(
                       NoAck, QPid, QName,
                       State#ch{consumer_mapping = CM1}),
            {ok, case NoWait of
                     true  -> consumer_monitor(ActualConsumerTag, State1);
                     false -> State1
                 end};
        {{error, exclusive_consume_unavailable} = E, _Q} ->
            E;
        {{error, global_qos_not_supported_for_queue_type} = E, _Q} ->
            E
    end.

maybe_stat(false, Q) -> rabbit_amqqueue:stat(Q);
maybe_stat(true, _Q) -> {ok, 0, 0}.

consumer_monitor(ConsumerTag,
                 State = #ch{consumer_mapping = ConsumerMapping,
                             queue_monitors   = QMons,
                             queue_consumers  = QCons}) ->
    {Q, _} = maps:get(ConsumerTag, ConsumerMapping),
    QPid = amqqueue:get_pid(Q),
    QRef = qpid_to_ref(QPid),
    CTags1 = case maps:find(QRef, QCons) of
                 {ok, CTags} -> gb_sets:insert(ConsumerTag, CTags);
                 error -> gb_sets:singleton(ConsumerTag)
             end,
    QCons1 = maps:put(QRef, CTags1, QCons),
    State#ch{queue_monitors  = maybe_monitor(QRef, QMons),
             queue_consumers = QCons1}.

track_delivering_queue(NoAck, QPid, QName,
                       State = #ch{queue_names = QNames,
                                   queue_monitors = QMons,
                                   delivering_queues = DQ}) ->
    QRef = qpid_to_ref(QPid),
    State#ch{queue_names = maps:put(QRef, QName, QNames),
             queue_monitors = maybe_monitor(QRef, QMons),
             delivering_queues = case NoAck of
                                     true  -> DQ;
                                     false -> sets:add_element(QRef, DQ)
                                 end}.

handle_publishing_queue_down(QPid, Reason,
                             State = #ch{unconfirmed = UC,
                                         queue_names = QNames})
  when ?IS_CLASSIC(QPid) ->
    case maps:get(QPid, QNames, none) of
        %% The queue is unknown, the confirm must have been processed already
        none   -> State;
        _QName ->
            case {rabbit_misc:is_abnormal_exit(Reason), Reason} of
                {true, _} ->
                    {RejectMXs, UC1} =
                        unconfirmed_messages:reject_all_for_queue(QPid, UC),
                    record_rejects(RejectMXs, State#ch{unconfirmed = UC1});
                {false, normal} ->
                    {ConfirmMXs, RejectMXs, UC1} =
                        unconfirmed_messages:forget_ref(QPid, UC),
                    %% Deleted queue is a special case.
                    %% Do not nack the "rejected" messages.
                    record_confirms(ConfirmMXs ++ RejectMXs,
                                    State#ch{unconfirmed = UC1});
                {false, _} ->
                    {ConfirmMXs, RejectMXs, UC1} =
                        unconfirmed_messages:forget_ref(QPid, UC),
                    State1 = record_confirms(ConfirmMXs,
                                             State#ch{unconfirmed = UC1}),
                    record_rejects(RejectMXs, State1)
            end
    end;
handle_publishing_queue_down(QPid, _Reason, State) when ?IS_QUORUM(QPid) ->
    %% this should never happen after the queue type refactoring in 3.9
    State.

handle_consuming_queue_down_or_eol(QRef,
                                   State = #ch{queue_consumers = QCons,
                                               queue_names = QNames}) ->
    ConsumerTags = case maps:find(QRef, QCons) of
                       error       -> gb_sets:new();
                       {ok, CTags} -> CTags
                   end,
    gb_sets:fold(
      fun (CTag, StateN = #ch{consumer_mapping = CMap}) ->
              QName = maps:get(QRef, QNames),
              case queue_down_consumer_action(CTag, CMap) of
                  remove ->
                      cancel_consumer(CTag, QName, StateN);
                  {recover, {NoAck, ConsumerPrefetch, Exclusive, Args}} ->
                      case catch basic_consume( %% [0]
                                   QName, NoAck, ConsumerPrefetch, CTag,
                                   Exclusive, Args, true, StateN) of
                          {ok, StateN1} -> StateN1;
                          _             -> cancel_consumer(CTag, QName, StateN)
                      end
              end
      end, State#ch{queue_consumers = maps:remove(QRef, QCons)}, ConsumerTags).

%% [0] There is a slight danger here that if a queue is deleted and
%% then recreated again the reconsume will succeed even though it was
%% not an HA failover. But the likelihood is not great and most users
%% are unlikely to care.

cancel_consumer(CTag, QName,
                State = #ch{cfg = #conf{capabilities = Capabilities},
                            consumer_mapping = CMap}) ->
    case rabbit_misc:table_lookup(
           Capabilities, <<"consumer_cancel_notify">>) of
        {bool, true} -> ok = send(#'basic.cancel'{consumer_tag = CTag,
                                                  nowait       = true}, State);
        _            -> ok
    end,
    rabbit_event:notify(consumer_deleted, [{consumer_tag, CTag},
                                           {channel,      self()},
                                           {queue,        QName}]),
    State#ch{consumer_mapping = maps:remove(CTag, CMap)}.

queue_down_consumer_action(CTag, CMap) ->
    {_, {_, _, _, Args} = ConsumeSpec} = maps:get(CTag, CMap),
    case rabbit_misc:table_lookup(Args, <<"x-cancel-on-ha-failover">>) of
        {bool, true} -> remove;
        _            -> {recover, ConsumeSpec}
    end.

handle_delivering_queue_down(QRef, State = #ch{delivering_queues = DQ}) ->
    State#ch{delivering_queues = sets:del_element(QRef, DQ)}.

binding_action(Fun, SourceNameBin0, DestinationType, DestinationNameBin0,
               RoutingKey, Arguments, VHostPath, ConnPid, AuthzContext,
               #user{username = Username} = User) ->
    ExchangeNameBin = strip_cr_lf(SourceNameBin0),
    DestinationNameBin = strip_cr_lf(DestinationNameBin0),
    DestinationName = name_to_resource(DestinationType, DestinationNameBin, VHostPath),
    check_write_permitted(DestinationName, User, AuthzContext),
    ExchangeName = rabbit_misc:r(VHostPath, exchange, ExchangeNameBin),
    [check_not_default_exchange(N) || N <- [DestinationName, ExchangeName]],
    check_read_permitted(ExchangeName, User, AuthzContext),
    case rabbit_exchange:lookup(ExchangeName) of
        {error, not_found} ->
            ok;
        {ok, Exchange}     ->
            check_read_permitted_on_topic(Exchange, User, RoutingKey, AuthzContext)
    end,
    case Fun(#binding{source      = ExchangeName,
                      destination = DestinationName,
                      key         = RoutingKey,
                      args        = Arguments},
             fun (_X, Q) when ?is_amqqueue(Q) ->
                     try rabbit_amqqueue:check_exclusive_access(Q, ConnPid)
                     catch exit:Reason -> {error, Reason}
                     end;
                 (_X, #exchange{}) ->
                     ok
             end,
             Username) of
        {error, {resources_missing, [{not_found, Name} | _]}} ->
            rabbit_amqqueue:not_found(Name);
        {error, {resources_missing, [{absent, Q, Reason} | _]}} ->
            rabbit_amqqueue:absent(Q, Reason);
        {error, binding_not_found} ->
            rabbit_misc:protocol_error(
              not_found, "no binding ~s between ~s and ~s",
              [RoutingKey, rabbit_misc:rs(ExchangeName),
               rabbit_misc:rs(DestinationName)]);
        {error, {binding_invalid, Fmt, Args}} ->
            rabbit_misc:protocol_error(precondition_failed, Fmt, Args);
        {error, #amqp_error{} = Error} ->
            rabbit_misc:protocol_error(Error);
        ok ->
            ok
    end.

basic_return(#basic_message{exchange_name = ExchangeName,
                            routing_keys  = [RoutingKey | _CcRoutes],
                            content       = Content},
             State = #ch{cfg = #conf{protocol = Protocol,
                                     writer_pid = WriterPid}},
             Reason) ->
    ?INCR_STATS(exchange_stats, ExchangeName, 1, return_unroutable, State),
    {_Close, ReplyCode, ReplyText} = Protocol:lookup_amqp_exception(Reason),
    ok = rabbit_writer:send_command(
           WriterPid,
           #'basic.return'{reply_code  = ReplyCode,
                           reply_text  = ReplyText,
                           exchange    = ExchangeName#resource.name,
                           routing_key = RoutingKey},
           Content).

reject(DeliveryTag, Requeue, Multiple,
       State = #ch{unacked_message_q = UAMQ, tx = Tx}) ->
    {Acked, Remaining} = collect_acks(UAMQ, DeliveryTag, Multiple),
    State1 = State#ch{unacked_message_q = Remaining},
    {noreply, case Tx of
                  none         -> internal_reject(Requeue, Acked, State1#ch.limiter, State1);
                  {Msgs, Acks} -> Acks1 = ack_cons(Requeue, Acked, Acks),
                                  State1#ch{tx = {Msgs, Acks1}}
              end}.

%% NB: Acked is in youngest-first order
internal_reject(Requeue, Acked, Limiter,
                State = #ch{queue_states = QueueStates0}) ->
    QueueStates = foreach_per_queue(
                    fun({QPid, CTag}, MsgIds, Acc0) ->
                            rabbit_amqqueue:reject(QPid, Requeue, {CTag, MsgIds},
                                                   self(), Acc0)
                    end, Acked, QueueStates0),
    ok = notify_limiter(Limiter, Acked),
    State#ch{queue_states = QueueStates}.

record_sent(Type, Tag, AckRequired,
            Msg = {QName, QPid, MsgId, Redelivered, _Message},
            State = #ch{cfg = #conf{channel = ChannelNum,
                                    trace_state = TraceState,
                                    user = #user{username = Username},
                                    conn_name = ConnName
                                   },
                        unacked_message_q = UAMQ,
                        next_tag          = DeliveryTag
                       }) ->
    ?INCR_STATS(queue_stats, QName, 1, case {Type, AckRequired} of
                                           {get, true}      -> get;
                                           {get, false}     -> get_no_ack;
                                           {deliver, true}  -> deliver;
                                           {deliver, false} -> deliver_no_ack
                                       end, State),
    case Redelivered of
        true  -> ?INCR_STATS(queue_stats, QName, 1, redeliver, State);
        false -> ok
    end,
    DeliveredAt = os:system_time(millisecond),
    rabbit_trace:tap_out(Msg, ConnName, ChannelNum, Username, TraceState),
    UAMQ1 = case AckRequired of
                true  -> ?QUEUE:in({DeliveryTag, Tag, DeliveredAt,
                                    {QPid, MsgId}}, UAMQ);
                false -> UAMQ
            end,
    State#ch{unacked_message_q = UAMQ1, next_tag = DeliveryTag + 1}.

%% NB: returns acks in youngest-first order
collect_acks(Q, 0, true) ->
    {lists:reverse(?QUEUE:to_list(Q)), ?QUEUE:new()};
collect_acks(Q, DeliveryTag, Multiple) ->
    collect_acks([], [], Q, DeliveryTag, Multiple).

collect_acks(ToAcc, PrefixAcc, Q, DeliveryTag, Multiple) ->
    case ?QUEUE:out(Q) of
        {{value, UnackedMsg = {CurrentDeliveryTag, _ConsumerTag, _Time, _Msg}},
         QTail} ->
            if CurrentDeliveryTag == DeliveryTag ->
                    {[UnackedMsg | ToAcc],
                     case PrefixAcc of
                         [] -> QTail;
                         _  -> ?QUEUE:join(
                                 ?QUEUE:from_list(lists:reverse(PrefixAcc)),
                                 QTail)
                     end};
               Multiple ->
                    collect_acks([UnackedMsg | ToAcc], PrefixAcc,
                                 QTail, DeliveryTag, Multiple);
               true ->
                    collect_acks(ToAcc, [UnackedMsg | PrefixAcc],
                                 QTail, DeliveryTag, Multiple)
            end;
        {empty, _} ->
            precondition_failed("unknown delivery tag ~w", [DeliveryTag])
    end.

%% NB: Acked is in youngest-first order
ack(Acked, State = #ch{queue_names = QNames,
                       queue_states = QueueStates0}) ->
    QueueStates =
        foreach_per_queue(
          fun ({QPid, CTag}, MsgIds, Acc0) ->
                  Acc = rabbit_amqqueue:ack(QPid, {CTag, MsgIds}, self(), Acc0),
                  incr_queue_stats(QPid, QNames, MsgIds, State),
                  Acc
          end, Acked, QueueStates0),
    ok = notify_limiter(State#ch.limiter, Acked),
    State#ch{queue_states = QueueStates}.

incr_queue_stats(QPid, QNames, MsgIds, State) ->
    case maps:find(qpid_to_ref(QPid), QNames) of
        {ok, QName} -> Count = length(MsgIds),
                       ?INCR_STATS(queue_stats, QName, Count, ack, State);
        error       -> ok
    end.

%% {Msgs, Acks}
%%
%% Msgs is a queue.
%%
%% Acks looks s.t. like this:
%% [{false,[5,4]},{true,[3]},{ack,[2,1]}, ...]
%%
%% Each element is a pair consisting of a tag and a list of
%% ack'ed/reject'ed msg ids. The tag is one of 'ack' (to ack), 'true'
%% (reject w requeue), 'false' (reject w/o requeue). The msg ids, as
%% well as the list overall, are in "most-recent (generally youngest)
%% ack first" order.
new_tx() -> {?QUEUE:new(), []}.

notify_queues(State = #ch{cfg = #conf{state = closing}}) ->
    {ok, State};
notify_queues(State = #ch{consumer_mapping  = Consumers,
                          cfg = Cfg,
                          delivering_queues = DQ }) ->
    QRefs0 = sets:to_list(
               sets:union(sets:from_list(consumer_queue_refs(Consumers)), DQ)),
    %% filter to only include pids to avoid trying to notify quorum queues
    QPids = [P || P <- QRefs0, ?IS_CLASSIC(P)],
    Timeout = get_operation_timeout(),
    {rabbit_amqqueue:notify_down_all(QPids, self(), Timeout),
     State#ch{cfg = Cfg#conf{state = closing}}}.

foreach_per_queue(_F, [], Acc) ->
    Acc;
foreach_per_queue(F, [{_DTag, CTag, _Time, {QPid, MsgId}}], Acc) ->
    %% quorum queue, needs the consumer tag
    F({QPid, CTag}, [MsgId], Acc);
foreach_per_queue(F, UAL, Acc) ->
    T = lists:foldl(fun ({_DTag, CTag, _Time, {QPid, MsgId}}, T) ->
                            rabbit_misc:gb_trees_cons({QPid, CTag}, MsgId, T)
                    end, gb_trees:empty(), UAL),
    rabbit_misc:gb_trees_fold(fun (Key, Val, Acc0) -> F(Key, Val, Acc0) end, Acc, T).

consumer_queue_refs(Consumers) ->
    lists:usort([qpid_to_ref(amqqueue:get_pid(Q))
                 || {_Key, {Q, _CParams}} <- maps:to_list(Consumers),
                    amqqueue:is_amqqueue(Q)]).

%% tell the limiter about the number of acks that have been received
%% for messages delivered to subscribed consumers, but not acks for
%% messages sent in a response to a basic.get (identified by their
%% consumer tag as an integer (the same as the delivery tag, required
%% quorum queues))
notify_limiter(Limiter, Acked) ->
    %% optimisation: avoid the potentially expensive 'foldl' in the
    %% common case.
     case rabbit_limiter:is_active(Limiter) of
        false -> ok;
        true  -> case lists:foldl(fun ({_, CTag, _, _}, Acc) when is_integer(CTag) ->
                                          %% Quorum queues use integer CTags
                                          %% classic queues use binaries
                                          %% Quorum queues do not interact
                                          %% with limiters
                                          Acc;
                                      ({_,    _, _, _}, Acc) -> Acc + 1
                                  end, 0, Acked) of
                     0     -> ok;
                     Count -> rabbit_limiter:ack(Limiter, Count)
                 end
    end.

deliver_to_queues({#delivery{message   = #basic_message{exchange_name = XName},
                             confirm   = false,
                             mandatory = false},
                   _RoutedToQs = []}, State) -> %% optimisation
    ?INCR_STATS(exchange_stats, XName, 1, publish, State),
    ?INCR_STATS(exchange_stats, XName, 1, drop_unroutable, State),
    State;
deliver_to_queues({Delivery = #delivery{message    = Message = #basic_message{
                                                       exchange_name = XName},
                                        mandatory  = Mandatory,
                                        confirm    = Confirm,
                                        msg_seq_no = MsgSeqNo},
                   DelQNames}, State = #ch{queue_names    = QNames,
                                           queue_monitors = QMons,
                                           queue_states = QueueStates0}) ->
    Qs = rabbit_amqqueue:lookup(DelQNames),
    {DeliveredQPids, DeliveredQQPids, QueueStates} =
        rabbit_amqqueue:deliver(Qs, Delivery, QueueStates0),
    AllDeliveredQRefs = DeliveredQPids ++ [N || {N, _} <- DeliveredQQPids],
    %% The maybe_monitor_all/2 monitors all queues to which we
    %% delivered. But we want to monitor even queues we didn't deliver
    %% to, since we need their 'DOWN' messages to clean
    %% queue_names. So we also need to monitor each QPid from
    %% queues. But that only gets the masters (which is fine for
    %% cleaning queue_names), so we need the union of both.
    %%
    %% ...and we need to add even non-delivered queues to queue_names
    %% since alternative algorithms to update queue_names less
    %% frequently would in fact be more expensive in the common case.
    {QNames1, QMons1} =
        lists:foldl(fun (Q, {QNames0, QMons0}) when ?is_amqqueue(Q) ->
            QPid = amqqueue:get_pid(Q),
            QRef = qpid_to_ref(QPid),
            QName = amqqueue:get_name(Q),
            case ?IS_CLASSIC(QRef) of
                true ->
                    SPids = amqqueue:get_slave_pids(Q),
                    NewQNames =
                        maps:from_list([{Ref, QName} || Ref <- [QRef | SPids]]),
                    {maps:merge(NewQNames, QNames0),
                     maybe_monitor_all([QPid | SPids], QMons0)};
                false ->
                    {maps:put(QRef, QName, QNames0), QMons0}
            end
        end,
        {QNames, QMons}, Qs),
    State1 = State#ch{queue_names    = QNames1,
                      queue_monitors = QMons1},
    %% NB: the order here is important since basic.returns must be
    %% sent before confirms.
    ok = process_routing_mandatory(Mandatory, AllDeliveredQRefs,
                                   Message, State1),
    AllDeliveredQNames = [ QName || QRef        <- AllDeliveredQRefs,
                                    {ok, QName} <- [maps:find(QRef, QNames1)]],
    State2 = process_routing_confirm(Confirm,
                                     AllDeliveredQRefs,
                                     AllDeliveredQNames,
                                     MsgSeqNo,
                                     XName, State1),
    case rabbit_event:stats_level(State, #ch.stats_timer) of
        fine ->
            ?INCR_STATS(exchange_stats, XName, 1, publish),
            [?INCR_STATS(queue_exchange_stats,
                         {amqqueue:get_name(Q), XName}, 1, publish) ||
                Q        <- Qs];
        _ ->
            ok
    end,
    State2#ch{queue_states = QueueStates}.

process_routing_mandatory(_Mandatory = true,
                          _RoutedToQs = [],
                          Msg, State) ->
    ok = basic_return(Msg, State, no_route),
    ok;
process_routing_mandatory(_Mandatory = false,
                          _RoutedToQs = [],
                          #basic_message{exchange_name = ExchangeName}, State) ->
    ?INCR_STATS(exchange_stats, ExchangeName, 1, drop_unroutable, State),
    ok;
process_routing_mandatory(_, _, _, _) ->
    ok.

process_routing_confirm(false, _, _, _, _, State) ->
    State;
process_routing_confirm(true, [], _, MsgSeqNo, XName, State) ->
    record_confirms([{MsgSeqNo, XName}], State);
process_routing_confirm(true, QRefs, QNames, MsgSeqNo, XName, State) ->
    State#ch{unconfirmed =
        unconfirmed_messages:insert(MsgSeqNo, QNames, QRefs, XName,
                                    State#ch.unconfirmed)}.

confirm(MsgSeqNos, QRef, State = #ch{queue_names = QNames, unconfirmed = UC}) ->
    %% NOTE: if queue name does not exist here it's likely that the ref also
    %% does not exist in unconfirmed messages.
    %% Neither does the 'ignore' atom, so it's a reasonable fallback.
    QName = maps:get(QRef, QNames, ignore),
    {ConfirmMXs, RejectMXs, UC1} =
        unconfirmed_messages:confirm_multiple_msg_ref(MsgSeqNos, QName, QRef, UC),
    %% NB: don't call noreply/1 since we don't want to send confirms.
    State1 = record_confirms(ConfirmMXs, State#ch{unconfirmed = UC1}),
    record_rejects(RejectMXs, State1).

send_confirms_and_nacks(State = #ch{tx = none, confirmed = [], rejected = []}) ->
    State;
send_confirms_and_nacks(State = #ch{tx = none, confirmed = C, rejected = R}) ->
    case rabbit_node_monitor:pause_partition_guard() of
        ok      ->
            Confirms = lists:append(C),
            Rejects = lists:append(R),
            ConfirmMsgSeqNos =
                lists:foldl(
                    fun ({MsgSeqNo, XName}, MSNs) ->
                        ?INCR_STATS(exchange_stats, XName, 1, confirm, State),
                        [MsgSeqNo | MSNs]
                    end, [], Confirms),
            RejectMsgSeqNos = [MsgSeqNo || {MsgSeqNo, _} <- Rejects],

            State1 = send_confirms(ConfirmMsgSeqNos,
                                   RejectMsgSeqNos,
                                   State#ch{confirmed = []}),
            %% TODO: msg seq nos, same as for confirms. Need to implement
            %% nack rates first.
            send_nacks(RejectMsgSeqNos,
                       ConfirmMsgSeqNos,
                       State1#ch{rejected = []});
        pausing -> State
    end;
send_confirms_and_nacks(State) ->
    case rabbit_node_monitor:pause_partition_guard() of
        ok      -> maybe_complete_tx(State);
        pausing -> State
    end.

send_nacks([], _, State) ->
    State;
send_nacks(_Rs, _, State = #ch{cfg = #conf{state = closing}}) -> %% optimisation
    State;
send_nacks(Rs, Cs, State) ->
    coalesce_and_send(Rs, Cs,
                      fun(MsgSeqNo, Multiple) ->
                              #'basic.nack'{delivery_tag = MsgSeqNo,
                                            multiple     = Multiple}
                      end, State).

send_confirms([], _, State) ->
    State;
send_confirms(_Cs, _, State = #ch{cfg = #conf{state = closing}}) -> %% optimisation
    State;
send_confirms([MsgSeqNo], _, State) ->
    ok = send(#'basic.ack'{delivery_tag = MsgSeqNo}, State),
    State;
send_confirms(Cs, Rs, State) ->
    coalesce_and_send(Cs, Rs,
                      fun(MsgSeqNo, Multiple) ->
                                  #'basic.ack'{delivery_tag = MsgSeqNo,
                                               multiple     = Multiple}
                      end, State).

coalesce_and_send(MsgSeqNos, NegativeMsgSeqNos, MkMsgFun, State = #ch{unconfirmed = UC}) ->
    SMsgSeqNos = lists:usort(MsgSeqNos),
    UnconfirmedCutoff = case unconfirmed_messages:is_empty(UC) of
                 true  -> lists:last(SMsgSeqNos) + 1;
                 false -> unconfirmed_messages:smallest(UC)
             end,
    Cutoff = lists:min([UnconfirmedCutoff | NegativeMsgSeqNos]),
    {Ms, Ss} = lists:splitwith(fun(X) -> X < Cutoff end, SMsgSeqNos),
    case Ms of
        [] -> ok;
        _  -> ok = send(MkMsgFun(lists:last(Ms), true), State)
    end,
    [ok = send(MkMsgFun(SeqNo, false), State) || SeqNo <- Ss],
    State.

ack_cons(Tag, Acked, [{Tag, Acks} | L]) -> [{Tag, Acked ++ Acks} | L];
ack_cons(Tag, Acked, Acks)              -> [{Tag, Acked} | Acks].

ack_len(Acks) -> lists:sum([length(L) || {ack, L} <- Acks]).

maybe_complete_tx(State = #ch{tx = {_, _}}) ->
    State;
maybe_complete_tx(State = #ch{unconfirmed = UC}) ->
    case unconfirmed_messages:is_empty(UC) of
        false -> State;
        true  -> complete_tx(State#ch{confirmed = []})
    end.

complete_tx(State = #ch{tx = committing}) ->
    ok = send(#'tx.commit_ok'{}, State),
    State#ch{tx = new_tx()};
complete_tx(State = #ch{tx = failed}) ->
    {noreply, State1} = handle_exception(
                          rabbit_misc:amqp_error(
                            precondition_failed, "partial tx completion", [],
                            'tx.commit'),
                          State),
    State1#ch{tx = new_tx()}.

infos(Items, State) -> [{Item, i(Item, State)} || Item <- Items].

infos(Items, Deadline, State) ->
    [begin
         Now = now_millis(),
         if
             Now > Deadline ->
                 throw(timeout);
             true ->
                {Item, i(Item, State)}
         end
     end || Item <- Items].

i(pid,            _)                               -> self();
i(connection,     #ch{cfg = #conf{conn_pid = ConnPid}}) -> ConnPid;
i(number,         #ch{cfg =  #conf{channel = Channel}}) -> Channel;
i(user,           #ch{cfg = #conf{user = User}}) -> User#user.username;
i(user_who_performed_action, Ch) -> i(user, Ch);
i(vhost,          #ch{cfg = #conf{virtual_host = VHost}}) -> VHost;
i(transactional,  #ch{tx               = Tx})      -> Tx =/= none;
i(confirm,        #ch{confirm_enabled  = CE})      -> CE;
i(name,           State)                           -> name(State);
i(consumer_count,          #ch{consumer_mapping = CM})    -> maps:size(CM);
i(messages_unconfirmed,    #ch{unconfirmed = UC})         -> unconfirmed_messages:size(UC);
i(messages_unacknowledged, #ch{unacked_message_q = UAMQ}) -> ?QUEUE:len(UAMQ);
i(messages_uncommitted,    #ch{tx = {Msgs, _Acks}})       -> ?QUEUE:len(Msgs);
i(messages_uncommitted,    #ch{})                         -> 0;
i(acks_uncommitted,        #ch{tx = {_Msgs, Acks}})       -> ack_len(Acks);
i(acks_uncommitted,        #ch{})                         -> 0;
i(pending_raft_commands,   #ch{queue_states = QS}) ->
    pending_raft_commands(QS);
i(state,                   #ch{cfg = #conf{state = running}}) -> credit_flow:state();
i(state,                   #ch{cfg = #conf{state = State}}) -> State;
i(prefetch_count,          #ch{cfg = #conf{consumer_prefetch = C}})    -> C;
i(global_prefetch_count, #ch{limiter = Limiter}) ->
    rabbit_limiter:get_prefetch_limit(Limiter);
i(interceptors, #ch{interceptor_state = IState}) ->
    IState;
i(garbage_collection, _State) ->
    rabbit_misc:get_gc_info(self());
i(reductions, _State) ->
    {reductions, Reductions} = erlang:process_info(self(), reductions),
    Reductions;
i(Item, _) ->
    throw({bad_argument, Item}).

pending_raft_commands(QStates) ->
    maps:fold(fun (_, V, Acc) ->
                      Acc + rabbit_fifo_client:pending_size(V)
              end, 0, QStates).

name(#ch{cfg = #conf{conn_name = ConnName, channel = Channel}}) ->
    list_to_binary(rabbit_misc:format("~s (~p)", [ConnName, Channel])).

emit_stats(State) -> emit_stats(State, []).

emit_stats(State, Extra) ->
    [{reductions, Red} | Coarse0] = infos(?STATISTICS_KEYS, State),
    %% First metric must be `idle_since` (if available), as expected by
    %% `rabbit_mgmt_format:format_channel_stats`. This is a performance
    %% optimisation that avoids traversing the whole list when only
    %% one element has to be formatted.
    rabbit_core_metrics:channel_stats(self(), Extra ++ Coarse0),
    rabbit_core_metrics:channel_stats(reductions, self(), Red).

erase_queue_stats(QName) ->
    rabbit_core_metrics:channel_queue_down({self(), QName}),
    erase({queue_stats, QName}),
    [begin
	 rabbit_core_metrics:channel_queue_exchange_down({self(), QX}),
	 erase({queue_exchange_stats, QX})
     end || {{queue_exchange_stats, QX = {QName0, _}}, _} <- get(),
	    QName0 =:= QName].

get_vhost(#ch{cfg = #conf{virtual_host = VHost}}) -> VHost.

get_user(#ch{cfg = #conf{user = User}}) -> User.

delete_stats({queue_stats, QName}) ->
    rabbit_core_metrics:channel_queue_down({self(), QName});
delete_stats({exchange_stats, XName}) ->
    rabbit_core_metrics:channel_exchange_down({self(), XName});
delete_stats({queue_exchange_stats, QX}) ->
    rabbit_core_metrics:channel_queue_exchange_down({self(), QX});
delete_stats(_) ->
    ok.

put_operation_timeout() ->
    put(channel_operation_timeout, ?CHANNEL_OPERATION_TIMEOUT).

get_operation_timeout() ->
    get(channel_operation_timeout).

%% Refactored and exported to allow direct calls from the HTTP API,
%% avoiding the usage of AMQP 0-9-1 from the management.

handle_method(#'exchange.bind'{destination = DestinationNameBin,
                               source      = SourceNameBin,
                               routing_key = RoutingKey,
                               arguments   = Arguments},
              ConnPid, AuthzContext, _CollectorId, VHostPath, User) ->
    binding_action(fun rabbit_binding:add/3,
                   SourceNameBin, exchange, DestinationNameBin,
                   RoutingKey, Arguments, VHostPath, ConnPid, AuthzContext, User);
handle_method(#'exchange.unbind'{destination = DestinationNameBin,
                                 source      = SourceNameBin,
                                 routing_key = RoutingKey,
                                 arguments   = Arguments},
              ConnPid, AuthzContext, _CollectorId, VHostPath, User) ->
    binding_action(fun rabbit_binding:remove/3,
                       SourceNameBin, exchange, DestinationNameBin,
                       RoutingKey, Arguments, VHostPath, ConnPid, AuthzContext, User);
handle_method(#'queue.unbind'{queue       = QueueNameBin,
                              exchange    = ExchangeNameBin,
                              routing_key = RoutingKey,
                              arguments   = Arguments},
              ConnPid, AuthzContext, _CollectorId, VHostPath, User) ->
    binding_action(fun rabbit_binding:remove/3,
                   ExchangeNameBin, queue, QueueNameBin,
                   RoutingKey, Arguments, VHostPath, ConnPid, AuthzContext, User);
handle_method(#'queue.bind'{queue       = QueueNameBin,
                            exchange    = ExchangeNameBin,
                            routing_key = RoutingKey,
                            arguments   = Arguments},
              ConnPid, AuthzContext, _CollectorId, VHostPath, User) ->
    binding_action(fun rabbit_binding:add/3,
                   ExchangeNameBin, queue, QueueNameBin,
                   RoutingKey, Arguments, VHostPath, ConnPid, AuthzContext, User);
%% Note that all declares to these are effectively passive. If it
%% exists it by definition has one consumer.
handle_method(#'queue.declare'{queue   = <<"amq.rabbitmq.reply-to",
                                           _/binary>> = QueueNameBin},
              _ConnPid, _AuthzContext, _CollectorPid, VHost, _User) ->
    StrippedQueueNameBin = strip_cr_lf(QueueNameBin),
    QueueName = rabbit_misc:r(VHost, queue, StrippedQueueNameBin),
    case declare_fast_reply_to(StrippedQueueNameBin) of
        exists    -> {ok, QueueName, 0, 1};
        not_found -> rabbit_amqqueue:not_found(QueueName)
    end;
handle_method(#'queue.declare'{queue       = QueueNameBin,
                               passive     = false,
                               durable     = DurableDeclare,
                               exclusive   = ExclusiveDeclare,
                               auto_delete = AutoDelete,
                               nowait      = NoWait,
                               arguments   = Args} = Declare,
              ConnPid, AuthzContext, CollectorPid, VHostPath,
              #user{username = Username} = User) ->
    Owner = case ExclusiveDeclare of
                true  -> ConnPid;
                false -> none
            end,
    StrippedQueueNameBin = strip_cr_lf(QueueNameBin),
    Durable = DurableDeclare andalso not ExclusiveDeclare,
    ActualNameBin = case StrippedQueueNameBin of
                        <<>>  -> rabbit_guid:binary(rabbit_guid:gen_secure(),
                                                    "amq.gen");
                        Other -> check_name('queue', Other)
                    end,
    QueueName = rabbit_misc:r(VHostPath, queue, ActualNameBin),
    check_configure_permitted(QueueName, User, AuthzContext),
    rabbit_core_metrics:queue_declared(QueueName),
    case rabbit_amqqueue:with(
           QueueName,
           fun (Q) -> ok = rabbit_amqqueue:assert_equivalence(
                             Q, Durable, AutoDelete, Args, Owner),
                      maybe_stat(NoWait, Q)
           end) of
        {ok, MessageCount, ConsumerCount} ->
            {ok, QueueName, MessageCount, ConsumerCount};
        {error, not_found} ->
            %% enforce the limit for newly declared queues only
            check_vhost_queue_limit(QueueName, VHostPath),
            DlxKey = <<"x-dead-letter-exchange">>,
            case rabbit_misc:r_arg(VHostPath, exchange, Args, DlxKey) of
               undefined ->
                   ok;
               {error, {invalid_type, Type}} ->
                    precondition_failed(
                      "invalid type '~s' for arg '~s' in ~s",
                      [Type, DlxKey, rabbit_misc:rs(QueueName)]);
               DLX ->
                   check_read_permitted(QueueName, User, AuthzContext),
                   check_write_permitted(DLX, User, AuthzContext),
                   ok
            end,
            case rabbit_amqqueue:declare(QueueName, Durable, AutoDelete,
                                         Args, Owner, Username) of
                {new, Q} when ?is_amqqueue(Q) ->
                    %% We need to notify the reader within the channel
                    %% process so that we can be sure there are no
                    %% outstanding exclusive queues being declared as
                    %% the connection shuts down.
                    QPid = amqqueue:get_pid(Q),
                    ok = case {Owner, CollectorPid} of
                             {none, _} -> ok;
                             {_, none} -> ok; %% Supports call from mgmt API
                             _    -> rabbit_queue_collector:register(
                                       CollectorPid, QPid)
                         end,
                    rabbit_core_metrics:queue_created(QueueName),
                    {ok, QueueName, 0, 0};
                {existing, _Q} ->
                    %% must have been created between the stat and the
                    %% declare. Loop around again.
                    handle_method(Declare, ConnPid, AuthzContext, CollectorPid, VHostPath,
                                  User);
                {absent, Q, Reason} ->
                    rabbit_amqqueue:absent(Q, Reason);
                {owner_died, _Q} ->
                    %% Presumably our own days are numbered since the
                    %% connection has died. Pretend the queue exists though,
                    %% just so nothing fails.
                    {ok, QueueName, 0, 0}
            end;
        {error, {absent, Q, Reason}} ->
            rabbit_amqqueue:absent(Q, Reason)
    end;
handle_method(#'queue.declare'{queue   = QueueNameBin,
                               nowait  = NoWait,
                               passive = true},
              ConnPid, _AuthzContext, _CollectorPid, VHostPath, _User) ->
    StrippedQueueNameBin = strip_cr_lf(QueueNameBin),
    QueueName = rabbit_misc:r(VHostPath, queue, StrippedQueueNameBin),
    Fun = fun (Q0) ->
              QStat = maybe_stat(NoWait, Q0),
              {QStat, Q0}
          end,
    %% Note: no need to check if Q is an #amqqueue, with_or_die does it
    {{ok, MessageCount, ConsumerCount}, Q} = rabbit_amqqueue:with_or_die(QueueName, Fun),
    ok = rabbit_amqqueue:check_exclusive_access(Q, ConnPid),
    {ok, QueueName, MessageCount, ConsumerCount};
handle_method(#'queue.delete'{queue     = QueueNameBin,
                              if_unused = IfUnused,
                              if_empty  = IfEmpty},
              ConnPid, AuthzContext, _CollectorPid, VHostPath,
              User = #user{username = Username}) ->
    StrippedQueueNameBin = strip_cr_lf(QueueNameBin),
    QueueName = qbin_to_resource(StrippedQueueNameBin, VHostPath),

    check_configure_permitted(QueueName, User, AuthzContext),
    case rabbit_amqqueue:with(
           QueueName,
           fun (Q) ->
                   rabbit_amqqueue:check_exclusive_access(Q, ConnPid),
                   rabbit_amqqueue:delete(Q, IfUnused, IfEmpty, Username)
           end,
           fun (not_found)            -> {ok, 0};
               %% TODO delete crashed should clean up fifo states?
               ({absent, Q, crashed}) -> rabbit_amqqueue:delete_crashed(Q, Username),
                                         {ok, 0};
               ({absent, Q, stopped}) -> rabbit_amqqueue:delete_crashed(Q, Username),
                                         {ok, 0};
               ({absent, Q, Reason})  -> rabbit_amqqueue:absent(Q, Reason)
           end) of
        {error, in_use} ->
            precondition_failed("~s in use", [rabbit_misc:rs(QueueName)]);
        {error, not_empty} ->
            precondition_failed("~s not empty", [rabbit_misc:rs(QueueName)]);
        {ok, Count} ->
            {ok, Count}
    end;
handle_method(#'exchange.delete'{exchange  = ExchangeNameBin,
                                 if_unused = IfUnused},
              _ConnPid, AuthzContext, _CollectorPid, VHostPath,
              User = #user{username = Username}) ->
    StrippedExchangeNameBin = strip_cr_lf(ExchangeNameBin),
    ExchangeName = rabbit_misc:r(VHostPath, exchange, StrippedExchangeNameBin),
    check_not_default_exchange(ExchangeName),
    check_exchange_deletion(ExchangeName),
    check_configure_permitted(ExchangeName, User, AuthzContext),
    case rabbit_exchange:delete(ExchangeName, IfUnused, Username) of
        {error, not_found} ->
            ok;
        {error, in_use} ->
            precondition_failed("~s in use", [rabbit_misc:rs(ExchangeName)]);
        ok ->
            ok
    end;
handle_method(#'queue.purge'{queue = QueueNameBin},
              ConnPid, AuthzContext, _CollectorPid, VHostPath, User) ->
    QueueName = qbin_to_resource(QueueNameBin, VHostPath),
    check_read_permitted(QueueName, User, AuthzContext),
    rabbit_amqqueue:with_exclusive_access_or_die(
      QueueName, ConnPid,
      fun (Q) -> rabbit_amqqueue:purge(Q) end);
handle_method(#'exchange.declare'{exchange    = ExchangeNameBin,
                                  type        = TypeNameBin,
                                  passive     = false,
                                  durable     = Durable,
                                  auto_delete = AutoDelete,
                                  internal    = Internal,
                                  arguments   = Args},
              _ConnPid, AuthzContext, _CollectorPid, VHostPath,
              #user{username = Username} = User) ->
    CheckedType = rabbit_exchange:check_type(TypeNameBin),
    ExchangeName = rabbit_misc:r(VHostPath, exchange, strip_cr_lf(ExchangeNameBin)),
    check_not_default_exchange(ExchangeName),
    check_configure_permitted(ExchangeName, User, AuthzContext),
    X = case rabbit_exchange:lookup(ExchangeName) of
            {ok, FoundX} -> FoundX;
            {error, not_found} ->
                check_name('exchange', strip_cr_lf(ExchangeNameBin)),
                AeKey = <<"alternate-exchange">>,
                case rabbit_misc:r_arg(VHostPath, exchange, Args, AeKey) of
                    undefined -> ok;
                    {error, {invalid_type, Type}} ->
                        precondition_failed(
                          "invalid type '~s' for arg '~s' in ~s",
                          [Type, AeKey, rabbit_misc:rs(ExchangeName)]);
                    AName     -> check_read_permitted(ExchangeName, User, AuthzContext),
                                 check_write_permitted(AName, User, AuthzContext),
                                 ok
                end,
                rabbit_exchange:declare(ExchangeName,
                                        CheckedType,
                                        Durable,
                                        AutoDelete,
                                        Internal,
                                        Args,
                                        Username)
        end,
    ok = rabbit_exchange:assert_equivalence(X, CheckedType, Durable,
                                            AutoDelete, Internal, Args);
handle_method(#'exchange.declare'{exchange    = ExchangeNameBin,
                                  passive     = true},
              _ConnPid, _AuthzContext, _CollectorPid, VHostPath, _User) ->
    ExchangeName = rabbit_misc:r(VHostPath, exchange, strip_cr_lf(ExchangeNameBin)),
    check_not_default_exchange(ExchangeName),
    _ = rabbit_exchange:lookup_or_die(ExchangeName).

handle_deliver(ConsumerTag, AckRequired,
               Msg = {_QName, QPid, _MsgId, Redelivered,
                      #basic_message{exchange_name = ExchangeName,
                                     routing_keys  = [RoutingKey | _CcRoutes],
                                     content       = Content}},
               State = #ch{cfg = #conf{writer_pid = WriterPid,
                                       writer_gc_threshold = GCThreshold},
                           next_tag   = DeliveryTag}) ->
    Deliver = #'basic.deliver'{consumer_tag = ConsumerTag,
                               delivery_tag = DeliveryTag,
                               redelivered  = Redelivered,
                               exchange     = ExchangeName#resource.name,
                               routing_key  = RoutingKey},
    case ?IS_CLASSIC(QPid) of
        true ->
            ok = rabbit_writer:send_command_and_notify(
                   WriterPid, QPid, self(), Deliver, Content);
        false ->
            ok = rabbit_writer:send_command(WriterPid, Deliver, Content)
    end,
    case GCThreshold of
        undefined -> ok;
        _         -> rabbit_basic:maybe_gc_large_msg(Content, GCThreshold)
    end,
    record_sent(deliver, ConsumerTag, AckRequired, Msg, State).

handle_basic_get(WriterPid, DeliveryTag, NoAck, MessageCount,
                 Msg = {QName, QPid, _MsgId, Redelivered,
                        #basic_message{exchange_name = ExchangeName,
                                       routing_keys  = [RoutingKey | _CcRoutes],
                                       content       = Content}}, State) ->
    ok = rabbit_writer:send_command(
           WriterPid,
           #'basic.get_ok'{delivery_tag  = DeliveryTag,
                           redelivered   = Redelivered,
                           exchange      = ExchangeName#resource.name,
                           routing_key   = RoutingKey,
                           message_count = MessageCount},
           Content),
    State1 = track_delivering_queue(NoAck, QPid, QName, State),
    {noreply, record_sent(get, DeliveryTag, not(NoAck), Msg, State1)}.

init_tick_timer(State = #ch{tick_timer = undefined}) ->
    {ok, Interval} = application:get_env(rabbit, channel_tick_interval),
    State#ch{tick_timer = erlang:send_after(Interval, self(), tick)};
init_tick_timer(State) ->
    State.

reset_tick_timer(State) ->
    State#ch{tick_timer = undefined}.

maybe_cancel_tick_timer(#ch{tick_timer = undefined} = State) ->
    State;
maybe_cancel_tick_timer(#ch{tick_timer = TRef,
                            unacked_message_q = UMQ} = State) ->
    case ?QUEUE:len(UMQ) of
        0 ->
            %% we can only cancel the tick timer if the unacked messages
            %% queue is empty.
            _ = erlang:cancel_timer(TRef),
            State#ch{tick_timer = undefined};
        _ ->
            %% let the timer continue
            State
    end.

%% only classic queues need monitoring so rather than special casing
%% everywhere monitors are set up we wrap it here for this module
maybe_monitor(QPid, QMons) when ?IS_CLASSIC(QPid) ->
    pmon:monitor(QPid, QMons);
maybe_monitor(_, QMons) ->
    QMons.

maybe_monitor_all([Item], S) -> maybe_monitor(Item, S); %% optimisation
maybe_monitor_all(Items,  S) -> lists:foldl(fun maybe_monitor/2, S, Items).

add_delivery_count_header(#{delivery_count := Count}, Msg) ->
    rabbit_basic:add_header(<<"x-delivery-count">>, long, Count, Msg);
add_delivery_count_header(_, Msg) ->
    Msg.

qpid_to_ref(Pid) when is_pid(Pid) -> Pid;
qpid_to_ref({Name, _}) -> Name;
%% assume it already is a ref
qpid_to_ref(Ref) -> Ref.

now_millis() ->
    erlang:monotonic_time(millisecond).

get_operation_timeout_and_deadline() ->
    % NB: can't use get_operation_timeout because
    % this code may not be running via the channel Pid
    Timeout = ?CHANNEL_OPERATION_TIMEOUT,
    Deadline =  now_millis() + Timeout,
    {Timeout, Deadline}.

queue_fold(Fun, Init, Q) ->
    case ?QUEUE:out(Q) of
        {empty, _Q}      -> Init;
        {{value, V}, Q1} -> queue_fold(Fun, Fun(V, Init), Q1)
    end.

evaluate_consumer_timeout(State0 = #ch{cfg = #conf{channel = Channel,
                                                   consumer_timeout = Timeout},
                                       unacked_message_q = UAMQ}) ->
    Now = os:system_time(millisecond),
    case ?QUEUE:peek(UAMQ) of
        {value, {_DTag, ConsumerTag, Time, {_QPid, _Msg}}}
          when is_integer(Timeout)
               andalso Time < Now - Timeout ->
            rabbit_log_channel:warning("Consumer ~s on channel ~w has timed out "
                                       "waiting on consumer acknowledgement. Timeout used: ~p ms",
                                       [rabbit_data_coercion:to_binary(ConsumerTag),
                                       Channel, Timeout]),
            Ex = rabbit_misc:amqp_error(precondition_failed,
                                        "consumer ack timed out on channel ~w",
                                        [Channel], none),
            handle_exception(Ex, State0);
        _ ->
            {noreply, State0}
    end.
