from math import pi, sin

SAMPLE_RATE = 44_100
INT16_MAX = 2**15 - 1

def synth(note):
    buf = [0] * 512
    for i, _ in enumerate(buf):
        note.phase = (note.phase + note.freq / SAMPLE_RATE) % 1.0
        # oscillator
        match note.waveform:
            case "saw": sample = 2 * note.phase - 1.0
            case "square": sample = 1.0 if note.phase < 0.5 else -1.0
            case "sine": sample = sin(2 * pi * note.phase)
            case "triangle": sample = 4 * abs(note.phase - 0.5) - 1.0
            case _: sample = 0.0
        # envelope
        target = 1 if note.playing else 0
        if target == 1:
            note.gain = min(note.gain + 1 / (0.010 * SAMPLE_RATE), 0.2)  # attack
        else:
            note.gain = max(note.gain - 1 / (0.050 * SAMPLE_RATE), 0)  # release

        # signal processing
        if note.waveshaping:
            drive = 2
            sample *= abs(sample) * drive
            #sample = tanh(drive * sample)
        if note.lowpass:
            note.lp += 0.05 * (sample - note.lp)
            sample = note.lp * note.gain
        else:
            sample = sample * note.gain
        # convert to 16-bit signed integer and feed to buffer
        buf[i] = int(sample * INT16_MAX)
    return buf