//! Decoding: reading protocol values from a byte stream.
use crate::context::Context;
use std::{io::Read, sync::Arc};

use crate::{DEFAULT_BUFFER_LEN, codec::error::Result};

macro_rules! impl_decode {
    ($type: ty) => {
        impl<Data> Decode<Data> for $type {
            // decode number using big endian
            fn decode(reader: &mut dyn Read, _: &Context<Data>) -> Result<Self>
            where
                Self: Sized,
            {
                const BYTES: usize = (<$type>::BITS / 8) as usize;
                let mut bytes = [0; BYTES];
                reader.read_exact(&mut bytes)?;
                Ok(<$type>::from_be_bytes(bytes))
            }
        }
    };
}

/// Read a value from a byte stream
pub trait Decode<Data> {
    fn decode(reader: &mut dyn Read, ctx: &Context<Data>) -> Result<Self>
    where
        Self: Sized;
}

impl<Data> Decode<Data> for bool {
    fn decode(reader: &mut dyn Read, _: &Context<Data>) -> Result<Self>
    where
        Self: Sized,
    {
        let mut byte = [0_u8];
        reader.read_exact(&mut byte)?;
        Ok(byte[0] != 0)
    }
}

impl<Data, T: Decode<Data>> Decode<Data> for Option<T> {
    fn decode(reader: &mut dyn Read, ctx: &Context<Data>) -> Result<Self>
    where
        Self: Sized,
    {
        let tag = u8::decode(reader, ctx)?;
        if tag == 0 {
            Ok(None)
        } else {
            Ok(Some(T::decode(reader, ctx)?))
        }
    }
}

impl<Data, T: Decode<Data>> Decode<Data> for Vec<T> {
    fn decode(reader: &mut dyn Read, ctx: &Context<Data>) -> Result<Self>
    where
        Self: Sized,
    {
        let len = usize::decode(reader, ctx)?;
        let mut vec = Vec::with_capacity(len);
        for _ in 0..len {
            vec.push(T::decode(reader, ctx)?);
        }
        Ok(vec)
    }
}

impl<Data> Decode<Data> for String {
    fn decode(reader: &mut dyn Read, _: &Context<Data>) -> Result<Self>
    where
        Self: Sized,
    {
        let mut bytes: Vec<u8> = Vec::new();
        reader.read_to_end(&mut bytes)?;
        Ok(String::from_utf8_lossy(&bytes).to_string())
    }
}

impl<Data> Decode<Data> for Arc<[u8]> {
    fn decode(reader: &mut dyn Read, _: &Context<Data>) -> Result<Self> {
        let mut buf = Vec::with_capacity(DEFAULT_BUFFER_LEN);
        reader.read_to_end(&mut buf)?;
        Ok(Arc::<[u8]>::from(buf.into_boxed_slice()))
    }
}

impl<Data, const S: usize> Decode<Data> for [u8; S] {
    fn decode(reader: &mut dyn Read, _: &Context<Data>) -> Result<Self>
    where
        Self: Sized,
    {
        let mut slice = [0_u8; S];
        reader.read_exact(&mut slice)?;
        Ok(slice)
    }
}

impl_decode!(u8);
impl_decode!(u16);
impl_decode!(u32);
impl_decode!(u64);
impl_decode!(u128);
impl_decode!(usize);

impl_decode!(i8);
impl_decode!(i16);
impl_decode!(i32);
impl_decode!(i64);
impl_decode!(i128);
impl_decode!(isize);

impl<Data> Decode<Data> for f64 {
    fn decode(reader: &mut dyn Read, ctx: &Context<Data>) -> Result<Self>
    where
        Self: Sized,
    {
        let bits = u64::decode(reader, ctx)?;
        let value = f64::from_bits(bits);
        Ok(value)
    }
}

impl<Data> Decode<Data> for f32 {
    fn decode(reader: &mut dyn Read, ctx: &Context<Data>) -> Result<Self>
    where
        Self: Sized,
    {
        let bits = u32::decode(reader, ctx)?;
        let value = f32::from_bits(bits);
        Ok(value)
    }
}