use bytes::{Buf, BufMut, BytesMut};

use log::*;

use std::{

    error::Error,

    fmt::{Debug, Display, Formatter},

    io,

    io::ErrorKind,

    marker::Unpin,

    time::Duration,

};

use tokio::{io::AsyncReadExt, time::timeout};

use crate::protocol::ProtocolError::Timeout;

use hedgewars_network_protocol::{

    messages::HwProtocolMessage,

    parser::HwProtocolError,

    parser::{malformed_message, message},

};

#[derive(Debug)]

pub enum ProtocolError {

    Eof,

    Timeout,

    Network(Box<dyn Error + Send>),

}

impl Display for ProtocolError {

    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {

        match self {

            ProtocolError::Eof => write!(f, "Connection reset by peer"),

            ProtocolError::Timeout => write!(f, "Read operation timed out"),

            ProtocolError::Network(source) => write!(f, "{:?}", source),

        }

    }

}

impl Error for ProtocolError {

    fn source(&self) -> Option<&(dyn Error + 'static)> {

        if let Self::Network(source) = self {

            Some(source.as_ref())

        } else {

            None

        }

    }

}

pub type Result<T> = std::result::Result<T, ProtocolError>;

pub struct ProtocolDecoder {

    buffer: BytesMut,

    read_timeout: Duration,

    is_recovering: bool,

}

impl ProtocolDecoder {

    pub fn new(read_timeout: Duration) -> ProtocolDecoder {

        ProtocolDecoder {

            buffer: BytesMut::with_capacity(1024),

            read_timeout,

            is_recovering: false,

        }

    }

    fn recover(&mut self) -> bool {

        self.is_recovering = match malformed_message(&self.buffer[..]) {

            Ok((tail, ())) => {

                let remaining = tail.len();

                self.buffer.advance(self.buffer.len() - remaining);

                false

            }

            _ => {

                self.buffer.clear();

                true

            }

        };

        !self.is_recovering

    }

    fn extract_message(&mut self) -> Option<HwProtocolMessage> {

        if !self.is_recovering || self.recover() {

            match message(&self.buffer[..]) {

                Ok((tail, message)) => {

                    let remaining = tail.len();

                    self.buffer.advance(self.buffer.len() - remaining);

                    return Some(message);

                }

                Err(nom::Err::Incomplete(_)) => {}

                Err(nom::Err::Failure(e) | nom::Err::Error(e)) => {

                    debug!("Invalid message: {:?}", e);

                    self.recover();

                }

            }

        }

        None

    }

    pub async fn read_from<R: AsyncReadExt + Unpin>(

        &mut self,

        stream: &mut R,

    ) -> Result<HwProtocolMessage> {

        use ProtocolError::*;

        loop {

                //todo!("ensure the buffer doesn't grow indefinitely")

                match timeout(self.read_timeout, stream.read_buf(&mut self.buffer)).await {

                    Err(_) => return Err(Timeout),

                    Ok(Err(e)) => return Err(Network(Box::new(e))),

                    Ok(Ok(0)) => return Err(Eof),

                    Ok(Ok(_)) => (),

                };

            }

            while !self.buffer.is_empty() {

                if let Some(result) = self.extract_message() {

                    return Ok(result);

                }

            }

        }

    }

}