#!/usr/bin/env python3
"""Gera os dois efeitos sonoros que trocam arquivos de terceiros sem licenca registrada (smack.wav e balloon_pop.wav).

Uso: python3 -I gen-sounds.py <smack.wav> <balloon_pop.wav>

Sons sinteticos (seno com queda de frequencia e ruido de um gerador congruente linear fixo), feitos para este site e
liberados em CC0 1.0 (nenhum direito reservado). Saida deterministica: PCM 16 bits, estereo, 44100 Hz.
"""
import math
import struct
import sys
import wave

RATE = 44100


class Lcg:
    def __init__(self, seed):
        self.s = seed

    def noise(self):
        self.s = (self.s * 1664525 + 1013904223) & 0xFFFFFFFF
        return self.s / 0x7FFFFFFF - 1.0


def write(path, samples):
    peak = max(abs(x) for x in samples) or 1.0
    frames = b''.join(struct.pack('<hh', *(int(max(-1.0, min(1.0, x / peak * 0.8)) * 32767),) * 2) for x in samples)
    with wave.open(path, 'wb') as w:
        w.setnchannels(2)
        w.setsampwidth(2)
        w.setframerate(RATE)
        w.writeframes(frames)


def smack():
    # Pancada: seno grave que cai de 220 Hz para 60 Hz + estalo de ruido filtrado, 0,3 s.
    r = Lcg(1)
    out, phase, lp = [], 0.0, 0.0
    for i in range(int(RATE * 0.3)):
        t = i / RATE
        f = 60 + 160 * math.exp(-t * 30)
        phase += 2 * math.pi * f / RATE
        lp += 0.25 * (r.noise() - lp)
        out.append(math.sin(phase) * math.exp(-t * 14) + lp * 1.4 * math.exp(-t * 40))
    return out


def pop():
    # Estouro: estalo de ruido agudo com queda rapida + um tom curto de 900 Hz para 300 Hz, 0,2 s.
    r = Lcg(7)
    out, phase, prev = [], 0.0, 0.0
    for i in range(int(RATE * 0.2)):
        t = i / RATE
        n = r.noise()
        hp = n - prev
        prev = n
        phase += 2 * math.pi * (300 + 600 * math.exp(-t * 60)) / RATE
        out.append(hp * math.exp(-t * 45) + 0.5 * math.sin(phase) * math.exp(-t * 35))
    return out


write(sys.argv[1], smack())
write(sys.argv[2], pop())