lib/AudioManager.ts

// Define the webkitAudioContext for older browser compatibility (e.g., Safari)
interface Window {
    webkitAudioContext?: typeof AudioContext;
}

/**
 * Manages all audio playback and recording stream routing for the application.
 * This is a singleton class, so you should import the `audioManager` instance.
 */
class AudioManager {
    private audioContext: AudioContext | null = null;
    private audioBuffers: Map<string, AudioBuffer> = new Map();
    private isInitialized = false;
    
    // This node will be the destination for all sounds that need to be recorded.
    private mediaStreamDestination: MediaStreamAudioDestinationNode | null = null;

    /**
     * Initializes the AudioContext. Must be called before any other methods.
     * This is safe to call multiple times.
     */
    public initialize() {
        if (this.isInitialized || this.audioContext) return;
        try {
            // Create a new AudioContext, using the webkit fallback if necessary.
            this.audioContext = new (window.AudioContext || (window as Window).webkitAudioContext)();
            this.isInitialized = true;
            console.log("[AudioManager] AudioContext Initialized.");
        } catch (e) {
            console.error("[AudioManager] Web Audio API is not supported in this browser.", e);
        }
    }

    /**
     * Resumes the AudioContext if it's suspended. This must be called from
     * within a user interaction event (e.g., a click handler).
     */
    public unlockAudio() {
        if (this.audioContext && this.audioContext.state === 'suspended') {
            this.audioContext.resume().then(() => {
                console.log("[AudioManager] AudioContext resumed successfully.");
            }).catch(e => console.error("[AudioManager] Error resuming AudioContext:", e));
        }
    }

    /**
     * Fetches an audio file and decodes it into an AudioBuffer.
     * @param name - A unique key to identify the sound.
     * @param url - The URL of the audio file.
     */
    public async loadSound(name: string, url: string): Promise<void> {
        if (!this.audioContext) {
             console.error("[AudioManager] AudioContext not initialized. Cannot load sound.");
             return Promise.reject("AudioContext not initialized");
        }
        if (this.audioBuffers.has(name)) return Promise.resolve();
        
        try {
            const response = await fetch(url, { mode: 'cors' }); 
            const arrayBuffer = await response.arrayBuffer();
            const audioBuffer = await this.audioContext.decodeAudioData(arrayBuffer);
            this.audioBuffers.set(name, audioBuffer);
            // console.log(`[AudioManager] Sound loaded: ${name}`);
        } catch (e) {
            console.error(`[AudioManager] Failed to load sound: ${name} from ${url}`, e);
            return Promise.reject(`Failed to load sound: ${name}`);
        }
    }

    /**
     * **[NEW METHOD]**
     * Retrieves a pre-loaded AudioBuffer by its name.
     * This is useful for getting metadata like the duration of a sound.
     * @param name - The key of the sound to retrieve.
     * @returns The AudioBuffer if found, otherwise null.
     */
    public getSoundBuffer(name: string): AudioBuffer | null {
        return this.audioBuffers.get(name) || null;
    }
    
    /**
     * Plays a pre-loaded sound.
     * @param name - The key of the sound to play.
     * @param volume - The volume to play the sound at (0.0 to 1.0).
     */
    public playSound(name: string, volume: number = 1) {
        if (!this.audioContext || !this.audioBuffers.has(name)) {
            // This can be noisy, so it's commented out, but useful for debugging.
            // console.warn(`[AudioManager] Sound not found or context not ready: ${name}`);
            return;
        }
        
        // Create a source node for the sound buffer.
        const source = this.audioContext.createBufferSource();
        source.buffer = this.audioBuffers.get(name)!;
        
        // Create a GainNode to control the volume of this specific sound instance.
        const gainNode = this.audioContext.createGain();
        gainNode.gain.value = volume;

        // The audio signal path:
        // Source -> GainNode -> ...
        source.connect(gainNode);

        // ... -> Main Output (Speakers)
        gainNode.connect(this.audioContext.destination);

        // ... -> Recording Stream (if active)
        if (this.mediaStreamDestination) {
            gainNode.connect(this.mediaStreamDestination);
        }

        source.start(0);
    }
    
    // --- RECORDING STREAM LIFECYCLE METHODS ---

    /**
     * **[IMPORTANT]** Creates the audio destination node for recording.
     * This must be called *before* you intend to start recording and *before*
     * any sounds that need to be recorded are played.
     */
    public startAudioStreamCapture() {
        if (!this.audioContext) {
            console.error("[AudioManager] AudioContext not initialized. Cannot start stream capture.");
            return;
        }
        if (!this.mediaStreamDestination) {
            console.log("[AudioManager] Creating new MediaStreamAudioDestinationNode for recording.");
            this.mediaStreamDestination = this.audioContext.createMediaStreamDestination();
        }
    }

    /**
     * Retrieves the audio stream for the MediaRecorder.
     * `startAudioStreamCapture` must have been called before this.
     * @returns A MediaStream containing the audio, or null if not ready.
     */
    public getAudioStream(): MediaStream | null {
        if (!this.mediaStreamDestination) {
            console.error(
                "[AudioManager] Audio stream capture was not started. Call startAudioStreamCapture() first."
            );
            return null;
        }
        return this.mediaStreamDestination.stream;
    }

    /**
     * Cleans up the recording stream destination.
     * Call this when the recording is finished.
     */
    public stopAudioStreamCapture() {
        if (this.mediaStreamDestination) {
            // Nullifying the reference is enough for it to be garbage collected.
            this.mediaStreamDestination = null;
            console.log("[AudioManager] Cleared MediaStreamAudioDestinationNode.");
        }
    }
}

// Export a single instance to be used throughout the application.
export const audioManager = new AudioManager();