// Singleton AudioContext for the whole tab.
// See ADR-004. Never closed during normal operation.

let _ctx: AudioContext | null = null;

type WebkitWindow = typeof window & {
  webkitAudioContext?: typeof AudioContext;
};

export function getAudioContext(): AudioContext {
  if (_ctx) return _ctx;
  const w = window as WebkitWindow;
  const Ctor = w.AudioContext ?? w.webkitAudioContext;
  if (!Ctor) {
    throw new Error('Web Audio API is not supported in this environment');
  }
  _ctx = new Ctor({ latencyHint: 'interactive' });
  return _ctx;
}

export async function unlockAudioContext(): Promise<void> {
  const ctx = getAudioContext();
  if (ctx.state === 'suspended') {
    try {
      await ctx.resume();
    } catch {
      // Resume requires a user gesture; caller should retry from one.
    }
  }
}

export function isAudioContextRunning(): boolean {
  return _ctx?.state === 'running';
}

// Test-only: drop the singleton between test cases.
export function _resetAudioContextForTesting(): void {
  _ctx = null;
}