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;

  @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(
      appBar: AppBar(
        title: const Text('Tasks'),
        bottom: TabBar(
          controller: _tabs,
          tabs: const [
            Tab(text: 'To Do'),
            Tab(text: 'In Progress'),
            Tab(text: 'Done'),
          ],
        ),
      ),
      body: tasksAsync.when(
        loading: () => const Center(child: CircularProgressIndicator()),
        error: (e, _) => Center(
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              Text('Error: $e'),
              TextButton(
                onPressed: () => ref.invalidate(tasksProvider),
                child: const Text('Retry'),
              ),
            ],
          ),
        ),
        data: (tasks) {
          final todo =
              tasks.where((t) => t.status == TaskStatus.todo).toList();
          final inProgress =
              tasks.where((t) => t.status == TaskStatus.inProgress).toList();
          final done =
              tasks.where((t) => t.status == TaskStatus.done).toList();

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

class _TaskList extends ConsumerWidget {
  final List<Task> tasks;
  const _TaskList({required this.tasks});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    if (tasks.isEmpty) {
      return const Center(child: Text('No tasks here.'));
    }
    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);
  }
}