ph-haptics 0.1.0

use crate::compiled::CompiledHapticDef;
use crate::dsl::{Instruction, LoopMode, Program};
use crate::error::Error;
use crate::motor::{DriveCommand, MotorConfig, MotorProfile, frac_to_level};
use ph_curves::{MonotonicCurve, MonotonicCurveLut256, Tickless};

/// One output frame produced by [`Runner::poll`].
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub struct Frame {
    /// Driver command for the current time.
    pub command: DriveCommand,
    /// Earliest wrapping `u32` clock value at which output may change.
    ///
    /// While this is `Some(deadline)`, [`Self::command`] is guaranteed not to
    /// change before `deadline`, so the caller may sleep until then. Compare or
    /// wait using wrapping arithmetic rather than absolute `<` / `>`. A deadline
    /// equal to the current poll time requests another poll at that same time to
    /// drain an immediate control-flow transition. `None` means there is no
    /// active or pending transition because the runner is idle or has finished.
    pub next_transition_ms: Option<u32>,
    /// Active instruction index in the current cycle.
    pub instruction_index: Option<usize>,
    /// `true` only when a finite program has completed.
    ///
    /// This is edge-triggered, not a latched state: it is set on the single
    /// [`Runner::poll`] that observes the end of the program, which also stops
    /// the runner. Later polls return an idle frame with `finished == false`.
    /// Act on completion when you first see it rather than polling for it.
    pub finished: bool,
}

impl Frame {
    const fn idle() -> Self {
        Self {
            command: DriveCommand::Off,
            next_transition_ms: None,
            instruction_index: None,
            finished: false,
        }
    }

    /// Returns `true` for an ordinary idle frame with no active instruction.
    ///
    /// The one-shot completion frame is not considered idle; it instead reports
    /// [`Self::is_finished`].
    pub const fn is_idle(&self) -> bool {
        self.instruction_index.is_none() && self.next_transition_ms.is_none() && !self.finished
    }

    /// Returns `true` when an instruction is active.
    pub const fn is_active(&self) -> bool {
        self.instruction_index.is_some() && !self.finished
    }

    /// Returns `true` when a finite program reached the end.
    pub const fn is_finished(&self) -> bool {
        self.finished
    }

    /// Convenience getter for driver command.
    pub const fn command(&self) -> DriveCommand {
        self.command
    }

    /// Return the earliest wrapping clock value at which output may change.
    ///
    /// See [`Frame::next_transition_ms`] for the sleep and same-timestamp polling
    /// contract.
    pub const fn next_transition_ms(&self) -> Option<u32> {
        self.next_transition_ms
    }
}

impl Default for Frame {
    fn default() -> Self {
        Self::idle()
    }
}

#[derive(Copy, Clone, Debug)]
struct Located<'a, C> {
    index: usize,
    instruction: &'a Instruction<C>,
    segment_start_ms: u32,
}

/// Executes a [`Program`] against an ERM or LRA motor configuration.
///
/// The caller supplies a free-running wrapping `u32` millisecond clock to
/// [`Runner::poll`] and applies the returned [`DriveCommand`]. Polling may then
/// pause until [`Frame::next_transition_ms`]; fixed-rate polling is unnecessary.
#[derive(Debug)]
pub struct Runner<'a, C = MonotonicCurveLut256>
where
    C: MonotonicCurve<u8, u8> + Copy,
{
    program: &'a Program<'a, C>,
    gamma_curve: Option<&'a MonotonicCurveLut256>,
    motor: MotorConfig,
    start_ms: u32,
    running: bool,
    /// Minimum level below which output snaps to off (from profile min_run_frac).
    min_level: u16,
    /// Maximum level ceiling (from profile max_frac).
    max_level: u16,
    /// Level to drive during a kick pulse (from profile kick_frac, clamped to max).
    kick_level: u16,
    /// Kick pulse duration in ms (from profile kick_ms).
    kick_duration_ms: u32,
    /// Set when output was floor-snapped to off (motor has stalled).
    needs_kick: bool,
    /// Whether a kick pulse is currently active.
    kick_active: bool,
    /// Absolute time at which an active kick pulse ends.
    kick_end_ms: u32,
}

impl<'a, C> Runner<'a, C>
where
    C: MonotonicCurve<u8, u8> + Copy,
{
    fn build(
        program: &'a Program<'a, C>,
        profile: Option<&'a MotorProfile>,
        motor: MotorConfig,
    ) -> Result<Self, Error> {
        if program.is_empty() {
            return Err(Error::EmptyProgram);
        }

        if program.motor() != motor.kind() {
            return Err(Error::MotorKindMismatch {
                expected: program.motor(),
                got: motor.kind(),
            });
        }

        let (min_level, max_level, kick_level, kick_duration_ms) = match profile {
            Some(p) => {
                let max = frac_to_level(p.max_frac);
                let kick = frac_to_level(p.kick_frac).min(max);
                (
                    frac_to_level(p.min_run_frac),
                    max,
                    kick,
                    u32::from(p.kick_ms),
                )
            }
            None => (0, 0, 0, 0),
        };

        Ok(Self {
            program,
            gamma_curve: profile.and_then(|profile| profile.gamma_curve),
            motor,
            start_ms: 0,
            running: false,
            min_level,
            max_level,
            kick_level,
            kick_duration_ms,
            needs_kick: false,
            kick_active: false,
            kick_end_ms: 0,
        })
    }

    /// Start playback at `now_ms`.
    pub fn start(&mut self, now_ms: u32) {
        self.start_ms = now_ms;
        self.running = true;
        // Motor is at rest — request a kick on the first above-min poll.
        self.needs_kick = self.kick_duration_ms > 0;
        self.kick_active = false;
        self.kick_end_ms = 0;
    }

    /// Restart playback from the beginning at `now_ms`.
    pub fn restart(&mut self, now_ms: u32) {
        self.start(now_ms);
    }

    /// Start playback at `now_ms` and return the first frame.
    pub fn start_and_poll(&mut self, now_ms: u32) -> Frame {
        self.start(now_ms);
        self.poll(now_ms)
    }

    /// Poll current output; if not running, start playback at `now_ms` first.
    pub fn poll_or_start(&mut self, now_ms: u32) -> Frame {
        if !self.running {
            self.start(now_ms);
        }
        self.poll(now_ms)
    }

    /// Stop playback.
    pub fn stop(&mut self) {
        self.running = false;
    }

    /// Whether the program is currently running.
    pub const fn is_running(&self) -> bool {
        self.running
    }

    /// Motor configuration assigned to this runner.
    pub const fn motor(&self) -> MotorConfig {
        self.motor
    }

    /// Current start timestamp used as cycle origin.
    pub const fn start_ms(&self) -> u32 {
        self.start_ms
    }

    /// Evaluate output for the wrapping millisecond clock value `now_ms`.
    ///
    /// The returned frame's deadline is the earliest time the command may
    /// change. Callers should wait with wrapping arithmetic and poll again at
    /// that deadline. If the deadline equals `now_ms`, poll again immediately to
    /// drain the control-flow transition. Completion is edge-triggered; see
    /// [`Frame::finished`].
    pub fn poll(&mut self, now_ms: u32) -> Frame {
        if !self.running {
            return Frame::idle();
        }

        let elapsed_ms = now_ms.wrapping_sub(self.start_ms);
        let located = locate_instruction(self.program, self.start_ms, elapsed_ms);

        let Some(located) = located else {
            self.running = false;
            return Frame {
                command: DriveCommand::Off,
                next_transition_ms: None,
                instruction_index: None,
                finished: true,
            };
        };

        let (level, lra_frequency_hz, next_transition_ms) =
            eval_instruction(located.instruction, located.segment_start_ms, now_ms);
        let mut level = level;

        // Floor enforcement in logical (pre-gamma) space. Codegen clamps authored
        // levels *up* to `min_run_frac` so they survive this check; anything still
        // below the floor here cannot spin the motor, so it snaps to full off.
        if self.min_level > 0 && level > 0 && level < self.min_level {
            level = 0;
        }

        // Re-arm kick whenever the motor is at rest (Pause, hold 0, or floor-snap).
        if level == 0 && self.kick_duration_ms > 0 {
            self.needs_kick = true;
            self.kick_active = false;
        }

        // Kick injection: when recovering from rest/stall, overdrive the motor
        // for kick_duration_ms so it overcomes static friction. The `level > 0`
        // guard matters when `min_level == 0`: without it a resting segment would
        // both arm and consume the kick on every poll, pushing `kick_end_ms`
        // forward forever and forcing a wake-up every `kick_ms` through a Pause.
        if self.needs_kick && level > 0 && level >= self.min_level {
            self.needs_kick = false;
            self.kick_active = true;
            self.kick_end_ms = now_ms.wrapping_add(self.kick_duration_ms);
        }
        // Expiry uses remaining-time half-range so kick_end_ms after a u32 wrap
        // still terminates; plain `now < kick_end` would keep the kick forever.
        let kick_remaining_ms = self.kick_end_ms.wrapping_sub(now_ms);
        if self.kick_active && (kick_remaining_ms == 0 || kick_remaining_ms > i32::MAX as u32) {
            self.kick_active = false;
        }
        let kick_active = self.kick_active;
        if kick_active && level > 0 {
            level = level.max(self.kick_level);
        }

        // Ceiling enforcement in logical (pre-gamma) space.
        if self.max_level > 0 && level > self.max_level {
            level = self.max_level;
        }

        let level = apply_gamma(level, self.gamma_curve);

        // Wake at kick expiry if it precedes the instruction deadline.
        let instruction_remaining_ms = next_transition_ms.wrapping_sub(now_ms);
        let next_transition_ms = if kick_active && kick_remaining_ms < instruction_remaining_ms {
            self.kick_end_ms
        } else {
            next_transition_ms
        };

        Frame {
            command: self.motor.drive(level, lra_frequency_hz),
            next_transition_ms: Some(next_transition_ms),
            instruction_index: Some(located.index),
            finished: false,
        }
    }
}

impl<'a> Runner<'a, MonotonicCurveLut256> {
    /// Build a runner directly from a generated [`CompiledHapticDef`].
    pub(crate) fn from_compiled(
        compiled: &'a CompiledHapticDef<'a>,
        motor: MotorConfig,
    ) -> Result<Self, Error> {
        Self::build(&compiled.program, compiled.profile, motor)
    }

    /// Build from a generated [`CompiledHapticDef`] and start at `now_ms`.
    pub(crate) fn from_compiled_started(
        compiled: &'a CompiledHapticDef<'a>,
        motor: MotorConfig,
        now_ms: u32,
    ) -> Result<Self, Error> {
        let mut runner = Self::build(&compiled.program, compiled.profile, motor)?;
        runner.start(now_ms);
        Ok(runner)
    }
}

fn locate_instruction<'a, C>(
    program: &'a Program<'a, C>,
    start_ms: u32,
    elapsed_ms: u32,
) -> Option<Located<'a, C>> {
    let cycle_duration = program.total_duration_ms();
    if cycle_duration == 0 {
        return None;
    }

    let cycle_elapsed = match program.loop_mode() {
        LoopMode::Once => {
            if elapsed_ms >= cycle_duration {
                return None;
            }
            elapsed_ms
        }
        LoopMode::Forever => elapsed_ms % cycle_duration,
        LoopMode::Count(n) => {
            let total = cycle_duration.saturating_mul(n);
            if elapsed_ms >= total {
                return None;
            }
            elapsed_ms % cycle_duration
        }
    };

    // Wrap-safe rebase: derive the active cycle origin from conceptual now and
    // in-cycle phase so long Forever/Count runs do not clamp at u32::MAX.
    let now_ms = start_ms.wrapping_add(elapsed_ms);
    let cycle_origin = now_ms.wrapping_sub(cycle_elapsed);
    let instructions = program.instructions();

    let mut index = 0usize;
    let mut offset = 0u32;

    while index < instructions.len() {
        let instruction = &instructions[index];
        let next_offset = offset.saturating_add(instruction.duration_ms());
        if cycle_elapsed < next_offset {
            return Some(Located {
                index,
                instruction,
                segment_start_ms: cycle_origin.wrapping_add(offset),
            });
        }
        offset = next_offset;
        index += 1;
    }

    None
}

fn eval_instruction<C>(
    instruction: &Instruction<C>,
    segment_start_ms: u32,
    now_ms: u32,
) -> (u16, Option<u16>, u32)
where
    C: MonotonicCurve<u8, u8> + Copy,
{
    match instruction {
        Instruction::Ramp(ramp) => {
            // ph-curves ≥ 0.2.1 TicklessSchedule is wrap-safe on free-running
            // u32 clocks, so feed wall-clock segment_start / now directly.
            let elapsed = now_ms.wrapping_sub(segment_start_ms).min(ramp.duration_ms);
            let schedule = ramp.curve.tickless_schedule(
                segment_start_ms,
                ramp.duration_ms,
                ramp.from,
                ramp.to,
                ramp.step,
                ramp.rounding,
                ramp.min_dt_ms,
            );
            let deadline = schedule.next_deadline(now_ms);

            // LRA Hz lerp stays segment-relative. Merge wakeups by converting
            // the amplitude deadline back to an offset before .min() — absolute
            // .min() on wrapped timestamps is wrong — then map to wall-clock.
            let amp_offset = deadline.deadline_ms.wrapping_sub(segment_start_ms);
            let (lra_freq, next_transition_offset_ms) =
                match (ramp.lra_frequency_hz, ramp.lra_frequency_hz_to) {
                    (Some(from_hz), Some(to_hz)) => {
                        let hz = lerp_lra_hz(from_hz, to_hz, elapsed, ramp.duration_ms);
                        let hz_deadline =
                            next_lra_hz_change_offset_ms(ramp.duration_ms, from_hz, to_hz, elapsed);
                        let next = match hz_deadline {
                            Some(hz_offset_ms) => amp_offset.min(hz_offset_ms),
                            None => amp_offset,
                        };
                        (Some(hz), next)
                    }
                    (freq, _) => (freq, amp_offset),
                };
            let next_transition_ms = segment_start_ms.wrapping_add(next_transition_offset_ms);

            (deadline.current_val, lra_freq, next_transition_ms)
        }
        Instruction::Hold {
            duration_ms,
            level,
            lra_frequency_hz,
        } => (
            *level,
            *lra_frequency_hz,
            segment_start_ms.wrapping_add(*duration_ms),
        ),
        Instruction::Pause { duration_ms } => {
            (0, None, segment_start_ms.wrapping_add(*duration_ms))
        }
    }
}

fn lerp_lra_hz(from_hz: u16, to_hz: u16, t_ms: u32, duration_ms: u32) -> u16 {
    // Widened to u64: `delta * t` overflows u32 for long sweeps (a 200 Hz delta
    // over a ramp of more than ~6 hours), which would panic in debug builds.
    let from = u64::from(from_hz);
    let to = u64::from(to_hz);
    let dur = u64::from(duration_ms.max(1));
    let t = u64::from(t_ms.min(duration_ms));
    let hz = if to >= from {
        from + (to - from) * t / dur
    } else {
        from - (from - to) * t / dur
    };
    hz as u16
}

/// Segment-relative ms of the next quantized LRA Hz change under linear lerp, if any.
fn next_lra_hz_change_offset_ms(
    duration_ms: u32,
    from_hz: u16,
    to_hz: u16,
    elapsed_ms: u32,
) -> Option<u32> {
    if from_hz == to_hz || duration_ms == 0 || elapsed_ms >= duration_ms {
        return None;
    }

    // Widened to u64 for the same overflow reason as `lerp_lra_hz`.
    let from = u64::from(from_hz);
    let to = u64::from(to_hz);
    let current = u64::from(lerp_lra_hz(from_hz, to_hz, elapsed_ms, duration_ms));
    let dur = u64::from(duration_ms);

    let t = if to >= from {
        let delta = to - from;
        if delta == 0 || current >= to {
            return None;
        }
        let need = current + 1 - from;
        (need * dur).div_ceil(delta)
    } else {
        let delta = from - to;
        if delta == 0 || current <= to {
            return None;
        }
        let need = from - current + 1;
        (need * dur).div_ceil(delta)
    };

    let t = t.max(u64::from(elapsed_ms) + 1);
    if t > dur {
        return None;
    }
    let mut t = t as u32;

    // Guard closed-form rounding: advance until the quantized Hz actually changes.
    let current_hz = current as u16;
    while t <= duration_ms {
        if lerp_lra_hz(from_hz, to_hz, t, duration_ms) != current_hz {
            return Some(t);
        }
        t = t.saturating_add(1);
    }
    None
}

fn apply_gamma(level: u16, gamma_curve: Option<&MonotonicCurveLut256>) -> u16 {
    if level == 0 {
        return 0;
    }
    let Some(curve) = gamma_curve else {
        return level;
    };

    let index = ((u32::from(level) * 255) + (u32::from(u16::MAX) / 2)) / u32::from(u16::MAX);
    let mapped = u32::from(curve.fwd_lut()[index as usize]);
    (((mapped * u32::from(u16::MAX)) + 127) / 255) as u16
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::compiled::CompiledHapticDef;
    use crate::dsl::{Instruction, LoopMode, Program, Ramp};
    use crate::motor::{DriveCommand, ErmConfig, LraConfig, MotorConfig, MotorKind, MotorProfile};
    use ph_curves::{MonotonicCurveLut256, Rounding};

    const fn linear_lut() -> [u8; 256] {
        let mut lut = [0u8; 256];
        let mut index = 0usize;

        while index < lut.len() {
            lut[index] = index as u8;
            index += 1;
        }

        lut
    }

    const fn square_lut() -> [u8; 256] {
        let mut lut = [0u8; 256];
        let mut index = 0usize;

        while index < lut.len() {
            let x = index as u32;
            let y = ((x * x) + 127) / 255;
            lut[index] = y as u8;
            index += 1;
        }

        lut
    }

    const fn monotonic_inv_lut(fwd: &[u8; 256]) -> [u8; 256] {
        let mut inv = [0u8; 256];
        let mut out = 0usize;

        while out < inv.len() {
            let mut input = 0usize;
            while input < fwd.len() && (fwd[input] as usize) < out {
                input += 1;
            }
            inv[out] = input as u8;
            out += 1;
        }

        inv
    }

    static LINEAR_FWD: [u8; 256] = linear_lut();
    static LINEAR_INV: [u8; 256] = linear_lut();
    const LINEAR: MonotonicCurveLut256 = MonotonicCurveLut256::new(&LINEAR_FWD, &LINEAR_INV);
    static SQUARE_FWD: [u8; 256] = square_lut();
    static SQUARE_INV: [u8; 256] = monotonic_inv_lut(&SQUARE_FWD);
    const SQUARE: MonotonicCurveLut256 = MonotonicCurveLut256::new(&SQUARE_FWD, &SQUARE_INV);

    #[test]
    fn erm_ramp_is_shaped_and_finishes() {
        let instructions = [Instruction::Ramp(Ramp::new(100, 0, u16::MAX, LINEAR))];
        let program = Program::new(MotorKind::Erm, &instructions);
        let compiled = CompiledHapticDef::new("demo", program, None);
        let mut runner =
            Runner::from_compiled(&compiled, MotorConfig::Erm(ErmConfig::new(255))).unwrap();
        runner.start(1_000);

        let start = runner.poll(1_000);
        assert_eq!(start.command, DriveCommand::Off);
        assert_eq!(start.instruction_index, Some(0));

        let mid = runner.poll(1_050);
        match mid.command {
            DriveCommand::Erm { duty } => assert!((120..=136).contains(&duty)),
            _ => panic!("expected ERM command"),
        }
        assert_eq!(mid.instruction_index, Some(0));
        assert!(mid.next_transition_ms.is_some());
        assert!(!mid.finished);

        let finished = runner.poll(1_101);
        assert_eq!(finished.command, DriveCommand::Off);
        assert_eq!(finished.next_transition_ms, None);
        assert_eq!(finished.instruction_index, None);
        assert!(finished.finished);
        assert!(!runner.is_running());
    }

    #[test]
    fn lra_hold_uses_frequency_override() {
        let instructions: [Instruction<MonotonicCurveLut256>; 1] =
            [Instruction::hold_with_lra_frequency(20, u16::MAX, 190)];
        let program = Program::new(MotorKind::Lra, &instructions);
        let compiled = CompiledHapticDef::new("demo", program, None);
        let mut runner =
            Runner::from_compiled(&compiled, MotorConfig::Lra(LraConfig::new(2047, 235))).unwrap();
        runner.start(0);

        let frame = runner.poll(0);
        assert_eq!(
            frame.command,
            DriveCommand::Lra {
                amplitude: 2047,
                frequency_hz: 190
            }
        );
        assert_eq!(frame.next_transition_ms, Some(20));
        assert!(!frame.finished);
    }

    #[test]
    fn repeat_forever_rolls_cycle_origin() {
        let instructions: [Instruction<MonotonicCurveLut256>; 1] =
            [Instruction::hold(10, u16::MAX)];
        let program = Program::new(MotorKind::Erm, &instructions).repeat_forever();
        let compiled = CompiledHapticDef::new("demo", program, None);
        let mut runner =
            Runner::from_compiled(&compiled, MotorConfig::Erm(ErmConfig::new(255))).unwrap();
        runner.start(0);

        let frame = runner.poll(25);
        assert_eq!(frame.command, DriveCommand::Erm { duty: 255 });
        assert_eq!(frame.next_transition_ms, Some(30));
        assert_eq!(frame.instruction_index, Some(0));
        assert!(!frame.finished);
    }

    #[test]
    fn lra_ramp_defaults_to_resonant_frequency() {
        let instructions = [Instruction::Ramp(Ramp::new(20, 0, u16::MAX, LINEAR))];
        let program = Program::new(MotorKind::Lra, &instructions);
        let compiled = CompiledHapticDef::new("demo", program, None);
        let mut runner =
            Runner::from_compiled(&compiled, MotorConfig::Lra(LraConfig::new(1023, 240))).unwrap();
        runner.start(0);

        let frame = runner.poll(10);
        match frame.command {
            DriveCommand::Lra {
                amplitude,
                frequency_hz,
            } => {
                assert!(amplitude > 0);
                assert_eq!(frequency_hz, 240);
            }
            _ => panic!("expected LRA command"),
        }
    }

    #[test]
    fn construction_validates_program_and_motor_kind() {
        let empty: [Instruction<MonotonicCurveLut256>; 0] = [];
        let program = Program::new(MotorKind::Erm, &empty);
        let compiled = CompiledHapticDef::new("empty", program, None);
        let error =
            Runner::from_compiled(&compiled, MotorConfig::Erm(ErmConfig::new(255))).unwrap_err();
        assert_eq!(error, Error::EmptyProgram);

        let instructions: [Instruction<MonotonicCurveLut256>; 1] = [Instruction::hold(5, 100)];
        let program = Program::new(MotorKind::Erm, &instructions);
        let compiled = CompiledHapticDef::new("erm", program, None);
        let error = Runner::from_compiled(&compiled, MotorConfig::Lra(LraConfig::new(1000, 240)))
            .unwrap_err();
        assert_eq!(
            error,
            Error::MotorKindMismatch {
                expected: MotorKind::Erm,
                got: MotorKind::Lra,
            }
        );
    }

    #[test]
    fn ergonomic_start_helpers_work() {
        let instructions: [Instruction<MonotonicCurveLut256>; 1] = [Instruction::hold(10, 1000)];
        let program = Program::new(MotorKind::Erm, &instructions);
        let compiled = CompiledHapticDef::new("demo", program, None);
        let mut runner =
            Runner::from_compiled(&compiled, MotorConfig::Erm(ErmConfig::new(255))).unwrap();
        let first = runner.poll_or_start(42);
        assert!(first.is_active());
        assert_eq!(runner.start_ms(), 42);

        let restarted = runner.start_and_poll(100);
        assert!(restarted.is_active());
        assert_eq!(runner.start_ms(), 100);

        runner.stop();
        let idle = runner.poll(110);
        assert!(idle.is_idle());
    }

    #[test]
    fn from_compiled_helpers_work() {
        let instructions = [Instruction::Ramp(Ramp::new(20, 0, u16::MAX, LINEAR))];
        let program = Program::new(MotorKind::Erm, &instructions);
        let compiled = CompiledHapticDef::new("demo", program, None);

        let mut runner =
            Runner::from_compiled(&compiled, MotorConfig::Erm(ErmConfig::new(255))).unwrap();
        runner.start(10);
        assert!(runner.is_running());
        assert_eq!(runner.start_ms(), 10);

        let mut from_compiled =
            Runner::from_compiled_started(&compiled, MotorConfig::Erm(ErmConfig::new(255)), 20)
                .unwrap();
        let frame = from_compiled.poll(25);
        assert!(frame.is_active());
        assert_eq!(from_compiled.motor().kind(), MotorKind::Erm);
    }

    #[test]
    fn profile_gamma_curve_maps_output_level() {
        let instructions: [Instruction<MonotonicCurveLut256>; 1] = [Instruction::hold(20, 32_768)];
        let program = Program::new(MotorKind::Erm, &instructions);
        let profile = MotorProfile::new(0, 255, 64, 255, Some(&SQUARE), 2, 1, 8);
        let compiled = CompiledHapticDef::new("gamma_hold", program, Some(&profile));
        let mut runner =
            Runner::from_compiled_started(&compiled, MotorConfig::Erm(ErmConfig::new(255)), 0)
                .unwrap();

        let frame = runner.poll(0);
        match frame.command {
            DriveCommand::Erm { duty } => assert!((60..=66).contains(&duty)),
            _ => panic!("expected ERM command"),
        }
    }

    #[test]
    fn floor_snaps_low_level_to_off() {
        // min_run_frac=153 (~60%), so levels below ~60% of u16::MAX should snap to 0.
        let instructions: [Instruction<MonotonicCurveLut256>; 1] = [Instruction::hold(20, 10_000)];
        let program = Program::new(MotorKind::Erm, &instructions);
        let profile = MotorProfile::new(0, 255, 153, 255, None, 2, 1, 8);
        let compiled = CompiledHapticDef::new("floor_test", program, Some(&profile));
        let mut runner =
            Runner::from_compiled_started(&compiled, MotorConfig::Erm(ErmConfig::new(255)), 0)
                .unwrap();

        let frame = runner.poll(0);
        assert_eq!(frame.command, DriveCommand::Off);
    }

    #[test]
    fn max_level_ceiling_clamps_output() {
        // max_frac=128 (~50%), hold at u16::MAX should be clamped down.
        let instructions: [Instruction<MonotonicCurveLut256>; 1] =
            [Instruction::hold(20, u16::MAX)];
        let program = Program::new(MotorKind::Erm, &instructions);
        let profile = MotorProfile::new(0, 128, 0, 128, None, 2, 1, 8);
        let compiled = CompiledHapticDef::new("max_test", program, Some(&profile));
        let mut runner =
            Runner::from_compiled_started(&compiled, MotorConfig::Erm(ErmConfig::new(1023)), 0)
                .unwrap();

        let frame = runner.poll(0);
        match frame.command {
            DriveCommand::Erm { duty } => {
                // max_frac=128 → max_level ≈ 32896.  scale(32896, 1023) ≈ 514
                assert!(duty <= 520, "duty {duty} should be clamped by max_level");
                assert!(duty > 0, "duty should be non-zero");
            }
            _ => panic!("expected ERM command"),
        }
    }

    #[test]
    fn kick_injection_after_floor_snap() {
        // First instruction: low level that gets floor-snapped → needs_kick.
        // Second instruction: level above min → kick should boost it.
        let instructions: [Instruction<MonotonicCurveLut256>; 2] = [
            Instruction::hold(5, 5_000),   // below min_run → snapped to off
            Instruction::hold(20, 40_000), // above min_run → should get kick
        ];
        let program = Program::new(MotorKind::Erm, &instructions);
        // kick_ms=10, kick_frac=255, min_run_frac=153 (~60%), max_frac=255
        let profile = MotorProfile::new(10, 255, 153, 255, None, 2, 1, 8);
        let compiled = CompiledHapticDef::new("kick_test", program, Some(&profile));
        let mut runner =
            Runner::from_compiled_started(&compiled, MotorConfig::Erm(ErmConfig::new(255)), 0)
                .unwrap();

        // t=0: first hold at 5000, below floor → Off + needs_kick set
        let frame0 = runner.poll(0);
        assert_eq!(frame0.command, DriveCommand::Off);

        // t=5: second hold at 40000, above floor → kick active, so level >= kick_level
        let frame1 = runner.poll(5);
        match frame1.command {
            DriveCommand::Erm { duty } => {
                // kick_frac=255 → kick_level=65535 → scale(65535,255)=255
                assert_eq!(duty, 255, "during kick pulse, duty should be at kick level");
            }
            _ => panic!("expected ERM command"),
        }

        // t=16: kick expired (kick_ms=10, started at t=5, ends at t=15)
        let frame2 = runner.poll(16);
        match frame2.command {
            DriveCommand::Erm { duty } => {
                // Normal level: 40000 → scale(40000, 255) ≈ 155
                assert!(
                    duty < 200,
                    "after kick expires, duty {duty} should be normal level"
                );
            }
            _ => panic!("expected ERM command"),
        }
    }

    #[test]
    fn kick_level_clamped_to_max() {
        // kick_frac=255 but max_frac=128 → kick_level should be clamped to max_level.
        let instructions: [Instruction<MonotonicCurveLut256>; 2] = [
            Instruction::hold(5, 5_000),   // below min → snapped to off
            Instruction::hold(20, 40_000), // above min → gets kick, but kick clamped to max
        ];
        let program = Program::new(MotorKind::Erm, &instructions);
        let profile = MotorProfile::new(10, 255, 64, 128, None, 2, 1, 8);
        let compiled = CompiledHapticDef::new("kick_max_test", program, Some(&profile));
        let mut runner =
            Runner::from_compiled_started(&compiled, MotorConfig::Erm(ErmConfig::new(1023)), 0)
                .unwrap();

        let _frame0 = runner.poll(0); // floor-snapped
        let frame1 = runner.poll(5); // kick active
        match frame1.command {
            DriveCommand::Erm { duty } => {
                // max_frac=128 → max_level ≈ 32896.  scale(32896, 1023) ≈ 514
                assert!(
                    duty <= 520,
                    "kick duty {duty} should be clamped by max_level"
                );
            }
            _ => panic!("expected ERM command"),
        }
    }

    #[test]
    fn pause_instruction_outputs_off() {
        let instructions: [Instruction<MonotonicCurveLut256>; 3] = [
            Instruction::hold(10, u16::MAX),
            Instruction::Pause { duration_ms: 20 },
            Instruction::hold(10, u16::MAX),
        ];
        let program = Program::new(MotorKind::Erm, &instructions);
        let compiled = CompiledHapticDef::new("pause_test", program, None);
        let mut runner =
            Runner::from_compiled_started(&compiled, MotorConfig::Erm(ErmConfig::new(255)), 0)
                .unwrap();

        // t=0: first hold
        let frame0 = runner.poll(0);
        assert_eq!(frame0.command, DriveCommand::Erm { duty: 255 });
        assert_eq!(frame0.instruction_index, Some(0));

        // t=10: pause
        let frame1 = runner.poll(10);
        assert_eq!(frame1.command, DriveCommand::Off);
        assert_eq!(frame1.instruction_index, Some(1));

        // t=30: third hold
        let frame2 = runner.poll(30);
        assert_eq!(frame2.command, DriveCommand::Erm { duty: 255 });
        assert_eq!(frame2.instruction_index, Some(2));

        // t=40: finished
        let frame3 = runner.poll(40);
        assert!(frame3.finished);
        assert!(frame3.is_finished());
    }

    #[test]
    fn initial_kick_fires_on_startup() {
        // With needs_kick=true at start, first poll above min_level triggers kick.
        let instructions: [Instruction<MonotonicCurveLut256>; 1] = [Instruction::hold(50, 40_000)];
        let program = Program::new(MotorKind::Erm, &instructions);
        let profile = MotorProfile::new(12, 255, 64, 255, None, 2, 1, 8);
        let compiled = CompiledHapticDef::new("startup_kick", program, Some(&profile));
        let mut runner =
            Runner::from_compiled_started(&compiled, MotorConfig::Erm(ErmConfig::new(255)), 0)
                .unwrap();

        // t=0: kick fires (needs_kick=true from start, level above min)
        let frame0 = runner.poll(0);
        match frame0.command {
            DriveCommand::Erm { duty } => assert_eq!(duty, 255, "kick should boost to max"),
            _ => panic!("expected ERM command"),
        }

        // t=12: kick expired, normal level
        let frame1 = runner.poll(12);
        match frame1.command {
            DriveCommand::Erm { duty } => {
                assert!(duty < 200, "after kick, duty {duty} should be normal level");
            }
            _ => panic!("expected ERM command"),
        }
    }

    #[test]
    fn next_transition_ms_reflects_kick_expiry() {
        // Hold for 100ms at a level above min. Kick should expire at kick_ms,
        // so next_transition_ms should be kick_end_ms rather than instruction end.
        let instructions: [Instruction<MonotonicCurveLut256>; 1] = [Instruction::hold(100, 50_000)];
        let program = Program::new(MotorKind::Erm, &instructions);
        let profile = MotorProfile::new(10, 255, 64, 255, None, 2, 1, 8);
        let compiled = CompiledHapticDef::new("kick_deadline", program, Some(&profile));
        let mut runner =
            Runner::from_compiled_started(&compiled, MotorConfig::Erm(ErmConfig::new(255)), 0)
                .unwrap();

        // t=0: kick fires, kick_end_ms=10. next_transition = min(100, 10) = 10
        let frame0 = runner.poll(0);
        assert_eq!(frame0.next_transition_ms, Some(10));

        // t=10: kick expired, next_transition = instruction end = 100
        let frame1 = runner.poll(10);
        assert_eq!(frame1.next_transition_ms, Some(100));
    }

    #[test]
    fn multi_instruction_locate_iterates_correctly() {
        let instructions: [Instruction<MonotonicCurveLut256>; 3] = [
            Instruction::hold(10, 10_000),
            Instruction::hold(10, 30_000),
            Instruction::hold(10, u16::MAX),
        ];
        let program = Program::new(MotorKind::Erm, &instructions);
        let compiled = CompiledHapticDef::new("multi", program, None);
        let mut runner =
            Runner::from_compiled_started(&compiled, MotorConfig::Erm(ErmConfig::new(255)), 0)
                .unwrap();

        // Each hold is 10ms, so t=5→idx0, t=15→idx1, t=25→idx2
        assert_eq!(runner.poll(5).instruction_index, Some(0));
        assert_eq!(runner.poll(15).instruction_index, Some(1));
        assert_eq!(runner.poll(25).instruction_index, Some(2));
    }

    #[test]
    fn kick_rearms_after_pause_between_pulses() {
        // Two above-min holds with a Pause between them. Kick must fire on both.
        let instructions: [Instruction<MonotonicCurveLut256>; 3] = [
            Instruction::hold(20, 40_000),
            Instruction::Pause { duration_ms: 15 },
            Instruction::hold(20, 40_000),
        ];
        let program = Program::new(MotorKind::Erm, &instructions);
        let profile = MotorProfile::new(10, 255, 64, 255, None, 2, 1, 8);
        let compiled = CompiledHapticDef::new("pause_kick", program, Some(&profile));
        let mut runner =
            Runner::from_compiled_started(&compiled, MotorConfig::Erm(ErmConfig::new(255)), 0)
                .unwrap();

        // t=0: first pulse gets startup kick
        let first = runner.poll(0);
        match first.command {
            DriveCommand::Erm { duty } => assert_eq!(duty, 255, "first pulse should kick"),
            _ => panic!("expected ERM command"),
        }

        // t=10: kick expired on first pulse
        let after_kick = runner.poll(10);
        match after_kick.command {
            DriveCommand::Erm { duty } => {
                assert!(duty < 200, "after first kick, duty {duty} should be normal");
            }
            _ => panic!("expected ERM command"),
        }

        // t=20: pause → Off and re-arm
        let pause = runner.poll(20);
        assert_eq!(pause.command, DriveCommand::Off);

        // t=35: second pulse must kick again
        let second = runner.poll(35);
        match second.command {
            DriveCommand::Erm { duty } => {
                assert_eq!(duty, 255, "second pulse after Pause should kick");
            }
            _ => panic!("expected ERM command"),
        }
    }

    #[test]
    fn lra_hz_to_wakes_between_coarse_amplitude_steps() {
        // Flat amplitude (tickless amplitude deadline = segment end only) with a
        // wide Hz sweep: polling solely at next_transition_ms must still advance Hz.
        let mut ramp = Ramp::new(1_000, u16::MAX, u16::MAX, LINEAR)
            .with_quantization(u16::MAX, Rounding::Nearest)
            .with_lra_frequency(100);
        ramp.lra_frequency_hz_to = Some(200);
        let instructions = [Instruction::Ramp(ramp)];
        let program = Program::new(MotorKind::Lra, &instructions);
        let compiled = CompiledHapticDef::new("hz_wake", program, None);
        let mut runner = Runner::from_compiled_started(
            &compiled,
            MotorConfig::Lra(LraConfig::new(2047, 240)),
            0,
        )
        .unwrap();

        let mut now = 0u32;
        let mut last_hz = None;
        let mut saw_hz_advance_before_amp_end = false;
        let mut polls = 0u32;

        while now < 1_000 && polls < 2_000 {
            let frame = runner.poll(now);
            let hz = match frame.command {
                DriveCommand::Lra { frequency_hz, .. } => frequency_hz,
                other => panic!("expected LRA command, got {other:?}"),
            };

            if let Some(prev) = last_hz
                && hz > prev
                && now < 1_000
            {
                saw_hz_advance_before_amp_end = true;
            }
            last_hz = Some(hz);

            let Some(next) = frame.next_transition_ms else {
                break;
            };
            if next <= now {
                break;
            }
            now = next;
            polls += 1;
        }

        assert!(
            saw_hz_advance_before_amp_end,
            "Hz should advance between coarse amplitude steps when following next_transition_ms"
        );
        assert!(
            last_hz.unwrap_or(0) > 100,
            "sweep should progress past starting Hz, last={last_hz:?}"
        );
    }

    /// Count the wake-ups a caller performs when it follows `next_transition_ms`
    /// exactly, over `window_ms` starting at t=0.
    fn count_wakeups(runner: &mut Runner<'_, MonotonicCurveLut256>, window_ms: u32) -> u32 {
        let mut now = 0u32;
        let mut wakeups = 0u32;

        while now < window_ms && wakeups < 10_000 {
            let frame = runner.poll(now);
            let Some(next) = frame.next_transition_ms else {
                break;
            };
            if next <= now {
                break;
            }
            now = next;
            wakeups += 1;
        }

        wakeups
    }

    #[test]
    fn pause_with_zero_min_level_does_not_storm_wakeups() {
        // Regression: with min_run_frac == 0 the kick used to arm and fire on
        // every poll of a resting segment, pushing kick_end_ms forward and
        // forcing a wake-up every kick_ms for the whole Pause.
        let instructions: [Instruction<MonotonicCurveLut256>; 2] =
            [Instruction::pause(5_000), Instruction::hold(20, 40_000)];
        let program = Program::new(MotorKind::Erm, &instructions);
        let profile = MotorProfile::new(10, 255, 0, 255, None, 2, 1, 8);
        let compiled = CompiledHapticDef::new("storm", program, Some(&profile));
        let mut runner =
            Runner::from_compiled_started(&compiled, MotorConfig::Erm(ErmConfig::new(255)), 0)
                .unwrap();

        assert_eq!(
            count_wakeups(&mut runner, 5_000),
            1,
            "a 5s pause should schedule exactly one wake-up at its end"
        );
    }

    #[test]
    fn kick_still_fires_after_pause_when_min_level_is_zero() {
        // The storm fix must not cost us the kick on the pulse after the Pause.
        let instructions: [Instruction<MonotonicCurveLut256>; 2] =
            [Instruction::pause(100), Instruction::hold(50, 40_000)];
        let program = Program::new(MotorKind::Erm, &instructions);
        let profile = MotorProfile::new(10, 255, 0, 255, None, 2, 1, 8);
        let compiled = CompiledHapticDef::new("kick_after_pause", program, Some(&profile));
        let mut runner =
            Runner::from_compiled_started(&compiled, MotorConfig::Erm(ErmConfig::new(255)), 0)
                .unwrap();

        assert_eq!(runner.poll(0).command, DriveCommand::Off);
        match runner.poll(100).command {
            DriveCommand::Erm { duty } => assert_eq!(duty, 255, "pulse after Pause should kick"),
            other => panic!("expected ERM command, got {other:?}"),
        }
        match runner.poll(111).command {
            DriveCommand::Erm { duty } => assert!(duty < 200, "kick should expire, got {duty}"),
            other => panic!("expected ERM command, got {other:?}"),
        }
    }

    #[test]
    fn level_scaling_to_zero_duty_reports_off() {
        // Regression: a non-zero level that scales to duty 0 used to emit
        // `Erm { duty: 0 }`, which reads as "driver on" to consumers.
        let instructions: [Instruction<MonotonicCurveLut256>; 1] = [Instruction::hold(20, 100)];
        let program = Program::new(MotorKind::Erm, &instructions);
        let compiled = CompiledHapticDef::new("tiny", program, None);
        let mut runner =
            Runner::from_compiled_started(&compiled, MotorConfig::Erm(ErmConfig::new(255)), 0)
                .unwrap();

        assert_eq!(runner.poll(0).command, DriveCommand::Off);
    }

    #[test]
    fn long_lra_sweep_does_not_overflow() {
        // `delta * t` overflowed u32 past ~6 hours of ramp; u64 math keeps it sane.
        let mut ramp = Ramp::new(20_000_000, u16::MAX, u16::MAX, LINEAR).with_lra_frequency(100);
        ramp.lra_frequency_hz_to = Some(300);
        let instructions = [Instruction::Ramp(ramp)];
        let program = Program::new(MotorKind::Lra, &instructions);
        let compiled = CompiledHapticDef::new("long_sweep", program, None);
        let mut runner = Runner::from_compiled_started(
            &compiled,
            MotorConfig::Lra(LraConfig::new(2047, 240)),
            0,
        )
        .unwrap();

        match runner.poll(10_000_000).command {
            DriveCommand::Lra { frequency_hz, .. } => assert_eq!(frequency_hz, 200),
            other => panic!("expected LRA command, got {other:?}"),
        }
    }

    #[test]
    fn forever_near_u32_max_keeps_segment_deadlines() {
        let instructions: [Instruction<MonotonicCurveLut256>; 1] =
            [Instruction::hold(10, u16::MAX)];
        let program = Program::new(MotorKind::Erm, &instructions).repeat_forever();
        let compiled = CompiledHapticDef::new("near_max", program, None);
        let mut runner =
            Runner::from_compiled(&compiled, MotorConfig::Erm(ErmConfig::new(255))).unwrap();
        runner.start(0);

        // 3ms into a 10ms cycle near the end of the u32 timeline.
        let now = (u32::MAX / 10) * 10 + 3;
        let frame = runner.poll(now);
        assert_eq!(frame.command, DriveCommand::Erm { duty: 255 });
        assert_eq!(frame.instruction_index, Some(0));
        assert_eq!(frame.next_transition_ms, Some(now.wrapping_add(7)));
        assert!(!frame.finished);
    }

    #[test]
    fn forever_continues_after_clock_wraparound() {
        let instructions: [Instruction<MonotonicCurveLut256>; 2] =
            [Instruction::hold(5, u16::MAX), Instruction::hold(5, 10_000)];
        let program = Program::new(MotorKind::Erm, &instructions).repeat_forever();
        let compiled = CompiledHapticDef::new("clock_wrap", program, None);
        let start = u32::MAX - 2;
        let mut runner =
            Runner::from_compiled_started(&compiled, MotorConfig::Erm(ErmConfig::new(255)), start)
                .unwrap();

        let frame = runner.poll(start.wrapping_add(7));
        assert_eq!(frame.instruction_index, Some(1));
        assert_eq!(frame.next_transition_ms, Some(start.wrapping_add(10)));
        assert!(!frame.finished);
    }

    #[test]
    fn ramp_and_lra_sweep_continue_after_clock_wraparound() {
        let mut ramp = Ramp::new(10, 0, u16::MAX, LINEAR).with_lra_frequency(100);
        ramp.lra_frequency_hz_to = Some(200);
        let instructions = [Instruction::Ramp(ramp)];
        let program = Program::new(MotorKind::Lra, &instructions);
        let compiled = CompiledHapticDef::new("ramp_clock_wrap", program, None);
        let start = u32::MAX - 5;
        let mut runner = Runner::from_compiled_started(
            &compiled,
            MotorConfig::Lra(LraConfig::new(1_000, 200)),
            start,
        )
        .unwrap();

        let now = start.wrapping_add(6);
        let frame = runner.poll(now);
        match frame.command {
            DriveCommand::Lra {
                amplitude,
                frequency_hz,
            } => {
                assert!(amplitude > 0, "ramp amplitude should advance after wrap");
                assert_eq!(frequency_hz, 160);
            }
            _ => panic!("expected LRA command"),
        }
        let next = frame.next_transition_ms.unwrap();
        assert!(next.wrapping_sub(now) <= 4);
    }

    #[test]
    fn kick_expires_after_clock_wraparound() {
        let instructions: [Instruction<MonotonicCurveLut256>; 1] = [Instruction::hold(50, 40_000)];
        let program = Program::new(MotorKind::Erm, &instructions);
        let profile = MotorProfile::new(10, 255, 64, 255, None, 2, 1, 8);
        let compiled = CompiledHapticDef::new("kick_clock_wrap", program, Some(&profile));
        let start = u32::MAX - 5;
        let mut runner =
            Runner::from_compiled_started(&compiled, MotorConfig::Erm(ErmConfig::new(255)), start)
                .unwrap();

        let kick = runner.poll(start);
        assert_eq!(kick.command, DriveCommand::Erm { duty: 255 });
        assert_eq!(kick.next_transition_ms, Some(start.wrapping_add(10)));

        let after_kick = runner.poll(start.wrapping_add(10));
        match after_kick.command {
            DriveCommand::Erm { duty } => {
                assert!(duty < 200, "after kick, duty {duty} should be normal level");
            }
            _ => panic!("expected ERM command"),
        }
    }

    #[test]
    fn count_near_u32_max_keeps_segment_deadlines() {
        let instructions: [Instruction<MonotonicCurveLut256>; 2] =
            [Instruction::hold(5, u16::MAX), Instruction::hold(5, 10_000)];
        // Enough repeats that total duration saturates well past u32::MAX.
        let program = Program::new(MotorKind::Erm, &instructions)
            .with_loop_mode(LoopMode::Count(u32::MAX / 10 + 100));
        let compiled = CompiledHapticDef::new("count_near_max", program, None);
        let mut runner =
            Runner::from_compiled(&compiled, MotorConfig::Erm(ErmConfig::new(255))).unwrap();
        runner.start(0);

        // 7ms into a 10ms cycle → second hold, 3ms remaining (stay below u32::MAX).
        let now = u32::MAX - 8; // MAX ≡ 5 (mod 10) ⇒ now ≡ 7 (mod 10)
        let frame = runner.poll(now);
        assert_eq!(frame.instruction_index, Some(1));
        assert_eq!(frame.next_transition_ms, Some(now.wrapping_add(3)));
    }
}