use crate::serial_core::codec::Codec;
use crate::serial_core::codecs::tactile_a::TactileACodec;
use crate::serial_core::frame::{FrameHandler, TactileAFrame, TestFrame};
use crate::serial_core::model::{HudChartState, HudPacket};
use crate::serial_core::record::Recording;
use anyhow::Result;
use tauri::{AppHandle, Emitter};
use tokio::io::{AsyncReadExt, AsyncWriteExt};
use tokio::time::{self, Duration, MissedTickBehavior};
use tokio_serial::SerialStream;
use tokio_util::sync::CancellationToken;
use std::future::pending;
use std::sync::{Arc, Mutex};
use std::time::Instant;
use log::{info, debug};
use crate::serial_core::record::{FrameTiming, RecordedFrame};

pub enum PollMode<F> {
    Disable,
    Enabled(Box<dyn PollRequester<F>>)
}

pub trait SerialFrame: Clone + Send + 'static {
    fn dts_ms(&self) -> u64;

    fn to_hud_packet(
        &self,
        chart_state: &mut HudChartState,
        display_values: Option<&[i32]>,
    ) -> Option<HudPacket>;
}

impl SerialFrame for TestFrame {
    fn dts_ms(&self) -> u64 {
        self.dts_ms
    }

    fn to_hud_packet(
        &self,
        chart_state: &mut HudChartState,
        display_values: Option<&[i32]>,
    ) -> Option<HudPacket> {
        Some(chart_state.apply_frame(self, display_values))
    }
}

impl SerialFrame for TactileAFrame {
    fn dts_ms(&self) -> u64 {
        match self {
            TactileAFrame::Req(_) => 0,
            TactileAFrame::Rep(rep) => rep.dts_ms,
        }
    }

    fn to_hud_packet(
        &self,
        chart_state: &mut HudChartState,
        display_values: Option<&[i32]>,
    ) -> Option<HudPacket> {
        match self {
            TactileAFrame::Req(_) => None,
            TactileAFrame::Rep(rep) => {
                let proxy = TestFrame {
                    header: rep.meta.header,
                    cmd: rep.meta.func_code,
                    length: rep.meta.except_data_len,
                    payload: rep.payload.clone(),
                    checksum: rep.meta.checksum,
                    dts_ms: rep.dts_ms,
                };

                Some(chart_state.apply_frame(&proxy, display_values))
            }
        }
    }
}

pub trait PollRequester<F>: Send {
    fn poll_interval(&self) -> Option<Duration> {
        None
    }

    fn should_request(&mut self) -> bool {
        true
    }

    fn next_request(&mut self) -> Result<Option<F>> {
        Ok(None)
    }

    fn on_rx_frame(&mut self, _frame: &F) {}
}

#[derive(Default)]
pub struct NoopPollRequester;

impl<F> PollRequester<F> for NoopPollRequester {}

pub struct TactileAPollRequester {
    period: Duration,
    cols: usize,
    rows: usize,
    awaiting_reply: bool,
    last_request_at: Option<Instant>,
    reply_timeout: Duration,
}

impl TactileAPollRequester {
    pub fn new(period: Duration, cols: usize, rows: usize, reply_timeout: Duration) -> Self {
        Self {
            period,
            cols,
            rows,
            awaiting_reply: false,
            last_request_at: None,
            reply_timeout,
        }
    }
}

impl PollRequester<TactileAFrame> for TactileAPollRequester {
    fn poll_interval(&self) -> Option<Duration> {
        Some(self.period)
    }

    fn should_request(&mut self) -> bool {
        if !self.awaiting_reply {
            return true;
        }
        let timed_out = self
            .last_request_at
            .map(|t| t.elapsed() >= self.reply_timeout)
            .unwrap_or(false);

        if timed_out {
            self.awaiting_reply = false;
            self.last_request_at = None;
            return true;
        }

        false
    }

    fn next_request(&mut self) -> Result<Option<TactileAFrame>> {
        let req = TactileACodec::build_req_frame(self.cols, self.rows)?;
        self.awaiting_reply = true;
        self.last_request_at = Some(Instant::now());
        Ok(Some(req))
    }

    fn on_rx_frame(&mut self, frame: &TactileAFrame) {
        if matches!(frame, TactileAFrame::Rep(_)) {
            self.awaiting_reply = false;
            self.last_request_at = None
        }
    }
}

pub async fn run_serial<C, H, T, F>(
    app: AppHandle,
    mut port: SerialStream,
    mut codec: C,
    mut handler: H,
    session_started_at: Instant,
    recording: Arc<Mutex<Recording<F>>>,
    cancel: CancellationToken,
) -> Result<()>
where
    F: SerialFrame,
    C: Codec<F> + Send + 'static,
    H: FrameHandler<F, T> + Send + 'static,
    T: Into<i32>
{
    run_serial_with_poll(
        app, port, codec, handler, session_started_at, recording, cancel, PollMode::Disable
    ).await
}

pub async fn run_serial_with_poll<C, H, T, F>(
    app: AppHandle,
    mut port: SerialStream,
    mut codec: C,
    mut handler: H,
    session_started_at: Instant,
    recording: Arc<Mutex<Recording<F>>>,
    cancel: CancellationToken,
    poll_mode: PollMode<F>
) -> Result<()>
where
    F: SerialFrame,
    C: Codec<F> + Send + 'static,
    H: FrameHandler<F, T> + Send + 'static,
    T: Into<i32>,
{
    let mut requester = match poll_mode {
        PollMode::Disable => None,
        PollMode::Enabled(r) => Some(r),
    };

    let mut poll_interval = requester
    .as_ref()
    .and_then(|r| r.poll_interval())
    .map(|d| {
        let mut it = time::interval(d);
        it.set_missed_tick_behavior(MissedTickBehavior::Skip);
        it
    });

    let mut chart_state = HudChartState::new();
    let mut buffer = [0u8; 1024];
    let mut prune_interval = time::interval(Duration::from_millis(450));
    prune_interval.set_missed_tick_behavior(MissedTickBehavior::Delay);

    
    loop {
        tokio::select! {
            _ = cancel.cancelled() => break,
            _ = async {
                match poll_interval.as_mut() {
                    Some(it) => {
                        it.tick().await;
                    }
                    None => pending::<()>().await,
                }
            } => {
                if let Some(r) = requester.as_mut() {
                    if r.should_request() {
                        if let Some(req) = r.next_request()? {
                            let bytes = codec.encode(&req)?;
                            port.write_all(&bytes).await?;
                        }
                    }
                }
            }
            _ = prune_interval.tick() => {
                if let Some(packet) = chart_state.prune_stale() {
                    app.emit("hud_stream", packet)?;
                }
            }
            read_result = port.read(&mut buffer) => {
                let n = read_result?;
                if n == 0 {
                    // Some serial drivers can resolve reads with 0 bytes repeatedly.
                    // Yield here so timer-driven poll requests are not starved by a busy loop.
                    tokio::task::yield_now().await;
                    continue;
                }

                let frames = codec.decode(&buffer[..n], session_started_at)?;
                for frame in frames {
                    if let Some(r) = requester.as_mut() {
                        r.on_rx_frame(&frame);
                    }

                    let decode_res = handler
                        .on_frame(&frame)
                        .await?
                        .map(|vals| vals.into_iter().map(Into::into).collect::<Vec<i32>>());

                    let mut record = recording.lock().map_err(|_| anyhow::anyhow!("recording state poisoned"))?;
                    record.push(RecordedFrame{
                        timing: FrameTiming { pts_ms: None, dts_ms: frame.dts_ms() },
                        frame: frame.clone(),
                    });

                    let display_values = if let Some(vals) = decode_res.as_ref() {
                        let summary = vals.iter().copied().sum::<i32>();
                        chart_state.record_summary(summary as f32);
                        chart_state.record_pressure_matrix(vals.as_slice());
                        Some(vec![summary])
                    } else {
                        None
                    };

                    if let Some(packet) = frame.to_hud_packet(&mut chart_state, display_values.as_deref()) {
                        app.emit("hud_stream", packet)?;
                    }
                }
            }
        }
    }
    Ok(())
}