use anyhow::Context;
use futures_util::Stream;
use gstreamer as gst;
use gstreamer_app as gst_app;
use lesavka_common::lesavka::AudioPacket;
use tokio_stream::wrappers::ReceiverStream;
use tonic::Status;
use tracing::{debug, trace};
use gst::prelude::*;

const EAR_ID: [&str; 2] = ["l", "r"];
const PIPE: &str = "appsrc name=audsrc is-live=true do-timestamp=true ! aacparse ! queue ! appsink name=asink emit-signals=true";

pub struct AudioStream {
    _pipe: gst::Pipeline,
    inner: ReceiverStream<Result<AudioPacket, Status>>,
}

impl Stream for AudioStream {
    type Item = Result<AudioPacket, 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)
    }
}

pub async fn eye_ear(
    dev: &str,
    id:  u32,
) -> anyhow::Result<AudioStream> {
    let ear = EAR_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.audio_0 ! queue ! \
         aacparse ! queue ! \
         appsink name=asink emit-signals=true max-buffers=64 drop=true"
    );
    let pipe: gst::Pipeline = gst::parse::launch(&desc)?
        .downcast()
        .expect("pipeline");

    let sink = pipe.by_name("asink").expect("asink").downcast::<gst_app::AppSink>().unwrap();
    let (tx, rx) = tokio::sync::mpsc::channel(8192);

    sink.set_callbacks(
        gst_app::AppSinkCallbacks::builder()
            .new_sample(move |s| {
                let samp = s.pull_sample().map_err(|_| gst::FlowError::Eos)?;
                let buf  = samp.buffer().ok_or(gst::FlowError::Error)?;
                let map  = buf.map_readable().map_err(|_| gst::FlowError::Error)?;
                let pts  = buf.pts().unwrap_or(gst::ClockTime::ZERO).nseconds()/1_000;
                let pkt  = AudioPacket { id, pts, data: map.as_slice().to_vec() };
                debug!(target:"lesavka_server::audio",
                       eye = id, bytes = pkt.data.len(), pts = pkt.pts,
                       "⬆️  pushed audio sample ear-{ear}");
                let _ = tx.try_send(Ok(pkt));
                Ok(gst::FlowSuccess::Ok)
            }).build()
    );

    pipe.set_state(gst::State::Playing)?;
    Ok(AudioStream{ _pipe: pipe, inner: ReceiverStream::new(rx) })
}