gupi-osint-board/src/audio.ts

// Lightweight game audio: one looping "scene music" track plus synthesized one-shot
// SFX. Zero dependencies. Browsers block autoplay until a user gesture, so music/SFX
// are primed on the first pointer interaction.
type Sfx = 'advance' | 'choice' | 'sting'
const MUSIC_VOLUME = 0.5

let ctx: AudioContext | null = null
function audioContext() {
  if (!ctx) { const AC = window.AudioContext || (window as unknown as { webkitAudioContext?: typeof AudioContext }).webkitAudioContext; if (AC) ctx = new AC() }
  return ctx
}

const music = typeof Audio !== 'undefined' ? new Audio() : null
if (music) music.loop = true
let currentUrl: string | null = null
let muted = false
let pending = false
let fadeTimer: number | undefined

function fade(target: number, done?: () => void) {
  if (!music) return
  window.clearInterval(fadeTimer)
  const step = (target - music.volume) / 12 || (target > music.volume ? 0.1 : -0.1)
  fadeTimer = window.setInterval(() => {
    if (!music) return
    const next = music.volume + step
    if ((step >= 0 && next >= target) || (step <= 0 && next <= target)) { music.volume = target; window.clearInterval(fadeTimer); done?.() }
    else music.volume = Math.max(0, Math.min(1, next))
  }, 40)
}

function startMusic() {
  if (!music || !currentUrl || muted) return
  const promise = music.play()
  if (promise) promise.then(() => { pending = false; fade(MUSIC_VOLUME) }).catch(() => { pending = true })
}

export const audio = {
  // A null url inherits whatever is already playing; a new url crossfades to it.
  setMusic(url: string | null) {
    if (!music || url === currentUrl) return
    currentUrl = url
    if (!url) { fade(0, () => music.pause()); pending = false; return }
    music.src = url
    music.volume = 0
    startMusic()
  },
  toggleMute() {
    muted = !muted
    if (muted) fade(0)
    else if (currentUrl) startMusic()
    return muted
  },
  isMuted() { return muted },
  sfx(kind: Sfx) {
    if (muted) return
    const context = audioContext()
    if (!context) return
    // Called from a click, so we can unlock the context right here if it's suspended.
    if (context.state === 'suspended') void context.resume()
    const osc = context.createOscillator(), gain = context.createGain()
    osc.type = 'triangle'
    const now = context.currentTime + 0.01
    const base = kind === 'choice' ? 500 : kind === 'sting' ? 260 : 420
    osc.frequency.setValueAtTime(base, now)
    if (kind === 'choice') osc.frequency.exponentialRampToValueAtTime(base * 1.5, now + 0.09) // a little up-chirp
    gain.gain.setValueAtTime(0.0001, now)
    gain.gain.exponentialRampToValueAtTime(0.16, now + 0.012)
    gain.gain.exponentialRampToValueAtTime(0.0001, now + 0.16)
    osc.connect(gain).connect(context.destination)
    osc.start(now); osc.stop(now + 0.18)
  },
  // Resume the context and retry pending music on a user gesture.
  resume() {
    void audioContext()?.resume?.()
    if (pending) startMusic()
  },
}

if (typeof window !== 'undefined') window.addEventListener('pointerdown', () => audio.resume())