import 'package:flutter/material.dart';

import '../../core/api/services/image_api.dart';
import '../../core/auth/auth_service.dart';
import '../../core/user/account_refresh.dart';
import '../../core/user/user_state.dart';
import '../../core/theme/app_spacing.dart';
import '../../shared/widgets/top_nav_bar.dart';
import 'models/category_item.dart';
import 'models/ext_config_item.dart';
import 'models/task_item.dart';
import 'widgets/home_tab_row.dart';
import 'widgets/video_card.dart';

/// 固定「pets」分类 id，用于展示 extConfig.items
const int kExtCategoryId = -1;

/// AI Video App home screen - tab 来自分类接口，Grid 来自任务列表或 extConfig.items
class HomeScreen extends StatefulWidget {
  const HomeScreen({super.key, this.isActive = true});

  final bool isActive;

  @override
  State<HomeScreen> createState() => _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> {
  List<CategoryItem> _categories = [];
  CategoryItem? _selectedCategory;
  List<TaskItem> _tasks = [];
  bool _categoriesLoading = true;
  bool _tasksLoading = false;
  int? _activeCardIndex;

  @override
  void initState() {
    super.initState();
    UserState.needShowVideoMenu.addListener(_onExtConfigChanged);
    UserState.extConfigItems.addListener(_onExtConfigChanged);
    AuthService.isLoginComplete.addListener(_onExtConfigChanged);
    UserState.homeReloadNonce.addListener(_onHomeReloadNonce);
    _loadCategories();
    if (widget.isActive) refreshAccount();
  }

  @override
  void dispose() {
    UserState.needShowVideoMenu.removeListener(_onExtConfigChanged);
    UserState.extConfigItems.removeListener(_onExtConfigChanged);
    AuthService.isLoginComplete.removeListener(_onExtConfigChanged);
    UserState.homeReloadNonce.removeListener(_onHomeReloadNonce);
    super.dispose();
  }

  void _onExtConfigChanged() {
    if (mounted) setState(() {});
  }

  void _onHomeReloadNonce() {
    if (!mounted) return;
    _loadCategories();
  }

  @override
  void didUpdateWidget(covariant HomeScreen oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (widget.isActive && !oldWidget.isActive) {
      refreshAccount();
    }
  }

  /// 仅 need_wait === true 时展示 Video 分类栏；其他（false/null/未解析）只显示图片列表
  bool get _showVideoMenu =>
      UserState.needShowVideoMenu.value == true;

  List<ExtConfigItem> get _parsedExtItems {
    final raw = UserState.extConfigItems.value;
    if (raw == null || raw.isEmpty) return [];
    return raw
        .map((e) => e is Map<String, dynamic>
            ? ExtConfigItem.fromJson(e)
            : ExtConfigItem.fromJson(Map<String, dynamic>.from(e as Map)))
        .toList();
  }

  /// 是否处于首次加载中（分类/任务/extConfig 尚未就绪）
  /// 登录未完成时不显示页面加载指示器，由登录遮罩负责
  bool get _isListLoading {
    if (!AuthService.isLoginComplete.value) return false;
    if (_showVideoMenu) {
      if (_categoriesLoading) return true;
      if (_selectedCategory?.id == kExtCategoryId) {
        return UserState.extConfigItems.value == null;
      }
      return _tasksLoading;
    }
    return UserState.extConfigItems.value == null;
  }

  /// 分类栏加载中时是否显示加载指示器（登录未完成时不显示）
  bool get _showCategoriesLoading =>
      AuthService.isLoginComplete.value && _categoriesLoading;

  /// 当前列表：need_wait false 时用 extConfig.items；true 且选中固定分类时用 extConfig.items；否则用 _tasks
  List<TaskItem> get _displayTasks {
    if (!_showVideoMenu) {
      return _extItemsToTaskItems(_parsedExtItems);
    }
    if (_selectedCategory?.id == kExtCategoryId) {
      return _extItemsToTaskItems(_parsedExtItems);
    }
    return _tasks;
  }

  static List<TaskItem> _extItemsToTaskItems(List<ExtConfigItem> items) {
    return items
        .map((e) => TaskItem(
              templateName: e.title,
              title: e.title,
              previewImageUrl: e.image,
              previewVideoUrl: null,
              taskType: e.title,
              ext: e.detail,
              credits480p: e.cost,
            ))
        .toList();
  }

  Future<void> _loadCategories() async {
    setState(() => _categoriesLoading = true);
    await AuthService.loginComplete;
    if (!mounted) return;
    final res = await ImageApi.getCategoryList();
    if (mounted) {
      if (res.isSuccess && res.data is List) {
        final list = (res.data as List)
            .map((e) => CategoryItem.fromJson(e as Map<String, dynamic>))
            .toList();
        if (UserState.needShowVideoMenu.value == true) {
          list.add(const CategoryItem(id: kExtCategoryId, name: 'pets', icon: null));
        }
        setState(() {
          _categories = list;
          _selectedCategory = list.isNotEmpty ? list.first : null;
          if (_selectedCategory != null) {
            if (_selectedCategory!.id == kExtCategoryId) {
              _tasks = [];
              _tasksLoading = false;
            } else {
              _loadTasks(_selectedCategory!.id);
            }
          }
        });
      } else {
        setState(() => _categories = []);
      }
      setState(() => _categoriesLoading = false);
    }
  }

  Future<void> _loadTasks(int categoryId) async {
    setState(() => _tasksLoading = true);
    final res = await ImageApi.getImg2VideoTasks(insignia: categoryId);
    if (mounted) {
      if (res.isSuccess && res.data is List) {
        final list = (res.data as List)
            .map((e) => TaskItem.fromJson(e as Map<String, dynamic>))
            .toList();
        setState(() {
          _tasks = list;
          _activeCardIndex = null;
        });
      } else {
        setState(() => _tasks = []);
      }
      setState(() => _tasksLoading = false);
    }
  }

  void _onTabChanged(CategoryItem c) {
    setState(() => _selectedCategory = c);
    if (c.id == kExtCategoryId) {
      setState(() {
        _tasks = [];
        _tasksLoading = false;
      });
    } else {
      _loadTasks(c.id);
    }
  }

  static const _placeholderImage =
      'https://images.unsplash.com/photo-1763929272543-0df093e4f659?w=400';

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: const Color(0xFFFAFAFA),
      appBar: PreferredSize(
        preferredSize: const Size.fromHeight(56),
        child: TopNavBar(
          title: 'PetsHero AI',
          credits: UserCreditsData.of(context)?.creditsDisplay ?? '--',
          onCreditsTap: () => Navigator.of(context).pushNamed('/recharge'),
        ),
      ),
      body: Column(
        children: [
          // 仅 need_wait == true 时展示顶部分类栏（Pencil: tabRow bK6o6）
          if (_showVideoMenu)
            Padding(
              padding: const EdgeInsets.symmetric(
                horizontal: AppSpacing.screenPadding,
                vertical: AppSpacing.xs,
              ),
              child: _showCategoriesLoading
                  ? const SizedBox(
                      height: 40,
                      child: Center(child: CircularProgressIndicator()))
                  : HomeTabRow(
                      categories: _categories,
                      selectedId: _selectedCategory?.id ?? -1,
                      onTabChanged: _onTabChanged,
                    ),
            ),
          Expanded(
            child: _isListLoading
                ? const Center(child: CircularProgressIndicator())
                : LayoutBuilder(
                    builder: (context, constraints) {
                      final tasks = _displayTasks;
                      return Center(
                        child: ConstrainedBox(
                          constraints: const BoxConstraints(maxWidth: 390),
                          child: GridView.builder(
                            padding: const EdgeInsets.fromLTRB(
                              AppSpacing.screenPadding,
                              AppSpacing.xl,
                              AppSpacing.screenPadding,
                              AppSpacing.screenPaddingLarge,
                            ),
                            gridDelegate:
                                const SliverGridDelegateWithFixedCrossAxisCount(
                              crossAxisCount: 2,
                              childAspectRatio: 165 / 248,
                              mainAxisSpacing: AppSpacing.xl,
                              crossAxisSpacing: AppSpacing.xl,
                            ),
                            itemCount: tasks.length,
                            itemBuilder: (context, index) {
                              final task = tasks[index];
                              final credits = task.credits480p != null
                                  ? task.credits480p.toString()
                                  : '50';
                              return VideoCard(
                                imageUrl:
                                    task.previewImageUrl ?? _placeholderImage,
                                videoUrl: task.previewVideoUrl,
                                credits: credits,
                                isActive: _activeCardIndex == index,
                                onPlayRequested: () =>
                                    setState(() => _activeCardIndex = index),
                                onStopRequested: () =>
                                    setState(() => _activeCardIndex = null),
                                onGenerateSimilar: () =>
                                    Navigator.of(context).pushNamed(
                                  '/generate',
                                  arguments: task,
                                ),
                              );
                            },
                          ),
                        ),
                      );
                    },
                  ),
          ),
        ],
      ),
    );
  }
}