#!/usr/bin/env python3
"""Generates exit.wav for the FredyGames build of Dave Gnukem.

The original data/sounds/exit.ogg is a track by Eric Matyas (soundimage.org), whose terms are not in the
game's repository, so this build leaves it out and plays this sound instead: a short rising arpeggio made
from square waves. It is original to the FredyGames build and released under CC0 1.0 (public domain).

  python3 -I make-exit-sound.py <output.wav>

Output is deterministic: 16-bit mono PCM, 22050 Hz.
"""
import math
import struct
import sys
import wave

RATE = 22050
NOTES = [(523.25, 0.09), (659.25, 0.09), (783.99, 0.09), (1046.5, 0.09), (1318.5, 0.28)]


def main(path):
    out = []
    for freq, length in NOTES:
        n = int(RATE * length)
        for i in range(n):
            t = i / RATE
            sq = 1.0 if math.sin(2 * math.pi * freq * t) >= 0 else -1.0
            env = min(1.0, t / 0.004) * math.exp(-t * 6) * min(1.0, (n - i) / (RATE * 0.01))
            out.append(0.35 * sq * env)
    with wave.open(path, "wb") as w:
        w.setnchannels(1)
        w.setsampwidth(2)
        w.setframerate(RATE)
        w.writeframes(b"".join(struct.pack("<h", int(max(-1, min(1, s)) * 32767)) for s in out))


if __name__ == "__main__":
    main(sys.argv[1])