// This file is part of the 64k demo project.
// It manages the low-level audio device and high-level audio state.
// Now uses backend abstraction for testability.

#include "audio.h"
#include "audio_backend.h"
#include "miniaudio_backend.h"
#include "ring_buffer.h"
#include "synth.h"
#include "util/asset_manager.h"

#define MINIAUDIO_IMPLEMENTATION
#include "miniaudio.h"

#include <stdio.h>

// Global ring buffer for audio streaming
static AudioRingBuffer g_ring_buffer;

// Global backend pointer for audio abstraction
static AudioBackend* g_audio_backend = nullptr;
static MiniaudioBackend g_default_backend;
static bool g_using_default_backend = false;

#if !defined(STRIP_ALL)
// Allow tests to inject a custom backend
void audio_set_backend(AudioBackend* backend) {
  g_audio_backend = backend;
}

// Get current backend (for tests)
AudioBackend* audio_get_backend() {
  return g_audio_backend;
}
#endif /* !defined(STRIP_ALL) */

int register_spec_asset(AssetId id) {
  size_t size;
  const uint8_t* data = GetAsset(id, &size);
  if (!data || size < sizeof(SpecHeader))
    return -1;

  const SpecHeader* header = (const SpecHeader*)data;
  const float* spectral_data = (const float*)(data + sizeof(SpecHeader));

  Spectrogram spec;
  spec.spectral_data_a = spectral_data;
  spec.spectral_data_b = spectral_data; // No double-buffer for static assets
  spec.num_frames = header->num_frames;

  return synth_register_spectrogram(&spec);
}

void audio_init() {
  synth_init();

  // Use default backend if none set
  if (g_audio_backend == nullptr) {
    g_audio_backend = &g_default_backend;
    g_using_default_backend = true;
  }

  g_audio_backend->init();
}

void audio_start() {
  if (g_audio_backend == nullptr) {
    printf("Cannot start: audio not initialized.\n");
    return;
  }
  g_audio_backend->start();
}

void audio_render_ahead(float music_time, float dt) {
  // Calculate how much audio is currently buffered
  int buffered_samples = g_ring_buffer.available_read();
  float buffered_time =
      (float)buffered_samples / (RING_BUFFER_SAMPLE_RATE * RING_BUFFER_CHANNELS);

  // Target: maintain look-ahead buffer
  const float target_lookahead =
      (float)RING_BUFFER_LOOKAHEAD_MS / 1000.0f;

  // Render in small chunks to keep synth time synchronized with tracker
  // Chunk size: one frame's worth of audio (~16.6ms @ 60fps)
  const int chunk_frames = (int)(dt * RING_BUFFER_SAMPLE_RATE);
  const int chunk_samples = chunk_frames * RING_BUFFER_CHANNELS;

  // Keep rendering small chunks until buffer is full enough
  while (buffered_time < target_lookahead) {
    const int frames_to_render = chunk_frames;
    if (frames_to_render <= 0) break;

    // Allocate temporary buffer (stereo)
    const int samples_to_render = frames_to_render * RING_BUFFER_CHANNELS;
    float* temp_buffer = new float[samples_to_render];

    // Render audio from synth (advances synth state incrementally)
    synth_render(temp_buffer, frames_to_render);

    // Write to ring buffer
    const int written = g_ring_buffer.write(temp_buffer, samples_to_render);

    // Notify backend of frames rendered (for testing/tracking)
    if (g_audio_backend != nullptr) {
      g_audio_backend->on_frames_rendered(written / RING_BUFFER_CHANNELS);
    }

    delete[] temp_buffer;

    // Update buffered time for next iteration
    buffered_time += (float)written / (RING_BUFFER_SAMPLE_RATE * RING_BUFFER_CHANNELS);

    // Safety: avoid infinite loop if buffer is full
    if (written < samples_to_render) break;
  }
}

float audio_get_playback_time() {
  const int64_t total_samples = g_ring_buffer.get_total_read();
  return (float)total_samples /
         (RING_BUFFER_SAMPLE_RATE * RING_BUFFER_CHANNELS);
}

// Expose ring buffer for backends
AudioRingBuffer* audio_get_ring_buffer() {
  return &g_ring_buffer;
}

#if !defined(STRIP_ALL)
void audio_render_silent(float duration_sec) {
  const int sample_rate = 32000;
  const int chunk_size = 512;
  int total_frames = (int)(duration_sec * sample_rate);
  float buffer[chunk_size * 2]; // Stereo

  while (total_frames > 0) {
    int frames_to_render =
        (total_frames > chunk_size) ? chunk_size : total_frames;
    synth_render(buffer, frames_to_render);
    total_frames -= frames_to_render;

    // Notify backend of frames rendered (for mock tracking)
    if (g_audio_backend != nullptr) {
      g_audio_backend->on_frames_rendered(frames_to_render);
    }
  }
}
#endif /* !defined(STRIP_ALL) */

void audio_update() {
}

void audio_shutdown() {
  if (g_audio_backend != nullptr) {
    g_audio_backend->shutdown();
  }
  synth_shutdown();

  // Clear backend pointer if using default
  if (g_using_default_backend) {
    g_audio_backend = nullptr;
    g_using_default_backend = false;
  }
}