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

SR = 44100

def synth_multi(path, freqs, dur=6.0, amp=0.5, am=0.3, sr=SR):
    n = int(sr*dur)
    out = [0.0]*n
    for f in freqs:
        for i in range(n):
            t = i/sr
            # each tone: carrier + gentle AM (makes it "resonant" for the detector)
            out[i] += math.sin(2*math.pi*f*t)*(1.0 + am*math.sin(2*math.pi*(f/8.0)*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/0.05, (dur-t)/0.1)
        a.append(max(-32767, min(32767, int(v*sc*32767*fade))))
    w = wave.open(path, 'wb')
    w.setnchannels(1); w.setsampwidth(2); w.setframerate(sr)
    w.writeframes(a.tobytes())
    w.close()
    print("wrote", path, "tones", len(freqs), "amp", amp)

if __name__ == '__main__':
    freqs = [int(f) for f in sys.argv[2].split(',')]
    synth_multi(sys.argv[1], freqs, dur=float(sys.argv[3]) if len(sys.argv)>3 else 6.0)