import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';

import '../../core/constants.dart';
import '../../data/models/task.dart';
import '../../providers/tasks_provider.dart';

class TasksListScreen extends ConsumerStatefulWidget {
  const TasksListScreen({super.key});

  @override
  ConsumerState<TasksListScreen> createState() => _TasksListScreenState();
}

class _TasksListScreenState extends ConsumerState<TasksListScreen>
    with SingleTickerProviderStateMixin {
  late final TabController _tabs;
  bool _showSearch = false;
  String _search = '';

  @override
  void initState() {
    super.initState();
    _tabs = TabController(length: 3, vsync: this);
  }

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

  @override
  Widget build(BuildContext context) {
    final tasksAsync = ref.watch(tasksProvider);

    return Scaffold(
      body: Column(
        children: [
          // Search field — appears above the tabs when active
          if (_showSearch)
            Padding(
              padding: const EdgeInsets.symmetric(horizontal: 4),
              child: Row(
                children: [
                  Expanded(
                    child: TextField(
                      autofocus: true,
                      decoration: const InputDecoration(
                        hintText: 'Search tasks…',
                        border: InputBorder.none,
                        prefixIcon: Icon(Icons.search),
                      ),
                      onChanged: (v) =>
                          setState(() => _search = v.trim().toLowerCase()),
                    ),
                  ),
                  IconButton(
                    icon: const Icon(Icons.close),
                    tooltip: 'Close search',
                    onPressed: () => setState(() {
                      _showSearch = false;
                      _search = '';
                    }),
                  ),
                ],
              ),
            ),
          // Tab bar row — search icon sits to the right of the tabs
          Row(
            children: [
              Expanded(
                child: TabBar(
                  controller: _tabs,
                  tabs: const [
                    Tab(text: 'To Do'),
                    Tab(text: 'In Progress'),
                    Tab(text: 'Done'),
                  ],
                ),
              ),
              if (!_showSearch)
                IconButton(
                  icon: const Icon(Icons.search),
                  tooltip: 'Search',
                  onPressed: () => setState(() => _showSearch = true),
                ),
            ],
          ),
          // Content
          Expanded(
            child: tasksAsync.when(
              loading: () => const Center(child: CircularProgressIndicator()),
              error: (_, _) => Center(
                child: Column(
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    const Icon(Icons.cloud_off, size: 48),
                    const SizedBox(height: 12),
                    const Text('Could not load tasks.'),
                    const SizedBox(height: 4),
                    TextButton(
                      onPressed: () => ref.invalidate(tasksProvider),
                      child: const Text('Retry'),
                    ),
                  ],
                ),
              ),
              data: (tasks) {
                final filtered = _search.isEmpty
                    ? tasks
                    : tasks
                        .where((t) =>
                            t.title.toLowerCase().contains(_search) ||
                            (t.description ?? '')
                                .toLowerCase()
                                .contains(_search))
                        .toList();

                final todo = filtered
                    .where((t) => t.status == TaskStatus.todo)
                    .toList();
                final inProgress = filtered
                    .where((t) => t.status == TaskStatus.inProgress)
                    .toList();
                final done = filtered
                    .where((t) => t.status == TaskStatus.done)
                    .toList();

                return RefreshIndicator(
                  onRefresh: () => ref.refresh(tasksProvider.future),
                  child: TabBarView(
                    controller: _tabs,
                    children: [
                      _TaskList(tasks: todo, search: _search),
                      _TaskList(tasks: inProgress, search: _search),
                      _TaskList(tasks: done, search: _search),
                    ],
                  ),
                );
              },
            ),
          ),
        ],
      ),
      floatingActionButton: FloatingActionButton(
        heroTag: 'tasks_fab',
        onPressed: () => context.push(Routes.taskNew),
        child: const Icon(Icons.add),
      ),
    );
  }
}

class _TaskList extends ConsumerWidget {
  final List<Task> tasks;
  final String search;
  const _TaskList({required this.tasks, this.search = ''});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    if (tasks.isEmpty) {
      return Center(
        child: Text(
          search.isEmpty ? 'No tasks here.' : 'No tasks match "$search".',
        ),
      );
    }
    return ListView.separated(
      itemCount: tasks.length,
      separatorBuilder: (_, _) => const Divider(height: 1),
      itemBuilder: (context, i) {
        final task = tasks[i];
        return ListTile(
          leading: _priorityIcon(task.priority),
          title: Text(task.title),
          subtitle: task.dueDate != null
              ? Text(
                  'Due: ${task.dueDate!.toLocal().toString().substring(0, 10)}')
              : null,
          onTap: () => context.push(
            Routes.taskEdit.replaceFirst(':id', '${task.id}'),
          ),
        );
      },
    );
  }

  Widget _priorityIcon(TaskPriority p) {
    final color = switch (p) {
      TaskPriority.high => Colors.red,
      TaskPriority.medium => Colors.orange,
      TaskPriority.low => Colors.green,
      TaskPriority.none => Colors.grey,
    };
    return Icon(Icons.flag, color: color);
  }
}