import React, { useState, useCallback, useRef, useEffect } from 'react';
import {
  View,
  Text,
  StyleSheet,
  FlatList,
  TextInput,
  TouchableOpacity,
  KeyboardAvoidingView,
  Platform,
  Alert,
  ActivityIndicator,
  Modal,
  ScrollView,
} from 'react-native';
import { Ionicons } from '@expo/vector-icons';
import { SafeAreaView } from 'react-native-safe-area-context';
import { useFocusEffect } from 'expo-router';
import { api } from '@/services/api';
import { useBeneficiary } from '@/contexts/BeneficiaryContext';
import { AppColors, BorderRadius, FontSizes, Spacing } from '@/constants/theme';
import type { Message } from '@/types';
import { useTTS } from '@/hooks/useTTS';
import { AVAILABLE_VOICES, getCurrentVoice, setVoice, type PiperVoice } from '@/services/sherpaTTS';

// Try to import speech recognition if available
let ExpoSpeechRecognitionModule: any = null;
let useSpeechRecognitionEvent: any = null;
try {
  const speechRecognition = require('expo-speech-recognition');
  ExpoSpeechRecognitionModule = speechRecognition.ExpoSpeechRecognitionModule;
  useSpeechRecognitionEvent = speechRecognition.useSpeechRecognitionEvent;
} catch (e) {
  console.log('expo-speech-recognition not available');
}

export default function ChatScreen() {
  const { currentBeneficiary, getBeneficiaryContext } = useBeneficiary();
  const [messages, setMessages] = useState<Message[]>([
    {
      id: '1',
      role: 'assistant',
      content: 'Hello! I\'m Julia, your AI assistant. How can I help you today?',
      timestamp: new Date(),
    },
  ]);
  const [input, setInput] = useState('');
  const [isSending, setIsSending] = useState(false);
  const [isListening, setIsListening] = useState(false);
  const [recognizedText, setRecognizedText] = useState('');
  const [showVoicePicker, setShowVoicePicker] = useState(false);
  const [selectedVoice, setSelectedVoice] = useState<PiperVoice>(getCurrentVoice());
  const [isChangingVoice, setIsChangingVoice] = useState(false);
  const [voiceModeEnabled, setVoiceModeEnabled] = useState(false); // Voice Mode toggle
  const flatListRef = useRef<FlatList>(null);
  const lastSendTimeRef = useRef<number>(0);
  const SEND_COOLDOWN_MS = 1000; // 1 second cooldown between messages

  // TTS hook for speaking responses
  const { speak, stop, isSpeaking } = useTTS();

  // Stop TTS and mic when navigating away from screen
  useFocusEffect(
    useCallback(() => {
      // Screen focused
      return () => {
        // Screen unfocused - cleanup
        stop(); // Stop any playing TTS
        if (ExpoSpeechRecognitionModule && isListening) {
          ExpoSpeechRecognitionModule.stop();
          setIsListening(false);
        }
        setVoiceModeEnabled(false); // Disable voice mode on leave
      };
    }, [stop, isListening])
  );

  // Handle voice change
  const handleVoiceChange = useCallback(async (voice: PiperVoice) => {
    if (voice.id === selectedVoice.id) {
      setShowVoicePicker(false);
      return;
    }

    setIsChangingVoice(true);
    try {
      const success = await setVoice(voice.id);
      if (success) {
        setSelectedVoice(voice);
        // Test the new voice
        speak(`Hello, I'm ${voice.name}. How can I help you?`);
      } else {
        Alert.alert('Error', `Failed to switch to ${voice.name} voice.`);
      }
    } catch (error) {
      Alert.alert('Error', 'Failed to change voice.');
    } finally {
      setIsChangingVoice(false);
      setShowVoicePicker(false);
    }
  }, [selectedVoice, speak]);

  // Speech recognition events (if available)
  useEffect(() => {
    if (!useSpeechRecognitionEvent) return;

    // Handle recognized speech result
    const resultSubscription = useSpeechRecognitionEvent('result', (event: any) => {
      const transcript = event.results?.[0]?.transcript || '';
      setRecognizedText(transcript);
      if (event.isFinal) {
        setInput(transcript);
        setIsListening(false);
      }
    });

    // Handle errors
    const errorSubscription = useSpeechRecognitionEvent('error', (event: any) => {
      console.log('Speech recognition error:', event.error);
      setIsListening(false);
    });

    // Handle end
    const endSubscription = useSpeechRecognitionEvent('end', () => {
      setIsListening(false);
    });

    return () => {
      resultSubscription?.remove?.();
      errorSubscription?.remove?.();
      endSubscription?.remove?.();
    };
  }, []);

  // Start voice input
  const startListening = useCallback(async () => {
    if (!ExpoSpeechRecognitionModule) {
      Alert.alert('Not Available', 'Voice input is not available on this device.');
      return;
    }

    // PREVENT SELF-RECORDING: Don't start mic while TTS is speaking
    if (isSpeaking) {
      console.log('[Voice] Blocked: TTS is still speaking');
      return;
    }

    try {
      const result = await ExpoSpeechRecognitionModule.requestPermissionsAsync();
      if (!result.granted) {
        Alert.alert('Permission Denied', 'Please enable microphone access to use voice input.');
        return;
      }

      // Enable voice mode when user starts listening
      setVoiceModeEnabled(true);
      setIsListening(true);
      setRecognizedText('');
      ExpoSpeechRecognitionModule.start({
        lang: 'en-US',
        interimResults: true,
        maxAlternatives: 1,
      });
    } catch (error) {
      console.error('Failed to start speech recognition:', error);
      setIsListening(false);
      Alert.alert('Error', 'Failed to start voice input.');
    }
  }, [isSpeaking]);

  // Stop voice input
  const stopListening = useCallback(() => {
    if (ExpoSpeechRecognitionModule) {
      ExpoSpeechRecognitionModule.stop();
    }
    setIsListening(false);
  }, []);

  const handleSend = useCallback(async () => {
    const trimmedInput = input.trim();
    if (!trimmedInput || isSending) return;

    // Debounce: prevent rapid-fire messages
    const now = Date.now();
    if (now - lastSendTimeRef.current < SEND_COOLDOWN_MS) {
      return;
    }
    lastSendTimeRef.current = now;

    // Security: require beneficiary to be selected
    if (!currentBeneficiary?.id) {
      Alert.alert(
        'Select Beneficiary',
        'Please select a beneficiary from the Dashboard tab before starting a conversation.',
        [{ text: 'OK' }]
      );
      return;
    }

    const userMessage: Message = {
      id: Date.now().toString(),
      role: 'user',
      content: trimmedInput,
      timestamp: new Date(),
    };

    setMessages((prev) => [...prev, userMessage]);
    setInput('');
    setIsSending(true);

    try {
      // Prepend beneficiary context to the question if available
      const beneficiaryContext = getBeneficiaryContext();
      const questionWithContext = beneficiaryContext
        ? `${beneficiaryContext} ${trimmedInput}`
        : trimmedInput;

      // Pass deployment_id from selected beneficiary (required, no fallback)
      const deploymentId = currentBeneficiary.id.toString();
      const response = await api.sendMessage(questionWithContext, deploymentId);

      if (response.ok && response.data?.response) {
        const responseText = response.data.response.body;
        const assistantMessage: Message = {
          id: (Date.now() + 1).toString(),
          role: 'assistant',
          content: responseText,
          timestamp: new Date(),
        };
        setMessages((prev) => [...prev, assistantMessage]);
        // Speak the response using neural TTS
        speak(responseText);
      } else {
        const errorMessage: Message = {
          id: (Date.now() + 1).toString(),
          role: 'assistant',
          content: 'Sorry, I encountered an error. Please try again.',
          timestamp: new Date(),
        };
        setMessages((prev) => [...prev, errorMessage]);
      }
    } catch (error) {
      const errorMessage: Message = {
        id: (Date.now() + 1).toString(),
        role: 'assistant',
        content: 'Sorry, I couldn\'t connect to the server. Please check your internet connection.',
        timestamp: new Date(),
      };
      setMessages((prev) => [...prev, errorMessage]);
    } finally {
      setIsSending(false);
    }
  }, [input, isSending, currentBeneficiary, getBeneficiaryContext]);

  const renderMessage = ({ item }: { item: Message }) => {
    const isUser = item.role === 'user';

    return (
      <View
        style={[
          styles.messageContainer,
          isUser ? styles.userMessageContainer : styles.assistantMessageContainer,
        ]}
      >
        {!isUser && (
          <View style={styles.avatarContainer}>
            <Text style={styles.avatarText}>J</Text>
          </View>
        )}
        <View
          style={[
            styles.messageBubble,
            isUser ? styles.userBubble : styles.assistantBubble,
          ]}
        >
          <Text
            style={[
              styles.messageText,
              isUser ? styles.userMessageText : styles.assistantMessageText,
            ]}
          >
            {item.content}
          </Text>
          <Text style={[styles.timestamp, isUser && styles.userTimestamp]}>
            {item.timestamp.toLocaleTimeString([], { hour: '2-digit', minute: '2-digit' })}
          </Text>
        </View>
      </View>
    );
  };

  return (
    <SafeAreaView style={styles.container} edges={['top']}>
      {/* Header */}
      <View style={styles.header}>
        <View style={styles.headerInfo}>
          <View style={styles.headerAvatar}>
            <Text style={styles.headerAvatarText}>J</Text>
          </View>
          <View>
            <Text style={styles.headerTitle}>Julia AI</Text>
            <Text style={styles.headerSubtitle}>
              {isSending
                ? 'Typing...'
                : currentBeneficiary
                  ? `About ${currentBeneficiary.name}`
                  : 'Online'}
            </Text>
          </View>
        </View>
        <View style={styles.headerButtons}>
          {/* Voice Mode Toggle */}
          {voiceModeEnabled && (
            <TouchableOpacity
              style={[styles.headerButton, styles.voiceModeActive]}
              onPress={() => {
                stop();
                stopListening();
                setVoiceModeEnabled(false);
              }}
            >
              <Ionicons name="mic" size={20} color={AppColors.white} />
              <Text style={styles.voiceModeText}>ON</Text>
            </TouchableOpacity>
          )}
          {/* TTS Speaking indicator */}
          {isSpeaking && (
            <TouchableOpacity
              style={[styles.headerButton, styles.speakingIndicator]}
              onPress={stop}
            >
              <Ionicons name="volume-high" size={20} color={AppColors.white} />
            </TouchableOpacity>
          )}
          {/* Voice Picker */}
          <TouchableOpacity
            style={styles.headerButton}
            onPress={() => setShowVoicePicker(true)}
          >
            <Ionicons name="volume-high-outline" size={24} color={AppColors.textPrimary} />
          </TouchableOpacity>
        </View>
      </View>

      {/* Messages */}
      <KeyboardAvoidingView
        style={styles.chatContainer}
        behavior={Platform.OS === 'ios' ? 'padding' : undefined}
        keyboardVerticalOffset={Platform.OS === 'ios' ? 90 : 0}
      >
        <FlatList
          ref={flatListRef}
          data={messages}
          keyExtractor={(item) => item.id}
          renderItem={renderMessage}
          contentContainerStyle={styles.messagesList}
          showsVerticalScrollIndicator={false}
          onContentSizeChange={() => flatListRef.current?.scrollToEnd({ animated: true })}
        />

        {/* Listening indicator */}
        {isListening && (
          <View style={styles.listeningIndicator}>
            <ActivityIndicator color={AppColors.primary} size="small" />
            <Text style={styles.listeningText}>
              {recognizedText || 'Listening...'}
            </Text>
            <TouchableOpacity onPress={stopListening} style={styles.stopButton}>
              <Ionicons name="close-circle" size={24} color={AppColors.error} />
            </TouchableOpacity>
          </View>
        )}

        {/* Input */}
        <View style={styles.inputContainer}>
          {/* Microphone button */}
          <TouchableOpacity
            style={[styles.micButton, isListening && styles.micButtonActive]}
            onPress={isListening ? stopListening : startListening}
            disabled={isSending}
          >
            <Ionicons
              name={isListening ? 'mic' : 'mic-outline'}
              size={22}
              color={isListening ? AppColors.white : AppColors.primary}
            />
          </TouchableOpacity>

          <TextInput
            style={styles.input}
            placeholder="Type a message..."
            placeholderTextColor={AppColors.textMuted}
            value={input}
            onChangeText={setInput}
            multiline
            maxLength={1000}
            editable={!isSending && !isListening}
            onSubmitEditing={handleSend}
          />
          <TouchableOpacity
            style={[styles.sendButton, (!input.trim() || isSending) && styles.sendButtonDisabled]}
            onPress={handleSend}
            disabled={!input.trim() || isSending}
          >
            <Ionicons
              name={isSending ? 'hourglass' : 'send'}
              size={20}
              color={input.trim() && !isSending ? AppColors.white : AppColors.textMuted}
            />
          </TouchableOpacity>
        </View>
      </KeyboardAvoidingView>

      {/* Voice Picker Modal */}
      <Modal
        visible={showVoicePicker}
        animationType="slide"
        transparent={true}
        onRequestClose={() => setShowVoicePicker(false)}
      >
        <View style={styles.modalOverlay}>
          <View style={styles.modalContent}>
            <View style={styles.modalHeader}>
              <Text style={styles.modalTitle}>Select Voice</Text>
              <TouchableOpacity
                style={styles.modalCloseButton}
                onPress={() => setShowVoicePicker(false)}
              >
                <Ionicons name="close" size={24} color={AppColors.textPrimary} />
              </TouchableOpacity>
            </View>

            <Text style={styles.modalSubtitle}>
              Neural TTS voices for Julia AI
            </Text>

            <ScrollView style={styles.voiceList}>
              {AVAILABLE_VOICES.map((voice) => (
                <TouchableOpacity
                  key={voice.id}
                  style={[
                    styles.voiceItem,
                    selectedVoice.id === voice.id && styles.voiceItemSelected,
                  ]}
                  onPress={() => handleVoiceChange(voice)}
                  disabled={isChangingVoice}
                >
                  <View style={styles.voiceIcon}>
                    <Ionicons
                      name={voice.gender === 'female' ? 'woman' : 'man'}
                      size={24}
                      color={selectedVoice.id === voice.id ? AppColors.white : AppColors.primary}
                    />
                  </View>
                  <View style={styles.voiceInfo}>
                    <Text
                      style={[
                        styles.voiceName,
                        selectedVoice.id === voice.id && styles.voiceNameSelected,
                      ]}
                    >
                      {voice.name}
                    </Text>
                    <Text
                      style={[
                        styles.voiceDescription,
                        selectedVoice.id === voice.id && styles.voiceDescriptionSelected,
                      ]}
                    >
                      {voice.description}
                    </Text>
                  </View>
                  {selectedVoice.id === voice.id && (
                    <Ionicons name="checkmark-circle" size={24} color={AppColors.white} />
                  )}
                  {isChangingVoice && selectedVoice.id !== voice.id && (
                    <ActivityIndicator size="small" color={AppColors.primary} />
                  )}
                </TouchableOpacity>
              ))}
            </ScrollView>

            <Text style={styles.voiceHint}>
              Tap a voice to hear a preview
            </Text>
          </View>
        </View>
      </Modal>
    </SafeAreaView>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: AppColors.surface,
  },
  header: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'space-between',
    paddingHorizontal: Spacing.md,
    paddingVertical: Spacing.sm,
    backgroundColor: AppColors.background,
    borderBottomWidth: 1,
    borderBottomColor: AppColors.border,
  },
  headerInfo: {
    flexDirection: 'row',
    alignItems: 'center',
  },
  headerAvatar: {
    width: 40,
    height: 40,
    borderRadius: BorderRadius.full,
    backgroundColor: AppColors.success,
    justifyContent: 'center',
    alignItems: 'center',
    marginRight: Spacing.sm,
  },
  headerAvatarText: {
    fontSize: FontSizes.lg,
    fontWeight: '600',
    color: AppColors.white,
  },
  headerTitle: {
    fontSize: FontSizes.lg,
    fontWeight: '600',
    color: AppColors.textPrimary,
  },
  headerSubtitle: {
    fontSize: FontSizes.sm,
    color: AppColors.success,
  },
  headerButtons: {
    flexDirection: 'row',
    alignItems: 'center',
    gap: 8,
  },
  headerButton: {
    padding: Spacing.xs,
  },
  voiceModeActive: {
    flexDirection: 'row',
    alignItems: 'center',
    backgroundColor: AppColors.primary,
    borderRadius: BorderRadius.md,
    paddingHorizontal: 10,
    paddingVertical: 6,
    gap: 4,
  },
  voiceModeText: {
    color: AppColors.white,
    fontSize: FontSizes.xs,
    fontWeight: '600',
  },
  speakingIndicator: {
    backgroundColor: AppColors.success,
    borderRadius: BorderRadius.md,
    padding: 6,
  },
  chatContainer: {
    flex: 1,
  },
  messagesList: {
    padding: Spacing.md,
    paddingBottom: Spacing.lg,
  },
  messageContainer: {
    flexDirection: 'row',
    marginBottom: Spacing.md,
    alignItems: 'flex-end',
  },
  userMessageContainer: {
    justifyContent: 'flex-end',
  },
  assistantMessageContainer: {
    justifyContent: 'flex-start',
  },
  avatarContainer: {
    width: 32,
    height: 32,
    borderRadius: BorderRadius.full,
    backgroundColor: AppColors.success,
    justifyContent: 'center',
    alignItems: 'center',
    marginRight: Spacing.xs,
  },
  avatarText: {
    fontSize: FontSizes.sm,
    fontWeight: '600',
    color: AppColors.white,
  },
  messageBubble: {
    maxWidth: '75%',
    padding: Spacing.sm + 4,
    borderRadius: BorderRadius.lg,
  },
  userBubble: {
    backgroundColor: AppColors.primary,
    borderBottomRightRadius: BorderRadius.sm,
  },
  assistantBubble: {
    backgroundColor: AppColors.background,
    borderBottomLeftRadius: BorderRadius.sm,
  },
  messageText: {
    fontSize: FontSizes.base,
    lineHeight: 22,
  },
  userMessageText: {
    color: AppColors.white,
  },
  assistantMessageText: {
    color: AppColors.textPrimary,
  },
  timestamp: {
    fontSize: FontSizes.xs,
    color: AppColors.textMuted,
    marginTop: Spacing.xs,
    alignSelf: 'flex-end',
  },
  userTimestamp: {
    color: 'rgba(255,255,255,0.7)',
  },
  inputContainer: {
    flexDirection: 'row',
    alignItems: 'flex-end',
    padding: Spacing.md,
    backgroundColor: AppColors.background,
    borderTopWidth: 1,
    borderTopColor: AppColors.border,
  },
  input: {
    flex: 1,
    backgroundColor: AppColors.surface,
    borderRadius: BorderRadius.xl,
    paddingHorizontal: Spacing.md,
    paddingVertical: Spacing.sm,
    fontSize: FontSizes.base,
    color: AppColors.textPrimary,
    maxHeight: 100,
    marginRight: Spacing.sm,
  },
  sendButton: {
    width: 44,
    height: 44,
    borderRadius: BorderRadius.full,
    backgroundColor: AppColors.primary,
    justifyContent: 'center',
    alignItems: 'center',
  },
  sendButtonDisabled: {
    backgroundColor: AppColors.surface,
  },
  micButton: {
    width: 44,
    height: 44,
    borderRadius: BorderRadius.full,
    backgroundColor: AppColors.surface,
    justifyContent: 'center',
    alignItems: 'center',
    marginRight: Spacing.sm,
    borderWidth: 1,
    borderColor: AppColors.primary,
  },
  micButtonActive: {
    backgroundColor: AppColors.primary,
    borderColor: AppColors.primary,
  },
  listeningIndicator: {
    flexDirection: 'row',
    alignItems: 'center',
    paddingHorizontal: Spacing.md,
    paddingVertical: Spacing.sm,
    backgroundColor: AppColors.surface,
    borderTopWidth: 1,
    borderTopColor: AppColors.border,
  },
  listeningText: {
    flex: 1,
    marginLeft: Spacing.sm,
    fontSize: FontSizes.sm,
    color: AppColors.textSecondary,
    fontStyle: 'italic',
  },
  stopButton: {
    padding: Spacing.xs,
  },
  // Voice Picker Modal styles
  modalOverlay: {
    flex: 1,
    backgroundColor: 'rgba(0, 0, 0, 0.5)',
    justifyContent: 'flex-end',
  },
  modalContent: {
    backgroundColor: AppColors.background,
    borderTopLeftRadius: BorderRadius.xl,
    borderTopRightRadius: BorderRadius.xl,
    paddingTop: Spacing.lg,
    paddingBottom: Spacing.xl + 20,
    maxHeight: '60%',
  },
  modalHeader: {
    flexDirection: 'row',
    justifyContent: 'space-between',
    alignItems: 'center',
    paddingHorizontal: Spacing.lg,
    marginBottom: Spacing.sm,
  },
  modalTitle: {
    fontSize: FontSizes.xl,
    fontWeight: '600',
    color: AppColors.textPrimary,
  },
  modalCloseButton: {
    padding: Spacing.xs,
  },
  modalSubtitle: {
    fontSize: FontSizes.sm,
    color: AppColors.textSecondary,
    paddingHorizontal: Spacing.lg,
    marginBottom: Spacing.md,
  },
  voiceList: {
    paddingHorizontal: Spacing.lg,
  },
  voiceItem: {
    flexDirection: 'row',
    alignItems: 'center',
    padding: Spacing.md,
    backgroundColor: AppColors.surface,
    borderRadius: BorderRadius.lg,
    marginBottom: Spacing.sm,
    borderWidth: 2,
    borderColor: 'transparent',
  },
  voiceItemSelected: {
    borderColor: AppColors.primary,
    backgroundColor: `${AppColors.primary}15`,
  },
  voiceIcon: {
    width: 48,
    height: 48,
    borderRadius: BorderRadius.full,
    backgroundColor: AppColors.primary + '20',
    justifyContent: 'center',
    alignItems: 'center',
    marginRight: Spacing.md,
  },
  voiceInfo: {
    flex: 1,
  },
  voiceName: {
    fontSize: FontSizes.base,
    fontWeight: '600',
    color: AppColors.textPrimary,
    marginBottom: 2,
  },
  voiceNameSelected: {
    color: AppColors.primary,
  },
  voiceDescription: {
    fontSize: FontSizes.sm,
    color: AppColors.textSecondary,
  },
  voiceDescriptionSelected: {
    color: AppColors.primary,
  },
  voiceHint: {
    fontSize: FontSizes.xs,
    color: AppColors.textSecondary,
    marginTop: 4,
  },
});