//! AZ-657 integration tests — RTSP session lifecycle, bounded
//! reconnect, AI-lock plumb.
//!
//! Uses a [`FakeRtspTransport`] (not a real RTSP server) to keep tests
//! deterministic and free of external fixtures. The session lifecycle
//! FSM in `FrameIngest::run` is the production deliverable; the real
//! retina-backed transport that talks to the camera lands in AZ-658
//! alongside the H.264 decoder.

use std::sync::atomic::{AtomicU32, Ordering};
use std::sync::Arc;
use std::time::Duration;

use async_trait::async_trait;
use bytes::Bytes;
use tokio::sync::mpsc;
use tokio::time::{timeout, Instant};

use frame_ingest::{
    BackoffPolicy, DecodeError, DecodedPixels, DecoderBackend, FrameDecoder, FrameIngest,
    OpenError, RtspPacket, RtspSessionConfig, RtspTransport, SessionState, StreamError,
};
use shared::models::frame::PixelFormat;

/// Test-only decoder that pushes one synthetic `DecodedPixels` per
/// call. Used by the AZ-657 lifecycle tests, which verify FSM /
/// reconnect / AI-lock semantics — they don't care what pixels the
/// decoder produced. The production decoder path is exercised
/// separately by `decoder_pipeline.rs` (AZ-658).
struct StubDecoder;

impl FrameDecoder for StubDecoder {
    fn backend(&self) -> DecoderBackend {
        DecoderBackend::Software
    }

    fn decode(&mut self, payload: &[u8], out: &mut Vec<DecodedPixels>) -> Result<(), DecodeError> {
        out.push(DecodedPixels {
            pixels: Bytes::copy_from_slice(payload),
            width: 320,
            height: 240,
            pix_fmt: PixelFormat::Nv12,
            decode_duration: Duration::from_micros(100),
        });
        Ok(())
    }
}

#[derive(Debug, Clone)]
enum Scripted {
    OpenOk,
    OpenFail(OpenErrKind),
    OpenHardFail,
    PacketOk,
    StreamDropped,
}

#[derive(Debug, Clone, Copy)]
enum OpenErrKind {
    Timeout,
    Network,
}

impl OpenErrKind {
    fn into_err(self) -> OpenError {
        match self {
            OpenErrKind::Timeout => OpenError::Timeout,
            OpenErrKind::Network => OpenError::Network("connection refused".to_string()),
        }
    }
}

/// Test-driven RTSP transport. The lifecycle loop pulls events from
/// an mpsc channel that the test pushes into. When the channel is
/// empty the transport parks (mirroring a healthy idle RTSP open
/// that blocks until the next packet arrives). The test ends the
/// session via `FrameIngestHandle::shutdown`, which the lifecycle
/// loop observes through `tokio::select!`.
struct FakeRtspTransport {
    rx: Arc<tokio::sync::Mutex<mpsc::UnboundedReceiver<Scripted>>>,
    opens: Arc<AtomicU32>,
    packets_sent: Arc<AtomicU32>,
}

/// Controller side of the fake transport. The test pushes events,
/// the lifecycle loop consumes them.
struct ScriptCtl {
    tx: mpsc::UnboundedSender<Scripted>,
}

impl ScriptCtl {
    fn push(&self, ev: Scripted) {
        self.tx.send(ev).expect("script controller channel closed");
    }
}

impl FakeRtspTransport {
    fn new() -> (Self, ScriptCtl, Arc<AtomicU32>, Arc<AtomicU32>) {
        let (tx, rx) = mpsc::unbounded_channel();
        let opens = Arc::new(AtomicU32::new(0));
        let packets_sent = Arc::new(AtomicU32::new(0));
        (
            Self {
                rx: Arc::new(tokio::sync::Mutex::new(rx)),
                opens: Arc::clone(&opens),
                packets_sent: Arc::clone(&packets_sent),
            },
            ScriptCtl { tx },
            opens,
            packets_sent,
        )
    }

    fn from_script(script: Vec<Scripted>) -> (Self, ScriptCtl, Arc<AtomicU32>, Arc<AtomicU32>) {
        let (t, ctl, o, p) = Self::new();
        for ev in script {
            ctl.push(ev);
        }
        (t, ctl, o, p)
    }

    async fn next_event(&self) -> Scripted {
        let mut rx = self.rx.lock().await;
        match rx.recv().await {
            Some(ev) => ev,
            // Sender dropped → park forever; the lifecycle observes
            // shutdown via select! and exits cleanly.
            None => std::future::pending().await,
        }
    }
}

#[async_trait]
impl RtspTransport for FakeRtspTransport {
    async fn open(&mut self, _config: &RtspSessionConfig) -> Result<(), OpenError> {
        self.opens.fetch_add(1, Ordering::Relaxed);
        match self.next_event().await {
            Scripted::OpenOk => Ok(()),
            Scripted::OpenFail(kind) => Err(kind.into_err()),
            Scripted::OpenHardFail => Err(OpenError::UnsupportedProfile {
                details: "H265 main10 not supported".to_string(),
            }),
            other => Err(OpenError::Network(format!(
                "fake transport: open called when script expected {other:?}"
            ))),
        }
    }

    async fn close(&mut self) {}

    async fn next_packet(&mut self) -> Result<RtspPacket, StreamError> {
        match self.next_event().await {
            Scripted::PacketOk => {
                self.packets_sent.fetch_add(1, Ordering::Relaxed);
                Ok(RtspPacket {
                    timestamp_rtp: 0,
                    payload: Bytes::from_static(b"nal-unit"),
                })
            }
            Scripted::StreamDropped => Err(StreamError::Dropped("scripted drop".to_string())),
            // Out-of-band events while streaming surface as a drop
            // so the FSM re-enters the reconnect ladder.
            other => Err(StreamError::Dropped(format!(
                "script expected non-packet: {other:?}"
            ))),
        }
    }
}

fn fast_backoff() -> BackoffPolicy {
    BackoffPolicy::new(Duration::from_millis(10), Duration::from_millis(40))
}

/// AC-1 — happy path: a single `OpenOk` followed by a packet must
/// bring the FSM to `Streaming` and emit a frame on the broadcast.
#[tokio::test]
async fn ac1_open_succeeds_and_session_reaches_streaming() {
    // Arrange
    let (transport, _ctl, opens, packets) =
        FakeRtspTransport::from_script(vec![Scripted::OpenOk, Scripted::PacketOk]);
    let ingest = FrameIngest::with_backoff(8, fast_backoff());
    let handle = ingest.handle();
    let mut frames = handle.subscribe();

    // Act
    let task = ingest.run(
        transport,
        StubDecoder,
        RtspSessionConfig::new("rtsp://fake/0"),
    );
    let first = timeout(Duration::from_secs(1), frames.recv())
        .await
        .expect("frame within 1 s")
        .expect("broadcast send succeeded");

    // Assert — receiving the frame proves Closed → Connecting →
    // Streaming was traversed; the FakeTransport parks after the
    // packet so the FSM stays in Streaming.
    assert!(!first.ai_locked, "ai_lock should default to false");
    assert_eq!(handle.session_state(), SessionState::Streaming);
    assert_eq!(opens.load(Ordering::Relaxed), 1);
    assert_eq!(packets.load(Ordering::Relaxed), 1);

    handle.shutdown();
    let _ = timeout(Duration::from_secs(1), task)
        .await
        .expect("lifecycle exits on shutdown");
}

/// AC-2 — bounded reconnect: an initial failure followed by a success
/// must increment `reopens_total` and converge to `Streaming`. The
/// backoff sleeps used (initial 10 ms, doubling) must be observed via
/// elapsed wall time.
#[tokio::test]
async fn ac2_bounded_reconnect_recovers_after_transient_failure() {
    // Arrange
    let (transport, _ctl, opens, _packets) = FakeRtspTransport::from_script(vec![
        Scripted::OpenFail(OpenErrKind::Network),
        Scripted::OpenFail(OpenErrKind::Timeout),
        Scripted::OpenOk,
        Scripted::PacketOk,
    ]);
    let ingest = FrameIngest::with_backoff(8, fast_backoff());
    let handle = ingest.handle();
    let mut frames = handle.subscribe();
    let started = Instant::now();

    // Act
    let task = ingest.run(
        transport,
        StubDecoder,
        RtspSessionConfig::new("rtsp://fake/0"),
    );
    let _ = timeout(Duration::from_secs(2), frames.recv())
        .await
        .expect("frame within 2 s")
        .expect("broadcast send succeeded");
    let elapsed = started.elapsed();

    // Assert
    assert!(
        elapsed >= Duration::from_millis(30),
        "must observe two backoff sleeps (10 ms + 20 ms = 30 ms), got {elapsed:?}"
    );
    assert_eq!(handle.session_state(), SessionState::Streaming);
    assert_eq!(opens.load(Ordering::Relaxed), 3);

    handle.shutdown();
    let _ = timeout(Duration::from_secs(1), task).await;
}

/// AC-2.b — stream drop after streaming starts must re-enter
/// `Failing` and reopen.
#[tokio::test]
async fn ac2b_stream_drop_increments_reopens_total() {
    // Arrange
    let (transport, _ctl, opens, _packets) = FakeRtspTransport::from_script(vec![
        Scripted::OpenOk,
        Scripted::PacketOk,
        Scripted::StreamDropped,
        Scripted::OpenOk,
        Scripted::PacketOk,
    ]);
    let ingest = FrameIngest::with_backoff(8, fast_backoff());
    let handle = ingest.handle();
    let mut frames = handle.subscribe();

    // Act
    let task = ingest.run(
        transport,
        StubDecoder,
        RtspSessionConfig::new("rtsp://fake/0"),
    );
    let _ = timeout(Duration::from_secs(1), frames.recv())
        .await
        .expect("first frame")
        .expect("first frame ok");
    let _ = timeout(Duration::from_secs(1), frames.recv())
        .await
        .expect("second frame")
        .expect("second frame ok");

    // Assert
    assert!(
        handle.reopens_total() >= 1,
        "stream drop must record at least one reopen, got {}",
        handle.reopens_total()
    );
    assert_eq!(opens.load(Ordering::Relaxed), 2);
    assert_eq!(handle.session_state(), SessionState::Streaming);

    handle.shutdown();
    let _ = timeout(Duration::from_secs(1), task).await;
}

/// AC-3 — SPS/PPS mismatch must hard-fail the session. The loop
/// exits and does NOT retry, leaving the FSM in `Failing` with no
/// further opens.
#[tokio::test]
async fn ac3_unsupported_profile_hard_fails_session() {
    // Arrange
    let (transport, _ctl, opens, _packets) =
        FakeRtspTransport::from_script(vec![Scripted::OpenHardFail]);
    let ingest = FrameIngest::with_backoff(8, fast_backoff());
    let handle = ingest.handle();

    // Act
    let task = ingest.run(
        transport,
        StubDecoder,
        RtspSessionConfig::new("rtsp://fake/0"),
    );
    let _ = timeout(Duration::from_secs(1), task)
        .await
        .expect("lifecycle loop exits on hard-fail");

    // Assert
    assert!(matches!(
        handle.session_state(),
        SessionState::Failing { .. }
    ));
    assert_eq!(opens.load(Ordering::Relaxed), 1, "no automatic retry");
}

/// AC-4 — AI-lock toggle: every frame emitted AFTER `set_ai_lock(true)`
/// must carry `ai_locked = true`. The test controls packet emission
/// timing via `ScriptCtl` so the toggle is guaranteed to precede the
/// second packet.
#[tokio::test]
async fn ac4_ai_lock_toggle_propagates_to_frames() {
    // Arrange
    let (transport, ctl, _opens, _packets) =
        FakeRtspTransport::from_script(vec![Scripted::OpenOk, Scripted::PacketOk]);
    let ingest = FrameIngest::with_backoff(8, fast_backoff());
    let handle = ingest.handle();
    let mut frames = handle.subscribe();

    // Act
    let task = ingest.run(
        transport,
        StubDecoder,
        RtspSessionConfig::new("rtsp://fake/0"),
    );
    let f1 = timeout(Duration::from_secs(1), frames.recv())
        .await
        .expect("first frame")
        .expect("first frame ok");
    handle.set_ai_lock(true);
    ctl.push(Scripted::PacketOk);
    let f2 = timeout(Duration::from_secs(1), frames.recv())
        .await
        .expect("second frame")
        .expect("second frame ok");

    // Assert
    assert!(!f1.ai_locked, "pre-toggle frame must be unlocked");
    assert!(
        f2.ai_locked,
        "post-toggle frame must carry ai_locked = true"
    );
    assert!(handle.ai_locked());

    handle.shutdown();
    let _ = timeout(Duration::from_secs(1), task).await;
}