import { DateSelector } from '@/components/DateSelector';
import { TaskCard } from '@/components/TaskCard';
import { HeaderBar } from '@/components/ui/HeaderBar';
import { Colors } from '@/constants/Colors';
import { TAB_BAR_BOTTOM_OFFSET, TAB_BAR_HEIGHT } from '@/constants/TabBar';
import { useColorScheme } from '@/hooks/useColorScheme';
import { tasksApi } from '@/services/tasksApi';
import { TaskListItem } from '@/types/goals';
import { getTodayIndexInMonth } from '@/utils/date';
import { useFocusEffect } from '@react-navigation/native';
import dayjs from 'dayjs';
import { LinearGradient } from 'expo-linear-gradient';
import { useRouter } from 'expo-router';
import React, { useCallback, useEffect, useMemo, useState } from 'react';
import { Alert, FlatList, RefreshControl, StatusBar, StyleSheet, Text, View } from 'react-native';
import { SafeAreaView } from 'react-native-safe-area-context';

export default function GoalsDetailScreen() {
  const theme = (useColorScheme() ?? 'light') as 'light' | 'dark';
  const colorTokens = Colors[theme];
  const router = useRouter();

  // 本地状态管理
  const [tasks, setTasks] = useState<TaskListItem[]>([]);
  const [tasksLoading, setTasksLoading] = useState(false);
  const [tasksError, setTasksError] = useState<string | null>(null);
  const [selectedDate, setSelectedDate] = useState<Date>(new Date());
  const [refreshing, setRefreshing] = useState(false);

  // 日期选择器相关状态
  const [selectedIndex, setSelectedIndex] = useState(getTodayIndexInMonth());

  // 加载任务列表
  const loadTasks = async (targetDate?: Date) => {
    try {
      setTasksLoading(true);
      setTasksError(null);

      const dateToUse = targetDate || selectedDate;
      console.log('Loading tasks for date:', dayjs(dateToUse).format('YYYY-MM-DD'));

      const response = await tasksApi.getTasks({
        startDate: dayjs(dateToUse).startOf('day').toISOString(),
        endDate: dayjs(dateToUse).endOf('day').toISOString(),
      });

      console.log('Tasks API response:', response);
      setTasks(response.list || []);
    } catch (error: any) {
      console.error('Failed to load tasks:', error);
      setTasksError(error.message || '获取任务列表失败');
      setTasks([]);
    } finally {
      setTasksLoading(false);
    }
  };

  // 页面聚焦时重新加载数据
  useFocusEffect(
    useCallback(() => {
      console.log('useFocusEffect - loading tasks');
      loadTasks();
    }, [])
  );

  // 下拉刷新
  const onRefresh = async () => {
    setRefreshing(true);
    try {
      await loadTasks();
    } finally {
      setRefreshing(false);
    }
  };

  // 处理错误提示
  useEffect(() => {
    if (tasksError) {
      Alert.alert('错误', tasksError);
      setTasksError(null);
    }
  }, [tasksError]);



  // 日期选择处理
  const onSelectDate = async (index: number, date: Date) => {
    console.log('Date selected:', dayjs(date).format('YYYY-MM-DD'));
    setSelectedIndex(index);
    setSelectedDate(date);
    // 重新加载对应日期的任务数据
    await loadTasks(date);
  };

  // 根据选中日期筛选任务，并将已完成的任务放到最后
  const filteredTasks = useMemo(() => {
    const selected = dayjs(selectedDate);
    const filtered = tasks.filter(task => {
      if (task.status === 'skipped') return false;
      const taskDate = dayjs(task.startDate);
      return taskDate.isSame(selected, 'day');
    });
    
    // 对筛选结果进行排序：已完成的任务放到最后
    return [...filtered].sort((a, b) => {
      const aCompleted = a.status === 'completed';
      const bCompleted = b.status === 'completed';
      
      // 如果a已完成而b未完成，a排在后面
      if (aCompleted && !bCompleted) {
        return 1;
      }
      // 如果b已完成而a未完成，b排在后面
      if (bCompleted && !aCompleted) {
        return -1;
      }
      // 如果都已完成或都未完成，保持原有顺序
      return 0;
    });
  }, [selectedDate, tasks]);

  const handleBackPress = () => {
    router.back();
  };

  // 渲染任务项
  const renderTaskItem = ({ item }: { item: TaskListItem }) => (
    <TaskCard
      task={item}
    />
  );

  // 渲染空状态
  const renderEmptyState = () => {
    const selectedDateStr = dayjs(selectedDate).format('YYYY年M月D日');
    
    if (tasksLoading) {
      return (
        <View style={styles.emptyState}>
          <Text style={[styles.emptyStateTitle, { color: colorTokens.text }]}>
            加载中...
          </Text>
        </View>
      );
    }
    
    return (
      <View style={styles.emptyState}>
        <Text style={[styles.emptyStateTitle, { color: colorTokens.text }]}>
          暂无任务
        </Text>
        <Text style={[styles.emptyStateSubtitle, { color: colorTokens.textSecondary }]}>
          {selectedDateStr} 没有任务安排
        </Text>
      </View>
    );
  };

  return (
    <SafeAreaView style={styles.container}>
      <StatusBar
        backgroundColor="transparent"
        translucent
      />

      {/* 背景渐变 */}
      <LinearGradient
        colors={['#F0F9FF', '#E0F2FE']}
        style={styles.gradientBackground}
        start={{ x: 0, y: 0 }}
        end={{ x: 1, y: 1 }}
      />

      {/* 装饰性圆圈 */}
      <View style={styles.decorativeCircle1} />
      <View style={styles.decorativeCircle2} />

      <View style={styles.content}>
        {/* 标题区域 */}
        <HeaderBar
          title="任务列表"
          onBack={handleBackPress}
          transparent={true}
          withSafeTop={false}
        />

        {/* 日期选择器 */}
        <View style={styles.dateSelector}>
          <DateSelector
            selectedIndex={selectedIndex}
            onDateSelect={onSelectDate}
            showMonthTitle={true}
            disableFutureDates={true}
          />
        </View>

        {/* 任务列表 */}
        <View style={styles.taskListContainer}>
          <FlatList
            data={filteredTasks}
            renderItem={renderTaskItem}
            keyExtractor={(item) => item.id}
            contentContainerStyle={styles.taskList}
            showsVerticalScrollIndicator={false}
            refreshControl={
              <RefreshControl
                refreshing={refreshing}
                onRefresh={onRefresh}
                colors={['#0EA5E9']}
                tintColor="#0EA5E9"
              />
            }
            ListEmptyComponent={renderEmptyState}
          />
        </View>
      </View>
    </SafeAreaView>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
  },
  gradientBackground: {
    position: 'absolute',
    left: 0,
    right: 0,
    top: 0,
    bottom: 0,
    opacity: 0.6,
  },
  decorativeCircle1: {
    position: 'absolute',
    top: -20,
    right: -20,
    width: 60,
    height: 60,
    borderRadius: 30,
    backgroundColor: '#0EA5E9',
    opacity: 0.1,
  },
  decorativeCircle2: {
    position: 'absolute',
    bottom: -15,
    left: -15,
    width: 40,
    height: 40,
    borderRadius: 20,
    backgroundColor: '#0EA5E9',
    opacity: 0.05,
  },
  content: {
    flex: 1,
  },

  // 日期选择器样式
  dateSelector: {
    paddingHorizontal: 20,
  },
  taskListContainer: {
    flex: 1,
    borderTopLeftRadius: 24,
    borderTopRightRadius: 24,
    overflow: 'hidden',
  },
  taskList: {
    paddingHorizontal: 20,
    paddingBottom: TAB_BAR_HEIGHT + TAB_BAR_BOTTOM_OFFSET + 20,
  },
  emptyState: {
    alignItems: 'center',
    justifyContent: 'center',
    paddingVertical: 60,
  },
  emptyStateTitle: {
    fontSize: 18,
    fontWeight: '600',
    marginBottom: 8,
  },
  emptyStateSubtitle: {
    fontSize: 14,
    textAlign: 'center',
    lineHeight: 20,
  },
});