import { useRef, useEffect, useCallback } from 'react';

// ─────────────────────────────────────────────────────────────
// Constants
// ─────────────────────────────────────────────────────────────

/** C5 frequency in Hz (523.25) */
const C5 = 523.25;

/** E5 frequency in Hz (659.25) */
const E5 = 659.25;

/** Duration of each tone in seconds (120 ms) */
const TONE_DURATION = 0.12;

/** Overall gain / volume (0.08 = 8%) */
const VOLUME = 0.08;

/** Exponential fade-out duration in seconds (450 ms) */
const FADE_DURATION = 0.45;

// ─────────────────────────────────────────────────────────────
// useSound
// ─────────────────────────────────────────────────────────────

/**
 * Hook for playing a notification chime using the Web Audio API.
 *
 * - Initialises an `AudioContext` lazily on the first user gesture
 *   (click or keydown) to comply with browser autoplay policies.
 * - Exposes `playNotificationSound()` which plays a two‑tone chime:
 *   C5 (523.25 Hz) for 120 ms → E5 (659.25 Hz) for 120 ms,
 *   with a shared exponential fade‑out envelope (0.08 → 0.001 over 450 ms).
 * - If the `AudioContext` is suspended, a warning is logged and the
 *   call is silently ignored.
 */
export function useSound() {
  const audioCtxRef = useRef<AudioContext | null>(null);
  const initializedRef = useRef(false);

  // ── Lazy initialisation on first user gesture ──────────────
  useEffect(() => {
    const initAudio = () => {
      if (initializedRef.current) return;

      try {
        audioCtxRef.current = new AudioContext();
        initializedRef.current = true;
      } catch (err) {
        console.warn('[useSound] Web Audio API is not available:', err);
      }

      // Remove both listeners after the first gesture
      window.removeEventListener('click', initAudio);
      window.removeEventListener('keydown', initAudio);
    };

    // Attach listeners for first gesture
    window.addEventListener('click', initAudio, { once: true });
    window.addEventListener('keydown', initAudio, { once: true });

    return () => {
      window.removeEventListener('click', initAudio);
      window.removeEventListener('keydown', initAudio);

      // Close AudioContext on unmount
      const ctx = audioCtxRef.current;
      if (ctx) {
        ctx.close().catch(() => {});
        audioCtxRef.current = null;
      }
      initializedRef.current = false;
    };
  }, []);

  // ── Play the two‑tone chime ────────────────────────────────
  const playNotificationSound = useCallback((): void => {
    const ctx = audioCtxRef.current;

    if (!ctx) {
      console.warn('[useSound] AudioContext has not been initialised yet');
      return;
    }

    if (ctx.state === 'suspended') {
      console.warn('[useSound] AudioContext is suspended — cannot play sound');
      return;
    }

    const now = ctx.currentTime;

    // Single shared gain node for both oscillators → unified fade‑out
    const gain = ctx.createGain();
    gain.gain.setValueAtTime(VOLUME, now);
    gain.gain.exponentialRampToValueAtTime(0.001, now + FADE_DURATION);
    gain.connect(ctx.destination);

    // Helper: create and schedule a single sine‑wave tone
    const playTone = (frequency: number, startTime: number): void => {
      const osc = ctx.createOscillator();
      osc.type = 'sine';
      osc.frequency.setValueAtTime(frequency, startTime);
      osc.connect(gain);
      osc.start(startTime);
      osc.stop(startTime + TONE_DURATION);
    };

    // Schedule the two tones
    playTone(C5, now);       // C5 starts immediately
    playTone(E5, now + TONE_DURATION); // E5 starts after C5 ends
  }, []);

  return { playNotificationSound };
}