//! re-export of [bytes] crate types.

pub use bytes::*;
pub use xitca_unsafe_collection::bytes::{BytesStr, EitherBuf, PagedBytesMut};

use core::fmt;

use std::io;

/// A new type for help implementing [io::Write] and [fmt::Write] traits.
pub struct BufMutWriter<'a, B>(pub &'a mut B);

impl<B: BufMut> io::Write for BufMutWriter<'_, B> {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.0.put_slice(buf);
        Ok(buf.len())
    }

    fn flush(&mut self) -> io::Result<()> {
        Ok(())
    }
}

impl<B: BufMut> fmt::Write for BufMutWriter<'_, B> {
    fn write_str(&mut self, s: &str) -> fmt::Result {
        self.0.put_slice(s.as_bytes());
        Ok(())
    }
}

/// trait generic over different types of buffer strategy.
pub trait BufInterest {
    /// flag if buffer want more data to be filled in.
    fn want_write_buf(&self) -> bool;

    /// flag if buffer want to write data to io.
    fn want_write_io(&self) -> bool;
}

/// trait generic over different types of read buffer strategy.
pub trait BufRead: BufInterest {
    /// read from IO and write into buffer.
    fn do_io<Io: io::Read>(&mut self, io: &mut Io) -> io::Result<()>;
}

/// trait generic over different types of write buffer strategy.
pub trait BufWrite: BufInterest {
    /// write into [BytesMut] with closure that output a Result type.
    /// the result type is used to hint buffer to stop wanting to flush IO on [BufWrite::do_io]
    /// or revert BytesMut to previous state before method was called.
    fn write_buf<F, T, E>(&mut self, func: F) -> Result<T, E>
    where
        F: FnOnce(&mut BytesMut) -> Result<T, E>;

    /// write into IO from buffer.
    fn do_io<Io: io::Write>(&mut self, io: &mut Io) -> io::Result<()>;
}

impl BufInterest for BytesMut {
    #[inline]
    fn want_write_buf(&self) -> bool {
        true
    }

    #[inline]
    fn want_write_io(&self) -> bool {
        !self.is_empty()
    }
}

impl BufRead for BytesMut {
    #[inline]
    fn do_io<Io: io::Read>(&mut self, io: &mut Io) -> io::Result<()> {
        buf_read(self, io)
    }
}

impl BufWrite for BytesMut {
    #[inline]
    fn write_buf<F, T, E>(&mut self, func: F) -> Result<T, E>
    where
        F: FnOnce(&mut Self) -> Result<T, E>,
    {
        let len = self.len();
        func(self).map_err(|e| {
            self.truncate(len);
            e
        })
    }

    #[cold]
    #[inline(never)]
    fn do_io<Io: io::Write>(&mut self, _: &mut Io) -> io::Result<()> {
        unimplemented!()
    }
}

pub struct WriteBuf {
    buf: BytesMut,
    want_flush: bool,
}

impl WriteBuf {
    #[inline]
    pub fn new() -> Self {
        Self {
            buf: BytesMut::new(),
            want_flush: false,
        }
    }

    #[inline]
    pub fn len(&self) -> usize {
        self.buf.len()
    }

    #[inline]
    pub fn is_empty(&self) -> bool {
        self.buf.is_empty()
    }

    #[inline]
    pub fn into_inner(self) -> BytesMut {
        self.buf
    }

    /// clear remaining bytes in buffer and set flush flag to false.
    /// this would make following [BufInterest::want_write_io] call return false.
    #[inline]
    pub fn clear(&mut self) {
        self.buf.clear();
        self.want_flush = false;
    }

    #[inline]
    pub fn buf(&self) -> &[u8] {
        &self.buf
    }
}

impl Default for WriteBuf {
    fn default() -> Self {
        Self::new()
    }
}

impl BufInterest for WriteBuf {
    #[inline]
    fn want_write_buf(&self) -> bool {
        self.buf.want_write_buf()
    }

    #[inline]
    fn want_write_io(&self) -> bool {
        self.buf.want_write_io() || self.want_flush
    }
}

impl BufWrite for WriteBuf {
    #[inline]
    fn write_buf<F, T, E>(&mut self, func: F) -> Result<T, E>
    where
        F: FnOnce(&mut BytesMut) -> Result<T, E>,
    {
        self.buf.write_buf(func).map(|t| {
            self.want_flush = false;
            t
        })
    }

    fn do_io<Io: io::Write>(&mut self, io: &mut Io) -> io::Result<()> {
        loop {
            if self.want_flush {
                match io::Write::flush(io) {
                    Ok(_) => self.want_flush = false,
                    Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {}
                    Err(e) => return Err(e),
                }
                break;
            }
            match io::Write::write(io, &self.buf) {
                Ok(0) => return Err(io::ErrorKind::WriteZero.into()),
                Ok(n) => {
                    self.buf.advance(n);
                    self.want_flush = self.buf.is_empty();
                }
                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => break,
                Err(e) => return Err(e),
            }
        }
        Ok(())
    }
}

impl<const P: usize> BufInterest for PagedBytesMut<P> {
    #[inline]
    fn want_write_buf(&self) -> bool {
        self.get_ref().want_write_buf()
    }

    #[inline]
    fn want_write_io(&self) -> bool {
        self.get_ref().want_write_io()
    }
}

impl<const P: usize> BufRead for PagedBytesMut<P> {
    #[inline]
    fn do_io<Io: io::Read>(&mut self, io: &mut Io) -> io::Result<()> {
        buf_read(self, io)
    }
}

fn buf_read<B, Io>(buf: &mut B, io: &mut Io) -> io::Result<()>
where
    Io: io::Read,
    B: Buf + BufMut,
{
    let len = buf.remaining();
    loop {
        match xitca_unsafe_collection::bytes::read_buf(io, buf) {
            Ok(0) => {
                if buf.remaining() == len {
                    return Err(io::ErrorKind::UnexpectedEof.into());
                };
                break;
            }
            Ok(_) => {}
            Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => break,
            Err(e) => {
                if buf.remaining() == len {
                    return Err(e);
                }
                break;
            }
        }
    }
    Ok(())
}

impl<L, R> BufInterest for EitherBuf<L, R>
where
    L: BufInterest,
    R: BufInterest,
{
    #[inline]
    fn want_write_buf(&self) -> bool {
        match *self {
            Self::Left(ref l) => l.want_write_buf(),
            Self::Right(ref r) => r.want_write_buf(),
        }
    }

    #[inline]
    fn want_write_io(&self) -> bool {
        match *self {
            Self::Left(ref l) => l.want_write_io(),
            Self::Right(ref r) => r.want_write_io(),
        }
    }
}

impl<L, R> BufWrite for EitherBuf<L, R>
where
    L: BufWrite,
    R: BufWrite,
{
    #[inline]
    fn write_buf<F, T, E>(&mut self, func: F) -> Result<T, E>
    where
        F: FnOnce(&mut BytesMut) -> Result<T, E>,
    {
        match *self {
            Self::Left(ref mut l) => l.write_buf(func),
            Self::Right(ref mut r) => r.write_buf(func),
        }
    }

    #[inline]
    fn do_io<Io>(&mut self, io: &mut Io) -> io::Result<()>
    where
        Io: io::Write,
    {
        match *self {
            Self::Left(ref mut l) => l.do_io(io),
            Self::Right(ref mut r) => r.do_io(io),
        }
    }
}