#include <math.h>

#include <spa/param/audio/format-utils.h>
#include <pipewire/pipewire.h>

#define M_PI_M2 (M_PI + M_PI)

#define DEFAULT_RATE 44100
#define DEFAULT_PERIOD 1.0 / DEFAULT_RATE

#define DEFAULT_CHANNELS 2
#define DEFAULT_VOLUME 0.7
#define DEFAULT_FREQ 500

#define DEFAULT_ACCUMULATOR -1

#define PWSTREAM_NAME "Dorne"

struct data {
  struct pw_main_loop *loop;
  struct pw_stream *stream;

  /*
   */
  double t, tcyc; // global time and cycle time 
  uint32_t frame, cycle;
};

#define NEW_DATA (struct data) \
                 {             \
                   .t = 0,     \
                   .tcyc = 0,  \
                   .frame = 0, \
                   .cycle = 0, \
                 }

typedef int16_t (*snd)(struct data*);

inline void data_progress(struct data *state) {
  state->t += DEFAULT_PERIOD / DEFAULT_FREQ;
  state->tcyc += DEFAULT_PERIOD / DEFAULT_FREQ;
  if (++state->frame == DEFAULT_FREQ) {
    state->tcyc -= DEFAULT_PERIOD;
    state->frame = 0;
    state->cycle++;
  } 
}

int16_t snd_sine(struct data *state) {
  int16_t val;
  
  /* sin() gives a value between -1.0 and 1.0, we first apply
   * the volume and then scale with 32767.0 to get a 16 bits value
   * between [-32767 32767].
   * Another common method to convert a double to
   * 16 bits is to multiple by 32768.0 and then clamp to
   * [-32768 32767] to get the full 16 bits range. */
  val = sin(state->tcyc * M_PI_M2 * DEFAULT_FREQ) * 32767.0 * DEFAULT_VOLUME;
  
  return val;
}

int graph_snd(snd f, struct data *state, double t_max, FILE *fstream) {
  int16_t val;
  if (fstream == NULL)
    return 1;
  
  fputs("x, sin(x)\n", fstream);
  while (state->t < t_max) {
    val = f(state);
    fprintf(fstream, "%f, %d\n", state->t, val);
    data_progress(state);
  }

  fclose(fstream);
  return 0;
}


/* [on_process] */
static void on_process(void *userdata) {
  struct data *data = userdata;
  struct pw_buffer *b;
  struct spa_buffer *buf;
  int n_frames, stride;
  int16_t *dst, val;
  int i, c;

  if ((b = pw_stream_dequeue_buffer(data->stream)) == NULL) {
    pw_log_warn("out of buffers: %m");
    return;
  }

  buf = b->buffer;
  if ((dst = buf->datas[0].data) == NULL)
    return;

  stride = sizeof(int16_t) * DEFAULT_CHANNELS;
  n_frames = buf->datas[0].maxsize / stride;
  if (b->requested)
    n_frames = SPA_MIN(b->requested, n_frames);

  for (i = 0; i < n_frames; i++) {
    val = snd_sine(data);
    for (c = 0; c < DEFAULT_CHANNELS; c++)
      *dst++ = val;
  }

  buf->datas[0].chunk->offset = 0;
  buf->datas[0].chunk->stride = stride;
  buf->datas[0].chunk->size = n_frames * stride;

  pw_stream_queue_buffer(data->stream, b);
}
/* [on_process] */

static const struct pw_stream_events stream_events = {
    PW_VERSION_STREAM_EVENTS,
    .process = on_process,
};

int main(int argc, char **argv) {
  struct data data = NEW_DATA;
  const struct spa_pod *params[1];
  uint8_t buffer[1024];
  struct spa_pod_builder b = SPA_POD_BUILDER_INIT(buffer, sizeof(buffer));

  // DEBUG: check sine wave is actually a sine wave
  FILE *fstream = fopen("sine.txt", "w");
  graph_snd(&snd_sine, &NEW_DATA, DEFAULT_PERIOD, fstream);
  exit(69);
  
  int pw_argc = 0;
  char **pw_argv = NULL;
  pw_init(&pw_argc, &pw_argv); // pw_init(&argc, &argv);

  data.loop = pw_main_loop_new(NULL);

  data.stream = pw_stream_new_simple(
      pw_main_loop_get_loop(data.loop), PWSTREAM_NAME,
      pw_properties_new(PW_KEY_MEDIA_TYPE, "Audio", PW_KEY_MEDIA_CATEGORY,
                        "Playback", PW_KEY_MEDIA_ROLE, "Music", NULL),
      &stream_events, &data);

  params[0] = spa_format_audio_raw_build(
      &b, SPA_PARAM_EnumFormat,
      &SPA_AUDIO_INFO_RAW_INIT(.format = SPA_AUDIO_FORMAT_S16,
                               .channels = DEFAULT_CHANNELS,
                               .rate = DEFAULT_RATE));

  pw_stream_connect(data.stream, PW_DIRECTION_OUTPUT, PW_ID_ANY,
                    PW_STREAM_FLAG_AUTOCONNECT | PW_STREAM_FLAG_MAP_BUFFERS |
                        PW_STREAM_FLAG_RT_PROCESS,
                    params, 1);

  // TODO: use pw_thread_loop instead of pw_main_loop
  pw_main_loop_run(data.loop);

  printf("exitting\n");
  pw_stream_destroy(data.stream);
  pw_main_loop_destroy(data.loop);

  return EXIT_SUCCESS;
}
/* [code] */