#include "synth.h"
#include <math.h>
#define SAMPLE_RATE 44100.0f

void play_note(Note *note, int16_t *buffer, int buffer_size) {
    for (int i = 0; i < buffer_size; i++) {
        // update phase counter
        note->phase = fmodf(note->phase + note->freq / SAMPLE_RATE, 1.0f);

        // oscillator
        float sample = 0.0f;
        switch (note->form) {
            case WAVE_SINE: sample = sinf(2.0f * (float) M_PI * note->phase); break;
            case WAVE_SAW: sample = 2.0f * note->phase - 1.0f; break;
            case WAVE_SQUARE: sample = note->phase < 0.5f ? 1.0f : -1.0f; break;
            case WAVE_TRIANGLE: sample = 4.0f * fabsf(note->phase - 0.5f) - 1.0f; break;
            default: break;
        }

        //note->lp += note->filter_cutoff * (sample - note->lp);
        //sample = note->lp;

        // basic attack / release
        // convert attack / release time to a number of steps to reach target gain
        float attack_step = 0.2f / ((note->attack_ms / 1000.0f) * SAMPLE_RATE);
        float release_step = 0.2f / ((note->release_ms / 1000.0f) * SAMPLE_RATE);
        note->gain = note->is_playing
            ? fminf(note->gain + attack_step, 0.2f)  // attack
            : fmaxf(note->gain - release_step, 0);   // release

        // convert sample to 16-bit signed integer and apply gain
        buffer[i] = (int16_t) (note->gain * sample * (float) INT16_MAX);
    }
}