truce_core/

events.rs

//! Event types crossing the host → plugin boundary.
//!
//! `EventBody` carries MIDI 1.0 and MIDI 2.0 channel-voice messages
//! in their **wire-native integer** shapes (7-bit `u8`, 14-bit
//! `u16`, 16-bit `u16`, 32-bit `u32`) so the framework's
//! representation round-trips exactly with the host's wire format.
//! Plugin code that wants float values reaches for the helpers in
//! [`truce_utils::midi`] (`norm_7bit`, `denorm_7bit`,
//! `norm_pitch_bend`, `denorm_pitch_bend`).
//!
//! Every MIDI variant carries a `group: u8` field (0..=15) that
//! UMP (Universal MIDI Packet) hosts use to address one of 16
//! groups × 16 channels = 256 logical channels. Format wrappers
//! that don't expose the group field (legacy MIDI 1.0 byte streams)
//! emit `0`.

/// A timestamped event within a process block.
///
/// `Copy` because every [`EventBody`] variant is POD - lets the
/// audio path move events without per-event clones.
#[derive(Clone, Copy, Debug)]
pub struct Event {
    /// Sample offset within the block (`0..num_samples`).
    pub sample_offset: u32,
    pub body: EventBody,
}

#[derive(Clone, Copy, Debug)]
pub enum EventBody {
    // -- MIDI 1.0 channel voice (wire-native 7-bit / 14-bit) --
    /// Note on. MIDI 1.0 quirk: a `NoteOn` with `velocity == 0` is
    /// a `NoteOff`. Format wrappers normalize that at parse time so
    /// plugin code can match `NoteOn` without checking velocity.
    NoteOn {
        group: u8,
        channel: u8,
        note: u8,
        velocity: u8,
    },
    NoteOff {
        group: u8,
        channel: u8,
        note: u8,
        velocity: u8,
    },
    /// Polyphonic key pressure (per-note aftertouch).
    Aftertouch {
        group: u8,
        channel: u8,
        note: u8,
        pressure: u8,
    },
    ChannelPressure {
        group: u8,
        channel: u8,
        pressure: u8,
    },
    ControlChange {
        group: u8,
        channel: u8,
        cc: u8,
        value: u8,
    },
    /// 14-bit pitch bend, raw code `0..=16383`. `8192` is center.
    /// See `truce_utils::midi::norm_pitch_bend` for the
    /// asymmetric-range conversion helper.
    PitchBend {
        group: u8,
        channel: u8,
        value: u16,
    },
    ProgramChange {
        group: u8,
        channel: u8,
        program: u8,
    },

    // -- MIDI 2.0 channel voice (wire-native 16/32-bit) --
    /// MIDI 2.0 `NoteOn`. `velocity` is `0..=65535`; unlike MIDI 1.0,
    /// a zero velocity is a genuine zero (`NoteOff` is its own
    /// dedicated message). `attribute_type` indicates how
    /// `attribute` should be interpreted: 0 = no attribute, 1 =
    /// manufacturer-specific, 2 = profile-specific, 3 = Pitch 7.9.
    NoteOn2 {
        group: u8,
        channel: u8,
        note: u8,
        velocity: u16,
        attribute_type: u8,
        attribute: u16,
    },
    NoteOff2 {
        group: u8,
        channel: u8,
        note: u8,
        velocity: u16,
        attribute_type: u8,
        attribute: u16,
    },
    /// MIDI 2.0 polyphonic key pressure (`pressure: u32`).
    PolyPressure2 {
        group: u8,
        channel: u8,
        note: u8,
        pressure: u32,
    },
    /// MIDI 2.0 per-note controller. `registered = true` for
    /// Registered Per-Note (RPN-like indexed list); `false` for
    /// Assignable Per-Note (free-form per-controller mapping).
    PerNoteCC {
        group: u8,
        channel: u8,
        note: u8,
        cc: u8,
        value: u32,
        registered: bool,
    },
    /// MIDI 2.0 per-note pitch bend (`value: u32`). `0x8000_0000`
    /// is center.
    PerNotePitchBend {
        group: u8,
        channel: u8,
        note: u8,
        value: u32,
    },
    /// MIDI 2.0 per-note management flags. Bit 0 = detach
    /// per-note controllers from active note; bit 1 = reset
    /// (set) per-note controllers to default values.
    PerNoteManagement {
        group: u8,
        channel: u8,
        note: u8,
        flags: u8,
    },
    /// MIDI 2.0 channel-wide control change (32-bit).
    ControlChange2 {
        group: u8,
        channel: u8,
        cc: u8,
        value: u32,
    },
    /// MIDI 2.0 channel pressure (32-bit aftertouch on the whole
    /// channel).
    ChannelPressure2 {
        group: u8,
        channel: u8,
        pressure: u32,
    },
    /// MIDI 2.0 channel pitch bend (32-bit). `0x8000_0000` is
    /// center.
    PitchBend2 {
        group: u8,
        channel: u8,
        value: u32,
    },
    /// MIDI 2.0 program change. Optional bank pair (MSB, LSB);
    /// MIDI 2.0's "B" flag is encoded as `Some` / `None`. When
    /// `None`, the host hasn't selected a bank and the program
    /// applies in the current bank.
    ProgramChange2 {
        group: u8,
        channel: u8,
        program: u8,
        bank: Option<(u8, u8)>,
    },
    /// MIDI 2.0 Registered Controller (the spec's RPN replacement,
    /// 32-bit). `bank` and `index` are the two 7-bit identifiers
    /// the spec reserves for Registered Parameter Numbers.
    RegisteredController {
        group: u8,
        channel: u8,
        bank: u8,
        index: u8,
        value: u32,
    },
    /// MIDI 2.0 Assignable Controller (the spec's NRPN
    /// replacement, 32-bit). `bank` and `index` are
    /// manufacturer-defined.
    AssignableController {
        group: u8,
        channel: u8,
        bank: u8,
        index: u8,
        value: u32,
    },

    // -- truce-internal automation --
    ParamChange {
        id: u32,
        value: f64,
    },
    /// Parameter modulation offset (CLAP-specific, zero on other
    /// formats). Effective value is `base + value`. The base value
    /// is unchanged.
    ParamMod {
        id: u32,
        note_id: i32,
        value: f64,
    },

    // -- Transport --
    Transport(TransportInfo),

    // -- System layer --
    /// System Exclusive (`SysEx`) message - MIDI 1.0 and MIDI 2.0
    /// alike. The payload bytes live in [`EventList::sysex_bytes`];
    /// resolve a body to its slice with
    /// `event_list.sysex_bytes(&body)` rather than indexing the
    /// pool directly. The bytes are the inner `SysEx` data
    /// **without** the leading `0xF0` start byte or trailing `0xF7`
    /// end byte - format wrappers strip those at the boundary so
    /// plugin code doesn't have to.
    ///
    /// Inlining the bytes in the variant would balloon every event's
    /// footprint to the worst-case (~64 KiB) - channel-voice events
    /// are <8 bytes today and we want to keep the per-event memory
    /// pressure on the audio thread proportional to that. The
    /// indices-into-a-pool layout pays the price (two-step access)
    /// for the `SysEx`-handling path only.
    SysEx {
        pool_offset: u32,
        len: u32,
    },
}

/// Host-populated transport snapshot. Constructed by every format
/// wrapper from the host's own transport struct via struct-literal
/// expressions, so this stays "exhaustive" (no `#[non_exhaustive]`,
/// which would block cross-crate construction). Adding a new field
/// is a coordinated workspace-wide change.
#[derive(Clone, Copy, Debug, Default)]
pub struct TransportInfo {
    pub playing: bool,
    pub recording: bool,
    pub tempo: f64,
    pub time_sig_num: u8,
    pub time_sig_den: u8,
    pub position_samples: i64,
    pub position_seconds: f64,
    pub position_beats: f64,
    pub bar_start_beats: f64,
    pub loop_active: bool,
    pub loop_start_beats: f64,
    pub loop_end_beats: f64,
}

impl TransportInfo {
    /// Synthetic transport for snapshot tests - playing at 120 BPM,
    /// 4/4, position 4.0 beats. Used as the default by every snapshot
    /// helper (`truce-egui`, `truce-slint`, `truce-iced`,
    /// `truce-test`) so that transport-aware widgets render a
    /// populated readout in marketing screenshots instead of a
    /// `(no host transport)` placeholder.
    #[must_use]
    pub fn for_screenshot() -> Self {
        Self {
            playing: true,
            tempo: 120.0,
            time_sig_num: 4,
            time_sig_den: 4,
            position_beats: 4.0,
            ..Self::default()
        }
    }
}

/// Default reserved capacity for per-instance `EventList`s held by
/// format wrappers. Sized to cover a heavy MIDI block (note bursts +
/// per-block automation changes) without growing past steady state.
///
/// Plugins can construct a smaller or larger list explicitly via
/// [`EventList::with_capacity`]; this const exists so the format
/// wrappers don't each pick their own magic number.
pub const EVENT_LIST_PREALLOC: usize = 256;

/// Default reserved capacity for the `SysEx` byte pool on
/// per-instance `EventList`s. 128 KiB ≈ 2× the worst-case single
/// payload (one 64 KiB firmware-update-shaped message) with
/// headroom for an interleaved burst of small messages in the
/// same block.
///
/// Sized at construction in [`EventList::with_capacity`]; never
/// re-allocates on the audio thread. A plugin that pushes beyond
/// this gets a [`PushError::PoolFull`] and the message is dropped;
/// truncating or splitting a `SysEx` makes it invalid.
///
/// Must agree with the `TRUCE_SYSEX_POOL_PREALLOC` C macro in the
/// shared shim header: the AU v3 Swift template (which can't import
/// Rust consts) reads the C macro to size its per-render output
/// scratch buffer, and a per-format unit test asserts the two values
/// match.
pub const SYSEX_POOL_PREALLOC: usize = 128 * 1024;

/// Why a push into the [`EventList`] failed. Today only `SysEx`
/// payloads can fail to land (the channel-voice [`EventList::push`]
/// path grows the backing `Vec` instead, since the audio-thread
/// contract there is "stay under [`EVENT_LIST_PREALLOC`]" rather
/// than "fail closed").
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum PushError {
    /// The `SysEx` byte pool is full. The message wasn't appended.
    /// Callers either drop it, surface it via a meter, or bump the
    /// pool size via [`EventList::with_capacity`] at construction.
    PoolFull,
}

impl core::fmt::Display for PushError {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        match self {
            Self::PoolFull => f.write_str("SysEx byte pool is full"),
        }
    }
}

impl std::error::Error for PushError {}

/// Ordered list of events within a process block.
///
/// `events` is the per-block event ring; `sysex_pool` is the
/// variable-byte arena that [`EventBody::SysEx`] entries index into.
/// Both are pre-allocated by [`EventList::with_capacity`] and reset
/// (length only - backing memory preserved) by [`Self::clear`], so
/// steady-state operation is allocation-free.
#[derive(Clone, Debug, Default)]
pub struct EventList {
    events: Vec<Event>,
    sysex_pool: Vec<u8>,
}

impl EventList {
    /// Construct an `EventList` with backing capacity already reserved.
    ///
    /// Format wrappers build their per-instance event lists at
    /// construction time and reuse them across blocks via `clear()`.
    /// Without this, the first `push` after `EventList::default()` hits
    /// the global allocator on the audio thread; pre-allocating with
    /// the max event count an audio block is likely to carry keeps
    /// the first block alloc-free.
    ///
    /// The `SysEx` byte pool is sized to [`SYSEX_POOL_PREALLOC`]
    /// regardless of `capacity` - `capacity` controls the event ring
    /// only.
    #[must_use]
    pub fn with_capacity(capacity: usize) -> Self {
        Self {
            events: Vec::with_capacity(capacity),
            sysex_pool: Vec::with_capacity(SYSEX_POOL_PREALLOC),
        }
    }

    /// Append an event. Note: `sample_offset` is **not** bounds-checked
    /// against any block size - callers that build event lists per
    /// block must validate `sample_offset < num_samples` themselves
    /// (the audio thread can't recover from an out-of-range offset, so
    /// we treat that as a contract violation rather than panicking).
    pub fn push(&mut self, event: Event) {
        self.events.push(event);
    }

    /// Append a `SysEx` event whose payload is copied into the pool.
    /// `data` is the inner `SysEx` bytes **without** the leading
    /// `0xF0` / trailing `0xF7` - wrappers strip those at the
    /// boundary.
    ///
    /// Returns [`PushError::PoolFull`] when the pool can't hold
    /// `data.len()` more bytes; the event is *not* appended and the
    /// pool is left unchanged. `SysEx` messages are atomic by spec,
    /// so the caller's choices are drop-and-flag (via a meter) or
    /// fail the host call. Splitting / truncating produces a corrupt
    /// message and is never the right answer.
    ///
    /// # Errors
    /// [`PushError::PoolFull`] when the pool is at capacity.
    pub fn push_sysex(&mut self, sample_offset: u32, data: &[u8]) -> Result<(), PushError> {
        let pool_offset = self.sysex_pool.len();
        if pool_offset + data.len() > self.sysex_pool.capacity() {
            return Err(PushError::PoolFull);
        }
        self.sysex_pool.extend_from_slice(data);
        // `as u32` casts are bounded: pool capacity is sized in the
        // hundreds of KiB at most, and the bounds check above keeps
        // `pool_offset + data.len()` under capacity, which itself
        // fits in `u32` by construction (`SYSEX_POOL_PREALLOC` ==
        // 128 KiB).
        #[allow(clippy::cast_possible_truncation)]
        self.events.push(Event {
            sample_offset,
            body: EventBody::SysEx {
                pool_offset: pool_offset as u32,
                len: data.len() as u32,
            },
        });
        Ok(())
    }

    /// Resolve a [`EventBody::SysEx`] entry to its payload bytes.
    /// Returns an empty slice for any other variant - the slice is
    /// indexed against the internal byte pool, so a non-`SysEx`
    /// body has nothing to point at.
    #[must_use]
    pub fn sysex_bytes(&self, body: &EventBody) -> &[u8] {
        match body {
            EventBody::SysEx { pool_offset, len } => {
                let start = *pool_offset as usize;
                let end = start + (*len as usize);
                &self.sysex_pool[start..end]
            }
            _ => &[],
        }
    }

    pub fn clear(&mut self) {
        self.events.clear();
        // `Vec::clear` preserves capacity; the pool stays
        // pre-allocated for the next block.
        self.sysex_pool.clear();
    }

    /// Stable sort by `sample_offset`. **Stability matters:** events
    /// with identical sample offsets stay in the order they were
    /// pushed, which is what plugins assume when they iterate (e.g.
    /// "MIDI on this sample then a CC on the same sample" stays in
    /// that order). Don't replace with `sort_unstable_by_key` - the
    /// stability guarantee is load-bearing.
    ///
    /// Sorting reorders [`Event`] entries only; `SysEx` pool
    /// offsets stay valid because the pool's bytes aren't moved.
    pub fn sort(&mut self) {
        self.events.sort_by_key(|e| e.sample_offset);
    }

    pub fn iter(&self) -> impl Iterator<Item = &Event> {
        self.events.iter()
    }

    #[must_use]
    pub fn get(&self, index: usize) -> Option<&Event> {
        self.events.get(index)
    }

    #[must_use]
    pub fn len(&self) -> usize {
        self.events.len()
    }

    #[must_use]
    pub fn is_empty(&self) -> bool {
        self.events.is_empty()
    }

    /// Current `SysEx` pool usage in bytes. Mainly useful in tests
    /// and for plug-in code that wants to surface "headroom
    /// remaining" in an editor.
    #[must_use]
    pub fn sysex_pool_used(&self) -> usize {
        self.sysex_pool.len()
    }

    /// Total `SysEx` pool capacity in bytes. Stable for the life of
    /// the `EventList` (no audio-thread reallocation).
    #[must_use]
    pub fn sysex_pool_capacity(&self) -> usize {
        self.sysex_pool.capacity()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn push_sysex_round_trip() {
        let mut list = EventList::with_capacity(8);
        let payload = b"\x7E\x00\x06\x01"; // device-inquiry reply body
        list.push_sysex(42, payload).expect("pool has room");

        assert_eq!(list.len(), 1);
        let event = list.iter().next().expect("one event");
        assert_eq!(event.sample_offset, 42);
        assert!(matches!(event.body, EventBody::SysEx { .. }));
        assert_eq!(list.sysex_bytes(&event.body), payload);
        assert_eq!(list.sysex_pool_used(), payload.len());
    }

    #[test]
    fn push_sysex_two_messages_carve_pool_independently() {
        let mut list = EventList::with_capacity(8);
        let a = b"\x01\x02\x03";
        let b = b"\x04\x05\x06\x07";
        list.push_sysex(0, a).unwrap();
        list.push_sysex(1, b).unwrap();

        let collected: Vec<_> = list.iter().collect();
        assert_eq!(list.sysex_bytes(&collected[0].body), a);
        assert_eq!(list.sysex_bytes(&collected[1].body), b);
        assert_eq!(list.sysex_pool_used(), a.len() + b.len());
    }

    #[test]
    fn push_sysex_pool_full_is_recoverable() {
        // Construct a tiny pool by going through `with_capacity` with a
        // post-hoc shrink - we can't pass a custom pool size today, so
        // exercise the failure path by overflowing the configured 128 KiB.
        let mut list = EventList::with_capacity(8);
        let big = vec![0u8; SYSEX_POOL_PREALLOC];
        list.push_sysex(0, &big)
            .expect("first fill is exactly the pool");
        let err = list.push_sysex(1, b"\x00").unwrap_err();
        assert_eq!(err, PushError::PoolFull);
        // No partial state: the rejected event isn't queued, the pool
        // length is unchanged.
        assert_eq!(list.len(), 1);
        assert_eq!(list.sysex_pool_used(), SYSEX_POOL_PREALLOC);
    }

    #[test]
    fn clear_preserves_pool_capacity() {
        let mut list = EventList::with_capacity(8);
        let cap_before = list.sysex_pool_capacity();
        list.push_sysex(0, b"\x00\x01\x02").unwrap();
        list.clear();
        assert!(list.is_empty());
        assert_eq!(list.sysex_pool_used(), 0);
        // The whole point of pre-allocation: clearing must not free.
        assert_eq!(list.sysex_pool_capacity(), cap_before);
    }

    #[test]
    fn sort_preserves_sysex_offsets() {
        let mut list = EventList::with_capacity(8);
        let early = b"\x10\x11";
        let late = b"\x20\x21\x22";
        list.push_sysex(100, late).unwrap();
        list.push_sysex(0, early).unwrap();
        list.sort();

        let collected: Vec<_> = list.iter().collect();
        // Sorted: sample_offset=0 comes first, then 100.
        assert_eq!(collected[0].sample_offset, 0);
        assert_eq!(list.sysex_bytes(&collected[0].body), early);
        assert_eq!(collected[1].sample_offset, 100);
        assert_eq!(list.sysex_bytes(&collected[1].body), late);
    }

    #[test]
    fn sysex_bytes_returns_empty_for_non_sysex() {
        let list = EventList::with_capacity(8);
        let body = EventBody::NoteOn {
            group: 0,
            channel: 0,
            note: 60,
            velocity: 100,
        };
        assert!(list.sysex_bytes(&body).is_empty());
    }
}