use ahash::AHashSet;
use std::marker::PhantomData;

use pyo3::exceptions::{PyTypeError, PyValueError};
use pyo3::ffi;
use pyo3::prelude::*;
use pyo3::types::{PyBool, PyDict, PyList, PyString};

use smallvec::SmallVec;

use crate::errors::{json_err, json_error, JsonError, JsonResult, DEFAULT_RECURSION_LIMIT};
use crate::number_decoder::{AbstractNumberDecoder, NumberAny, NumberRange};
use crate::parse::{Parser, Peek};
use crate::py_lossless_float::{get_decimal_type, FloatMode};
use crate::py_string_cache::{StringCacheAll, StringCacheKeys, StringCacheMode, StringMaybeCache, StringNoCache};
use crate::string_decoder::{StringDecoder, Tape};
use crate::{JsonErrorType, LosslessFloat, PartialMode};

#[derive(Default)]
#[allow(clippy::struct_excessive_bools)]
pub struct PythonParse {
    /// Whether to allow `(-)Infinity` and `NaN` values.
    pub allow_inf_nan: bool,
    /// Whether to cache strings to avoid constructing new Python objects,
    pub cache_mode: StringCacheMode,
    /// Whether to allow partial JSON data.
    pub partial_mode: PartialMode,
    /// Whether to catch duplicate keys in objects.
    pub catch_duplicate_keys: bool,
    /// How to return floats: as a `float` (`'float'`), `Decimal` (`'decimal'`) or
    /// [`LosslessFloat`] (`'lossless-float'`)
    pub float_mode: FloatMode,
}

impl PythonParse {
    /// Parse a JSON value from a byte slice and return a Python object.
    ///
    /// # Arguments
    ///
    /// - `py`: [Python](https://docs.rs/pyo3/latest/pyo3/marker/struct.Python.html) marker token.
    /// - `json_data`: The JSON data to parse.
    ///   this should have a significant improvement on performance but increases memory slightly.
    ///
    /// # Returns
    ///
    /// A [PyObject](https://docs.rs/pyo3/latest/pyo3/type.PyObject.html) representing the parsed JSON value.
    pub fn python_parse<'py>(self, py: Python<'py>, json_data: &[u8]) -> JsonResult<Bound<'py, PyAny>> {
        macro_rules! ppp {
            ($string_cache:ident, $key_check:ident, $parse_number:ident) => {
                PythonParser::<$string_cache, $key_check, $parse_number>::parse(
                    py,
                    json_data,
                    self.allow_inf_nan,
                    self.partial_mode,
                )
            };
        }
        macro_rules! ppp_group {
            ($string_cache:ident) => {
                match (self.catch_duplicate_keys, self.float_mode) {
                    (true, FloatMode::Float) => ppp!($string_cache, DuplicateKeyCheck, ParseNumberLossy),
                    (true, FloatMode::Decimal) => ppp!($string_cache, DuplicateKeyCheck, ParseNumberDecimal),
                    (true, FloatMode::LosslessFloat) => ppp!($string_cache, DuplicateKeyCheck, ParseNumberLossless),
                    (false, FloatMode::Float) => ppp!($string_cache, NoopKeyCheck, ParseNumberLossy),
                    (false, FloatMode::Decimal) => ppp!($string_cache, NoopKeyCheck, ParseNumberDecimal),
                    (false, FloatMode::LosslessFloat) => ppp!($string_cache, NoopKeyCheck, ParseNumberLossless),
                }
            };
        }

        match self.cache_mode {
            StringCacheMode::All => ppp_group!(StringCacheAll),
            StringCacheMode::Keys => ppp_group!(StringCacheKeys),
            StringCacheMode::None => ppp_group!(StringNoCache),
        }
    }
}

/// Map a `JsonError` to a `PyErr` which can be raised as an exception in Python as a `ValueError`.
pub fn map_json_error(json_data: &[u8], json_error: &JsonError) -> PyErr {
    PyValueError::new_err(json_error.description(json_data))
}

struct PythonParser<'j, StringCache, KeyCheck, ParseNumber> {
    _string_cache: PhantomData<StringCache>,
    _key_check: PhantomData<KeyCheck>,
    _parse_number: PhantomData<ParseNumber>,
    parser: Parser<'j>,
    tape: Tape,
    recursion_limit: u8,
    allow_inf_nan: bool,
    partial_mode: PartialMode,
}

impl<StringCache: StringMaybeCache, KeyCheck: MaybeKeyCheck, ParseNumber: MaybeParseNumber>
    PythonParser<'_, StringCache, KeyCheck, ParseNumber>
{
    fn parse<'py>(
        py: Python<'py>,
        json_data: &[u8],
        allow_inf_nan: bool,
        partial_mode: PartialMode,
    ) -> JsonResult<Bound<'py, PyAny>> {
        let mut slf = PythonParser {
            _string_cache: PhantomData::<StringCache>,
            _key_check: PhantomData::<KeyCheck>,
            _parse_number: PhantomData::<ParseNumber>,
            parser: Parser::new(json_data),
            tape: Tape::default(),
            recursion_limit: DEFAULT_RECURSION_LIMIT,
            allow_inf_nan,
            partial_mode,
        };

        let peek = slf.parser.peek()?;
        let v = slf.py_take_value(py, peek)?;
        if !slf.partial_mode.is_active() {
            slf.parser.finish()?;
        }
        Ok(v)
    }

    fn py_take_value<'py>(&mut self, py: Python<'py>, peek: Peek) -> JsonResult<Bound<'py, PyAny>> {
        match peek {
            Peek::Null => {
                self.parser.consume_null()?;
                Ok(py.None().into_bound(py))
            }
            Peek::True => {
                self.parser.consume_true()?;
                Ok(PyBool::new(py, true).to_owned().into_any())
            }
            Peek::False => {
                self.parser.consume_false()?;
                Ok(PyBool::new(py, false).to_owned().into_any())
            }
            Peek::String => {
                let s = self
                    .parser
                    .consume_string::<StringDecoder>(&mut self.tape, self.partial_mode.allow_trailing_str())?;
                Ok(StringCache::get_value(py, s).into_any())
            }
            Peek::Array => {
                let peek_first = match self.parser.array_first() {
                    Ok(Some(peek)) => peek,
                    Err(e) if !self.allow_partial_err(&e) => return Err(e),
                    Ok(None) | Err(_) => return Ok(PyList::empty(py).into_any()),
                };

                let mut vec: SmallVec<[Bound<'_, PyAny>; 8]> = SmallVec::with_capacity(8);
                if let Err(e) = self.parse_array(py, peek_first, &mut vec) {
                    if !self.allow_partial_err(&e) {
                        return Err(e);
                    }
                }

                Ok(PyList::new(py, vec)
                    .map_err(|e| py_err_to_json_err(&e, self.parser.index))?
                    .into_any())
            }
            Peek::Object => {
                let dict = PyDict::new(py);
                if let Err(e) = self.parse_object(py, &dict) {
                    if !self.allow_partial_err(&e) {
                        return Err(e);
                    }
                }
                Ok(dict.into_any())
            }
            _ => ParseNumber::parse_number(py, &mut self.parser, peek, self.allow_inf_nan),
        }
    }

    fn parse_array<'py>(
        &mut self,
        py: Python<'py>,
        peek_first: Peek,
        vec: &mut SmallVec<[Bound<'py, PyAny>; 8]>,
    ) -> JsonResult<()> {
        let v = self.check_take_value(py, peek_first)?;
        vec.push(v);
        while let Some(peek) = self.parser.array_step()? {
            let v = self.check_take_value(py, peek)?;
            vec.push(v);
        }
        Ok(())
    }

    fn parse_object<'py>(&mut self, py: Python<'py>, dict: &Bound<'py, PyDict>) -> JsonResult<()> {
        let set_item = |key: Bound<'py, PyString>, value: Bound<'py, PyAny>| {
            let r = unsafe { ffi::PyDict_SetItem(dict.as_ptr(), key.as_ptr(), value.as_ptr()) };
            // AFAIK this shouldn't happen since the key will always be a string  which is hashable
            // we panic here rather than returning a result and using `?` below as it's up to 14% faster
            // presumably because there are fewer branches
            assert_ne!(r, -1, "PyDict_SetItem failed");
        };
        let mut check_keys = KeyCheck::default();
        if let Some(first_key) = self.parser.object_first::<StringDecoder>(&mut self.tape)? {
            let first_key_s = first_key.as_str();
            check_keys.check(first_key_s, self.parser.index)?;
            let first_key = StringCache::get_key(py, first_key);
            let peek = self.parser.peek()?;
            let first_value = self.check_take_value(py, peek)?;
            set_item(first_key, first_value);
            while let Some(key) = self.parser.object_step::<StringDecoder>(&mut self.tape)? {
                let key_s = key.as_str();
                check_keys.check(key_s, self.parser.index)?;
                let key = StringCache::get_key(py, key);
                let peek = self.parser.peek()?;
                let value = self.check_take_value(py, peek)?;
                set_item(key, value);
            }
        }
        Ok(())
    }

    fn allow_partial_err(&self, e: &JsonError) -> bool {
        if self.partial_mode.is_active() {
            e.allowed_if_partial()
        } else {
            false
        }
    }

    fn check_take_value<'py>(&mut self, py: Python<'py>, peek: Peek) -> JsonResult<Bound<'py, PyAny>> {
        self.recursion_limit = match self.recursion_limit.checked_sub(1) {
            Some(limit) => limit,
            None => return json_err!(RecursionLimitExceeded, self.parser.index),
        };

        let r = self.py_take_value(py, peek);

        self.recursion_limit += 1;
        r
    }
}

const PARTIAL_ERROR: &str = "Invalid partial mode, should be `'off'`, `'on'`, `'trailing-strings'` or a `bool`";

impl<'py> FromPyObject<'py> for PartialMode {
    fn extract_bound(ob: &Bound<'py, PyAny>) -> PyResult<Self> {
        if let Ok(bool_mode) = ob.downcast::<PyBool>() {
            Ok(bool_mode.is_true().into())
        } else if let Ok(str_mode) = ob.extract::<&str>() {
            match str_mode {
                "off" => Ok(Self::Off),
                "on" => Ok(Self::On),
                "trailing-strings" => Ok(Self::TrailingStrings),
                _ => Err(PyValueError::new_err(PARTIAL_ERROR)),
            }
        } else {
            Err(PyTypeError::new_err(PARTIAL_ERROR))
        }
    }
}

trait MaybeKeyCheck: Default {
    fn check(&mut self, key: &str, index: usize) -> JsonResult<()>;
}

#[derive(Default)]
struct NoopKeyCheck;

impl MaybeKeyCheck for NoopKeyCheck {
    fn check(&mut self, _key: &str, _index: usize) -> JsonResult<()> {
        Ok(())
    }
}

#[derive(Default)]
struct DuplicateKeyCheck(AHashSet<String>);

impl MaybeKeyCheck for DuplicateKeyCheck {
    fn check(&mut self, key: &str, index: usize) -> JsonResult<()> {
        if self.0.insert(key.to_owned()) {
            Ok(())
        } else {
            Err(JsonError::new(JsonErrorType::DuplicateKey(key.to_owned()), index))
        }
    }
}

trait MaybeParseNumber {
    fn parse_number<'py>(
        py: Python<'py>,
        parser: &mut Parser,
        peek: Peek,
        allow_inf_nan: bool,
    ) -> JsonResult<Bound<'py, PyAny>>;
}

struct ParseNumberLossy;

impl MaybeParseNumber for ParseNumberLossy {
    fn parse_number<'py>(
        py: Python<'py>,
        parser: &mut Parser,
        peek: Peek,
        allow_inf_nan: bool,
    ) -> JsonResult<Bound<'py, PyAny>> {
        match parser.consume_number::<NumberAny>(peek.into_inner(), allow_inf_nan) {
            Ok(number) => Ok(number
                .into_pyobject(py)
                .map_err(|e| py_err_to_json_err(&e, parser.index))?
                .into_any()),
            Err(e) => {
                if !peek.is_num() {
                    Err(json_error!(ExpectedSomeValue, parser.index))
                } else {
                    Err(e)
                }
            }
        }
    }
}

struct ParseNumberLossless;

impl MaybeParseNumber for ParseNumberLossless {
    fn parse_number<'py>(
        py: Python<'py>,
        parser: &mut Parser,
        peek: Peek,
        allow_inf_nan: bool,
    ) -> JsonResult<Bound<'py, PyAny>> {
        match parser.consume_number::<NumberRange>(peek.into_inner(), allow_inf_nan) {
            Ok(number_range) => {
                let bytes = parser.slice(number_range.range).unwrap();
                let obj = if number_range.is_int {
                    NumberAny::decode(bytes, 0, peek.into_inner(), allow_inf_nan)?
                        .0
                        .into_pyobject(py)
                        .map_err(|e| py_err_to_json_err(&e, parser.index))?
                } else {
                    LosslessFloat::new_unchecked(bytes.to_vec())
                        .into_pyobject(py)
                        .map_err(|e| py_err_to_json_err(&e, parser.index))?
                        .into_any()
                };
                Ok(obj)
            }
            Err(e) => {
                if !peek.is_num() {
                    Err(json_error!(ExpectedSomeValue, parser.index))
                } else {
                    Err(e)
                }
            }
        }
    }
}

struct ParseNumberDecimal;

impl MaybeParseNumber for ParseNumberDecimal {
    fn parse_number<'py>(
        py: Python<'py>,
        parser: &mut Parser,
        peek: Peek,
        allow_inf_nan: bool,
    ) -> JsonResult<Bound<'py, PyAny>> {
        match parser.consume_number::<NumberRange>(peek.into_inner(), allow_inf_nan) {
            Ok(number_range) => {
                let bytes = parser.slice(number_range.range).unwrap();
                if number_range.is_int {
                    let obj = NumberAny::decode(bytes, 0, peek.into_inner(), allow_inf_nan)?
                        .0
                        .into_pyobject(py)
                        .map_err(|e| py_err_to_json_err(&e, parser.index))?;
                    Ok(obj.into_any())
                } else {
                    let decimal_type = get_decimal_type(py).map_err(|e| py_err_to_json_err(&e, parser.index))?;
                    // SAFETY: NumberRange::decode has already confirmed that bytes are a valid JSON number,
                    // and therefore valid str
                    let float_str = unsafe { std::str::from_utf8_unchecked(bytes) };
                    decimal_type
                        .call1((float_str,))
                        .map_err(|e| py_err_to_json_err(&e, parser.index))
                }
            }
            Err(e) => {
                if !peek.is_num() {
                    Err(json_error!(ExpectedSomeValue, parser.index))
                } else {
                    Err(e)
                }
            }
        }
    }
}

fn py_err_to_json_err(e: &PyErr, index: usize) -> JsonError {
    JsonError::new(JsonErrorType::InternalError(e.to_string()), index)
}
