import 'package:flutter/material.dart';
import 'package:drag_and_drop_lists/drag_and_drop_lists.dart';
import 'package:go_router/go_router.dart';
import 'package:lucide_icons/lucide_icons.dart';
import '../../../../core/di/injection.dart';
import '../../../../core/router/app_routes.dart';
import '../../../../core/theme/design_tokens.dart';
import '../../../home/ui/navigation/home_return_policy.dart';
import '../../../../shared/widgets/app_pull_refresh_feedback.dart';
import '../../../../shared/widgets/app_pressable.dart';
import '../../../../shared/widgets/back_title_page_header.dart';
import '../../../../shared/widgets/error_retry_surface.dart';
import '../../../../shared/widgets/full_screen_loading.dart';
import '../../../../shared/widgets/toast/toast.dart';
import '../../../../shared/widgets/toast/toast_type.dart';
import '../../../calendar/ui/calendar_state_manager.dart';
import '../../../calendar/ui/widgets/bottom_dock.dart';
import '../../data/todo_api.dart';
import '../../data/todo_repository.dart';

class TodoQuadrantsScreen extends StatefulWidget {
  const TodoQuadrantsScreen({super.key});

  @override
  State<TodoQuadrantsScreen> createState() => _TodoQuadrantsScreenState();
}

class _TodoQuadrantsScreenState extends State<TodoQuadrantsScreen> {
  final TodoApi _todoApi = sl<TodoApi>();
  final TodoRepository _todoRepository = sl<TodoRepository>();

  List<TodoResponse> _todos = [];
  bool _isLoading = true;
  bool _isPullRefreshing = false;
  bool _loadingTodosRequest = false;
  bool _isReordering = false;
  String? _error;

  Future<void> _onItemReorder(
    int oldItemIndex,
    int oldListIndex,
    int newItemIndex,
    int newListIndex,
  ) async {
    if (_isReordering) {
      return;
    }

    final sourceQuadrant = _quadrantByListIndex(oldListIndex);
    final targetQuadrant = _quadrantByListIndex(newListIndex);
    final sourceItems = _sortedQuadrantTodos(sourceQuadrant);
    if (oldItemIndex < 0 || oldItemIndex >= sourceItems.length) {
      return;
    }

    final todoId = sourceItems[oldItemIndex].id;
    final previousTodos = List<TodoResponse>.from(_todos);
    try {
      setState(() {
        _isReordering = true;
      });

      final reordered = _reorderTodos(
        todoId: todoId,
        sourceQuadrant: sourceQuadrant,
        targetQuadrant: targetQuadrant,
        insertIndex: newItemIndex,
      );
      if (reordered == null) {
        return;
      }

      setState(() => _todos = reordered.todos);

      await _todoApi.reorderTodos(
        reordered.changedTodos
            .map(
              (updated) => TodoReorderItemPayload(
                id: updated.id,
                priority: updated.priority,
                order: updated.order,
              ),
            )
            .toList(growable: false),
      );
    } catch (e) {
      if (!mounted) return;
      setState(() {
        _todos = previousTodos;
      });
      Toast.show(context, '移动失败', type: ToastType.error);
    } finally {
      if (mounted) {
        setState(() {
          _isReordering = false;
        });
      }
    }
  }

  int _quadrantByListIndex(int listIndex) {
    switch (listIndex) {
      case 0:
        return 1;
      case 1:
        return 3;
      case 2:
        return 2;
      default:
        return 1;
    }
  }

  _ReorderResult? _reorderTodos({
    required String todoId,
    required int sourceQuadrant,
    required int targetQuadrant,
    required int insertIndex,
  }) {
    final byId = {for (final todo in _todos) todo.id: todo};
    final moving = byId[todoId];
    if (moving == null) {
      return null;
    }

    final sourceList = _sortedQuadrantTodos(sourceQuadrant);
    final targetList = sourceQuadrant == targetQuadrant
        ? sourceList
        : _sortedQuadrantTodos(targetQuadrant);

    final sourceIndex = sourceList.indexWhere((todo) => todo.id == todoId);
    if (sourceIndex == -1) {
      return null;
    }

    final mutableSource = List<TodoResponse>.from(sourceList);
    final extracted = mutableSource.removeAt(sourceIndex);

    int targetIndex = insertIndex;
    if (sourceQuadrant == targetQuadrant && sourceIndex < targetIndex) {
      targetIndex -= 1;
    }

    if (targetIndex < 0) {
      targetIndex = 0;
    }

    final mutableTarget = sourceQuadrant == targetQuadrant
        ? mutableSource
        : List<TodoResponse>.from(targetList);

    if (targetIndex > mutableTarget.length) {
      targetIndex = mutableTarget.length;
    }

    final moved = extracted.copyWith(priority: targetQuadrant);
    mutableTarget.insert(targetIndex, moved);

    final updatedById = <String, TodoResponse>{};
    void reindex(List<TodoResponse> list, int priority) {
      for (var index = 0; index < list.length; index += 1) {
        final current = list[index];
        final updated = current.copyWith(priority: priority, order: index);
        list[index] = updated;
        if (current.priority != updated.priority ||
            current.order != updated.order) {
          updatedById[updated.id] = updated;
        }
      }
    }

    if (sourceQuadrant == targetQuadrant) {
      reindex(mutableTarget, targetQuadrant);
    } else {
      reindex(mutableSource, sourceQuadrant);
      reindex(mutableTarget, targetQuadrant);
    }

    if (updatedById.isEmpty) {
      return null;
    }

    final updatedTodos = _todos
        .map((todo) => updatedById[todo.id] ?? todo)
        .toList(growable: false);

    return _ReorderResult(
      todos: updatedTodos,
      changedTodos: updatedById.values.toList(growable: false),
    );
  }

  @override
  void initState() {
    super.initState();
    _loadTodos();
  }

  Future<void> _loadTodos({bool showPageLoader = true}) async {
    if (_loadingTodosRequest || _isPullRefreshing) {
      return;
    }
    _loadingTodosRequest = true;

    setState(() {
      if (showPageLoader) {
        _isLoading = true;
        _error = null;
      } else {
        _isPullRefreshing = true;
      }
    });

    try {
      final todos = await _todoRepository.getPendingTodos(
        forceRefresh: !showPageLoader,
      );
      if (!mounted) {
        return;
      }
      setState(() {
        _todos = todos;
        _isLoading = false;
        _isPullRefreshing = false;
        _error = null;
      });
    } catch (e) {
      if (!mounted) {
        return;
      }
      if (showPageLoader) {
        setState(() {
          _error = e.toString();
          _isLoading = false;
          _isPullRefreshing = false;
        });
      } else {
        setState(() => _isPullRefreshing = false);
        Toast.show(context, '刷新失败，请稍后重试', type: ToastType.error);
      }
    } finally {
      _loadingTodosRequest = false;
    }
  }

  Future<void> _onPullRefresh() async {
    await _loadTodos(showPageLoader: false);
  }

  List<TodoResponse> get _importantUrgent => _sortedQuadrantTodos(1);

  List<TodoResponse> get _urgentNotImportant => _sortedQuadrantTodos(3);

  List<TodoResponse> get _importantNotUrgent => _sortedQuadrantTodos(2);

  List<TodoResponse> _sortedQuadrantTodos(int quadrantValue) {
    final list = _todos.where((t) => t.priority == quadrantValue).toList();
    list.sort((a, b) {
      final byOrder = a.order.compareTo(b.order);
      if (byOrder != 0) {
        return byOrder;
      }
      return a.createdAt.compareTo(b.createdAt);
    });
    return list;
  }

  Future<void> _completeTodo(TodoResponse todo) async {
    try {
      await _todoRepository.completeTodo(todo.id);
      if (mounted) {
        Toast.show(context, '已完成', type: ToastType.success);
      }
      try {
        await _loadTodos();
      } catch (_) {
        // ignore reload error
      }
    } catch (e) {
      if (mounted) {
        Toast.show(context, '完成失败: $e', type: ToastType.error);
      }
    }
  }

  void _navigateToDetail(TodoResponse todo) {
    context.push(AppRoutes.todoDetail(todo.id));
  }

  Future<void> _addTodo() async {
    final created = await context.push<bool>(AppRoutes.todoCreate);
    if (created == true) {
      await _loadTodos();
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: AppColors.todoBg,
      body: PopScope(
        canPop: false,
        onPopInvokedWithResult: (didPop, result) {
          if (!didPop) {
            returnToHomePreserveState(context, forceGoHome: true);
          }
        },
        child: SafeArea(
          child: Column(
            children: [
              _buildHeader(),
              Expanded(child: _buildContent(withScroll: true)),
              _buildBottomDock(),
            ],
          ),
        ),
      ),
    );
  }

  Widget _buildHeader() {
    return BackTitlePageHeader(
      title: '待办事项',
      showBackButton: false,
      trailing: Row(
        mainAxisSize: MainAxisSize.min,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          AppPressable(
            borderRadius: BorderRadius.circular(AppRadius.full),
            onTap: _loadTodos,
            child: Container(
              width: 36,
              height: 36,
              decoration: BoxDecoration(
                color: AppColors.messageBtnWrap,
                borderRadius: BorderRadius.circular(AppRadius.full),
                border: Border.all(color: AppColors.messageBtnBorder),
              ),
              child: const Icon(
                LucideIcons.refreshCcw,
                size: 18,
                color: AppColors.slate600,
              ),
            ),
          ),
          const SizedBox(width: AppSpacing.sm),
          AppPressable(
            borderRadius: BorderRadius.circular(AppRadius.full),
            onTap: _addTodo,
            child: Container(
              width: 36,
              height: 36,
              decoration: BoxDecoration(
                color: AppColors.blue600,
                borderRadius: BorderRadius.circular(AppRadius.full),
                boxShadow: [
                  BoxShadow(
                    color: AppColors.blue300.withValues(alpha: 0.28),
                    blurRadius: AppRadius.lg,
                    offset: const Offset(0, AppSpacing.xs),
                  ),
                ],
              ),
              child: const Icon(
                LucideIcons.plus,
                size: 18,
                color: AppColors.white,
              ),
            ),
          ),
        ],
      ),
    );
  }

  Widget _buildContent({bool withScroll = false}) {
    if (_isLoading) {
      return const FullScreenLoading();
    }

    if (_error != null) {
      return ErrorRetrySurface(message: '加载失败: $_error', onRetry: _loadTodos);
    }

    final content = _buildDragBoard();

    if (withScroll) {
      return Stack(
        children: [
          RefreshIndicator.noSpinner(onRefresh: _onPullRefresh, child: content),
          Align(
            alignment: Alignment.topCenter,
            child: AppPullRefreshFeedback(visible: _isPullRefreshing),
          ),
        ],
      );
    }

    return content;
  }

  Widget _buildDragBoard() {
    final quadrants = [
      _QuadrantMeta(
        value: 1,
        title: '重要紧急',
        textColor: AppColors.g1Text,
        dividerColor: AppColors.g1Divider,
        borderColor: AppColors.g1Border,
        items: _importantUrgent,
      ),
      _QuadrantMeta(
        value: 3,
        title: '紧急不重要',
        textColor: AppColors.g2Text,
        dividerColor: AppColors.g2Divider,
        borderColor: AppColors.g2Border,
        items: _urgentNotImportant,
      ),
      _QuadrantMeta(
        value: 2,
        title: '重要不紧急',
        textColor: AppColors.g3Text,
        dividerColor: AppColors.g3Divider,
        borderColor: AppColors.g3Border,
        items: _importantNotUrgent,
      ),
    ];

    final lists = quadrants
        .map(
          (meta) => DragAndDropList(
            canDrag: false,
            header: _buildQuadrantHeader(meta),
            contentsWhenEmpty: _buildEmptyQuadrant(),
            lastTarget: const SizedBox(height: AppSpacing.lg),
            decoration: BoxDecoration(
              color: AppColors.todoCardBg,
              borderRadius: BorderRadius.circular(14),
              border: Border.all(color: meta.borderColor),
            ),
            children: meta.items
                .map(
                  (item) => DragAndDropItem(
                    child: Padding(
                      padding: const EdgeInsets.symmetric(
                        horizontal: AppSpacing.sm,
                      ),
                      child: _TodoItemWidget(
                        item: item,
                        onComplete: () => _completeTodo(item),
                        onTap: () => _navigateToDetail(item),
                      ),
                    ),
                  ),
                )
                .toList(growable: false),
          ),
        )
        .toList(growable: false);

    return SingleChildScrollView(
      padding: const EdgeInsets.fromLTRB(
        AppSpacing.lg,
        AppSpacing.xs,
        AppSpacing.lg,
        96,
      ),
      child: DragAndDropLists(
        children: lists,
        onItemReorder: _onItemReorder,
        onListReorder: (oldListIndex, newListIndex) {},
        listDivider: const SizedBox(height: AppSpacing.md),
        itemDivider: Padding(
          padding: const EdgeInsets.symmetric(horizontal: AppSpacing.md),
          child: Container(height: 1, color: AppColors.slate100),
        ),
        listPadding: EdgeInsets.zero,
        itemDecorationWhileDragging: BoxDecoration(
          color: AppColors.todoCardBg,
          borderRadius: BorderRadius.circular(AppRadius.md),
          border: Border.all(color: AppColors.borderSecondary),
          boxShadow: [
            BoxShadow(
              color: AppColors.slate200.withValues(alpha: 0.6),
              blurRadius: AppRadius.md,
              offset: const Offset(0, AppSpacing.xs),
            ),
          ],
        ),
        itemGhost: const SizedBox(height: 42),
        itemDragOnLongPress: true,
        lastItemTargetHeight: AppSpacing.xl,
        disableScrolling: true,
      ),
    );
  }

  Widget _buildQuadrantHeader(_QuadrantMeta meta) {
    return Column(
      mainAxisSize: MainAxisSize.min,
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        Padding(
          padding: const EdgeInsets.fromLTRB(10, 10, 10, 8),
          child: Row(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            crossAxisAlignment: CrossAxisAlignment.center,
            children: [
              Text(
                meta.title,
                style: TextStyle(
                  fontFamily: 'Inter',
                  fontSize: 15,
                  fontWeight: FontWeight.w700,
                  color: meta.textColor,
                ),
              ),
              Text(
                '${meta.items.length}项',
                style: TextStyle(
                  fontFamily: 'Inter',
                  fontSize: 12,
                  fontWeight: FontWeight.w700,
                  color: meta.textColor,
                ),
              ),
            ],
          ),
        ),
        Container(height: 1, color: meta.dividerColor),
        const SizedBox(height: AppSpacing.sm),
      ],
    );
  }

  Widget _buildEmptyQuadrant() {
    return SizedBox(
      height: 60,
      child: Center(
        child: Text(
          '暂无待办',
          style: TextStyle(
            fontFamily: 'Inter',
            fontSize: 13,
            color: AppColors.slate400,
          ),
        ),
      ),
    );
  }

  Widget _buildBottomDock() {
    return BottomDock(
      activeTab: DockTab.todo,
      onTodoTap: () {},
      onCalendarTap: () {
        final manager = sl<CalendarStateManager>();
        final viewType = manager.viewType;
        final date = manager.selectedDate;
        final dateStr =
            '${date.year}-${date.month.toString().padLeft(2, '0')}-${date.day.toString().padLeft(2, '0')}';
        if (viewType == CalendarViewType.month) {
          context.push(AppRoutes.calendarMonth);
        } else {
          context.push('${AppRoutes.calendarDayWeek}?date=$dateStr');
        }
      },
      onHomeTap: () => returnToHomePreserveState(context, forceGoHome: true),
    );
  }
}

class _ReorderResult {
  final List<TodoResponse> todos;
  final List<TodoResponse> changedTodos;

  const _ReorderResult({required this.todos, required this.changedTodos});
}

class _QuadrantMeta {
  final int value;
  final String title;
  final Color textColor;
  final Color dividerColor;
  final Color borderColor;
  final List<TodoResponse> items;

  const _QuadrantMeta({
    required this.value,
    required this.title,
    required this.textColor,
    required this.dividerColor,
    required this.borderColor,
    required this.items,
  });
}

class _TodoItemWidget extends StatefulWidget {
  final TodoResponse item;
  final VoidCallback onComplete;
  final VoidCallback onTap;

  const _TodoItemWidget({
    required this.item,
    required this.onComplete,
    required this.onTap,
  });

  @override
  State<_TodoItemWidget> createState() => _TodoItemWidgetState();
}

class _TodoItemWidgetState extends State<_TodoItemWidget>
    with SingleTickerProviderStateMixin {
  bool _isChecked = false;
  late AnimationController _controller;
  late Animation<double> _scaleAnimation;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      duration: const Duration(milliseconds: 200),
      vsync: this,
    );
    _scaleAnimation = Tween<double>(
      begin: 0.0,
      end: 1.0,
    ).animate(CurvedAnimation(parent: _controller, curve: Curves.easeOutBack));
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  void _handleCheckTap() async {
    if (_isChecked) return;

    setState(() {
      _isChecked = true;
    });
    _controller.forward().then((_) {
      widget.onComplete();
    });
  }

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: widget.onTap,
      child: SizedBox(
        height: 42,
        child: Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          crossAxisAlignment: CrossAxisAlignment.center,
          children: [
            Expanded(
              child: Text(
                widget.item.title,
                style: const TextStyle(
                  fontFamily: 'Inter',
                  fontSize: 13,
                  fontWeight: FontWeight.w600,
                  color: AppColors.slate700,
                ),
              ),
            ),
            GestureDetector(
              onTap: _handleCheckTap,
              child: AnimatedBuilder(
                animation: _controller,
                builder: (context, child) {
                  return Container(
                    width: 20,
                    height: 20,
                    decoration: BoxDecoration(
                      color: _isChecked ? AppColors.blue600 : Colors.white,
                      border: Border.all(
                        color: _isChecked
                            ? AppColors.blue600
                            : AppColors.slate300,
                        width: 1.5,
                      ),
                      borderRadius: BorderRadius.circular(4),
                    ),
                    child: _isChecked
                        ? Transform.scale(
                            scale: _scaleAnimation.value,
                            child: const Icon(
                              Icons.check,
                              size: 14,
                              color: Colors.white,
                            ),
                          )
                        : null,
                  );
                },
              ),
            ),
          ],
        ),
      ),
    );
  }
}