use gstreamer as gst;
use gstreamer_app as gst_app;
use gst::prelude::*;
use lesavka_common::lesavka::VideoPacket;
use winit::{
    event_loop::EventLoop,
    window::{Window, WindowAttributes},
};

const DESC: &str = concat!(
    "appsrc name=src is-live=true format=time do-timestamp=true block=false ! ",
    "queue max-size-buffers=0 max-size-bytes=0 max-size-time=0 leaky=downstream ! ",
    "capsfilter caps=video/x-h264,stream-format=byte-stream,alignment=au ! ",
    "h264parse disable-passthrough=true ! decodebin ! ",
    "queue ! videoconvert ! autovideosink sync=false"
);

pub struct MonitorWindow {
    id:     u32,
    _window: Window,
    src:    gst_app::AppSrc,
}

impl MonitorWindow {
    pub fn new(id: u32, el: &EventLoop<()>) -> anyhow::Result<Self> {
        gst::init()?;                                        // idempotent

        /* ---------- Wayland / X11 window ------------- */
        let window = el
            .create_window(
                WindowAttributes::default()
                    .with_title(format!("Lesavka‑monitor‑{id}"))
                    .with_decorations(true),
            )?;

        /* ---------- GStreamer pipeline --------------- */
        let caps = gst::Caps::builder("video/x-h264")
            .field("stream-format", &"byte-stream")
            .field("alignment", &"au")
            .build();

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

        let src = pipeline
            .by_name("src")
            .expect("appsrc element not found")
            .downcast::<gst_app::AppSrc>()
            .expect("appsrc down‑cast");

        src.set_caps(Some(&caps));
        src.set_format(gst::Format::Time);        // downstream clock
        src.set_property("blocksize", &0u32);     // one AU per buffer
        // NOTE: set_property() and friends return (), so no `?`
        src.set_property("do-timestamp", &true);

        src.set_latency(gst::ClockTime::NONE, gst::ClockTime::NONE);
        pipeline.set_state(gst::State::Playing)?;

        Ok(Self { id, _window: window, src })
    }

    /// Feed one H.264 access‑unit into the pipeline.
    pub fn push_packet(&self, pkt: VideoPacket) {
        // Mutable so we can set the PTS:
        let mut buf = gst::Buffer::from_slice(pkt.data);
        if let Some(ref mut b) = buf.get_mut() {
            b.set_pts(Some(gst::ClockTime::from_useconds(pkt.pts)));
        }
        let _ = self.src.push_buffer(buf); // ignore Eos / flushing
    }
}