use std::collections::HashMap;
use std::convert::TryFrom;
use std::hash::{BuildHasher, Hash};
use std::{char, str, u8};

use byteorder::{BigEndian, ByteOrder};
use bytes::Bytes;
use bytestring::ByteString;
use chrono::{DateTime, TimeZone, Utc};
use fxhash::FxHashMap;
use ordered_float::OrderedFloat;
use uuid::Uuid;

use crate::codec::{self, ArrayDecode, Decode, DecodeFormatted};
use crate::errors::AmqpParseError;
use crate::framing::{self, AmqpFrame, SaslFrame, HEADER_LEN};
use crate::protocol::{self, CompoundHeader};
use crate::types::{
    Descriptor, List, Multiple, Str, Symbol, Variant, VariantMap, VecStringMap, VecSymbolMap,
};

macro_rules! be_read {
    ($input:ident, $fn:ident, $size:expr) => {{
        decode_check_len!($input, $size);
        let x = BigEndian::$fn($input);
        Ok((&$input[$size..], x))
    }};
}

fn read_u8(input: &[u8]) -> Result<(&[u8], u8), AmqpParseError> {
    decode_check_len!(input, 1);
    Ok((&input[1..], input[0]))
}

fn read_i8(input: &[u8]) -> Result<(&[u8], i8), AmqpParseError> {
    decode_check_len!(input, 1);
    Ok((&input[1..], input[0] as i8))
}

fn read_bytes_u8(input: &[u8]) -> Result<(&[u8], &[u8]), AmqpParseError> {
    let (input, len) = read_u8(input)?;
    let len = len as usize;
    decode_check_len!(input, len);
    let (bytes, input) = input.split_at(len);
    Ok((input, bytes))
}

fn read_bytes_u32(input: &[u8]) -> Result<(&[u8], &[u8]), AmqpParseError> {
    let result: Result<(&[u8], u32), AmqpParseError> = be_read!(input, read_u32, 4);
    let (input, len) = result?;
    let len = len as usize;
    decode_check_len!(input, len);
    let (bytes, input) = input.split_at(len);
    Ok((input, bytes))
}

#[macro_export]
macro_rules! validate_code {
    ($fmt:ident, $code:expr) => {
        if $fmt != $code {
            return Err(AmqpParseError::InvalidFormatCode($fmt));
        }
    };
}

impl DecodeFormatted for bool {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        match fmt {
            codec::FORMATCODE_BOOLEAN => read_u8(input).map(|(i, o)| (i, o != 0)),
            codec::FORMATCODE_BOOLEAN_TRUE => Ok((input, true)),
            codec::FORMATCODE_BOOLEAN_FALSE => Ok((input, false)),
            _ => Err(AmqpParseError::InvalidFormatCode(fmt)),
        }
    }
}

impl DecodeFormatted for u8 {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        validate_code!(fmt, codec::FORMATCODE_UBYTE);
        read_u8(input)
    }
}

impl DecodeFormatted for u16 {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        validate_code!(fmt, codec::FORMATCODE_USHORT);
        be_read!(input, read_u16, 2)
    }
}

impl DecodeFormatted for u32 {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        match fmt {
            codec::FORMATCODE_UINT => be_read!(input, read_u32, 4),
            codec::FORMATCODE_SMALLUINT => read_u8(input).map(|(i, o)| (i, u32::from(o))),
            codec::FORMATCODE_UINT_0 => Ok((input, 0)),
            _ => Err(AmqpParseError::InvalidFormatCode(fmt)),
        }
    }
}

impl DecodeFormatted for u64 {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        match fmt {
            codec::FORMATCODE_ULONG => be_read!(input, read_u64, 8),
            codec::FORMATCODE_SMALLULONG => read_u8(input).map(|(i, o)| (i, u64::from(o))),
            codec::FORMATCODE_ULONG_0 => Ok((input, 0)),
            _ => Err(AmqpParseError::InvalidFormatCode(fmt)),
        }
    }
}

impl DecodeFormatted for i8 {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        validate_code!(fmt, codec::FORMATCODE_BYTE);
        read_i8(input)
    }
}

impl DecodeFormatted for i16 {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        validate_code!(fmt, codec::FORMATCODE_SHORT);
        be_read!(input, read_i16, 2)
    }
}

impl DecodeFormatted for i32 {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        match fmt {
            codec::FORMATCODE_INT => be_read!(input, read_i32, 4),
            codec::FORMATCODE_SMALLINT => read_i8(input).map(|(i, o)| (i, i32::from(o))),
            _ => Err(AmqpParseError::InvalidFormatCode(fmt)),
        }
    }
}

impl DecodeFormatted for i64 {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        match fmt {
            codec::FORMATCODE_LONG => be_read!(input, read_i64, 8),
            codec::FORMATCODE_SMALLLONG => read_i8(input).map(|(i, o)| (i, i64::from(o))),
            _ => Err(AmqpParseError::InvalidFormatCode(fmt)),
        }
    }
}

impl DecodeFormatted for f32 {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        validate_code!(fmt, codec::FORMATCODE_FLOAT);
        be_read!(input, read_f32, 4)
    }
}

impl DecodeFormatted for f64 {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        validate_code!(fmt, codec::FORMATCODE_DOUBLE);
        be_read!(input, read_f64, 8)
    }
}

impl DecodeFormatted for char {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        validate_code!(fmt, codec::FORMATCODE_CHAR);
        let result: Result<(&[u8], u32), AmqpParseError> = be_read!(input, read_u32, 4);
        let (i, o) = result?;
        if let Some(c) = char::from_u32(o) {
            Ok((i, c))
        } else {
            Err(AmqpParseError::InvalidChar(o))
        } // todo: replace with CharTryFromError once try_from is stabilized
    }
}

impl DecodeFormatted for DateTime<Utc> {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        validate_code!(fmt, codec::FORMATCODE_TIMESTAMP);
        be_read!(input, read_i64, 8).map(|(i, o)| (i, datetime_from_millis(o)))
    }
}

impl DecodeFormatted for Uuid {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        validate_code!(fmt, codec::FORMATCODE_UUID);
        decode_check_len!(input, 16);
        let uuid = Uuid::from_slice(&input[..16])?;
        Ok((&input[16..], uuid))
    }
}

impl DecodeFormatted for Bytes {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        match fmt {
            codec::FORMATCODE_BINARY8 => {
                read_bytes_u8(input).map(|(i, o)| (i, Bytes::copy_from_slice(o)))
            }
            codec::FORMATCODE_BINARY32 => {
                read_bytes_u32(input).map(|(i, o)| (i, Bytes::copy_from_slice(o)))
            }
            _ => Err(AmqpParseError::InvalidFormatCode(fmt)),
        }
    }
}

impl DecodeFormatted for ByteString {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        match fmt {
            codec::FORMATCODE_STRING8 => {
                let (input, bytes) = read_bytes_u8(input)?;
                Ok((input, ByteString::try_from(bytes)?))
            }
            codec::FORMATCODE_STRING32 => {
                let (input, bytes) = read_bytes_u32(input)?;
                Ok((input, ByteString::try_from(bytes)?))
            }
            _ => Err(AmqpParseError::InvalidFormatCode(fmt)),
        }
    }
}

impl DecodeFormatted for Str {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        match fmt {
            codec::FORMATCODE_STRING8 => {
                let (input, bytes) = read_bytes_u8(input)?;
                Ok((input, Str::from_str(str::from_utf8(bytes)?)))
            }
            codec::FORMATCODE_STRING32 => {
                let (input, bytes) = read_bytes_u32(input)?;
                Ok((input, Str::from_str(str::from_utf8(bytes)?)))
            }
            _ => Err(AmqpParseError::InvalidFormatCode(fmt)),
        }
    }
}

impl DecodeFormatted for Symbol {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        match fmt {
            codec::FORMATCODE_SYMBOL8 => {
                let (input, bytes) = read_bytes_u8(input)?;
                Ok((input, Symbol::from_slice(str::from_utf8(bytes)?)))
            }
            codec::FORMATCODE_SYMBOL32 => {
                let (input, bytes) = read_bytes_u32(input)?;
                Ok((input, Symbol::from_slice(str::from_utf8(bytes)?)))
            }
            _ => Err(AmqpParseError::InvalidFormatCode(fmt)),
        }
    }
}

impl ArrayDecode for Symbol {
    fn array_decode(input: &[u8]) -> Result<(&[u8], Self), AmqpParseError> {
        let (input, bytes) = read_bytes_u32(input)?;
        Ok((input, Symbol::from_slice(str::from_utf8(bytes)?)))
    }
}

impl<K: Decode + Eq + Hash, V: Decode, S: BuildHasher + Default> DecodeFormatted
    for HashMap<K, V, S>
{
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        let (input, header) = decode_map_header(input, fmt)?;
        let mut map_input = &input[..header.size as usize];
        let count = header.count / 2;
        let mut map: HashMap<K, V, S> =
            HashMap::with_capacity_and_hasher(count as usize, Default::default());
        for _ in 0..count {
            let (input1, key) = K::decode(map_input)?;
            let (input2, value) = V::decode(input1)?;
            map_input = input2;
            map.insert(key, value); // todo: ensure None returned?
        }
        // todo: validate map_input is empty
        Ok((&input[header.size as usize..], map))
    }
}

impl<T: DecodeFormatted> DecodeFormatted for Vec<T> {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        let (input, header) = decode_array_header(input, fmt)?;
        let item_fmt = input[0]; // todo: support descriptor
        let mut input = &input[1..];
        let mut result: Vec<T> = Vec::with_capacity(header.count as usize);
        for _ in 0..header.count {
            let (new_input, decoded) = T::decode_with_format(input, item_fmt)?;
            result.push(decoded);
            input = new_input;
        }
        Ok((input, result))
    }
}

impl DecodeFormatted for VecSymbolMap {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        let (input, header) = decode_map_header(input, fmt)?;
        let mut map_input = &input[..header.size as usize];
        let count = header.count / 2;
        let mut map = Vec::with_capacity(count as usize);
        for _ in 0..count {
            let (input1, key) = Symbol::decode(map_input)?;
            let (input2, value) = Variant::decode(input1)?;
            map_input = input2;
            map.push((key, value)); // todo: ensure None returned?
        }
        // todo: validate map_input is empty
        Ok((&input[header.size as usize..], VecSymbolMap(map)))
    }
}

impl DecodeFormatted for VecStringMap {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        let (input, header) = decode_map_header(input, fmt)?;
        let mut map_input = &input[..header.size as usize];
        let count = header.count / 2;
        let mut map = Vec::with_capacity(count as usize);
        for _ in 0..count {
            let (input1, key) = Str::decode(map_input)?;
            let (input2, value) = Variant::decode(input1)?;
            map_input = input2;
            map.push((key, value)); // todo: ensure None returned?
        }
        // todo: validate map_input is empty
        Ok((&input[header.size as usize..], VecStringMap(map)))
    }
}

impl<T: ArrayDecode + DecodeFormatted> DecodeFormatted for Multiple<T> {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        match fmt {
            codec::FORMATCODE_ARRAY8 | codec::FORMATCODE_ARRAY32 => {
                let (input, items) = Vec::<T>::decode_with_format(input, fmt)?;
                Ok((input, Multiple(items)))
            }
            _ => {
                let (input, item) = T::decode_with_format(input, fmt)?;
                Ok((input, Multiple(vec![item])))
            }
        }
    }
}

impl DecodeFormatted for List {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        let (mut input, header) = decode_list_header(input, fmt)?;
        let mut result: Vec<Variant> = Vec::with_capacity(header.count as usize);
        for _ in 0..header.count {
            let (new_input, decoded) = Variant::decode(input)?;
            result.push(decoded);
            input = new_input;
        }
        Ok((input, List(result)))
    }
}

impl DecodeFormatted for Variant {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        match fmt {
            codec::FORMATCODE_NULL => Ok((input, Variant::Null)),
            codec::FORMATCODE_BOOLEAN => {
                bool::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Boolean(o)))
            }
            codec::FORMATCODE_BOOLEAN_FALSE => Ok((input, Variant::Boolean(false))),
            codec::FORMATCODE_BOOLEAN_TRUE => Ok((input, Variant::Boolean(true))),
            codec::FORMATCODE_UINT_0 => Ok((input, Variant::Uint(0))),
            codec::FORMATCODE_ULONG_0 => Ok((input, Variant::Ulong(0))),
            codec::FORMATCODE_UBYTE => {
                u8::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Ubyte(o)))
            }
            codec::FORMATCODE_USHORT => {
                u16::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Ushort(o)))
            }
            codec::FORMATCODE_UINT => {
                u32::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Uint(o)))
            }
            codec::FORMATCODE_ULONG => {
                u64::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Ulong(o)))
            }
            codec::FORMATCODE_BYTE => {
                i8::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Byte(o)))
            }
            codec::FORMATCODE_SHORT => {
                i16::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Short(o)))
            }
            codec::FORMATCODE_INT => {
                i32::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Int(o)))
            }
            codec::FORMATCODE_LONG => {
                i64::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Long(o)))
            }
            codec::FORMATCODE_SMALLUINT => {
                u32::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Uint(o)))
            }
            codec::FORMATCODE_SMALLULONG => {
                u64::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Ulong(o)))
            }
            codec::FORMATCODE_SMALLINT => {
                i32::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Int(o)))
            }
            codec::FORMATCODE_SMALLLONG => {
                i64::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Long(o)))
            }
            codec::FORMATCODE_FLOAT => f32::decode_with_format(input, fmt)
                .map(|(i, o)| (i, Variant::Float(OrderedFloat(o)))),
            codec::FORMATCODE_DOUBLE => f64::decode_with_format(input, fmt)
                .map(|(i, o)| (i, Variant::Double(OrderedFloat(o)))),
            // codec::FORMATCODE_DECIMAL32 => x::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Decimal(o))),
            // codec::FORMATCODE_DECIMAL64 => x::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Decimal(o))),
            // codec::FORMATCODE_DECIMAL128 => x::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Decimal(o))),
            codec::FORMATCODE_CHAR => {
                char::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Char(o)))
            }
            codec::FORMATCODE_TIMESTAMP => DateTime::<Utc>::decode_with_format(input, fmt)
                .map(|(i, o)| (i, Variant::Timestamp(o))),
            codec::FORMATCODE_UUID => {
                Uuid::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Uuid(o)))
            }
            codec::FORMATCODE_BINARY8 => {
                Bytes::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Binary(o)))
            }
            codec::FORMATCODE_BINARY32 => {
                Bytes::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Binary(o)))
            }
            codec::FORMATCODE_STRING8 => ByteString::decode_with_format(input, fmt)
                .map(|(i, o)| (i, Variant::String(o.into()))),
            codec::FORMATCODE_STRING32 => ByteString::decode_with_format(input, fmt)
                .map(|(i, o)| (i, Variant::String(o.into()))),
            codec::FORMATCODE_SYMBOL8 => {
                Symbol::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Symbol(o)))
            }
            codec::FORMATCODE_SYMBOL32 => {
                Symbol::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Symbol(o)))
            }
            codec::FORMATCODE_LIST0 => Ok((input, Variant::List(List(vec![])))),
            codec::FORMATCODE_LIST8 => {
                List::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::List(o)))
            }
            codec::FORMATCODE_LIST32 => {
                List::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::List(o)))
            }
            codec::FORMATCODE_MAP8 => FxHashMap::<Variant, Variant>::decode_with_format(input, fmt)
                .map(|(i, o)| (i, Variant::Map(VariantMap::new(o)))),
            codec::FORMATCODE_MAP32 => {
                FxHashMap::<Variant, Variant>::decode_with_format(input, fmt)
                    .map(|(i, o)| (i, Variant::Map(VariantMap::new(o))))
            }
            // codec::FORMATCODE_ARRAY8 => Vec::<Variant>::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Array(o))),
            // codec::FORMATCODE_ARRAY32 => Vec::<Variant>::decode_with_format(input, fmt).map(|(i, o)| (i, Variant::Array(o))),
            codec::FORMATCODE_DESCRIBED => {
                let (input, descriptor) = Descriptor::decode(input)?;
                let (input, value) = Variant::decode(input)?;
                Ok((input, Variant::Described((descriptor, Box::new(value)))))
            }
            _ => Err(AmqpParseError::InvalidFormatCode(fmt)),
        }
    }
}

impl<T: DecodeFormatted> DecodeFormatted for Option<T> {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        match fmt {
            codec::FORMATCODE_NULL => Ok((input, None)),
            _ => T::decode_with_format(input, fmt).map(|(i, o)| (i, Some(o))),
        }
    }
}

impl DecodeFormatted for Descriptor {
    fn decode_with_format(input: &[u8], fmt: u8) -> Result<(&[u8], Self), AmqpParseError> {
        match fmt {
            codec::FORMATCODE_SMALLULONG => {
                u64::decode_with_format(input, fmt).map(|(i, o)| (i, Descriptor::Ulong(o)))
            }
            codec::FORMATCODE_ULONG => {
                u64::decode_with_format(input, fmt).map(|(i, o)| (i, Descriptor::Ulong(o)))
            }
            codec::FORMATCODE_SYMBOL8 => {
                Symbol::decode_with_format(input, fmt).map(|(i, o)| (i, Descriptor::Symbol(o)))
            }
            codec::FORMATCODE_SYMBOL32 => {
                Symbol::decode_with_format(input, fmt).map(|(i, o)| (i, Descriptor::Symbol(o)))
            }
            _ => Err(AmqpParseError::InvalidFormatCode(fmt)),
        }
    }
}

impl Decode for AmqpFrame {
    fn decode(input: &[u8]) -> Result<(&[u8], Self), AmqpParseError> {
        let (input, channel_id) = decode_frame_header(input, framing::FRAME_TYPE_AMQP)?;
        let (input, performative) = protocol::Frame::decode(input)?;
        Ok((input, AmqpFrame::new(channel_id, performative)))
    }
}

impl Decode for SaslFrame {
    fn decode(input: &[u8]) -> Result<(&[u8], Self), AmqpParseError> {
        let (input, _) = decode_frame_header(input, framing::FRAME_TYPE_SASL)?;
        let (input, frame) = protocol::SaslFrameBody::decode(input)?;
        Ok((input, SaslFrame { body: frame }))
    }
}

fn decode_frame_header(
    input: &[u8],
    expected_frame_type: u8,
) -> Result<(&[u8], u16), AmqpParseError> {
    decode_check_len!(input, 4);
    let doff = input[0];
    let frame_type = input[1];
    if frame_type != expected_frame_type {
        return Err(AmqpParseError::UnexpectedFrameType(frame_type));
    }

    let channel_id = BigEndian::read_u16(&input[2..]);
    let doff = doff as usize * 4;
    if doff < HEADER_LEN {
        return Err(AmqpParseError::InvalidSize);
    }
    let ext_header_len = doff - HEADER_LEN;
    decode_check_len!(input, ext_header_len + 4);
    let input = &input[ext_header_len + 4..]; // skipping remaining two header bytes and ext header
    Ok((input, channel_id))
}

fn decode_array_header(input: &[u8], fmt: u8) -> Result<(&[u8], CompoundHeader), AmqpParseError> {
    match fmt {
        codec::FORMATCODE_ARRAY8 => decode_compound8(input),
        codec::FORMATCODE_ARRAY32 => decode_compound32(input),
        _ => Err(AmqpParseError::InvalidFormatCode(fmt)),
    }
}

pub(crate) fn decode_list_header(
    input: &[u8],
    fmt: u8,
) -> Result<(&[u8], CompoundHeader), AmqpParseError> {
    match fmt {
        codec::FORMATCODE_LIST0 => Ok((input, CompoundHeader::empty())),
        codec::FORMATCODE_LIST8 => decode_compound8(input),
        codec::FORMATCODE_LIST32 => decode_compound32(input),
        _ => Err(AmqpParseError::InvalidFormatCode(fmt)),
    }
}

pub(crate) fn decode_map_header(
    input: &[u8],
    fmt: u8,
) -> Result<(&[u8], CompoundHeader), AmqpParseError> {
    match fmt {
        codec::FORMATCODE_MAP8 => decode_compound8(input),
        codec::FORMATCODE_MAP32 => decode_compound32(input),
        _ => Err(AmqpParseError::InvalidFormatCode(fmt)),
    }
}

fn decode_compound8(input: &[u8]) -> Result<(&[u8], CompoundHeader), AmqpParseError> {
    decode_check_len!(input, 2);
    let size = input[0] - 1; // -1 for 1 byte count
    let count = input[1];
    Ok((
        &input[2..],
        CompoundHeader {
            size: u32::from(size),
            count: u32::from(count),
        },
    ))
}

fn decode_compound32(input: &[u8]) -> Result<(&[u8], CompoundHeader), AmqpParseError> {
    decode_check_len!(input, 8);
    let size = BigEndian::read_u32(input) - 4; // -4 for 4 byte count
    let count = BigEndian::read_u32(&input[4..]);
    Ok((&input[8..], CompoundHeader { size, count }))
}

fn datetime_from_millis(millis: i64) -> DateTime<Utc> {
    let seconds = millis / 1000;
    if seconds < 0 {
        // In order to handle time before 1970 correctly, we need to subtract a second
        // and use the nanoseconds field to add it back. This is a result of the nanoseconds
        // parameter being u32
        let nanoseconds = ((1000 + (millis - (seconds * 1000))) * 1_000_000).abs() as u32;
        Utc.timestamp(seconds - 1, nanoseconds)
    } else {
        let nanoseconds = ((millis - (seconds * 1000)) * 1_000_000).abs() as u32;
        Utc.timestamp(seconds, nanoseconds)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::codec::Encode;
    use bytes::{BufMut, BytesMut};

    const LOREM: &str = include_str!("lorem.txt");

    macro_rules! decode_tests {
        ($($name:ident: $kind:ident, $test:expr, $expected:expr,)*) => {
        $(
            #[test]
            fn $name() {
                let b1 = &mut BytesMut::with_capacity(($test).encoded_size());
                ($test).encode(b1);
                assert_eq!($expected, unwrap_value($kind::decode(b1)));
            }
        )*
        }
    }

    decode_tests! {
        ubyte: u8, 255_u8, 255_u8,
        ushort: u16, 350_u16, 350_u16,

        uint_zero: u32, 0_u32, 0_u32,
        uint_small: u32, 128_u32, 128_u32,
        uint_big: u32, 2147483647_u32, 2147483647_u32,

        ulong_zero: u64, 0_u64, 0_u64,
        ulong_small: u64, 128_u64, 128_u64,
        uulong_big: u64, 2147483649_u64, 2147483649_u64,

        byte: i8, -128_i8, -128_i8,
        short: i16, -255_i16, -255_i16,

        int_zero: i32, 0_i32, 0_i32,
        int_small: i32, -50000_i32, -50000_i32,
        int_neg: i32, -128_i32, -128_i32,

        long_zero: i64, 0_i64, 0_i64,
        long_big: i64, -2147483647_i64, -2147483647_i64,
        long_small: i64, -128_i64, -128_i64,

        float: f32, 1.234_f32, 1.234_f32,
        double: f64, 1.234_f64, 1.234_f64,

        test_char: char, '💯', '💯',

        uuid: Uuid, Uuid::from_slice(&[4, 54, 67, 12, 43, 2, 98, 76, 32, 50, 87, 5, 1, 33, 43, 87]).expect("parse error"),
        Uuid::parse_str("0436430c2b02624c2032570501212b57").expect("parse error"),

        binary_short: Bytes, Bytes::from(&[4u8, 5u8][..]), Bytes::from(&[4u8, 5u8][..]),
        binary_long: Bytes, Bytes::from(&[4u8; 500][..]), Bytes::from(&[4u8; 500][..]),

        string_short: ByteString, ByteString::from("Hello there"), ByteString::from("Hello there"),
        string_long: ByteString, ByteString::from(LOREM), ByteString::from(LOREM),

        // symbol_short: Symbol, Symbol::from("Hello there"), Symbol::from("Hello there"),
        // symbol_long: Symbol, Symbol::from(LOREM), Symbol::from(LOREM),

        variant_ubyte: Variant, Variant::Ubyte(255_u8), Variant::Ubyte(255_u8),
        variant_ushort: Variant, Variant::Ushort(350_u16), Variant::Ushort(350_u16),

        variant_uint_zero: Variant, Variant::Uint(0_u32), Variant::Uint(0_u32),
        variant_uint_small: Variant, Variant::Uint(128_u32), Variant::Uint(128_u32),
        variant_uint_big: Variant, Variant::Uint(2147483647_u32), Variant::Uint(2147483647_u32),

        variant_ulong_zero: Variant, Variant::Ulong(0_u64), Variant::Ulong(0_u64),
        variant_ulong_small: Variant, Variant::Ulong(128_u64), Variant::Ulong(128_u64),
        variant_ulong_big: Variant, Variant::Ulong(2147483649_u64), Variant::Ulong(2147483649_u64),

        variant_byte: Variant, Variant::Byte(-128_i8), Variant::Byte(-128_i8),
        variant_short: Variant, Variant::Short(-255_i16), Variant::Short(-255_i16),

        variant_int_zero: Variant, Variant::Int(0_i32), Variant::Int(0_i32),
        variant_int_small: Variant, Variant::Int(-50000_i32), Variant::Int(-50000_i32),
        variant_int_neg: Variant, Variant::Int(-128_i32), Variant::Int(-128_i32),

        variant_long_zero: Variant, Variant::Long(0_i64), Variant::Long(0_i64),
        variant_long_big: Variant, Variant::Long(-2147483647_i64), Variant::Long(-2147483647_i64),
        variant_long_small: Variant, Variant::Long(-128_i64), Variant::Long(-128_i64),

        variant_float: Variant, Variant::Float(OrderedFloat(1.234_f32)), Variant::Float(OrderedFloat(1.234_f32)),
        variant_double: Variant, Variant::Double(OrderedFloat(1.234_f64)), Variant::Double(OrderedFloat(1.234_f64)),

        variant_char: Variant, Variant::Char('💯'), Variant::Char('💯'),

        variant_uuid: Variant, Variant::Uuid(Uuid::from_slice(&[4, 54, 67, 12, 43, 2, 98, 76, 32, 50, 87, 5, 1, 33, 43, 87]).expect("parse error")),
        Variant::Uuid(Uuid::parse_str("0436430c2b02624c2032570501212b57").expect("parse error")),

        variant_binary_short: Variant, Variant::Binary(Bytes::from(&[4u8, 5u8][..])), Variant::Binary(Bytes::from(&[4u8, 5u8][..])),
        variant_binary_long: Variant, Variant::Binary(Bytes::from(&[4u8; 500][..])), Variant::Binary(Bytes::from(&[4u8; 500][..])),

        variant_string_short: Variant, Variant::String(ByteString::from("Hello there").into()), Variant::String(ByteString::from("Hello there").into()),
        variant_string_long: Variant, Variant::String(ByteString::from(LOREM).into()), Variant::String(ByteString::from(LOREM).into()),

        // variant_symbol_short: Variant, Variant::Symbol(Symbol::from("Hello there")), Variant::Symbol(Symbol::from("Hello there")),
        // variant_symbol_long: Variant, Variant::Symbol(Symbol::from(LOREM)), Variant::Symbol(Symbol::from(LOREM)),
    }

    fn unwrap_value<T>(res: Result<(&[u8], T), AmqpParseError>) -> T {
        let r = res.map(|(_i, o)| o);
        assert!(r.is_ok());
        r.unwrap()
    }

    #[test]
    fn test_bool_true() {
        let b1 = &mut BytesMut::with_capacity(0);
        b1.put_u8(0x41);
        assert_eq!(true, unwrap_value(bool::decode(b1)));

        let b2 = &mut BytesMut::with_capacity(0);
        b2.put_u8(0x56);
        b2.put_u8(0x01);
        assert_eq!(true, unwrap_value(bool::decode(b2)));
    }

    #[test]
    fn test_bool_false() {
        let b1 = &mut BytesMut::with_capacity(0);
        b1.put_u8(0x42u8);
        assert_eq!(false, unwrap_value(bool::decode(b1)));

        let b2 = &mut BytesMut::with_capacity(0);
        b2.put_u8(0x56);
        b2.put_u8(0x00);
        assert_eq!(false, unwrap_value(bool::decode(b2)));
    }

    /// UTC with a precision of milliseconds. For example, 1311704463521
    /// represents the moment 2011-07-26T18:21:03.521Z.
    #[test]
    fn test_timestamp() {
        let b1 = &mut BytesMut::with_capacity(0);
        let datetime = Utc.ymd(2011, 7, 26).and_hms_milli(18, 21, 3, 521);
        datetime.encode(b1);

        let expected = Utc.ymd(2011, 7, 26).and_hms_milli(18, 21, 3, 521);
        assert_eq!(expected, unwrap_value(DateTime::<Utc>::decode(b1)));
    }

    #[test]
    fn test_timestamp_pre_unix() {
        let b1 = &mut BytesMut::with_capacity(0);
        let datetime = Utc.ymd(1968, 7, 26).and_hms_milli(18, 21, 3, 521);
        datetime.encode(b1);

        let expected = Utc.ymd(1968, 7, 26).and_hms_milli(18, 21, 3, 521);
        assert_eq!(expected, unwrap_value(DateTime::<Utc>::decode(b1)));
    }

    #[test]
    fn variant_null() {
        let mut b = BytesMut::with_capacity(0);
        Variant::Null.encode(&mut b);
        let t = unwrap_value(Variant::decode(&mut b));
        assert_eq!(Variant::Null, t);
    }

    #[test]
    fn variant_bool_true() {
        let b1 = &mut BytesMut::with_capacity(0);
        b1.put_u8(0x41);
        assert_eq!(Variant::Boolean(true), unwrap_value(Variant::decode(b1)));

        let b2 = &mut BytesMut::with_capacity(0);
        b2.put_u8(0x56);
        b2.put_u8(0x01);
        assert_eq!(Variant::Boolean(true), unwrap_value(Variant::decode(b2)));
    }

    #[test]
    fn variant_bool_false() {
        let b1 = &mut BytesMut::with_capacity(0);
        b1.put_u8(0x42u8);
        assert_eq!(Variant::Boolean(false), unwrap_value(Variant::decode(b1)));

        let b2 = &mut BytesMut::with_capacity(0);
        b2.put_u8(0x56);
        b2.put_u8(0x00);
        assert_eq!(Variant::Boolean(false), unwrap_value(Variant::decode(b2)));
    }

    /// UTC with a precision of milliseconds. For example, 1311704463521
    /// represents the moment 2011-07-26T18:21:03.521Z.
    #[test]
    fn variant_timestamp() {
        let b1 = &mut BytesMut::with_capacity(0);
        let datetime = Utc.ymd(2011, 7, 26).and_hms_milli(18, 21, 3, 521);
        Variant::Timestamp(datetime).encode(b1);

        let expected = Utc.ymd(2011, 7, 26).and_hms_milli(18, 21, 3, 521);
        assert_eq!(
            Variant::Timestamp(expected),
            unwrap_value(Variant::decode(b1))
        );
    }

    #[test]
    fn variant_timestamp_pre_unix() {
        let b1 = &mut BytesMut::with_capacity(0);
        let datetime = Utc.ymd(1968, 7, 26).and_hms_milli(18, 21, 3, 521);
        Variant::Timestamp(datetime).encode(b1);

        let expected = Utc.ymd(1968, 7, 26).and_hms_milli(18, 21, 3, 521);
        assert_eq!(
            Variant::Timestamp(expected),
            unwrap_value(Variant::decode(b1))
        );
    }

    #[test]
    fn option_i8() {
        let b1 = &mut BytesMut::with_capacity(0);
        Some(42i8).encode(b1);

        assert_eq!(Some(42), unwrap_value(Option::<i8>::decode(b1)));

        let b2 = &mut BytesMut::with_capacity(0);
        let o1: Option<i8> = None;
        o1.encode(b2);

        assert_eq!(None, unwrap_value(Option::<i8>::decode(b2)));
    }

    #[test]
    fn option_string() {
        let b1 = &mut BytesMut::with_capacity(0);
        Some(ByteString::from("hello")).encode(b1);

        assert_eq!(
            Some(ByteString::from("hello")),
            unwrap_value(Option::<ByteString>::decode(b1))
        );

        let b2 = &mut BytesMut::with_capacity(0);
        let o1: Option<ByteString> = None;
        o1.encode(b2);

        assert_eq!(None, unwrap_value(Option::<ByteString>::decode(b2)));
    }
}