// client/src/output/audio.rs

use anyhow::{Context, Result};
use gstreamer as gst;
use gstreamer_app as gst_app;
use gst::prelude::*;
use gst::MessageView::*;
use tracing::{error, info, warn, debug};

use lesavka_common::lesavka::AudioPacket;

pub struct AudioOut {
    pipeline: gst::Pipeline,
    src: gst_app::AppSrc,
}

impl AudioOut {
    pub fn new() -> anyhow::Result<Self> {
        gst::init().context("initialising GStreamer")?;

        // ── 1. Decide which sink element to instantiate ────────────────────
        let sink = pick_sink_element()?;

        // Operator can request a tee to /tmp via LESAVKA_TAP_AUDIO=1
        let tee_dump = std::env::var("LESAVKA_TAP_AUDIO")
            .ok()
            .as_deref()
            .map(|v| v == "1")
            .unwrap_or(false);

        // ── 2. Assemble pipeline description string ────────────────────────
        let mut pipe = format!(
            "appsrc name=src is-live=true format=time do-timestamp=true \
            block=false ! \
            queue leaky=downstream ! \
            aacparse ! avdec_aac ! audioresample ! audioconvert ! {}",
            sink,
        );
        if tee_dump {
            pipe = format!(
                "appsrc name=src is-live=true format=time do-timestamp=true block=false ! \
                tee name=t ! \
                queue leaky=downstream ! aacparse ! avdec_aac ! audioresample ! audioconvert ! {} \
                t. ! queue ! filesink location=/tmp/lesavka-audio.aac",
                sink,
            );
            warn!("💾 tee to /tmp/lesavka-audio.aac enabled (LESAVKA_TAP_AUDIO=1)");
        }

        // ── 3. Create the pipeline & fetch the AppSrc ───────────────────────
        let pipeline: gst::Pipeline = gst::parse::launch(&pipe)?
            .downcast::<gst::Pipeline>()
            .expect("not a pipeline");

        let src: gst_app::AppSrc = pipeline
            .by_name("src")
            .expect("no src element")
            .downcast::<gst_app::AppSrc>()
            .expect("src not an AppSrc");
        
        src.set_caps(Some(&gst::Caps::builder("audio/mpeg")
            .field("mpegversion",   &4i32)         // AAC
            .field("stream-format", &"adts")       // ADTS frames
            .field("rate",          &48_000i32)    // 48 kHz
            .field("channels",      &2i32)         // stereo
            .build()
        ));
        src.set_format(gst::Format::Time);
        
        // ── 4. Log *all* warnings/errors from the bus ──────────────────────
        let bus = pipeline.bus().unwrap();
        std::thread::spawn(move || {
            for msg in bus.iter_timed(gst::ClockTime::NONE) {
                match msg.view() {
                    Error(e) => error!("💥 gst error from {:?}: {} ({})",
                                       msg.src().map(|s| s.path_string()),
                                       e.error(), e.debug().unwrap_or_default()),
                    Warning(w) => warn!("⚠️ gst warning from {:?}: {} ({})",
                                        msg.src().map(|s| s.path_string()),
                                        w.error(), w.debug().unwrap_or_default()),
                    Element(e) => debug!("🔎 gst element message: {}", e
                        .structure()
                        .map(|s| s.to_string())
                        .unwrap_or_default()),
                    StateChanged(s) if s.current() == gst::State::Playing => {
                        if msg
                            .src()
                            .map(|s| s.is::<gst::Pipeline>())
                            .unwrap_or(false)
                        {
                            info!("🔊 audio pipeline PLAYING (sink='{}')", sink);
                        } else {
                            debug!("🔊 element {} now PLAYING",
                                    msg.src().map(|s| s.name()).unwrap_or_default());
                        }
                    },
                    _ => {}
                }
            }
        });

        pipeline.set_state(gst::State::Playing).context("starting audio pipeline")?;

        Ok(Self { pipeline, src })
    }

    pub fn push(&self, pkt: AudioPacket) {
        let mut buf = gst::Buffer::from_slice(pkt.data);
        buf.get_mut()
            .unwrap()
            .set_pts(Some(gst::ClockTime::from_useconds(pkt.pts)));
        if let Err(e) = self.src.push_buffer(buf) {
            warn!("📉 AppSrc push failed: {e:?}");
        }
    }
}

impl Drop for AudioOut {
    fn drop(&mut self) {
        // put the whole pipeline back to NULL so GStreamer can dispose cleanly
        let _ = self.pipeline.set_state(gst::State::Null);
    }
}

/*──────────────── helper: sink selection ─────────────────────────────*/
fn pick_sink_element() -> Result<String> {
    // 1. Operator override
    if let Ok(s) = std::env::var("LESAVKA_AUDIO_SINK") {
        info!("💪 sink overridden via LESAVKA_AUDIO_SINK={}", s);
        return Ok(s);
    }

    // 2. Query PipeWire for default & running sinks
    let sinks = list_pw_sinks();                 // Vec<(name,state)>
    for (n, st) in &sinks {
        if *st == "RUNNING" {
            info!("🔈 using default RUNNING sink '{}'", n);
            return Ok(format!("pulsesink device={}", n));
        }
    }

    // 3. First RUNNING sink
    if let Some((n, _)) = sinks.iter().find(|(_, st)| *st == "RUNNING") {
        warn!("🏃 picking first RUNNING sink '{}'", n);
        return Ok(format!("pulsesink device={}", n));
    }

    // 4. Anything
    if let Some((n, _)) = sinks.first() {
        warn!("🎲 picking first sink '{}'", n);
        return Ok(format!("pulsesink device={}", n));
    }

    // Fallback - let autoaudiosink try its luck
    warn!("🫣 no PipeWire sinks readable - falling back to autoaudiosink");
    Ok("autoaudiosink".to_string())
}

fn list_pw_sinks() -> Vec<(String, String)> {
    let mut out = Vec::new();
    if out.is_empty() {
        // ── PulseAudio / pactl fallback ────────────────────────────────
        if let Ok(info) = std::process::Command::new("pactl")
            .args(["info"])
            .output()
            .map(|o| String::from_utf8_lossy(&o.stdout).to_string())
        {
            if let Some(line) = info.lines().find(|l| l.starts_with("Default Sink:")) {
                let def = line["Default Sink:".len()..].trim();
                return vec![(def.to_string(), "UNKNOWN".to_string())];
            }
        }
    }

    out
}