/**
 * Speech Recognition Hook
 *
 * Wraps @jamsch/expo-speech-recognition for easy use in components.
 * Provides start/stop controls, recognized text, and status states.
 *
 * NOTE: Gracefully handles missing native module (Expo Go)
 * - In Expo Go: isAvailable = false, all methods are no-ops
 * - In Dev Build: Full functionality
 *
 * Usage:
 * ```typescript
 * const { startListening, stopListening, isListening, recognizedText, error } = useSpeechRecognition();
 *
 * // Start listening (will request permissions if needed)
 * await startListening();
 *
 * // Stop and get final result
 * stopListening();
 *
 * // recognizedText contains the transcript
 * ```
 */

import { useState, useCallback, useRef, useEffect } from 'react';
import { Platform } from 'react-native';

// Try to import the native module - may fail in Expo Go
let ExpoSpeechRecognitionModule: any = null;
let useSpeechRecognitionEvent: any = () => {}; // no-op by default

try {
  const speechRecognition = require('expo-speech-recognition');
  ExpoSpeechRecognitionModule = speechRecognition.ExpoSpeechRecognitionModule;
  useSpeechRecognitionEvent = speechRecognition.useSpeechRecognitionEvent;
} catch (e) {
  console.warn('[SpeechRecognition] Native module not available (Expo Go?). Speech recognition disabled.');
}

export interface UseSpeechRecognitionOptions {
  /** Language for recognition (default: 'en-US') */
  lang?: string;
  /** Whether to return interim results while speaking (default: true) */
  interimResults?: boolean;
  /** Whether to continue listening after pause (default: false) */
  continuous?: boolean;
  /** Whether to add punctuation (iOS only, default: true) */
  addsPunctuation?: boolean;
  /** Callback when speech recognition result is available */
  onResult?: (transcript: string, isFinal: boolean) => void;
  /** Callback when an error occurs */
  onError?: (error: string) => void;
  /** Callback when speech recognition starts */
  onStart?: () => void;
  /** Callback when speech recognition ends */
  onEnd?: () => void;
  /** Callback when voice activity is detected (first interim result) - useful for interrupting TTS */
  onVoiceDetected?: () => void;
}

export interface UseSpeechRecognitionReturn {
  /** Start listening for speech */
  startListening: () => Promise<boolean>;
  /** Stop listening and finalize result */
  stopListening: () => void;
  /** Abort listening without processing */
  abortListening: () => void;
  /** Whether currently listening */
  isListening: boolean;
  /** Whether speech recognition is available on this device */
  isAvailable: boolean;
  /** Current recognized text (updates in real-time if interimResults=true) */
  recognizedText: string;
  /** Partial transcript (interim result, not final) */
  partialTranscript: string;
  /** Error message if any */
  error: string | null;
  /** Clear the recognized text and error */
  reset: () => void;
}

export function useSpeechRecognition(
  options: UseSpeechRecognitionOptions = {}
): UseSpeechRecognitionReturn {
  const {
    lang = 'en-US',
    interimResults = true,
    continuous = false,
    addsPunctuation = true,
    onResult,
    onError,
    onStart,
    onEnd,
    onVoiceDetected,
  } = options;

  const [isListening, setIsListening] = useState(false);
  const [isAvailable, setIsAvailable] = useState(!!ExpoSpeechRecognitionModule);
  const [recognizedText, setRecognizedText] = useState('');
  const [partialTranscript, setPartialTranscript] = useState('');
  const [error, setError] = useState<string | null>(null);

  // Track if we're in the middle of starting to prevent double-starts
  const isStartingRef = useRef(false);
  // Track if voice has been detected in current session (for onVoiceDetected callback)
  const voiceDetectedRef = useRef(false);
  // Track last partial transcript for iOS fix (iOS never sends isFinal:true)
  const lastPartialRef = useRef('');

  // Check availability on mount
  useEffect(() => {
    if (!ExpoSpeechRecognitionModule) {
      setIsAvailable(false);
      return;
    }

    const checkAvailability = async () => {
      try {
        // Check if we can get permissions (indirect availability check)
        const status = await ExpoSpeechRecognitionModule.getPermissionsAsync();
        // If we can query permissions, the module is available
        setIsAvailable(true);
        console.log('[SpeechRecognition] Available, permission status:', status.status);
      } catch (err) {
        console.warn('[SpeechRecognition] Not available:', err);
        setIsAvailable(false);
      }
    };
    checkAvailability();
  }, []);

  // Event: Recognition started
  useSpeechRecognitionEvent('start', () => {
    console.log('[SpeechRecognition] Started');
    setIsListening(true);
    setError(null);
    isStartingRef.current = false;
    voiceDetectedRef.current = false; // Reset voice detection flag for new session
    onStart?.();
  });

  // Event: Recognition ended
  useSpeechRecognitionEvent('end', () => {
    console.log('[SpeechRecognition] Ended');

    // iOS FIX: iOS never sends isFinal:true, so we send last partial as final when STT ends
    const lastPartial = lastPartialRef.current;
    if (lastPartial && lastPartial.trim().length > 0) {
      console.log('[SpeechRecognition] 🍎 iOS FIX - Sending last partial as final:', lastPartial);
      setRecognizedText(lastPartial);
      onResult?.(lastPartial, true); // Send as final=true
      lastPartialRef.current = ''; // Clear after sending
    }

    setIsListening(false);
    setPartialTranscript('');
    isStartingRef.current = false;
    voiceDetectedRef.current = false; // Reset for next session
    onEnd?.();
  });

  // Event: Result available
  useSpeechRecognitionEvent('result', (event: any) => {
    const results = event.results;
    if (results && results.length > 0) {
      const result = results[results.length - 1];
      const transcript = result?.transcript || '';
      const isFinal = event.isFinal ?? false;

      console.log('[SpeechRecognition] Result:', transcript.slice(0, 50), 'final:', isFinal);

      // Trigger onVoiceDetected on first result (voice activity detected)
      if (!voiceDetectedRef.current && transcript.length > 0) {
        voiceDetectedRef.current = true;
        console.log('[SpeechRecognition] Voice activity detected');
        onVoiceDetected?.();
      }

      if (isFinal) {
        setRecognizedText(transcript);
        setPartialTranscript('');
        lastPartialRef.current = ''; // Clear after final
      } else {
        setPartialTranscript(transcript);
        lastPartialRef.current = transcript; // Save for iOS fix
      }

      onResult?.(transcript, isFinal);
    }
  });

  // Event: Error occurred
  useSpeechRecognitionEvent('error', (event: any) => {
    const errorCode = event.error || '';
    const errorMessage = event.message || errorCode || 'Speech recognition error';

    // "no-speech" is normal when user is silent — ignore completely
    if (errorCode === 'no-speech') {
      console.log('[SpeechRecognition] No speech detected (silence) - ignoring');
      setIsListening(false);
      isStartingRef.current = false;
      return;
    }

    console.warn('[SpeechRecognition] Error:', errorMessage);
    setError(errorMessage);
    onError?.(errorMessage);
    setIsListening(false);
    isStartingRef.current = false;
  });

  /**
   * Start listening for speech
   * @returns true if started successfully, false otherwise
   */
  const startListening = useCallback(async (): Promise<boolean> => {
    if (!ExpoSpeechRecognitionModule) {
      console.warn('[SpeechRecognition] Cannot start - native module not available');
      return false;
    }

    if (isListening || isStartingRef.current) {
      console.log('[SpeechRecognition] Already listening or starting');
      return false;
    }

    if (!isAvailable) {
      const msg = 'Speech recognition is not available on this device';
      console.warn('[SpeechRecognition]', msg);
      setError(msg);
      onError?.(msg);
      return false;
    }

    isStartingRef.current = true;
    setError(null);
    setRecognizedText('');
    setPartialTranscript('');

    try {
      // Request permissions
      const permissionResult = await ExpoSpeechRecognitionModule.requestPermissionsAsync();

      if (!permissionResult.granted) {
        const msg = 'Microphone permission denied';
        console.warn('[SpeechRecognition]', msg);
        setError(msg);
        onError?.(msg);
        isStartingRef.current = false;
        return false;
      }

      console.log('[SpeechRecognition] Starting with lang:', lang);

      // Start recognition
      ExpoSpeechRecognitionModule.start({
        lang,
        interimResults,
        continuous,
        addsPunctuation: Platform.OS === 'ios' ? addsPunctuation : undefined,
        // Android: use CLOUD recognition for better quality
        // On-device models often have worse accuracy
        // Setting to false allows the system to use Google's cloud ASR
        requiresOnDeviceRecognition: false,
        // Android-specific: longer silence timeout for more natural pauses
        // CRITICAL FIX: Increased from 2000ms to 4000ms to prevent premature speech cutoff
        // This allows users to pause between sentences without being cut off
        androidIntentOptions: Platform.OS === 'android' ? {
          EXTRA_SPEECH_INPUT_COMPLETE_SILENCE_LENGTH_MILLIS: 4000,  // 4 sec silence before final (was 2000)
          EXTRA_SPEECH_INPUT_POSSIBLY_COMPLETE_SILENCE_LENGTH_MILLIS: 3000,  // 3 sec pause detection (was 1500)
        } : undefined,
      });

      return true;
    } catch (err) {
      const msg = err instanceof Error ? err.message : 'Failed to start speech recognition';
      console.warn('[SpeechRecognition] Start error:', msg);
      setError(msg);
      onError?.(msg);
      isStartingRef.current = false;
      return false;
    }
  }, [isListening, isAvailable, lang, interimResults, continuous, addsPunctuation, onError]);

  /**
   * Stop listening and process final result
   */
  const stopListening = useCallback(() => {
    if (!ExpoSpeechRecognitionModule) return;

    if (!isListening && !isStartingRef.current) {
      console.log('[SpeechRecognition] Not listening, nothing to stop');
      return;
    }

    console.log('[SpeechRecognition] Stopping...');
    try {
      ExpoSpeechRecognitionModule.stop();
    } catch (err) {
      console.warn('[SpeechRecognition] Stop error:', err);
    }
  }, [isListening]);

  /**
   * Abort listening without processing
   */
  const abortListening = useCallback(() => {
    if (!ExpoSpeechRecognitionModule) return;

    if (!isListening && !isStartingRef.current) {
      return;
    }

    console.log('[SpeechRecognition] Aborting...');
    try {
      ExpoSpeechRecognitionModule.abort();
    } catch (err) {
      console.warn('[SpeechRecognition] Abort error:', err);
    }

    setIsListening(false);
    setPartialTranscript('');
    isStartingRef.current = false;
  }, [isListening]);

  /**
   * Reset state
   */
  const reset = useCallback(() => {
    setRecognizedText('');
    setPartialTranscript('');
    setError(null);
  }, []);

  return {
    startListening,
    stopListening,
    abortListening,
    isListening,
    isAvailable,
    recognizedText,
    partialTranscript,
    error,
    reset,
  };
}