/**
 * 学习资料主页：学科分类网格
 */
import React, { useCallback, useEffect, useMemo, useState } from 'react';
import {
  View,
  StyleSheet,
  ScrollView,
  TouchableOpacity,
  StatusBar,
  RefreshControl,
} from 'react-native';
import { SafeAreaView, useSafeAreaInsets } from 'react-native-safe-area-context';
import { useRouter } from 'expo-router';
import { MaterialCommunityIcons } from '@expo/vector-icons';

import {
  spacing,
  fontSizes,
  borderRadius,
  shadows,
  useAppColors,
  useResolvedColorScheme,
  type AppColors,
} from '../../theme';
import * as hrefs from '../../navigation/hrefs';
import { Text, ResponsiveContainer, Loading } from '../../components/common';
import { useResponsive, useResponsiveSpacing, useBreakpointGTE } from '../../hooks/useResponsive';
import type { MaterialSubject } from '../../types/material';
import { materialRepository } from '../../data/repositories/MaterialRepository';

export const MaterialsScreen: React.FC = () => {
  const colors = useAppColors();
  const resolvedScheme = useResolvedColorScheme();
  const statusBarStyle = resolvedScheme === 'dark' ? 'light-content' : 'dark-content';
  const styles = useMemo(() => createMaterialsStyles(colors), [colors]);
  const router = useRouter();
  const insets = useSafeAreaInsets();
  const { isMobile } = useResponsive();
  const isWideScreen = useBreakpointGTE('lg');
  const responsivePadding = useResponsiveSpacing({ xs: 8, sm: 12, md: 16, lg: 24, xl: 32 });

  const [subjects, setSubjects] = useState<MaterialSubject[]>([]);
  const [isLoading, setIsLoading] = useState(true);
  const [isRefreshing, setIsRefreshing] = useState(false);
  const [error, setError] = useState<string | null>(null);

  const scrollBottomInset = isMobile ? 88 + insets.bottom + spacing.md : spacing['3xl'];

  const loadSubjects = useCallback(async () => {
    try {
      setError(null);
      const data = await materialRepository.getSubjects();
      setSubjects(data);
    } catch (err) {
      setError('加载学科列表失败');
      console.error('Failed to load subjects:', err);
    } finally {
      setIsLoading(false);
      setIsRefreshing(false);
    }
  }, []);

  useEffect(() => {
    loadSubjects();
  }, [loadSubjects]);

  const handleRefresh = useCallback(() => {
    setIsRefreshing(true);
    loadSubjects();
  }, [loadSubjects]);

  const onOpenSubject = useCallback(
    (subjectId: string) => {
      router.push(hrefs.hrefMaterialSubject(subjectId));
    },
    [router]
  );

  const cardStyle = useMemo(
    () => ({
      backgroundColor: colors.background.paper,
      borderRadius: 16,
      overflow: 'hidden' as const,
      shadowColor: '#000',
      shadowOffset: { width: 0, height: 2 },
      shadowOpacity: 0.06,
      shadowRadius: 8,
      elevation: 2,
    }),
    [colors]
  );

  const renderSubjectCard = (subject: MaterialSubject) => (
    <TouchableOpacity
      key={subject.id}
      style={[styles.subjectCard, cardStyle]}
      onPress={() => onOpenSubject(subject.id)}
      activeOpacity={0.85}
    >
      <View style={[styles.subjectIconCircle, { backgroundColor: subject.color }]}>
        <MaterialCommunityIcons name={subject.icon as any} size={28} color="#FFFFFF" />
      </View>
      <View style={styles.subjectContent}>
        <Text variant="body" style={styles.subjectName}>
          {subject.name}
        </Text>
        <Text variant="caption" color={colors.text.secondary} style={styles.subjectDesc}>
          {subject.description || `${subject.material_count} 份资料`}
        </Text>
      </View>
      <View style={styles.subjectMeta}>
        <Text variant="caption" color={colors.text.hint}>
          {subject.material_count}
        </Text>
        <MaterialCommunityIcons name="chevron-right" size={20} color={colors.text.hint} />
      </View>
    </TouchableOpacity>
  );

  const renderContent = () => {
    if (isLoading) {
      return (
        <View style={styles.centerContainer}>
          <Loading size="large" />
        </View>
      );
    }

    if (error) {
      return (
        <View style={styles.centerContainer}>
          <MaterialCommunityIcons name="alert-circle-outline" size={48} color={colors.text.hint} />
          <Text variant="body" color={colors.text.secondary} style={styles.errorText}>
            {error}
          </Text>
          <TouchableOpacity onPress={loadSubjects} style={styles.retryButton}>
            <Text variant="body" color={colors.primary.main}>
              重试
            </Text>
          </TouchableOpacity>
        </View>
      );
    }

    return (
      <>
        <Text variant="caption" color={colors.text.secondary} style={styles.pageSubtitle}>
          按学科分类浏览学习资料
        </Text>
        <View style={styles.subjectsGrid}>{subjects.map(renderSubjectCard)}</View>
      </>
    );
  };

  return (
    <SafeAreaView style={styles.container} edges={['top', 'bottom']}>
      <StatusBar barStyle={statusBarStyle} backgroundColor={colors.background.default} />

      {/* Header */}
      <View style={[styles.header, isWideScreen && styles.headerWide]}>
        <View style={styles.headerLeft}>
          <TouchableOpacity onPress={() => router.back()} style={styles.backButton}>
            <MaterialCommunityIcons name="arrow-left" size={24} color={colors.text.primary} />
          </TouchableOpacity>
        </View>
        <View style={styles.headerCenter}>
          <Text style={[styles.headerTitle, isWideScreen && styles.headerTitleWide]}>
            学习资料
          </Text>
        </View>
        <View style={styles.headerRight}>
          <TouchableOpacity style={styles.searchButton}>
            <MaterialCommunityIcons name="magnify" size={24} color={colors.text.primary} />
          </TouchableOpacity>
        </View>
      </View>

      {/* Content */}
      {isWideScreen ? (
        <ResponsiveContainer maxWidth={800}>
          <ScrollView
            style={styles.scroll}
            contentContainerStyle={[styles.scrollContent, { paddingBottom: scrollBottomInset }]}
            showsVerticalScrollIndicator={false}
            refreshControl={
              <RefreshControl
                refreshing={isRefreshing}
                onRefresh={handleRefresh}
                tintColor={colors.primary.main}
              />
            }
          >
            {renderContent()}
          </ScrollView>
        </ResponsiveContainer>
      ) : (
        <ScrollView
          style={styles.scroll}
          contentContainerStyle={[
            styles.scrollContent,
            { paddingBottom: scrollBottomInset, paddingHorizontal: responsivePadding },
          ]}
          showsVerticalScrollIndicator={false}
          refreshControl={
            <RefreshControl
              refreshing={isRefreshing}
              onRefresh={handleRefresh}
              tintColor={colors.primary.main}
            />
          }
        >
          {renderContent()}
        </ScrollView>
      )}
    </SafeAreaView>
  );
};

export default MaterialsScreen;

function createMaterialsStyles(colors: AppColors) {
  const headerBg = colors.background.default;
  return StyleSheet.create({
    container: {
      flex: 1,
      backgroundColor: colors.background.default,
    },
    header: {
      flexDirection: 'row',
      alignItems: 'center',
      justifyContent: 'space-between',
      paddingHorizontal: spacing.md,
      paddingVertical: spacing.md,
      backgroundColor: headerBg,
      ...shadows.sm,
    },
    headerWide: {
      paddingHorizontal: spacing.lg,
      paddingVertical: spacing.lg,
    },
    headerLeft: {
      width: 44,
      alignItems: 'flex-start',
    },
    backButton: {
      padding: spacing.xs,
    },
    headerCenter: {
      flexDirection: 'row',
      alignItems: 'center',
    },
    headerTitle: {
      fontSize: 19,
      fontWeight: '700',
      color: colors.text.primary,
    },
    headerTitleWide: {
      fontSize: 22,
    },
    headerRight: {
      width: 44,
      alignItems: 'flex-end',
    },
    searchButton: {
      padding: spacing.xs,
    },
    scroll: {
      flex: 1,
      backgroundColor: headerBg,
    },
    scrollContent: {
      paddingTop: spacing.md,
      flexGrow: 1,
      backgroundColor: headerBg,
    },
    pageSubtitle: {
      marginBottom: spacing.lg,
      lineHeight: fontSizes.sm * 1.45,
    },
    subjectsGrid: {
      gap: spacing.md,
    },
    subjectCard: {
      flexDirection: 'row',
      alignItems: 'center',
      paddingVertical: spacing.lg,
      paddingHorizontal: spacing.lg,
    },
    subjectIconCircle: {
      width: 56,
      height: 56,
      borderRadius: borderRadius.full,
      alignItems: 'center',
      justifyContent: 'center',
    },
    subjectContent: {
      flex: 1,
      marginLeft: spacing.md,
      marginRight: spacing.sm,
    },
    subjectName: {
      fontWeight: '700',
      fontSize: fontSizes.md + 1,
      color: colors.text.primary,
    },
    subjectDesc: {
      marginTop: 4,
    },
    subjectMeta: {
      flexDirection: 'row',
      alignItems: 'center',
      gap: spacing.xs,
    },
    centerContainer: {
      flex: 1,
      justifyContent: 'center',
      alignItems: 'center',
      paddingVertical: spacing['3xl'],
    },
    errorText: {
      marginTop: spacing.md,
      textAlign: 'center',
    },
    retryButton: {
      marginTop: spacing.md,
      paddingVertical: spacing.sm,
      paddingHorizontal: spacing.lg,
    },
  });
}