#![allow(non_snake_case)]

use anyhow::anyhow;
use async_tungstenite::tungstenite::Message as WebSocketMessage;
use futures::{SinkExt as _, StreamExt as _};
pub use proto::{Message as _, *};
use std::time::Instant;
use std::{fmt::Debug, io};

const KIB: usize = 1024;
const MIB: usize = KIB * 1024;
const MAX_BUFFER_LEN: usize = MIB;

/// A stream of protobuf messages.
pub struct MessageStream<S> {
    stream: S,
    encoding_buffer: Vec<u8>,
}

#[allow(clippy::large_enum_variant)]
#[derive(Debug)]
pub enum Message {
    Envelope(Envelope),
    Ping,
    Pong,
}

impl<S> MessageStream<S> {
    pub fn new(stream: S) -> Self {
        Self {
            stream,
            encoding_buffer: Vec::new(),
        }
    }

    pub fn inner_mut(&mut self) -> &mut S {
        &mut self.stream
    }
}

impl<S> MessageStream<S>
where
    S: futures::Sink<WebSocketMessage, Error = anyhow::Error> + Unpin,
{
    pub async fn write(&mut self, message: Message) -> Result<(), anyhow::Error> {
        #[cfg(any(test, feature = "test-support"))]
        const COMPRESSION_LEVEL: i32 = -7;

        #[cfg(not(any(test, feature = "test-support")))]
        const COMPRESSION_LEVEL: i32 = 4;

        match message {
            Message::Envelope(message) => {
                self.encoding_buffer.reserve(message.encoded_len());
                message
                    .encode(&mut self.encoding_buffer)
                    .map_err(io::Error::from)?;
                let buffer =
                    zstd::stream::encode_all(self.encoding_buffer.as_slice(), COMPRESSION_LEVEL)
                        .unwrap();

                self.encoding_buffer.clear();
                self.encoding_buffer.shrink_to(MAX_BUFFER_LEN);
                self.stream.send(WebSocketMessage::Binary(buffer)).await?;
            }
            Message::Ping => {
                self.stream
                    .send(WebSocketMessage::Ping(Default::default()))
                    .await?;
            }
            Message::Pong => {
                self.stream
                    .send(WebSocketMessage::Pong(Default::default()))
                    .await?;
            }
        }

        Ok(())
    }
}

impl<S> MessageStream<S>
where
    S: futures::Stream<Item = Result<WebSocketMessage, anyhow::Error>> + Unpin,
{
    pub async fn read(&mut self) -> Result<(Message, Instant), anyhow::Error> {
        while let Some(bytes) = self.stream.next().await {
            let received_at = Instant::now();
            match bytes? {
                WebSocketMessage::Binary(bytes) => {
                    zstd::stream::copy_decode(bytes.as_slice(), &mut self.encoding_buffer).unwrap();
                    let envelope = Envelope::decode(self.encoding_buffer.as_slice())
                        .map_err(io::Error::from)?;

                    self.encoding_buffer.clear();
                    self.encoding_buffer.shrink_to(MAX_BUFFER_LEN);
                    return Ok((Message::Envelope(envelope), received_at));
                }
                WebSocketMessage::Ping(_) => return Ok((Message::Ping, received_at)),
                WebSocketMessage::Pong(_) => return Ok((Message::Pong, received_at)),
                WebSocketMessage::Close(_) => break,
                _ => {}
            }
        }
        Err(anyhow!("connection closed"))
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[gpui::test]
    async fn test_buffer_size() {
        let (tx, rx) = futures::channel::mpsc::unbounded();
        let mut sink = MessageStream::new(tx.sink_map_err(|_| anyhow!("")));
        sink.write(Message::Envelope(Envelope {
            payload: Some(envelope::Payload::UpdateWorktree(UpdateWorktree {
                root_name: "abcdefg".repeat(10),
                ..Default::default()
            })),
            ..Default::default()
        }))
        .await
        .unwrap();
        assert!(sink.encoding_buffer.capacity() <= MAX_BUFFER_LEN);
        sink.write(Message::Envelope(Envelope {
            payload: Some(envelope::Payload::UpdateWorktree(UpdateWorktree {
                root_name: "abcdefg".repeat(1000000),
                ..Default::default()
            })),
            ..Default::default()
        }))
        .await
        .unwrap();
        assert!(sink.encoding_buffer.capacity() <= MAX_BUFFER_LEN);

        let mut stream = MessageStream::new(rx.map(anyhow::Ok));
        stream.read().await.unwrap();
        assert!(stream.encoding_buffer.capacity() <= MAX_BUFFER_LEN);
        stream.read().await.unwrap();
        assert!(stream.encoding_buffer.capacity() <= MAX_BUFFER_LEN);
    }
}