#include "synth.h"
#include "audio/window.h"
#include <atomic>
#include <string.h> // For memset

struct Voice {
  bool active;
  int spectrogram_id;
  float volume;
  float pan_left;
  float pan_right;

  int current_spectral_frame;
  int total_spectral_frames;

  float time_domain_buffer[DCT_SIZE];
  int buffer_pos;

  const volatile float *active_spectral_data;
};

static struct {
  Spectrogram spectrograms[MAX_SPECTROGRAMS];
  const volatile float *active_spectrogram_data[MAX_SPECTROGRAMS];
  bool spectrogram_registered[MAX_SPECTROGRAMS];
} g_synth_data;

static Voice g_voices[MAX_VOICES];
static float g_current_output_peak = 0.0f; // Global peak for visualization

void synth_init() {
  memset(&g_synth_data, 0, sizeof(g_synth_data));
  memset(g_voices, 0, sizeof(g_voices));
  g_current_output_peak = 0.0f;
}

void synth_shutdown() {
  // Nothing to do here since we are not allocating memory
}

int synth_register_spectrogram(const Spectrogram *spec) {
  for (int i = 0; i < MAX_SPECTROGRAMS; ++i) {
    if (!g_synth_data.spectrogram_registered[i]) {
      g_synth_data.spectrograms[i] = *spec;
      g_synth_data.active_spectrogram_data[i] = spec->spectral_data_a;
      g_synth_data.spectrogram_registered[i] = true;
      return i;
    }
  }
  return -1; // No free slots
}

void synth_unregister_spectrogram(int spectrogram_id) {
  if (spectrogram_id >= 0 && spectrogram_id < MAX_SPECTROGRAMS) {
    g_synth_data.spectrogram_registered[spectrogram_id] = false;
  }
}

float *synth_begin_update(int spectrogram_id) {
  if (spectrogram_id < 0 || spectrogram_id >= MAX_SPECTROGRAMS ||
      !g_synth_data.spectrogram_registered[spectrogram_id]) {
    return nullptr;
  }

  const volatile float *active_ptr =
      g_synth_data.active_spectrogram_data[spectrogram_id];

  if (active_ptr == g_synth_data.spectrograms[spectrogram_id].spectral_data_a) {
    return g_synth_data.spectrograms[spectrogram_id].spectral_data_b;
  } else {
    return g_synth_data.spectrograms[spectrogram_id].spectral_data_a;
  }
}

void synth_commit_update(int spectrogram_id) {
  if (spectrogram_id < 0 || spectrogram_id >= MAX_SPECTROGRAMS ||
      !g_synth_data.spectrogram_registered[spectrogram_id]) {
    return;
  }

  const volatile float *old_active_ptr =
      g_synth_data.active_spectrogram_data[spectrogram_id];
  const float *new_active_ptr =
      (old_active_ptr ==
       g_synth_data.spectrograms[spectrogram_id].spectral_data_a)
          ? g_synth_data.spectrograms[spectrogram_id].spectral_data_b
          : g_synth_data.spectrograms[spectrogram_id].spectral_data_a;

  // Atomic swap using GCC/Clang builtins for thread safety
  __atomic_store_n(
      (const float **)&g_synth_data.active_spectrogram_data[spectrogram_id],
      new_active_ptr, __ATOMIC_RELEASE);
}

void synth_trigger_voice(int spectrogram_id, float volume, float pan) {
  if (spectrogram_id < 0 || spectrogram_id >= MAX_SPECTROGRAMS ||
      !g_synth_data.spectrogram_registered[spectrogram_id]) {
    return;
  }

  for (int i = 0; i < MAX_VOICES; ++i) {
    if (!g_voices[i].active) {
      Voice &v = g_voices[i];
      v.active = true;
      v.spectrogram_id = spectrogram_id;
      v.volume = volume;

      // Simple linear panning
      v.pan_left = (pan > 0.0f) ? (1.0f - pan) : 1.0f;
      v.pan_right = (pan < 0.0f) ? (1.0f + pan) : 1.0f;

      v.current_spectral_frame = 0;
      v.total_spectral_frames =
          g_synth_data.spectrograms[spectrogram_id].num_frames;
      v.buffer_pos = DCT_SIZE; // Force IDCT on first render
      v.active_spectral_data =
          g_synth_data.active_spectrogram_data[spectrogram_id];

      return; // Voice triggered
    }
  }
}

void synth_render(float *output_buffer, int num_frames) {
  float window[WINDOW_SIZE];
  hamming_window_512(window);

  float current_peak_in_frame = 0.0f;

  for (int i = 0; i < num_frames; ++i) {
    float left_sample = 0.0f;
    float right_sample = 0.0f;

    for (int v_idx = 0; v_idx < MAX_VOICES; ++v_idx) {
      Voice &v = g_voices[v_idx];
      if (!v.active)
        continue;

      if (v.buffer_pos >= DCT_SIZE) {
        if (v.current_spectral_frame >= v.total_spectral_frames) {
          v.active = false;
          continue;
        }

        // Fetch the latest active spectrogram pointer for this voice
        v.active_spectral_data =
            g_synth_data.active_spectrogram_data[v.spectrogram_id];

        const float *spectral_frame = (const float *)v.active_spectral_data +
                                      (v.current_spectral_frame * DCT_SIZE);

        float windowed_frame[DCT_SIZE];
        for (int j = 0; j < DCT_SIZE; ++j) {
          windowed_frame[j] = spectral_frame[j] * window[j];
        }

        idct_512(windowed_frame, v.time_domain_buffer);

        v.buffer_pos = 0;
        v.current_spectral_frame++;
      }

      float voice_sample = v.time_domain_buffer[v.buffer_pos] * v.volume;
      left_sample += voice_sample * v.pan_left;
      right_sample += voice_sample * v.pan_right;

      v.buffer_pos++;
    }

    output_buffer[i * 2] = left_sample;
    output_buffer[i * 2 + 1] = right_sample;

    current_peak_in_frame =
        fmaxf(current_peak_in_frame, fmaxf(fabsf(left_sample), fabsf(right_sample)));
  }
  g_current_output_peak = current_peak_in_frame;
}

int synth_get_active_voice_count() {
  int count = 0;
  for (int i = 0; i < MAX_VOICES; ++i) {
    if (g_voices[i].active) {
      count++;
    }
  }
  return count;
}

float synth_get_output_peak() { return g_current_output_peak; }