#include <math.h>

#include "config.h"

struct stfu_phaser stfu_pump_phaser(struct stfu_phaser phaser);
struct stfu_phaser stfu_set_phaser_frequency(struct stfu_phaser phaser,
                                             float frequency);

/* Useful for feeding into phase parameters of oscillators and such.
 * Repeats over [-PI, PI)
 */
struct stfu_phaser {
  float v, a;
} stfu_init_phaser(float frequency) {
  struct stfu_phaser r = {0};
  r = stfu_set_phaser_frequency(r, frequency);
  return r;
}

struct stfu_phaser stfu_pump_phaser(struct stfu_phaser phaser) {
  phaser.v += phaser.a;
  if (phaser.v >= (float)M_PI)
    phaser.v -= (float)M_PI * 2.0f;
  return phaser;
}

struct stfu_phaser stfu_set_phaser_frequency(struct stfu_phaser phaser,
                                             float frequency) {
  phaser.a = 2 * ((float)M_PI / (float)STFU_AUDIO_FRAME_RATE) * frequency;
  return phaser;
}