import math, random, wave, struct
SR=48000; random.seed(11)
HARM=(1.00, 0.85, 0.10, 0.02)

def note(f, dur, tau, amp=1.0):
    n=int(SR*dur); o=[]
    for i in range(n):
        t=i/SR
        s=sum(a*math.sin(2*math.pi*f*(k+1)*t) for k,a in enumerate(HARM))
        o.append(s*amp*min(1.0,t/0.004)*math.exp(-t/tau))
    return o

def thump(f, dur, amp):
    """Instrumento 2: golpe grave com queda de tom. Da impacto no ataque e
    morre em 90ms — engorda sem alongar."""
    n=int(SR*dur); o=[]; ph=0.0
    for i in range(n):
        t=i/SR
        ph += 2*math.pi*(f*(1+1.2*math.exp(-t/0.02)))/SR
        o.append(math.sin(ph)*amp*math.exp(-t/(dur*0.30)))
    return o

def air(dur, amp, cutoff=5000):
    """Instrumento 3: sopro curto de ruido filtrado. Brilho no inicio, sem cauda."""
    n=int(SR*dur)
    y=0.0; a=1-math.exp(-2*math.pi*cutoff/SR); o=[]
    for i in range(n):
        t=i/SR
        y += a*(random.uniform(-1,1)-y)
        o.append(y*amp*min(1.0,t/0.008)*math.exp(-t/(dur*0.22)))
    return o

def mix(layers,total):
    b=[0.0]*total
    for off,s in layers:
        for i,v in enumerate(s):
            if off+i<total: b[off+i]+=v
    return b

def peak_rms(x, win=int(SR*0.01)):
    return max(math.sqrt(sum(v*v for v in x[i:i+win])/win) for i in range(0,len(x)-win,win))

def write(name, buf, target):
    g=target/max(1e-9,peak_rms(buf))
    pk=max(abs(s*g) for s in buf)
    if pk>0.97: g*=0.97/pk
    with wave.open(name,'w') as w:
        w.setnchannels(1); w.setsampwidth(2); w.setframerate(SR)
        w.writeframes(b''.join(struct.pack('<h',int(max(-1,min(1,s*g))*32767)) for s in buf))
    print(f"{name}: pico RMS {peak_rms([s*g for s in buf]):.3f}, {len(buf)/SR:.2f}s")

C3,G3,C4,E4,G4,C5 = 130.81,196.00,261.63,329.63,392.00,523.25
step=int(SR*0.033)   # arpejo bem rapido: acorde montado em 100ms

# Decaimentos ~metade dos anteriores (0.20 vs 0.38). Total 0.62s vs 1.08s.
write('stream_started.wav', mix([
    (0,      thump(85, 0.14, 0.55)),        # impacto
    (0,      air(0.13, 0.16)),              # brilho
    (0,      note(C3, 0.60, 0.22, 0.80)),
    (0,      note(G3, 0.58, 0.20, 0.45)),
    (0,      note(C4, 0.56, 0.20)),
    (step,   note(E4, 0.54, 0.19)),
    (2*step, note(G4, 0.52, 0.18)),
    (3*step, note(C5, 0.50, 0.16, 0.70)),
], int(SR*0.62)), 0.42)