import React, { useEffect, useRef, useState } from 'react';
import {
  View,
  Text,
  TouchableOpacity,
  FlatList,
  StyleSheet,
  Animated,
  Dimensions,
  Pressable,
} from 'react-native';
import type { Conversation } from '../../store/chatTypes';
import { colors, spacing, typography, borderRadius } from '../../theme/lightTheme';

const DRAWER_WIDTH = Math.min(Dimensions.get('window').width * 0.80, 310);

interface Props {
  visible: boolean;
  conversations: Conversation[];
  activeConversationId: string | null;
  onClose: () => void;
  onNewChat: () => void;
  onSelectConversation: (id: string) => void;
  onDeleteConversation: (id: string) => void;
}

function formatDate(ts: number): string {
  const diffDays = Math.floor((Date.now() - ts) / 86400000);
  if (diffDays === 0) return "Aujourd'hui";
  if (diffDays === 1) return 'Hier';
  if (diffDays < 7) return `Il y a ${diffDays} j`;
  return new Date(ts).toLocaleDateString('fr-FR', { day: 'numeric', month: 'short' });
}

export default function ChatDrawer({
  visible,
  conversations,
  activeConversationId,
  onClose,
  onNewChat,
  onSelectConversation,
  onDeleteConversation,
}: Props) {
  const translateX = useRef(new Animated.Value(-DRAWER_WIDTH)).current;
  const backdropOpacity = useRef(new Animated.Value(0)).current;
  // Keep mounted during the close animation
  const [mounted, setMounted] = useState(false);

  useEffect(() => {
    if (visible) {
      setMounted(true);
      Animated.parallel([
        Animated.timing(translateX, {
          toValue: 0,
          duration: 250,
          useNativeDriver: true,
        }),
        Animated.timing(backdropOpacity, {
          toValue: 0.5,
          duration: 250,
          useNativeDriver: true,
        }),
      ]).start();
    } else {
      Animated.parallel([
        Animated.timing(translateX, {
          toValue: -DRAWER_WIDTH,
          duration: 210,
          useNativeDriver: true,
        }),
        Animated.timing(backdropOpacity, {
          toValue: 0,
          duration: 210,
          useNativeDriver: true,
        }),
      ]).start(() => setMounted(false));
    }
  }, [visible, translateX, backdropOpacity]);

  if (!mounted) return null;

  const sorted = [...conversations].sort((a, b) => b.updatedAt - a.updatedAt);

  const renderItem = ({ item }: { item: Conversation }) => {
    const isActive = item.id === activeConversationId;
    const lastMsg = item.messages[item.messages.length - 1];
    return (
      <TouchableOpacity
        style={[styles.convItem, isActive && styles.convItemActive]}
        onPress={() => { onSelectConversation(item.id); onClose(); }}
        activeOpacity={0.75}
      >
        <View style={styles.convItemContent}>
          <Text
            style={[styles.convTitle, isActive && styles.convTitleActive]}
            numberOfLines={1}
          >
            {item.title}
          </Text>
          <Text style={styles.convMeta}>
            {item.messages.length} msg · {formatDate(item.updatedAt)}
          </Text>
          {lastMsg ? (
            <Text style={styles.convPreview} numberOfLines={1}>
              {lastMsg.role === 'user' ? '👤 ' : '🤖 '}
              {lastMsg.content}
            </Text>
          ) : (
            <Text style={styles.convPreviewEmpty}>Vide</Text>
          )}
        </View>
        <TouchableOpacity
          style={styles.deleteBtn}
          onPress={() => onDeleteConversation(item.id)}
          hitSlop={{ top: 10, bottom: 10, left: 10, right: 10 }}
        >
          <Text style={styles.deleteBtnText}>✕</Text>
        </TouchableOpacity>
      </TouchableOpacity>
    );
  };

  return (
    <View style={StyleSheet.absoluteFillObject} pointerEvents="box-none">
      {/* Backdrop */}
      <Animated.View
        style={[styles.backdrop, { opacity: backdropOpacity }]}
        pointerEvents={visible ? 'auto' : 'none'}
      >
        <Pressable style={StyleSheet.absoluteFillObject} onPress={onClose} />
      </Animated.View>

      {/* Drawer panel */}
      <Animated.View style={[styles.drawer, { transform: [{ translateX }] }]}>
        {/* Header */}
        <View style={styles.drawerHeader}>
          <Text style={styles.drawerTitle}>Conversations</Text>
          <TouchableOpacity
            onPress={onClose}
            hitSlop={{ top: 10, bottom: 10, left: 10, right: 10 }}
          >
            <Text style={styles.closeBtnText}>✕</Text>
          </TouchableOpacity>
        </View>

        {/* New chat button */}
        <TouchableOpacity
          style={styles.newChatBtn}
          onPress={() => { onNewChat(); onClose(); }}
          activeOpacity={0.85}
        >
          <Text style={styles.newChatBtnText}>＋  Nouveau chat</Text>
        </TouchableOpacity>

        {/* Conversations list */}
        <FlatList
          data={sorted}
          keyExtractor={item => item.id}
          renderItem={renderItem}
          contentContainerStyle={styles.listContent}
          showsVerticalScrollIndicator={false}
          ListEmptyComponent={
            <Text style={styles.emptyText}>Aucune conversation</Text>
          }
        />
      </Animated.View>
    </View>
  );
}

const styles = StyleSheet.create({
  backdrop: {
    ...StyleSheet.absoluteFillObject,
    backgroundColor: colors.textPrimary,
  },
  drawer: {
    position: 'absolute',
    left: 0,
    top: 0,
    bottom: 0,
    width: DRAWER_WIDTH,
    backgroundColor: colors.surface,
    shadowColor: colors.textPrimary,
    shadowOffset: { width: 4, height: 0 },
    shadowOpacity: 0.25,
    shadowRadius: 12,
    elevation: 16,
  },
  drawerHeader: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'space-between',
    paddingHorizontal: spacing.lg,
    paddingTop: spacing.xxl,
    paddingBottom: spacing.md,
    borderBottomWidth: StyleSheet.hairlineWidth,
    borderBottomColor: colors.border,
  },
  drawerTitle: {
    fontSize: typography.sizes.lg,
    fontWeight: typography.weights.semibold,
    color: colors.textPrimary,
  },
  closeBtnText: {
    fontSize: 18,
    color: colors.textSecondary,
  },
  newChatBtn: {
    margin: spacing.md,
    paddingVertical: spacing.md,
    backgroundColor: colors.primary,
    borderRadius: borderRadius.lg,
    alignItems: 'center',
  },
  newChatBtnText: {
    color: colors.surface,
    fontSize: typography.sizes.md,
    fontWeight: typography.weights.semibold,
  },
  listContent: {
    paddingHorizontal: spacing.sm,
    paddingBottom: spacing.xxl,
  },
  convItem: {
    flexDirection: 'row',
    alignItems: 'center',
    paddingVertical: spacing.sm,
    paddingHorizontal: spacing.md,
    borderRadius: borderRadius.lg,
    marginBottom: 2,
  },
  convItemActive: {
    backgroundColor: colors.surfaceSecondary,
    borderLeftWidth: 3,
    borderLeftColor: colors.primary,
  },
  convItemContent: {
    flex: 1,
    marginRight: spacing.sm,
  },
  convTitle: {
    fontSize: typography.sizes.sm,
    fontWeight: typography.weights.medium,
    color: colors.textPrimary,
    marginBottom: 2,
  },
  convTitleActive: {
    color: colors.primary,
    fontWeight: typography.weights.semibold,
  },
  convMeta: {
    fontSize: 11,
    color: colors.textTertiary,
    marginBottom: 2,
  },
  convPreview: {
    fontSize: 12,
    color: colors.textSecondary,
  },
  convPreviewEmpty: {
    fontSize: 12,
    color: colors.textTertiary,
    fontStyle: 'italic',
  },
  deleteBtn: {
    padding: 4,
  },
  deleteBtnText: {
    fontSize: 14,
    color: colors.textTertiary,
  },
  emptyText: {
    textAlign: 'center',
    color: colors.textTertiary,
    marginTop: spacing.xl,
    fontSize: typography.sizes.sm,
  },
});