nooise 2.5.4

//! The one publication boundary for user-audible live state.
//!
//! `LiveSessionSnapshot` is an immutable generation of controls, automation,
//! tonal state, mute state, and the transport; every writer goes through `LiveSession::transact` so the
//! audio thread only ever reads one coherent generation.

use super::*;

pub(crate) type MuteState = [bool; TAB_COUNT];

/// One coherent, immutable generation of every user-audible live-session
/// value shared by the UI and audio threads.
#[derive(Clone)]
pub(crate) struct LiveSessionSnapshot {
    pub(crate) generation: u64,
    /// Live-only invalidation for pending slot-targeted edits. Parameter
    /// changes leave it alone; replacing any slot kind advances it.
    pub(crate) module_topology_revision: u64,
    /// Live-only invalidation of palette targets when authored lanes change.
    pub(crate) automation_revision: u64,
    pub(crate) controls: FluidControls,
    pub(crate) automation: AutomationState,
    pub(crate) tonal_sequence: TonalSequenceState,
    pub(crate) muted: MuteState,
    /// Lead play-mode presses. Live-only: never written to a song code.
    pub(crate) lead_play: LeadPlayState,
    pub(crate) gestures: GestureState,
    /// Whether the beat clock runs. Live-only: a stopped song is silence,
    /// not a state worth sharing, so a loaded code always plays.
    pub(crate) transport: Transport,
    /// Counts explicit restarts, including stop/play between audio reads.
    pub(crate) transport_restart: u64,
}

impl LiveSessionSnapshot {
    pub(crate) fn from_song(song: &SongState) -> Self {
        Self {
            generation: 0,
            module_topology_revision: 0,
            automation_revision: 0,
            controls: song.controls.clone(),
            automation: song.automation.clone(),
            muted: song.muted,
            lead_play: LeadPlayState::default(),
            gestures: song.gestures.restored(),
            transport: Transport::Playing,
            transport_restart: 0,
            tonal_sequence: song.tonal_sequence.clone().unwrap_or_else(|| {
                TonalSequenceState::from_phrase(wrapped_index(
                    song.controls.tonal.phrase,
                    TONAL_PHRASES.len(),
                ))
            }),
        }
    }

    #[cfg(test)]
    pub(crate) fn from_controls(controls: FluidControls) -> Self {
        Self {
            generation: 0,
            module_topology_revision: 0,
            automation_revision: 0,
            tonal_sequence: TonalSequenceState::from_phrase(wrapped_index(
                controls.tonal.phrase,
                TONAL_PHRASES.len(),
            )),
            controls,
            automation: AutomationState::default(),
            muted: [false; TAB_COUNT],
            lead_play: LeadPlayState::default(),
            gestures: GestureState::default(),
            transport: Transport::Playing,
            transport_restart: 0,
        }
    }
}

#[derive(Clone)]
pub(crate) struct LiveSession {
    published: Arc<ArcSwap<LiveSessionSnapshot>>,
    /// Audio-owned monotonic clock; gestures store their anchors in the
    /// aggregate snapshot, while readers sample this clock without a lock.
    audio_seconds_bits: Arc<AtomicU64>,
    audio_beat_bits: Arc<AtomicU64>,
}

impl LiveSession {
    pub(crate) fn new(snapshot: LiveSessionSnapshot) -> Self {
        Self {
            published: Arc::new(ArcSwap::from_pointee(snapshot)),
            audio_seconds_bits: Arc::new(AtomicU64::new(0)),
            audio_beat_bits: Arc::new(AtomicU64::new(0)),
        }
    }

    pub(crate) fn load(&self) -> Arc<LiveSessionSnapshot> {
        self.published.load_full()
    }

    pub(crate) fn audio_seconds(&self) -> f64 {
        f64::from_bits(self.audio_seconds_bits.load(Ordering::Relaxed))
    }

    pub(crate) fn audio_beat(&self) -> f64 {
        f64::from_bits(self.audio_beat_bits.load(Ordering::Relaxed))
    }

    pub(crate) fn publish_audio_beat(&self, beat: f64) {
        self.audio_beat_bits
            .store(beat.to_bits(), Ordering::Relaxed);
    }

    pub(crate) fn publish_audio_seconds(&self, seconds: f64) {
        self.audio_seconds_bits
            .store(seconds.to_bits(), Ordering::Relaxed);
    }

    /// Apply a pure aggregate edit with optimistic retry. A conflicting writer
    /// causes the edit to be recomputed from the newer generation, preventing
    /// stale clone-and-store updates from overwriting one another.
    pub(crate) fn transact<E>(
        &self,
        mut edit: impl FnMut(&mut LiveSessionSnapshot) -> Result<(), E>,
    ) -> Result<Arc<LiveSessionSnapshot>, E> {
        loop {
            let current = self.published.load_full();
            let mut next = current.as_ref().clone();
            edit(&mut next)?;
            if Tab::all().iter().any(|&tab| {
                current
                    .controls
                    .modules
                    .for_tab(tab)
                    .zip(next.controls.modules.for_tab(tab))
                    .is_some_and(|(before, after)| {
                        before
                            .iter()
                            .zip(after)
                            .any(|(before, after)| before.kind.to_bits() != after.kind.to_bits())
                    })
            }) {
                next.module_topology_revision = current.module_topology_revision.wrapping_add(1);
                next.automation.captures.retain(|address, _| {
                    let Some((before, _)) = module_slot_row(address.id(), &current.controls) else {
                        return true;
                    };
                    module_slot_row(address.id(), &next.controls)
                        .is_some_and(|(after, _)| before.kind == after.kind)
                });
            }
            if !current.automation.same_lanes(&next.automation) {
                next.automation_revision = current.automation_revision.wrapping_add(1);
            }
            next.generation = current.generation.wrapping_add(1);
            let next = Arc::new(next);
            let previous = self.published.compare_and_swap(&current, Arc::clone(&next));
            if Arc::ptr_eq(&previous, &current) {
                return Ok(next);
            }
        }
    }

    pub(crate) fn update(
        &self,
        mut edit: impl FnMut(&mut LiveSessionSnapshot),
    ) -> Arc<LiveSessionSnapshot> {
        self.transact::<std::convert::Infallible>(|snapshot| {
            edit(snapshot);
            Ok(())
        })
        .expect("infallible live-session transaction")
    }
}

#[cfg(test)]
mod tests {
    use std::sync::Barrier;
    use std::thread;

    #[test]
    fn module_topology_revision_tracks_replacement_but_not_parameter_edits() {
        let session =
            LiveSession::new(LiveSessionSnapshot::from_controls(FluidControls::default()));
        session.update(|snapshot| snapshot.controls.modules.bass[0].time = 1234.0);
        assert_eq!(session.load().module_topology_revision, 0);
        session.update(|snapshot| snapshot.controls.modules.bass[0] = ModuleSlot::default());
        session.update(|snapshot| snapshot.controls.modules.bass[0] = preset_slot("filter", 1.0));
        assert_eq!(session.load().module_topology_revision, 2);
    }

    use super::*;

    #[test]
    fn transaction_publishes_the_complete_aggregate_once() {
        let session =
            LiveSession::new(LiveSessionSnapshot::from_controls(FluidControls::default()));
        let before = session.load();

        let published = session.update(|snapshot| {
            snapshot.controls.master.bpm = 91.0;
            snapshot
                .automation
                .open_or_create(ControlAddress::new("master.bpm"));
            snapshot.tonal_sequence.evolution_count = 7;
            snapshot.muted[Tab::Master as usize] = true;
        });

        assert_eq!(published.generation, before.generation + 1);
        assert_eq!(published.controls.master.bpm, 91.0);
        assert!(
            published
                .automation
                .route(ControlAddress::new("master.bpm"))
                .is_some()
        );
        assert_eq!(published.tonal_sequence.evolution_count, 7);
        assert!(published.muted[Tab::Master as usize]);
        assert!(Arc::ptr_eq(&published, &session.load()));
    }

    #[test]
    fn failed_transaction_does_not_publish() {
        let session =
            LiveSession::new(LiveSessionSnapshot::from_controls(FluidControls::default()));
        let before = session.load();
        let result = session.transact(|snapshot| {
            snapshot.controls.master.bpm = 200.0;
            Err::<(), _>("rejected")
        });

        assert!(matches!(result, Err("rejected")));
        assert!(Arc::ptr_eq(&before, &session.load()));
    }

    #[test]
    fn concurrent_writers_do_not_lose_updates_or_mix_generations() {
        const WRITES: usize = 100;
        let session =
            LiveSession::new(LiveSessionSnapshot::from_controls(FluidControls::default()));
        let barrier = Arc::new(Barrier::new(3));
        let mut writers = Vec::new();
        for writer in 0..2 {
            let session = session.clone();
            let barrier = Arc::clone(&barrier);
            writers.push(thread::spawn(move || {
                barrier.wait();
                for _ in 0..WRITES {
                    session.update(|snapshot| {
                        if writer == 0 {
                            snapshot.controls.master.bpm += 1.0;
                        } else {
                            snapshot.tonal_sequence.evolution_count += 1;
                        }
                    });
                }
            }));
        }
        barrier.wait();
        for writer in writers {
            writer.join().unwrap();
        }

        let snapshot = session.load();
        assert_eq!(snapshot.generation, (WRITES * 2) as u64);
        assert_eq!(
            snapshot.controls.master.bpm,
            FluidControls::default().master.bpm + WRITES as f32
        );
        assert_eq!(snapshot.tonal_sequence.evolution_count, WRITES as u64);
    }
}