path: root/src/tests/test_variable_tempo.cc

// This file is part of the 64k demo project.
// It tests variable tempo system with music_time scaling.
// Verifies 2x speed-up and 2x slow-down reset tricks.

#include "audio/audio.h"
#include "audio/audio_engine.h"
#include "audio/backend/mock_audio_backend.h"
#include "audio/tracker.h"
#include <assert.h>
#include <cmath>
#include <stdio.h>

#if !defined(STRIP_ALL)

// Helper: Setup audio engine for testing
static void setup_audio_test(MockAudioBackend& backend, AudioEngine& engine) {
  audio_set_backend(&backend);
  engine.init();
  engine.load_music_data(&g_tracker_score, g_tracker_samples,
                         g_tracker_sample_assets, g_tracker_samples_count);
}

// Helper: Simulate tempo advancement with fixed steps
static void simulate_tempo(AudioEngine& engine, float& music_time,
                           float duration, float tempo_scale, float dt = 0.1f) {
  const int steps = (int)(duration / dt);
  for (int i = 0; i < steps; ++i) {
    music_time += dt * tempo_scale;
    engine.update(music_time, dt * tempo_scale);
  }
}

// Helper: Simulate tempo with variable scaling function
static void simulate_tempo_fn(AudioEngine& engine, float& music_time,
                              float& physical_time, float duration, float dt,
                              float (*tempo_fn)(float)) {
  const int steps = (int)(duration / dt);
  for (int i = 0; i < steps; ++i) {
    physical_time += dt;
    const float tempo_scale = tempo_fn(physical_time);
    music_time += dt * tempo_scale;
    engine.update(music_time, dt * tempo_scale);
  }
}

void test_basic_tempo_scaling() {
  printf("Test: Basic tempo scaling (1.0x, 2.0x, 0.5x)...\n");

  MockAudioBackend backend;
  AudioEngine engine;
  setup_audio_test(backend, engine);

  // Test 1: Normal tempo (1.0x)
  {
    backend.clear_events();
    float music_time = 0.0f;
    simulate_tempo(engine, music_time, 1.0f, 1.0f);
    printf("  1.0x tempo: music_time = %.3f (expected ~1.0)\n", music_time);
    assert(std::abs(music_time - 1.0f) < 0.01f);
  }

  // Test 2: Fast tempo (2.0x)
  {
    backend.clear_events();
    engine.reset();
    float music_time = 0.0f;
    simulate_tempo(engine, music_time, 1.0f, 2.0f);
    printf("  2.0x tempo: music_time = %.3f (expected ~2.0)\n", music_time);
    assert(std::abs(music_time - 2.0f) < 0.01f);
  }

  // Test 3: Slow tempo (0.5x)
  {
    backend.clear_events();
    engine.reset();
    float music_time = 0.0f;
    simulate_tempo(engine, music_time, 1.0f, 0.5f);
    printf("  0.5x tempo: music_time = %.3f (expected ~0.5)\n", music_time);
    assert(std::abs(music_time - 0.5f) < 0.01f);
  }

  engine.shutdown();
  printf("  ✓ Basic tempo scaling works correctly\n");
}

void test_2x_speedup_reset_trick() {
  printf("Test: 2x SPEED-UP reset trick...\n");

  MockAudioBackend backend;
  AudioEngine engine;
  setup_audio_test(backend, engine);

  float music_time = 0.0f;
  float physical_time = 0.0f;
  const float dt = 0.1f;

  // Phase 1: Accelerate from 1.0x to 2.0x over 5 seconds
  printf("  Phase 1: Accelerating 1.0x → 2.0x\n");
  auto accel_fn = [](float t) { return fminf(1.0f + (t / 5.0f), 2.0f); };
  simulate_tempo_fn(engine, music_time, physical_time, 5.0f, dt, accel_fn);

  const float tempo_scale = accel_fn(physical_time);
  printf("    After 5s physical: tempo=%.2fx, music_time=%.3f\n", tempo_scale,
         music_time);
  assert(tempo_scale >= 1.99f);

  // Phase 2: RESET - back to 1.0x tempo
  printf("  Phase 2: RESET to 1.0x tempo\n");
  const float music_time_before_reset = music_time;
  simulate_tempo(engine, music_time, 2.0f, 1.0f, dt);

  printf("    After reset + 2s: tempo=1.0x, music_time=%.3f\n", music_time);
  const float music_time_delta = music_time - music_time_before_reset;
  printf("    Music time delta: %.3f (expected ~2.0)\n", music_time_delta);
  assert(std::abs(music_time_delta - 2.0f) < 0.1f);

  engine.shutdown();
  printf("  ✓ 2x speed-up reset trick verified\n");
}

void test_2x_slowdown_reset_trick() {
  printf("Test: 2x SLOW-DOWN reset trick...\n");

  MockAudioBackend backend;
  AudioEngine engine;
  setup_audio_test(backend, engine);

  float music_time = 0.0f;
  float physical_time = 0.0f;
  const float dt = 0.1f;

  // Phase 1: Decelerate from 1.0x to 0.5x over 5 seconds
  printf("  Phase 1: Decelerating 1.0x → 0.5x\n");
  auto decel_fn = [](float t) { return fmaxf(1.0f - (t / 10.0f), 0.5f); };
  simulate_tempo_fn(engine, music_time, physical_time, 5.0f, dt, decel_fn);

  const float tempo_scale = decel_fn(physical_time);
  printf("    After 5s physical: tempo=%.2fx, music_time=%.3f\n", tempo_scale,
         music_time);
  assert(tempo_scale <= 0.51f);

  // Phase 2: RESET - back to 1.0x tempo
  printf("  Phase 2: RESET to 1.0x tempo\n");
  const float music_time_before_reset = music_time;
  simulate_tempo(engine, music_time, 2.0f, 1.0f, dt);

  printf("    After reset + 2s: tempo=1.0x, music_time=%.3f\n", music_time);
  const float music_time_delta = music_time - music_time_before_reset;
  printf("    Music time delta: %.3f (expected ~2.0)\n", music_time_delta);
  assert(std::abs(music_time_delta - 2.0f) < 0.1f);

  engine.shutdown();
  printf("  ✓ 2x slow-down reset trick verified\n");
}

void test_pattern_density_swap() {
  printf("Test: Pattern density swap at reset points...\n");

  MockAudioBackend backend;
  AudioEngine engine;
  setup_audio_test(backend, engine);

  float music_time = 0.0f;

  // Phase 1: Sparse pattern at normal tempo
  printf("  Phase 1: Sparse pattern, normal tempo\n");
  simulate_tempo(engine, music_time, 3.0f, 1.0f);
  const size_t sparse_events = backend.get_events().size();
  printf("    Events during sparse phase: %zu\n", sparse_events);

  // Phase 2: Accelerate to 2.0x
  printf("  Phase 2: Accelerating to 2.0x\n");
  simulate_tempo(engine, music_time, 2.0f, 2.0f);
  const size_t events_at_2x = backend.get_events().size() - sparse_events;
  printf("    Additional events during 2.0x: %zu\n", events_at_2x);

  // Phase 3: Reset to 1.0x
  printf("  Phase 3: Reset to 1.0x (simulating denser pattern)\n");
  const size_t events_before_reset_phase = backend.get_events().size();
  simulate_tempo(engine, music_time, 2.0f, 1.0f);
  const size_t events_after_reset = backend.get_events().size();

  printf("    Events during reset phase: %zu\n",
         events_after_reset - events_before_reset_phase);
  assert(backend.get_events().size() > 0);

  engine.shutdown();
  printf("  ✓ Pattern density swap points verified\n");
}

void test_continuous_acceleration() {
  printf("Test: Continuous acceleration from 0.5x to 2.0x...\n");

  MockAudioBackend backend;
  AudioEngine engine;
  setup_audio_test(backend, engine);

  float music_time = 0.0f;
  float physical_time = 0.0f;
  const float dt = 0.05f;
  const float min_tempo = 0.5f;
  const float max_tempo = 2.0f;

  printf("  Accelerating 0.5x → 2.0x over 10 seconds\n");

  auto accel_fn = [min_tempo, max_tempo](float t) {
    const float progress = t / 10.0f;
    return fmaxf(
        min_tempo,
        fminf(max_tempo, min_tempo + progress * (max_tempo - min_tempo)));
  };

  const int steps = (int)(10.0f / dt);
  for (int i = 0; i < steps; ++i) {
    physical_time += dt;
    const float tempo_scale = accel_fn(physical_time);
    music_time += dt * tempo_scale;
    engine.update(music_time, dt * tempo_scale);
    if (i % 50 == 0) {
      printf("    t=%.1fs: tempo=%.2fx, music_time=%.3f\n", physical_time,
             tempo_scale, music_time);
    }
  }

  const float final_tempo = accel_fn(physical_time);
  printf("  Final: tempo=%.2fx, music_time=%.3f\n", final_tempo, music_time);
  assert(final_tempo >= 1.99f);

  // Verify music_time (integral: 0.5*10 + 1.5*10²/(2*10) = 12.5)
  const float expected_music_time = 12.5f;
  printf("  Expected music_time: %.3f, actual: %.3f\n", expected_music_time,
         music_time);
  assert(std::abs(music_time - expected_music_time) < 0.5f);

  engine.shutdown();
  printf("  ✓ Continuous acceleration verified\n");
}

void test_oscillating_tempo() {
  printf("Test: Oscillating tempo (sine wave)...\n");

  MockAudioBackend backend;
  AudioEngine engine;
  setup_audio_test(backend, engine);

  float music_time = 0.0f;
  float physical_time = 0.0f;
  const float dt = 0.05f;

  printf("  Oscillating tempo: 0.8x ↔ 1.2x\n");

  auto oscil_fn = [](float t) { return 1.0f + 0.2f * sinf(t * 2.0f); };

  const int steps = 100;
  for (int i = 0; i < steps; ++i) {
    physical_time += dt;
    const float tempo_scale = oscil_fn(physical_time);
    music_time += dt * tempo_scale;
    engine.update(music_time, dt * tempo_scale);
    if (i % 25 == 0) {
      printf("    t=%.2fs: tempo=%.3fx, music_time=%.3f\n", physical_time,
             tempo_scale, music_time);
    }
  }

  printf("  Final: physical_time=%.2fs, music_time=%.3f (expected ~%.2f)\n",
         physical_time, music_time, physical_time);
  assert(std::abs(music_time - physical_time) < 0.5f);

  engine.shutdown();
  printf("  ✓ Oscillating tempo verified\n");
}

#endif /* !defined(STRIP_ALL) */

int main() {
#if !defined(STRIP_ALL)
  printf("Running Variable Tempo tests...\n\n");
  test_basic_tempo_scaling();
  test_2x_speedup_reset_trick();
  test_2x_slowdown_reset_trick();
  test_pattern_density_swap();
  test_continuous_acceleration();
  test_oscillating_tempo();
  printf("\n✅ All Variable Tempo tests PASSED\n");
  return 0;
#else
  printf("Variable Tempo tests skipped (STRIP_ALL enabled)\n");
  return 0;
#endif /* !defined(STRIP_ALL) */
}