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use std::future::Future;

use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
use tracing::*;

use crate::constants::MAX_FRAME_BODY_LEN;
use crate::errors::ConnError;
use crate::frame::{FrameBody, FrameType};
use crate::traits::{AsyncRecvFrame, AsyncSendFrame};

/// Wrapper around a arbitrary reader/writer type to implement corresponding frame
/// send/recv traits.
pub struct StreamFramer<T: Sync + Send + Unpin> {
    inner: T,
    read_buf: Vec<u8>,
    write_buf: Vec<u8>,
}

impl<T: Sync + Send + Unpin> StreamFramer<T> {
    pub fn new(inner: T) -> Self {
        Self {
            inner,
            read_buf: Vec::new(),
            write_buf: Vec::new(),
        }
    }

    pub fn inner(&self) -> &T {
        &self.inner
    }

    pub fn inner_mut(&mut self) -> &mut T {
        &mut self.inner
    }

    pub fn into_inner(self) -> T {
        self.inner
    }
}

impl<T: AsyncRead + Sync + Send + Unpin> AsyncRecvFrame for StreamFramer<T> {
    fn recv_frame_async(&mut self) -> impl Future<Output = Result<FrameBody, ConnError>> + Send {
        async {
            // Read the flags, safety check.
            let flags = self.inner.read_u8().await?;
            if flags != 0 {
                return Err(ConnError::UnknownFlags(flags));
            }

            // Read the type, make sure we recognize it.
            let ty_tag = self.inner.read_u8().await?;
            if FrameType::try_from(ty_tag).is_err() {
                return Err(ConnError::UnknownFrameType(ty_tag));
            }

            // Read the length, make sure it's not oversized.
            let len = self.inner.read_u32().await? as usize;
            if len > MAX_FRAME_BODY_LEN {
                return Err(ConnError::FrameTooLarge(len));
            }

            // *now* we can read and parse the vec
            self.read_buf.resize(len, 0);
            self.inner.read_exact(&mut self.read_buf).await?;
            let frame = FrameBody::from_buf(&self.read_buf)?;
            let ty = frame.ty();
            trace!(?ty, %len, "recvd frame");
            self.read_buf.clear();

            // Sanity check.
            // TODO remove this eventually
            if u8::from(frame.ty()) != ty_tag {
                return Err(ConnError::MalformedFrame);
            }

            Ok(frame)
        }
    }
}

impl<T: AsyncWrite + Sync + Send + Unpin> AsyncSendFrame for StreamFramer<T> {
    fn send_frame_async(
        &mut self,
        body: &FrameBody,
    ) -> impl Future<Output = Result<(), ConnError>> + Send {
        async {
            let ty = body.ty();
            let flags = 0u8; // TODO support more, like per-frame signing
            let ty_tag: u8 = ty.into();

            body.into_vec(&mut self.write_buf)?; // FIXME this sucks, use a write buf
            let len = self.write_buf.len();

            if len > MAX_FRAME_BODY_LEN {
                return Err(ConnError::FrameTooLarge(len));
            }

            trace!(?ty, %len, "sending frame");

            self.inner.write_u8(flags).await?;
            self.inner.write_u8(ty_tag).await?;
            self.inner.write_u32(len as u32).await?;
            self.inner.write_all(&self.write_buf).await?;
            self.write_buf.clear();

            Ok(())
        }
    }
}