#!/usr/bin/env python3
import wave, array, math, sys

SR = 44100

def synth(path, freqs, dur=6.0, amp=1.0, gain_dbs=None, sr=SR):
    # amp = target peak amplitude (1.0 = full scale)
    n = int(sr*dur)
    out = [0.0]*n
    if gain_dbs is None:
        gain_dbs = [-20*math.log10(len(freqs))*0 + 0]*len(freqs)  # equal
    for k, f in enumerate(freqs):
        g = 1.0/len(freqs) if len(gain_dbs) != len(freqs) else 10**(gain_dbs[k]/20)
        for i in range(n):
            t = i/sr
            out[i] += g*math.sin(2*math.pi*f*t)
    peak = max(abs(v) for v in out) or 1.0
    sc = amp/peak
    a = array.array('h')
    for i, v in enumerate(out):
        t = i/sr
        fade = min(1.0, t/0.03, (dur-t)/0.05)
        a.append(max(-32767, min(32767, int(v*sc*fade*32767))))
    w = wave.open(path, 'wb')
    w.setnchannels(1); w.setsampwidth(2); w.setframerate(sr)
    w.writeframes(a.tobytes())
    w.close()

if __name__ == '__main__':
    # usage: synth.py <freq> [<amp level dBFS or amplitude>] [<path>]
    import os
    freq = float(sys.argv[1])
    amp = 1.0
    path = '/home/m/soothe-bt/tone.wav'
    for a in sys.argv[2:]:
        try:
            amp = float(a)
        except ValueError:
            path = a
    synth(path, [freq], amp=amp)
    print("wrote", path, freq, "Hz amp", amp)