import React, { useState, useCallback, useMemo, useRef, useEffect } from 'react';
import {
  View,
  StyleSheet,
  TextInput,
  TouchableOpacity,
  Alert,
  ActivityIndicator,
  Clipboard,
  FlatList,
  RefreshControl,
  Animated,
  KeyboardAvoidingView,
  Platform,
  ScrollView,
} from 'react-native';
import { SafeAreaView } from 'react-native-safe-area-context';
import { useRouter } from 'expo-router';
import { MaterialCommunityIcons } from '@expo/vector-icons';

import { spacing, borderRadius, fontSizes, useAppColors, type AppColors } from '../../theme';
import Avatar from '../../components/common/Avatar';
import Text from '../../components/common/Text';
import { groupService } from '@/services/message';
import { groupManager } from '../../stores/group';
import { GroupResponse, JoinType } from '../../types/dto';
import { useCursorPagination } from '../../hooks/useCursorPagination';
import { EmptyState } from '../../components/common';

function createJoinGroupStyles(colors: AppColors) {
  return StyleSheet.create({
    container: {
      flex: 1,
      backgroundColor: colors.background.paper,
    },
    keyboardView: {
      flex: 1,
    },
    scrollContent: {
      flexGrow: 1,
      paddingHorizontal: 28,
      paddingTop: 40,
      paddingBottom: 40,
    },
    content: {
      flex: 1,
      maxWidth: 400,
      width: '100%',
      alignSelf: 'center',
    },

    // 标题区域
    titleSection: {
      marginBottom: 32,
      marginTop: 12,
    },
    title: {
      fontSize: 28,
      fontWeight: '700',
      color: colors.text.primary,
      lineHeight: 36,
    },
    underline: {
      width: 40,
      height: 4,
      backgroundColor: colors.primary.main,
      borderRadius: 2,
      marginTop: 12,
      marginBottom: 12,
    },
    subtitle: {
      fontSize: 15,
      color: colors.text.secondary,
    },

    // 搜索区域
    searchSection: {
      marginBottom: 24,
    },
    inputLabel: {
      fontSize: 14,
      fontWeight: '500',
      color: colors.text.secondary,
      marginBottom: 10,
    },
    searchRow: {
      flexDirection: 'row',
      alignItems: 'center',
    },
    inputWrapper: {
      flex: 1,
      flexDirection: 'row',
      alignItems: 'center',
      backgroundColor: colors.background.default,
      borderRadius: 14,
      paddingHorizontal: 18,
      height: 56,
      borderWidth: 1,
      borderColor: 'transparent',
    },
    input: {
      flex: 1,
      fontSize: 16,
      color: colors.text.primary,
      height: 56,
    },
    searchBtn: {
      width: 56,
      height: 56,
      borderRadius: 14,
      backgroundColor: colors.primary.main,
      alignItems: 'center',
      justifyContent: 'center',
      marginLeft: spacing.sm,
    },
    searchBtnDisabled: {
      opacity: 0.5,
    },

    // 搜索结果区域
    searchResultSection: {
      marginBottom: 24,
    },
    sectionTitle: {
      fontSize: 14,
      fontWeight: '500',
      color: colors.text.secondary,
      marginBottom: 12,
    },
    emptyText: {
      textAlign: 'center',
      fontSize: 14,
      color: colors.text.hint,
      fontWeight: '500',
      paddingVertical: spacing.lg,
    },

    // 群卡片
    groupCard: {
      backgroundColor: colors.background.default,
      borderRadius: 16,
      padding: spacing.lg,
      marginBottom: spacing.md,
    },
    groupHeader: {
      flexDirection: 'row',
      alignItems: 'center',
      marginBottom: spacing.sm,
    },
    groupMeta: {
      marginLeft: spacing.md,
      flex: 1,
    },
    groupName: {
      fontWeight: '700',
      fontSize: 16,
      color: colors.text.primary,
      marginBottom: 2,
    },
    groupDesc: {
      fontSize: 13,
      color: colors.text.secondary,
      lineHeight: 20,
      marginTop: spacing.sm,
    },
    groupInfoRow: {
      marginTop: spacing.sm,
      marginBottom: spacing.xs,
      flexDirection: 'row',
      justifyContent: 'space-between',
    },
    groupInfoText: {
      fontSize: 12,
      color: colors.text.secondary,
    },
    groupNoRow: {
      flexDirection: 'row',
      alignItems: 'center',
      justifyContent: 'space-between',
      marginBottom: spacing.md,
    },
    groupNoText: {
      fontSize: 12,
      color: colors.text.secondary,
    },
    copyBtn: {
      flexDirection: 'row',
      alignItems: 'center',
      paddingHorizontal: spacing.sm,
      paddingVertical: 4,
      borderRadius: borderRadius.sm,
      backgroundColor: colors.primary.light + '15',
    },
    copyBtnText: {
      marginLeft: 4,
      fontSize: 12,
      fontWeight: '600',
      color: colors.primary.main,
    },
    submitBtn: {
      flexDirection: 'row',
      alignItems: 'center',
      justifyContent: 'center',
      borderRadius: 14,
      backgroundColor: colors.primary.main,
      height: 48,
    },
    submitBtnDisabled: {
      opacity: 0.5,
    },
    submitText: {
      marginLeft: spacing.xs,
      fontWeight: '700',
      fontSize: 15,
      color: colors.text.inverse,
    },

    // 推荐区域
    recommendSection: {
      flex: 1,
    },
    loadingFooter: {
      paddingVertical: spacing.md,
      alignItems: 'center',
    },
    loadMoreBtn: {
      paddingVertical: spacing.md,
      alignItems: 'center',
    },
    loadMoreText: {
      fontSize: 14,
      fontWeight: '500',
      color: colors.primary.main,
    },
    noMoreText: {
      textAlign: 'center',
      paddingVertical: spacing.md,
      fontWeight: '500',
      fontSize: 13,
      color: colors.text.hint,
    },
  });
}

const JoinGroupScreen: React.FC = () => {
  const colors = useAppColors();
  const styles = useMemo(() => createJoinGroupStyles(colors), [colors]);
  const router = useRouter();
  const [keyword, setKeyword] = useState('');
  const [searching, setSearching] = useState(false);
  const [joiningGroupId, setJoiningGroupId] = useState<string | null>(null);
  const [searchedGroup, setSearchedGroup] = useState<GroupResponse | null>(null);
  const [searched, setSearched] = useState(false);

  // 动画值
  const fadeAnim = useRef(new Animated.Value(0)).current;
  const slideAnim = useRef(new Animated.Value(20)).current;

  useEffect(() => {
    Animated.parallel([
      Animated.timing(fadeAnim, {
        toValue: 1,
        duration: 400,
        useNativeDriver: true,
      }),
      Animated.timing(slideAnim, {
        toValue: 0,
        duration: 400,
        useNativeDriver: true,
      }),
    ]).start();
  }, []);

  // 使用游标分页 Hook 管理群组列表
  const {
    list: groups,
    isLoading,
    isRefreshing,
    hasMore,
    loadMore,
    refresh,
    error,
  } = useCursorPagination(
    async ({ cursor, pageSize }) => {
      return await groupService.getGroupsCursor({
        cursor,
        page_size: pageSize,
      });
    },
    { pageSize: 20 }
  );

  const getJoinTypeText = (joinType: JoinType) => {
    if (joinType === 0) return '允许加入';
    if (joinType === 1) return '需要审批';
    return '禁止加入';
  };

  const handleSearch = async () => {
    const trimmed = keyword.trim();
    if (!trimmed) {
      Alert.alert('提示', '请输入群ID进行搜索');
      return;
    }

    setSearching(true);
    setSearched(true);
    try {
      const result = await groupManager.getGroup(trimmed, true);
      setSearchedGroup(result);
    } catch (error: any) {
      setSearchedGroup(null);
      const message = error?.response?.data?.message || error?.message || '';
      if (String(message).includes('不存在') || error?.response?.status === 404) {
        Alert.alert('未找到', '未搜索到该群聊，请确认群ID是否正确');
      } else {
        Alert.alert('搜索失败', '请稍后重试');
      }
    } finally {
      setSearching(false);
    }
  };

  const handleJoin = async (group: GroupResponse) => {
    if (!group?.id) return;
    setJoiningGroupId(String(group.id));
    try {
      await groupService.joinGroup(group.id);
      Alert.alert('成功', '操作已提交', [
        {
          text: '确定',
          onPress: () => router.back(),
        },
      ]);
    } catch (error: any) {
      const message =
        error?.response?.data?.message ||
        error?.message ||
        '操作失败，请稍后重试';
      Alert.alert('操作失败', String(message));
    } finally {
      setJoiningGroupId(null);
    }
  };

  const handleCopyGroupId = (groupId: string) => {
    Clipboard.setString(groupId);
    Alert.alert('已复制', '群号已复制到剪贴板');
  };

  const formatGroupNo = (id: string) => {
    const raw = id;
    if (raw.length <= 12) return raw;
    return `${raw.slice(0, 6)}...${raw.slice(-4)}`;
  };

  const renderGroupItem = ({ item: group }: { item: GroupResponse }) => {
    const isJoining = joiningGroupId === String(group.id);

    return (
      <View style={styles.groupCard}>
        <View style={styles.groupHeader}>
          <Avatar source={group.avatar} size={52} name={group.name} />
          <View style={styles.groupMeta}>
            <Text style={styles.groupName} numberOfLines={1}>
              {group.name}
            </Text>
          </View>
        </View>
        {!!group.description && (
          <Text style={styles.groupDesc}>
            {group.description}
          </Text>
        )}
        <View style={styles.groupInfoRow}>
          <Text style={styles.groupInfoText}>
            成员 {group.member_count}/{group.max_members}
          </Text>
          <Text style={styles.groupInfoText}>
            {getJoinTypeText(group.join_type)}
          </Text>
        </View>
        <View style={styles.groupNoRow}>
          <Text style={styles.groupNoText}>
            群号：{formatGroupNo(group.id)}
          </Text>
          <TouchableOpacity style={styles.copyBtn} onPress={() => handleCopyGroupId(group.id)}>
            <MaterialCommunityIcons name="content-copy" size={14} color={colors.primary.main} />
            <Text style={styles.copyBtnText}>
              复制
            </Text>
          </TouchableOpacity>
        </View>
        <TouchableOpacity
          style={[styles.submitBtn, isJoining && styles.submitBtnDisabled]}
          onPress={() => handleJoin(group)}
          disabled={isJoining}
        >
          {isJoining ? (
            <ActivityIndicator color={colors.text.inverse} />
          ) : (
            <>
              <MaterialCommunityIcons name="send-outline" size={18} color={colors.text.inverse} />
              <Text style={styles.submitText}>
                申请入群
              </Text>
            </>
          )}
        </TouchableOpacity>
      </View>
    );
  };

  const renderEmptyList = () => {
    if (isLoading) return null;
    return (
      <EmptyState
        title="暂无群组"
        description="还没有可加入的群组"
        icon="account-group-outline"
      />
    );
  };

  const renderSearchResult = () => {
    if (!searched) return null;

    if (searchedGroup) {
      return (
        <View style={styles.searchResultSection}>
          <Text style={styles.sectionTitle}>搜索结果</Text>
          {renderGroupItem({ item: searchedGroup })}
        </View>
      );
    }

    if (!searching) {
      return (
        <View style={styles.searchResultSection}>
          <Text style={styles.sectionTitle}>搜索结果</Text>
          <Text style={styles.emptyText}>
            暂无搜索结果，请检查群ID后重试
          </Text>
        </View>
      );
    }

    return null;
  };

  return (
    <SafeAreaView style={styles.container} edges={['top', 'bottom']}>
      <KeyboardAvoidingView
        behavior={Platform.OS === 'ios' ? 'padding' : 'height'}
        style={styles.keyboardView}
      >
        <ScrollView
          contentContainerStyle={styles.scrollContent}
          keyboardShouldPersistTaps="handled"
          showsVerticalScrollIndicator={false}
          refreshControl={
            <RefreshControl
              refreshing={isRefreshing}
              onRefresh={refresh}
              colors={[colors.primary.main]}
              tintColor={colors.primary.main}
            />
          }
        >
          <Animated.View
            style={[
              styles.content,
              {
                opacity: fadeAnim,
                transform: [{ translateY: slideAnim }],
              },
            ]}
          >
            {/* 标题区域 */}
            <View style={styles.titleSection}>
              <Text style={styles.title}>加入群聊</Text>
              <View style={styles.underline} />
              <Text style={styles.subtitle}>搜索群ID或浏览推荐群组</Text>
            </View>

            {/* 搜索区域 */}
            <View style={styles.searchSection}>
              <Text style={styles.inputLabel}>搜索群聊（群ID）</Text>
              <View style={styles.searchRow}>
                <View style={styles.inputWrapper}>
                  <TextInput
                    value={keyword}
                    onChangeText={setKeyword}
                    placeholder="例如：7391234567890"
                    placeholderTextColor={colors.text.hint}
                    style={styles.input}
                    editable={!searching && !joiningGroupId}
                    autoCapitalize="none"
                    cursorColor={colors.primary.main}
                    selectionColor={`${colors.primary.main}40`}
                  />
                </View>
                <TouchableOpacity
                  style={[
                    styles.searchBtn,
                    (!keyword.trim() || searching || !!joiningGroupId) && styles.searchBtnDisabled,
                  ]}
                  onPress={handleSearch}
                  disabled={!keyword.trim() || searching || !!joiningGroupId}
                >
                  {searching ? (
                    <ActivityIndicator color={colors.text.inverse} />
                  ) : (
                    <MaterialCommunityIcons name="magnify" size={22} color={colors.text.inverse} />
                  )}
                </TouchableOpacity>
              </View>
            </View>

            {/* 搜索结果 */}
            {renderSearchResult()}

            {/* 推荐群组 */}
            <View style={styles.recommendSection}>
              <Text style={styles.sectionTitle}>推荐群组</Text>
              {groups.length === 0 && !isLoading ? (
                renderEmptyList()
              ) : (
                <>
                  {groups.map((group) => (
                    <View key={String(group.id)}>
                      {renderGroupItem({ item: group })}
                    </View>
                  ))}
                  {isLoading && (
                    <View style={styles.loadingFooter}>
                      <ActivityIndicator color={colors.primary.main} />
                    </View>
                  )}
                  {hasMore && !isLoading && (
                    <TouchableOpacity style={styles.loadMoreBtn} onPress={loadMore}>
                      <Text style={styles.loadMoreText}>
                        加载更多
                      </Text>
                    </TouchableOpacity>
                  )}
                  {!hasMore && groups.length > 0 && (
                    <Text style={styles.noMoreText}>
                      没有更多群组了
                    </Text>
                  )}
                </>
              )}
            </View>
          </Animated.View>
        </ScrollView>
      </KeyboardAvoidingView>
    </SafeAreaView>
  );
};

export default JoinGroupScreen;