// server/src/video.rs

use anyhow::Context;
use gstreamer as gst;
use gstreamer_app as gst_app;
use gst::prelude::*;
use gst::{log, MessageView};
use lesavka_common::lesavka::VideoPacket;
use tokio_stream::wrappers::ReceiverStream;
use tonic::Status;
use tracing::{debug, warn, error, info, enabled, trace, Level};
use futures_util::Stream;

const EYE_ID: [&str; 2] = ["l", "r"];
static START: std::sync::OnceLock<gst::ClockTime> = std::sync::OnceLock::new();

pub struct VideoStream {
    _pipeline: gst::Pipeline,
    inner: ReceiverStream<Result<VideoPacket, Status>>,
}

impl Stream for VideoStream {
    type Item = Result<VideoPacket, Status>;
    fn poll_next(
        mut self: std::pin::Pin<&mut Self>,
        cx: &mut std::task::Context<'_>,
    ) -> std::task::Poll<Option<Self::Item>> {
        Stream::poll_next(std::pin::Pin::new(&mut self.inner), cx)
    }
}

impl Drop for VideoStream {
    fn drop(&mut self) {
        // shut down nicely – avoids the “dispose element … READY/PLAYING …” spam
        let _ = self._pipeline.set_state(gst::State::Null);
    }
}

pub async fn eye_ball(
    dev: &str,
    id: u32,
    _max_bitrate_kbit: u32,
) -> anyhow::Result<VideoStream> {
    let eye = EYE_ID[id as usize];
    gst::init().context("gst init")?;

    let desc = format!(
        "v4l2src device=\"{dev}\" io-mode=mmap do-timestamp=true ! queue ! \
         tsdemux name=d  d.video_0 ! queue ! \
         h264parse disable-passthrough=true config-interval=-1 ! \
         video/x-h264,stream-format=byte-stream,alignment=au ! \
         appsink name=sink emit-signals=true max-buffers=32 drop=true"
    );
    // let desc = format!(
    //     "v4l2src device={dev} io-mode=mmap ! \
    //     queue max-size-buffers=0 max-size-bytes=0 max-size-time=0 ! tsdemux name=d ! \
    //     video/x-h264,stream-format=byte-stream,alignment=au,profile=high ! tsdemux name=d ! \
    //     d. ! h264parse    config-interval=1 ! queue ! appsink name=vsink  emit-signals=true \
    //     d. ! aacparse ! queue ! h264parse config-interval=1 ! appsink name=sink \
    //     emit-signals=true drop=false sync=false"
    // );

    let pipeline = gst::parse::launch(&desc)?
        .downcast::<gst::Pipeline>()
        .expect("not a pipeline");

    // let pipeline: gst::Pipeline = gst::parse_launch(&desc)?
    //     .downcast()
    //     .expect("not a pipeline");

    let sink = pipeline
        .by_name("sink")
        .expect("appsink")
        .dynamic_cast::<gst_app::AppSink>()
        .expect("appsink down-cast");

    let (tx, rx) = tokio::sync::mpsc::channel(8192);

    /* ----- BUS WATCH: show errors & warnings immediately --------------- */
    let bus = pipeline.bus().expect("bus");
    let eye_clone = eye.to_owned();
    std::thread::spawn(move || {
        for msg in bus.iter_timed(gst::ClockTime::NONE) {
            use gst::MessageView::*;
            match msg.view() {
                Error(err) => {
                    tracing::error!(target:"lesavka_server::video",
                                    eye = %eye_clone,
                                    "💥 pipeline error: {} ({})",
                                    err.error(), err.debug().unwrap_or_default());
                }
                Warning(w) => {
                    tracing::warn!(target:"lesavka_server::video",
                                   eye = %eye_clone,
                                   "⚠️  pipeline warning: {} ({})",
                                   w.error(), w.debug().unwrap_or_default());
                }
                Info(i) => {
                    tracing::info!(target:"lesavka_server::video",
                                   eye = %eye_clone,
                                   "📌  pipeline info: {} ({})",
                                   i.error(), i.debug().unwrap_or_default());
                }
                StateChanged(s) if s.current() == gst::State::Playing => {
                    tracing::info!(target:"lesavka_server::video",
                                   eye = %eye_clone,
                                   "🎬 pipeline PLAYING");
                }
                _ => {}
            }
        }
    });

    sink.set_callbacks(
        gst_app::AppSinkCallbacks::builder()
            .new_sample(move |sink| {
                /* -------- pull frame ---------- */
                let sample = sink.pull_sample().map_err(|_| gst::FlowError::Eos)?;
                let buffer = sample.buffer().ok_or(gst::FlowError::Error)?;

                /* -------- map once, reuse ----- */
                let map = buffer.map_readable().map_err(|_| gst::FlowError::Error)?;

                /* -------- basic counters ------ */
                static FRAME: std::sync::atomic::AtomicU64 =
                    std::sync::atomic::AtomicU64::new(0);
                let n = FRAME.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
                if n % 120 == 0 {
                    trace!(target: "lesavka_server::video", "eye-{eye}: delivered {n} frames");
                    if enabled!(Level::TRACE) {
                        let path = format!("/tmp/eye-{eye}-srv-{:05}.h264", n);
                        std::fs::write(&path, map.as_slice()).ok();
                    }
                } else if n < 10 {
                    debug!(target: "lesavka_server::video",
                           eye = eye, frame = n, bytes = map.len(),
                           pts = ?buffer.pts(), "⬆️  pushed video sample eye-{eye}");
                }

                /* -------- detect SPS / IDR ---- */
                if enabled!(Level::DEBUG) {
                    if let Some(&nal) = map.as_slice().get(4) {
                        if (nal & 0x1F) == 0x05 /* IDR */ {
                            debug!("eye-{eye}: IDR");
                        }
                    }
                }

                /* -------- timestamps ---------- */
                let origin = *START.get_or_init(|| buffer.pts().unwrap_or(gst::ClockTime::ZERO));
                let pts_us = buffer
                    .pts()
                    .unwrap_or(gst::ClockTime::ZERO)
                    .saturating_sub(origin)
                    .nseconds()
                    / 1_000;

                /* -------- ship over gRPC ----- */
                let data = map.as_slice().to_vec();
                let size = data.len();
                let pkt = VideoPacket { id, pts: pts_us, data };
                match tx.try_send(Ok(pkt)) {
                    Ok(_) => {
                        trace!(target:"lesavka_server::video",
                               eye = %eye,
                               size = size,
                               "📤 sent");
                    }
                    Err(tokio::sync::mpsc::error::TrySendError::Full(_)) => {
                        static DROP_CNT: std::sync::atomic::AtomicU64 =
                            std::sync::atomic::AtomicU64::new(0);
                        let c = DROP_CNT.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
                        if c % 120 == 0 {
                            debug!(target:"lesavka_server::video",
                                   eye = %eye,
                                   dropped = c,
                                   "⏳ channel full – dropping frames");
                        }
                    }
                    Err(e) => error!("mpsc send err: {e}"),
                }

                Ok(gst::FlowSuccess::Ok)
            })
            .build(),
    );

    pipeline.set_state(gst::State::Playing).context("🎥 starting video pipeline eye-{eye}")?;
    let bus = pipeline.bus().unwrap();
    loop {
        match bus.timed_pop(gst::ClockTime::NONE) {
            Some(msg) if matches!(msg.view(), MessageView::StateChanged(s)
                        if s.current() == gst::State::Playing) => break,
            Some(_) => continue,
            None => continue,
        }
    }
    Ok(VideoStream { _pipeline: pipeline, inner: ReceiverStream::new(rx) })
}