defmodule ExDoc.Language.Erlang do
  @moduledoc false

  @behaviour ExDoc.Language

  alias ExDoc.Language.Source
  alias ExDoc.{Autolink, Refs}

  @impl true
  @spec module_data(atom, any, any) ::
          :skip
          | %{
              callback_types: [:callback, ...],
              docs: any,
              id: binary,
              language: ExDoc.Language.Erlang,
              source_line: pos_integer,
              source_file: Path.t(),
              source_basedir: Path.t(),
              module: module,
              nesting_info: nil,
              private: %{abst_code: any, callbacks: map, optional_callbacks: any, specs: map},
              title: binary,
              type: :behaviour | :module
            }
  def module_data(module, docs_chunk, _config) do
    if abst_code = Source.get_abstract_code(module) do
      id = Atom.to_string(module)
      source_basedir = Source.fetch_basedir!(abst_code, module)

      {source_file, source_line} =
        Source.fetch_module_location!(abst_code, source_basedir, module)

      type = module_type(module)

      %{
        module: module,
        docs: docs_chunk,
        language: __MODULE__,
        id: id,
        title: id,
        type: type,
        source_line: source_line,
        source_file: source_file,
        source_basedir: source_basedir,
        callback_types: [:callback],
        nesting_info: nil,
        private: %{
          abst_code: abst_code,
          specs: Source.get_specs(abst_code, source_basedir),
          callbacks: Source.get_callbacks(abst_code, source_basedir),
          optional_callbacks: Source.get_optional_callbacks(module, type)
        }
      }
    else
      ExDoc.Utils.warn("skipping docs for module #{inspect(module)}, reason: :no_debug_info", [])
      :skip
    end
  end

  @impl true
  def function_data(entry, module_data) do
    {{kind, name, arity}, _anno, _signature, doc_content, metadata} = entry

    # TODO: Edoc on Erlang/OTP24.1+ includes private functions in
    # the chunk, so we manually yank them out for now.
    if kind == :function and doc_content != :hidden and
         function_exported?(module_data.module, name, arity) do
      function_data(name, arity, doc_content, module_data, metadata)
    else
      :skip
    end
  end

  defp equiv_data(module, file, line, metadata, prefix \\ "") do
    case metadata[:equiv] do
      nil ->
        nil

      equiv when is_binary(equiv) ->
        ## We try to parse the equiv in order to link to the target
        with {:ok, toks, _} <- :erl_scan.string(:unicode.characters_to_list(equiv <> ".")),
             {:ok, [{:call, _, {:atom, _, func}, args}]} <- :erl_parse.parse_exprs(toks) do
          "Equivalent to [`#{equiv}`](`#{prefix}#{func}/#{length(args)}`)."
        else
          {:ok, [{:op, _, :/, {:atom, _, _}, {:integer, _, _}}]} ->
            "Equivalent to `#{prefix}#{equiv}`."

          _ ->
            "Equivalent to `#{equiv}`."
        end
        |> ExDoc.DocAST.parse!("text/markdown")

      equiv ->
        ExDoc.Utils.warn("invalid equiv #{inspect(equiv)}",
          file: file,
          line: line,
          module: module
        )

        nil
    end
  end

  defp function_data(name, arity, _doc_content, module_data, metadata) do
    specs =
      case Map.fetch(module_data.private.specs, {name, arity}) do
        {:ok, spec} ->
          [spec]

        :error ->
          case Map.fetch(module_data.private.specs, {module_data.module, name, arity}) do
            {:ok, spec} ->
              [spec]

            :error ->
              []
          end
      end

    {file, line} = Source.fetch_function_location!(module_data, {name, arity})

    %{
      doc_fallback: fn -> equiv_data(module_data.module, file, line, metadata) end,
      extra_annotations: [],
      source_line: line,
      source_file: file,
      specs: specs
    }
  end

  @impl true
  def callback_data(entry, module_data) do
    {{_kind, name, arity}, anno, signature, _doc, metadata} = entry

    extra_annotations =
      if {name, arity} in module_data.private.optional_callbacks, do: ["optional"], else: []

    {specs, anno} =
      case Map.fetch(module_data.private.callbacks, {name, arity}) do
        {:ok, spec} ->
          {[spec], elem(spec, 1)}

        :error ->
          {[], anno}
      end

    %{
      doc_fallback: fn ->
        equiv_data(
          module_data.module,
          Source.anno_file(anno),
          Source.anno_line(anno),
          metadata,
          "c:"
        )
      end,
      source_line: Source.anno_line(anno),
      source_file: Source.anno_file(anno),
      signature: signature,
      specs: specs,
      extra_annotations: extra_annotations
    }
  end

  @impl true
  def type_data(entry, module_data) do
    {{kind, name, arity}, anno, signature, _doc, metadata} = entry

    case Source.fetch_type!(module_data, name, arity) do
      %{} = map ->
        %{
          doc_fallback: fn ->
            equiv_data(module_data.module, map.source_file, map.source_line, metadata, "t:")
          end,
          type: map.type,
          source_line: map.source_line,
          source_file: map.source_file,
          spec: map.attr,
          signature: signature,
          extra_annotations: []
        }

      nil ->
        %{
          doc_fallback: fn ->
            equiv_data(module_data.module, nil, Source.anno_line(anno), metadata, "t:")
          end,
          type: kind,
          source_line: Source.anno_line(anno),
          spec: nil,
          signature: signature,
          extra_annotations: []
        }
    end
  end

  @impl true
  def autolink_doc(ast, opts) do
    config = struct!(Autolink, opts)
    true = config.language == __MODULE__

    config = %{config | force_module_prefix: true}
    walk_doc(ast, config)
  end

  @impl true
  def autolink_spec(nil, _opts) do
    nil
  end

  def autolink_spec({:attribute, _, :opaque, ast}, _opts) do
    {name, _, args} = ast

    args =
      for arg <- args do
        {:var, _, name} = arg
        Atom.to_string(name)
      end
      |> Enum.intersperse(", ")

    IO.iodata_to_binary([Atom.to_string(name), "(", args, ")"])
  end

  def autolink_spec(ast, opts) do
    config = struct!(Autolink, opts)

    {name, anno, quoted} =
      case ast do
        {:attribute, anno, kind, {mfa, ast}} when kind in [:spec, :callback] ->
          {mn, name} =
            case mfa do
              {name, _} -> {name, name}
              {module, name, _} -> {{module, name}, name}
            end

          {mn, anno, Enum.map(ast, &Code.Typespec.spec_to_quoted(name, &1))}

        {:attribute, anno, :type, ast} ->
          {name, _, _} = ast
          {name, anno, Code.Typespec.type_to_quoted(ast)}
      end

    formatted = format_spec(ast)
    config = %{config | file: Source.anno_file(anno), line: Source.anno_line(anno)}
    autolink_spec(quoted, name, formatted, config)
  end

  @impl true
  def highlight_info() do
    %{
      language_name: "erlang",
      lexer: Makeup.Lexers.ErlangLexer,
      opts: []
    }
  end

  @impl true
  def format_spec_attribute(%ExDoc.TypeNode{type: type}), do: "-#{type}"
  def format_spec_attribute(%ExDoc.FunctionNode{type: :callback}), do: "-callback"
  def format_spec_attribute(%ExDoc.FunctionNode{}), do: "-spec"

  ## Autolink

  defp walk_doc(list, config) when is_list(list) do
    Enum.map(list, &walk_doc(&1, config))
  end

  defp walk_doc(binary, _) when is_binary(binary) do
    binary
  end

  defp walk_doc({:pre, _, _, _} = ast, _config) do
    ast
  end

  defp walk_doc({:code, attrs, [code], meta} = ast, config) when is_binary(code) do
    config = %{config | line: meta[:line]}

    case Autolink.url(code, :regular_link, config) do
      url when is_binary(url) ->
        code =
          code
          |> remove_prefix()
          |> remove_fragment()

        {:a, [href: url], [{:code, attrs, [code], meta}], %{}}

      _ ->
        ast
    end
  end

  defp walk_doc({:a, attrs, inner, meta} = ast, config) do
    case attrs[:rel] do
      "https://erlang.org/doc/link/seeerl" ->
        {fragment, url} = extract_fragment(attrs[:href] || "", "#")

        case String.split(url, ":") do
          [module] ->
            walk_doc({:a, [href: "`m:#{maybe_quote(module)}#{fragment}`"], inner, meta}, config)

          [app, module] ->
            inner = strip_app(inner, app)
            walk_doc({:a, [href: "`m:#{maybe_quote(module)}#{fragment}`"], inner, meta}, config)

          _ ->
            warn_ref(attrs[:href], config)
            inner
        end

      "https://erlang.org/doc/link/seemfa" ->
        {prefix, url} =
          case String.split(attrs[:href], "Module:") do
            [url] ->
              {"", url}

            [left, right] ->
              {"c:", left <> right}
          end

        {mfa, inner} =
          case String.split(url, ":") do
            [mfa] ->
              {mfa, inner}

            [app, mfa] ->
              {mfa, strip_app(inner, app)}
          end

        walk_doc({:a, [href: "`#{prefix}#{fixup(mfa)}`"], inner, meta}, config)

      "https://erlang.org/doc/link/seetype" ->
        {type, inner} =
          case String.split(attrs[:href], ":") do
            [type] ->
              {type, inner}

            [app, type] ->
              {type, strip_app(inner, app)}
          end

        type =
          case String.split(type, "(") do
            [type] ->
              type

            [type, _] ->
              type <> "/0"
          end

        walk_doc({:a, [href: "`t:#{fixup(type)}`"], inner, meta}, config)

      "https://erlang.org/doc/link/" <> see ->
        warn_ref(attrs[:href] <> " (#{see})", %{config | id: nil})
        inner

      _ ->
        case Autolink.custom_link(attrs, config) do
          :remove_link ->
            remove_link(ast)

          nil ->
            ast

          url ->
            {:a, Keyword.put(attrs, :href, url), inner, meta}
        end
    end
  end

  defp walk_doc({tag, attrs, ast, meta}, config) do
    {tag, attrs, walk_doc(ast, config), meta}
  end

  defp remove_link({:a, _attrs, inner, _meta}) do
    inner
  end

  defp remove_prefix("c:" <> rest), do: rest
  defp remove_prefix("m:" <> rest), do: rest
  defp remove_prefix("t:" <> rest), do: rest
  defp remove_prefix("\\" <> rest), do: rest
  defp remove_prefix(rest), do: rest

  defp remove_fragment(string) do
    string |> String.split("#") |> hd()
  end

  defp extract_fragment(url, prefix) do
    case String.split(url, "#", parts: 2) do
      [url] -> {"", url}
      [url, fragment] -> {prefix <> fragment, url}
    end
  end

  defp fixup(mfa) do
    {m, fa} =
      case String.split(mfa, "#") do
        ["", mfa] ->
          {"", mfa}

        [m, fa] ->
          {"#{maybe_quote(m)}:", fa}
      end

    [f, a] = String.split(fa, "/")
    m <> maybe_quote(f) <> "/" <> a
  end

  defp maybe_quote(m) do
    to_string(:io_lib.write_atom(String.to_atom(m)))
  end

  defp strip_app([{:code, attrs, [code], meta}], app) do
    [{:code, attrs, strip_app(code, app), meta}]
  end

  defp strip_app(code, app) when is_binary(code) do
    String.trim_leading(code, "//#{app}/")
  end

  defp strip_app(other, _app) do
    other
  end

  defp warn_ref(href, config) do
    message = "invalid reference: #{href}"
    nil = config.id
    Autolink.maybe_warn(config, message, nil, %{})
  end

  defp final_url({kind, name, arity}, _config) do
    Autolink.fragment(kind, name, arity)
  end

  defp final_url({kind, module, name, arity}, config) do
    tool = Autolink.tool(module, config)
    Autolink.app_module_url(tool, module, Autolink.fragment(kind, name, arity), config)
  end

  @impl true
  def parse_module_function(string) do
    case String.split(string, ":") do
      [module_string, function_string] ->
        with {:module, module} <- parse_module(module_string, :custom_link),
             {:function, function} <- parse_function(function_string) do
          {:remote, module, function}
        end

      [function_string] ->
        with {:function, function} <- parse_function(function_string) do
          {:local, function}
        end

      _ ->
        :error
    end
  end

  defp parse_function(string) do
    with {:ok, toks, _} <- :erl_scan.string(String.to_charlist("fun #{string}/0.")),
         {:ok, [{:fun, _, {:function, name, _arity}}]} <- :erl_parse.parse_exprs(toks) do
      {:function, name}
    else
      _ ->
        :error
    end
  end

  @impl true
  def try_autoimported_function(name, arity, mode, config, original_text) do
    if :erl_internal.bif(name, arity) do
      Autolink.remote_url({:function, :erlang, name, arity}, config, original_text,
        warn?: false,
        mode: mode
      )
    end
  end

  @impl true
  def try_builtin_type(name, arity, mode, config, original_text) do
    if :erl_internal.is_type(name, arity) do
      Autolink.remote_url({:type, :erlang, name, arity}, config, original_text,
        warn?: false,
        mode: mode
      )
    end
  end

  @impl true
  def parse_module(string, _mode) do
    case :erl_scan.string(String.to_charlist(string)) do
      {:ok, [{:atom, _, module}], _} when is_atom(module) ->
        {:module, module}

      _ ->
        :error
    end
  end

  # Traverses quoted and formatted string of the typespec AST, replacing refs with links.
  #
  # Let's say we have this typespec:
  #
  #     -spec f(X) -> #{atom() => bar(), integer() => X}.
  #
  # We traverse the AST and find types and their string representations:
  #
  #     -spec f(X) -> #{atom() => bar(), integer() => X}.
  #                     ^^^^      ^^^    ^^^^^^^
  #
  #     atom/0    => atom
  #     bar/0     => bar
  #     integer/0 => integer
  #
  # We then traverse the formatted string, *in order*, replacing the type strings with links:
  #
  #     "atom("    => "atom("
  #     "bar("     => "<a>bar</a>("
  #     "integer(" => "integer("
  #
  # Finally we end up with:
  #
  #     -spec f(X) -> #{atom() => <a>bar</a>(), integer() => X}.
  #
  # All of this hassle is to preserve the original *text layout* of the initial representation,
  # all the spaces, newlines, etc.
  defp autolink_spec(quoted, name, formatted, config) do
    acc =
      for quoted <- List.wrap(quoted) do
        {_quoted, acc} =
          Macro.prewalk(quoted, [], fn
            # module.name(args)
            {{:., _, [module, name]}, _, args}, acc ->
              {{:t, [], args}, [{pp({module, name}), {module, name, length(args)}} | acc]}

            {name, _, _}, acc when name in [:<<>>, :..] ->
              {nil, acc}

            # -1, +1
            {op, _, [int]}, acc when is_integer(int) and op in [:+, :-] ->
              {nil, acc}

            # fun() (spec_to_quoted expands it to (... -> any())
            {:->, _, [[{name, _, _}], {:any, _, _}]}, acc when name == :... ->
              {nil, acc}

            # record{type :: remote:type/arity}
            {:field_type, _, [name, {{:., _, [r_mod, r_type]}, _, args}]}, acc ->
              {{name, [], args}, [{pp({r_mod, r_type}), {r_mod, r_type, length(args)}} | acc]}

            # #{x :: t()}
            {:field_type, _, [name, type]}, acc when is_atom(name) ->
              {[type], acc}

            {name, _, args} = ast, acc when is_atom(name) and is_list(args) ->
              arity = length(args)

              cond do
                name == :record and acc != [] ->
                  {ast, acc}

                name in [:"::", :when, :%{}, :{}, :|, :->, :...] ->
                  {ast, acc}

                # %{required(...) => ..., optional(...) => ...}
                name in [:required, :optional] and arity == 1 ->
                  {ast, acc}

                # name(args)
                true ->
                  {ast, [{pp(name), {name, arity}} | acc]}
              end

            other, acc ->
              {other, acc}
          end)

        acc
        |> Enum.reverse()
        # drop the name of the typespec
        |> Enum.drop(1)
      end
      |> Enum.concat()

    put(acc)

    # Drop and re-add type name (it, the first element in acc, is dropped there too)
    #
    #     1. foo() :: bar()
    #     2.    () :: bar()
    #     3.    () :: <a>bar</a>()
    #     4. foo() :: <a>bar</a>()
    name = pp(name)
    formatted = trim_name(formatted, name)
    formatted = replace(formatted, acc, config)
    name <> formatted
  end

  defp trim_name(string, name) do
    name_size = byte_size(name)
    binary_part(string, name_size, byte_size(string) - name_size)
  end

  defp replace(formatted, [], _config) do
    formatted
  end

  defp replace(formatted, acc, config) do
    String.replace(formatted, Enum.map(acc, &"#{elem(&1, 0)}("), fn string ->
      string = String.trim_trailing(string, "(")
      {other, ref} = pop()

      if string != other do
        Autolink.maybe_warn(
          config,
          "internal inconsistency, please submit bug: #{inspect(string)} != #{inspect(other)}",
          nil,
          nil
        )
      end

      what =
        case config.current_kfa do
          {:function, _, _} -> :spec
          {kind, _, _} -> kind
        end

      url =
        case ref do
          {name, arity} ->
            ref = {:type, config.current_module, name, arity}
            visibility = Refs.get_visibility(ref)

            cond do
              config.skip_code_autolink_to.("t:#{name}/#{arity}") ->
                nil

              visibility in [:public] ->
                final_url({:type, name, arity}, config)

              :erl_internal.is_type(name, arity) ->
                final_url({:type, :erlang, name, arity}, config)

              true ->
                Autolink.maybe_warn(
                  config,
                  "#{what} references type \"#{name}/#{arity}\" but it is " <>
                    Autolink.format_visibility(visibility, :type),
                  nil,
                  nil
                )

                nil
            end

          {module, name, arity} ->
            ref = {:type, module, name, arity}
            visibility = Refs.get_visibility(ref)

            cond do
              config.skip_code_autolink_to.("t:#{module}:#{name}/#{arity}") ->
                nil

              visibility in [:public] ->
                final_url(ref, config)

              true ->
                Autolink.maybe_warn(
                  config,
                  "#{what} references type \"#{module}:#{name}/#{arity}\" but it is " <>
                    Autolink.format_visibility(visibility, :type),
                  nil,
                  nil
                )

                nil
            end
        end

      if url do
        ~s|<a href="#{url}">#{string}</a>(|
      else
        string <> "("
      end
    end)
  end

  defp put(items) do
    Process.put({__MODULE__, :stack}, items)
  end

  defp pop() do
    [head | tail] = Process.get({__MODULE__, :stack})
    put(tail)
    head
  end

  defp pp(name) when is_atom(name) do
    :io_lib.format("~p", [name]) |> IO.iodata_to_binary()
  end

  defp pp({module, name}) when is_atom(module) and is_atom(name) do
    :io_lib.format("~p:~p", [module, name]) |> IO.iodata_to_binary()
  end

  defp format_spec(ast) do
    {:attribute, _, type, _} = ast

    # `-type ` => 6
    offset = byte_size(Atom.to_string(type)) + 2

    options = [linewidth: 98 + offset]

    :erl_pp.attribute(ast, options)
    |> IO.chardata_to_string()
    |> String.trim()
    |> String.trim_leading("-#{Atom.to_string(type)} ")
  end

  ## Helpers

  defp module_type(module) do
    cond do
      function_exported?(module, :behaviour_info, 1) ->
        :behaviour

      true ->
        :module
    end
  end
end
