lockstep/app/src/main/cpp/TempoController.cpp

//
// Created by david on 14.06.2026.
//

#include "TempoController.h"

TempoController::TempoController(std::atomic<bool> *have_stretch_factor, std::atomic<double> *stretch_factor) :
    have_stretch_factor(have_stretch_factor),
    stretch_factor(stretch_factor),
    lastBeatT(0.0),
    lastStepT(0.0)
{
    this->have_stretch_factor->store(false);
    this->stretch_factor->store(1.0);
}

void TempoController::reset(std::vector<double> beatTimes) {
    std::lock_guard<std::mutex> lock(mMutex);
    beatTimesSec.assign(beatTimes.begin(), beatTimes.end());
    lastBeatT = (0.0);
    lastStepT = (0.0);
}

void TempoController::resume() {}
void TempoController::pause() {}

void TempoController::seekTo(double oldMarkerPosSec, double newMarkerPosSec) {
    std::lock_guard<std::mutex> lock(mMutex);
    double dt = newMarkerPosSec - oldMarkerPosSec;
    lastBeatT += dt;
    lastStepT += dt;
}

/**
 * must be thread-safe since these are called from different threads
 * @param t marker position in sec of original music time
 */
void TempoController::onBeat(double t) {
    std::lock_guard<std::mutex> lock(mMutex);
    if(lastBeatT != 0.0) dtBeat = t - lastBeatT;
    lastBeatT = t;
    setStretchFactor();
}

/**
 * must be thread-safe since these are called from different threads
 * @param t time in sec of accelerometer timebase
 */
void TempoController::onStep(double t) {
    std::lock_guard<std::mutex> lock(mMutex);
    if(lastStepT != 0.0) dtStep = t - lastStepT;
    lastStepT = t;
    setStretchFactor();
}

void TempoController::setStretchFactor() {
    if(dtBeat == 0.0 || dtStep == 0.0) return;
    double ratio = dtStep / dtBeat;
    ratio = std::min(3.3, ratio);
    ratio = std::max(0.3, ratio);
    this->have_stretch_factor->store(true);
    this->stretch_factor->store(ratio);
}