pipecrab-runtime 0.6.0

//! Run-loop behavior: interrupt barge-in, sys-preempts-data, pass-through.
//!
//! All deterministic and tokio-free, driven by `futures::executor::block_on`.
//! Frames go in through the pipeline's `input` ([`Outbound`]) and come out
//! through its `output` ([`Inbound`]) — the same abstraction every stage uses.
//!
//! The interrupt test parks `perform` on a `oneshot` the test never fires, so
//! the only way the driver can terminate is by abandoning that `perform` — the
//! test hanging would itself be the failure signal; the assertions confirm the
//! mechanism (the receiver was dropped, and `decide_system(Interrupt)` ran).

use std::sync::Arc;
use std::sync::Mutex;
use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};

use async_trait::async_trait;
use futures::channel::{mpsc, oneshot};
use futures::executor::block_on;
use futures::future::join;
use futures::sink::SinkExt;
use futures::stream::StreamExt;
use pipecrab_core::{
    AudioChunk, AudioFormat, DataFrame, Decision, Direction, Processor, SystemFrame, Transcript,
};
use pipecrab_runtime::{Outbound, PipelineBuilder, Received, Stage, StageError};

// --- Test 1: an Interrupt abandons an in-flight perform and runs decide_system.

/// `perform` signals that it started, then parks forever on a `oneshot` the
/// test never fires. `decide_system(Interrupt)` flips the shared flag.
struct BlockingStage {
    block_rx: Mutex<Option<oneshot::Receiver<()>>>,
    started: mpsc::Sender<()>,
    interrupted: Arc<AtomicBool>,
}

impl Processor for BlockingStage {
    type Effect = ();
    fn decide_data(&mut self, _frame: &DataFrame) -> Decision<()> {
        Decision::drop().emit(()) // drop the input; emit one effect to perform
    }
    fn decide_system(&mut self, _dir: Direction, frame: &SystemFrame) -> Decision<()> {
        if matches!(frame, SystemFrame::Interrupt) {
            self.interrupted.store(true, Ordering::SeqCst);
        }
        Decision::drop()
    }
}

#[cfg_attr(target_arch = "wasm32", async_trait(?Send))]
#[cfg_attr(not(target_arch = "wasm32"), async_trait)]
impl Stage for BlockingStage {
    async fn perform(&self, _effect: (), _out: &Outbound) -> Result<(), StageError> {
        let _ = self.started.clone().send(()).await;
        let rx = self
            .block_rx
            .lock()
            .unwrap()
            .take()
            .expect("perform runs once");
        let _ = rx.await; // never fires; the receiver drops when perform is abandoned
        Ok(())
    }
}

#[test]
fn interrupt_abandons_perform_and_runs_decide_system() {
    block_on(async {
        let interrupted = Arc::new(AtomicBool::new(false));
        let (started_tx, mut started_rx) = mpsc::channel::<()>(1);
        let (block_tx, block_rx) = oneshot::channel::<()>();

        let stage = BlockingStage {
            block_rx: Mutex::new(Some(block_rx)),
            started: started_tx,
            interrupted: interrupted.clone(),
        };
        let (ends, driver) = PipelineBuilder::new().stage(stage).build().start();
        let input = ends.input; // Outbound: send into the pipeline head
        let _output = ends.output; // keep the tail's output channel open

        let feeder = async move {
            input
                .send_data(Transcript::user_final("go").into())
                .await
                .unwrap();
            started_rx.next().await.expect("perform must start");
            input
                .send_system(Direction::Down, SystemFrame::Interrupt)
                .await
                .unwrap();
            // Returning drops `input` -> head inbound closes -> the driver exits.
        };

        join(feeder, driver).await;

        assert!(
            interrupted.load(Ordering::SeqCst),
            "decide_system(Interrupt) must have run"
        );
        assert!(
            block_tx.is_canceled(),
            "the in-flight perform must have been dropped (its receiver gone)",
        );
    });
}

// --- Test 2: a system frame preempts a backed-up data lane.

/// Counts data frames in `decide_data`; on a `Start` frame, records how many had
/// been processed at that moment.
struct CountingStage {
    data_count: Arc<AtomicUsize>,
    data_at_preempt: Arc<Mutex<Option<usize>>>,
}

impl Processor for CountingStage {
    type Effect = ();
    fn decide_data(&mut self, _frame: &DataFrame) -> Decision<()> {
        self.data_count.fetch_add(1, Ordering::SeqCst);
        Decision::drop() // no effect -> perform is never called
    }
    fn decide_system(&mut self, _dir: Direction, frame: &SystemFrame) -> Decision<()> {
        // Record on `Start`, a frame that preempts but does *not* flush — this
        // isolates lane preemption from the interrupt data-flush (tested below).
        if matches!(frame, SystemFrame::Start) {
            *self.data_at_preempt.lock().unwrap() = Some(self.data_count.load(Ordering::SeqCst));
        }
        Decision::drop()
    }
}

#[cfg_attr(target_arch = "wasm32", async_trait(?Send))]
#[cfg_attr(not(target_arch = "wasm32"), async_trait)]
impl Stage for CountingStage {
    async fn perform(&self, _effect: (), _out: &Outbound) -> Result<(), StageError> {
        Ok(())
    }
}

#[test]
fn sys_preempts_backed_up_data() {
    block_on(async {
        let data_count = Arc::new(AtomicUsize::new(0));
        let data_at_preempt = Arc::new(Mutex::new(None));
        let stage = CountingStage {
            data_count: data_count.clone(),
            data_at_preempt: data_at_preempt.clone(),
        };
        let (ends, driver) = PipelineBuilder::new().stage(stage).build().start();
        let input = ends.input;
        let _output = ends.output;

        // Back up the data lane, then enqueue a (non-flushing) Start behind it.
        for i in 0..8 {
            input
                .send_data(Transcript::user_final(i.to_string()).into())
                .await
                .unwrap();
        }
        input
            .send_system(Direction::Down, SystemFrame::Start)
            .await
            .unwrap();
        drop(input);

        driver.await;

        assert_eq!(
            data_at_preempt.lock().unwrap().clone(),
            Some(0),
            "the Start frame must jump the 8-frame data backlog",
        );
        assert_eq!(
            data_count.load(Ordering::SeqCst),
            8,
            "all backed-up data is still processed afterward"
        );
    });
}

// --- Test 3: an un-overridden stage is a transparent pass-through.

/// Every `Processor`/`Stage` method left at its default.
struct PassThrough;

impl Processor for PassThrough {
    type Effect = ();
}

#[cfg_attr(target_arch = "wasm32", async_trait(?Send))]
#[cfg_attr(not(target_arch = "wasm32"), async_trait)]
impl Stage for PassThrough {
    async fn perform(&self, _effect: (), _out: &Outbound) -> Result<(), StageError> {
        Ok(())
    }
}

#[test]
fn pass_through_forwards_data() {
    block_on(async {
        let (ends, driver) = PipelineBuilder::new().stage(PassThrough).build().start();
        let input = ends.input;
        let mut output = ends.output;

        let feeder = async move {
            input
                .send_data(Transcript::user_final("hi").into())
                .await
                .unwrap();
            // Dropping `input` at block end closes the head -> shutdown.
        };

        join(feeder, driver).await;

        match output.recv().await {
            Some(Received::Data(DataFrame::Transcript(s))) => assert_eq!(&*s.text, "hi"),
            other => panic!("expected forwarded Transcript(hi), got {other:?}"),
        }
    });
}

// --- Test 4: an Interrupt flushes the data backlog, keeping transport-audio.

fn input_audio(id: u8) -> DataFrame {
    DataFrame::InputAudio {
        bytes: Arc::from(&[id][..]),
        sample_rate: 16_000,
        num_channels: 1,
    }
}

#[test]
fn interrupt_flushes_data_keeping_survivors_in_order() {
    block_on(async {
        // PassThrough forwards everything, so without the flush all four data
        // frames would reach `output`; with it, only the two InputAudio survive.
        let (ends, driver) = PipelineBuilder::new().stage(PassThrough).build().start();
        let input = ends.input;
        let mut output = ends.output;

        // Back up the data lane with survivors interleaved with droppable frames,
        // then an Interrupt behind it — sys-biased recv handles it first, while
        // the whole backlog is still queued.
        input.send_data(input_audio(1)).await.unwrap();
        input
            .send_data(Transcript::user_final("drop me").into())
            .await
            .unwrap();
        input.send_data(input_audio(2)).await.unwrap();
        let audio = AudioChunk::new(Arc::from(&[0.0f32, 0.0][..]), AudioFormat::new(48_000, 1));
        input.send_data(DataFrame::Audio(audio)).await.unwrap();
        input
            .send_system(Direction::Down, SystemFrame::Interrupt)
            .await
            .unwrap();
        drop(input);

        driver.await;

        // Drain the data lane: only the two InputAudio frames, in arrival order.
        let mut ids = Vec::new();
        while let Ok(frame) = output.data.try_recv() {
            match frame {
                DataFrame::InputAudio { bytes, .. } => ids.push(bytes[0]),
                other => panic!("a non-survivor leaked past the flush: {other:?}"),
            }
        }
        assert_eq!(
            ids,
            vec![1, 2],
            "survivors kept in order; droppable frames flushed"
        );
    });
}

// --- Test 5: a pipeline is a stage, so pipelines nest.

#[test]
fn nested_pipeline_forwards_through_both_levels() {
    block_on(async {
        // Inner pipeline is a single pass-through; nest it inside an outer one
        // that also has a pass-through. A frame must traverse both levels.
        let inner = PipelineBuilder::new().stage(PassThrough).build();
        let (ends, driver) = PipelineBuilder::new()
            .stage(inner)
            .stage(PassThrough)
            .build()
            .start();
        let input = ends.input;
        let mut output = ends.output;

        let feeder = async move {
            input
                .send_data(Transcript::user_final("deep").into())
                .await
                .unwrap();
        };

        join(feeder, driver).await;

        match output.recv().await {
            Some(Received::Data(DataFrame::Transcript(s))) => assert_eq!(&*s.text, "deep"),
            other => panic!("expected forwarded Transcript(deep), got {other:?}"),
        }
    });
}

struct DistinctEffect;

struct DistinctEffectStage;

impl Processor for DistinctEffectStage {
    type Effect = DistinctEffect;
}

#[cfg_attr(target_arch = "wasm32", async_trait(?Send))]
#[cfg_attr(not(target_arch = "wasm32"), async_trait)]
impl Stage for DistinctEffectStage {
    async fn perform(&self, _effect: DistinctEffect, _out: &Outbound) -> Result<(), StageError> {
        Ok(())
    }
}

#[test]
fn pipeline_composes_stages_with_distinct_effect_types() {
    let _pipeline = PipelineBuilder::new()
        .stage(PassThrough)
        .stage(DistinctEffectStage)
        .build();
}

/// On native targets the pipeline driver must be `Send`, so it can be handed to
/// a multi-threaded executor (`tokio::spawn`). On wasm32 it is `!Send` and is
/// driven by `spawn_local`; this assertion is native-only by construction.
#[cfg(not(target_arch = "wasm32"))]
#[test]
fn driver_is_send_on_native() {
    fn assert_send<T: Send>(_: &T) {}
    struct Noop;
    impl Processor for Noop {
        type Effect = ();
    }
    #[cfg_attr(target_arch = "wasm32", async_trait(?Send))]
    #[cfg_attr(not(target_arch = "wasm32"), async_trait)]
    impl Stage for Noop {
        async fn perform(&self, _e: (), _out: &Outbound) -> Result<(), StageError> {
            Ok(())
        }
    }
    let pipeline = PipelineBuilder::new().stage(Noop).build();
    let (_ends, driver) = pipeline.start();
    assert_send(&driver);
}