// server/src/video.rs

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

static START: std::sync::OnceLock<gst::ClockTime> = std::sync::OnceLock::new();

pub async fn eye_ball(
    dev: &str,
    id: u32,
    _max_bitrate_kbit: u32,
) -> anyhow::Result<ReceiverStream<Result<VideoPacket, Status>>> {
    gst::init().context("gst init")?;

    let desc = format!(
        "v4l2src device={dev} io-mode=mmap ! \
         video/x-h264,stream-format=byte-stream,alignment=au ! \
         h264parse config-interval=1 ! \
         appsink name=sink emit-signals=true drop=true sync=false"
    );

    let pipeline = gst::parse::launch(&desc)?
        .downcast::<gst::Pipeline>()
        .expect("pipeline down‑cast");

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

    let (tx, rx) = tokio::sync::mpsc::channel(256);

    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)?;

                /* -------- 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!("eye{id}: delivered {n} frames");
                }

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

                // write first IDR to disk (quick sanity check)
                if n == 0 {
                    std::fs::write(format!("/tmp/eye{id}-idr.h264"), map.as_slice()).ok();
                }

                /* -------- detect SPS / IDR ---- */
                if enabled!(Level::DEBUG) {
                    if let Some(&nal) = map.as_slice().get(4) {
                        if (nal & 0x1F) == 0x05 /* IDR */ {
                            debug!("eye{id}: 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 pkt = VideoPacket {
                    id,
                    pts: pts_us,
                    data: map.as_slice().to_vec(),
                };
                let _ = tx.try_send(Ok(pkt));

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

    pipeline.set_state(gst::State::Playing)?;
    Ok(ReceiverStream::new(rx))
}