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

import '../../core/exceptions.dart';
import '../../data/models/task.dart';
import '../../providers/api_client_provider.dart';
import '../../providers/tasks_provider.dart';
import '../../widgets/project_selector.dart';

class TaskEditScreen extends ConsumerStatefulWidget {
  final int? taskId;
  const TaskEditScreen({super.key, this.taskId});

  @override
  ConsumerState<TaskEditScreen> createState() => _TaskEditScreenState();
}

class _TaskEditScreenState extends ConsumerState<TaskEditScreen> {
  final _formKey = GlobalKey<FormState>();
  final _titleController = TextEditingController();
  final _descController = TextEditingController();
  TaskStatus _status = TaskStatus.todo;
  TaskPriority _priority = TaskPriority.medium;
  DateTime? _dueDate;
  int? _projectId;
  bool _saving = false;

  // Future is created once in initState so FutureBuilder never restarts it.
  late final Future<void> _initFuture;

  @override
  void initState() {
    super.initState();
    _initFuture =
        widget.taskId != null ? _loadExisting() : Future.value();
  }

  @override
  void dispose() {
    _titleController.dispose();
    _descController.dispose();
    super.dispose();
  }

  Future<void> _loadExisting() async {
    final task =
        await ref.read(tasksRepositoryProvider).getOne(widget.taskId!);
    _titleController.text = task.title;
    _descController.text = task.description ?? '';
    _status = task.status;
    _priority = task.priority;
    _dueDate = task.dueDate;
    _projectId = task.projectId;
  }

  Future<void> _save() async {
    if (!_formKey.currentState!.validate()) return;
    setState(() => _saving = true);
    try {
      if (widget.taskId == null) {
        await ref.read(tasksProvider.notifier).create(
              title: _titleController.text.trim(),
              description: _descController.text.trim().isEmpty
                  ? null
                  : _descController.text.trim(),
              status: _status,
              priority: _priority,
              dueDate: _dueDate,
              projectId: _projectId,
            );
      } else {
        await ref.read(tasksProvider.notifier).updateTask(widget.taskId!, {
          'title': _titleController.text.trim(),
          'body': _descController.text.trim().isEmpty
              ? null
              : _descController.text.trim(),
          'status': _status.value,
          'priority': _priority.value,
          'due_date': _dueDate?.toIso8601String(),
          'project_id': _projectId,
        });
      }
      if (mounted) context.pop();
    } on AppException catch (e) {
      if (mounted) {
        ScaffoldMessenger.of(context)
            .showSnackBar(SnackBar(content: Text(e.message)));
      }
    } finally {
      if (mounted) setState(() => _saving = false);
    }
  }

  Future<void> _delete() async {
    final confirm = await showDialog<bool>(
      context: context,
      builder: (dialogContext) => AlertDialog(
        title: const Text('Delete task?'),
        content: Text(_titleController.text),
        actions: [
          TextButton(
              onPressed: () => Navigator.pop(dialogContext, false),
              child: const Text('Cancel')),
          TextButton(
              onPressed: () => Navigator.pop(dialogContext, true),
              child: const Text('Delete')),
        ],
      ),
    );
    if (confirm == true) {
      await ref.read(tasksProvider.notifier).delete(widget.taskId!);
      if (mounted) context.pop();
    }
  }

  Future<void> _pickDate() async {
    final date = await showDatePicker(
      context: context,
      initialDate: _dueDate ?? DateTime.now(),
      firstDate: DateTime(2020),
      lastDate: DateTime(2100),
    );
    if (date != null) setState(() => _dueDate = date);
  }

  @override
  Widget build(BuildContext context) {
    return FutureBuilder(
      future: _initFuture,
      builder: (context, snapshot) {
        return Scaffold(
          appBar: AppBar(
            title: Text(widget.taskId == null ? 'New Task' : 'Edit Task'),
            actions: [
              if (widget.taskId != null)
                IconButton(
                  icon: const Icon(Icons.delete),
                  onPressed: _delete,
                ),
              IconButton(
                icon: _saving
                    ? const SizedBox(
                        width: 20,
                        height: 20,
                        child: CircularProgressIndicator(strokeWidth: 2),
                      )
                    : const Icon(Icons.check),
                onPressed: _saving ? null : _save,
              ),
            ],
          ),
          body: snapshot.connectionState == ConnectionState.waiting
              ? const Center(child: CircularProgressIndicator())
              : Align(
                  alignment: Alignment.topCenter,
                  child: ConstrainedBox(
                    constraints: const BoxConstraints(maxWidth: 600),
                    child: Form(
                      key: _formKey,
                      child: ListView(
                        padding: const EdgeInsets.all(16),
                    children: [
                      TextFormField(
                        controller: _titleController,
                        decoration: const InputDecoration(
                          labelText: 'Title',
                          border: OutlineInputBorder(),
                        ),
                        validator: (v) =>
                            (v == null || v.trim().isEmpty) ? 'Required' : null,
                      ),
                      const SizedBox(height: 16),
                      TextFormField(
                        controller: _descController,
                        decoration: const InputDecoration(
                          labelText: 'Description (optional)',
                          border: OutlineInputBorder(),
                        ),
                        maxLines: 3,
                      ),
                      const SizedBox(height: 16),
                      DropdownButtonFormField<TaskStatus>(
                        initialValue: _status,
                        decoration: const InputDecoration(
                          labelText: 'Status',
                          border: OutlineInputBorder(),
                        ),
                        items: TaskStatus.values
                            .map((s) => DropdownMenuItem(
                                value: s, child: Text(s.label)))
                            .toList(),
                        onChanged: (v) => setState(() => _status = v!),
                      ),
                      const SizedBox(height: 16),
                      DropdownButtonFormField<TaskPriority>(
                        initialValue: _priority,
                        decoration: const InputDecoration(
                          labelText: 'Priority',
                          border: OutlineInputBorder(),
                        ),
                        items: TaskPriority.values
                            .map((p) => DropdownMenuItem(
                                value: p, child: Text(p.label)))
                            .toList(),
                        onChanged: (v) => setState(() => _priority = v!),
                      ),
                      const SizedBox(height: 16),
                      ListTile(
                        contentPadding: EdgeInsets.zero,
                        title: Text(_dueDate == null
                            ? 'No due date'
                            : 'Due: ${_dueDate!.toLocal().toString().substring(0, 10)}'),
                        leading: const Icon(Icons.calendar_today),
                        trailing: _dueDate != null
                            ? IconButton(
                                icon: const Icon(Icons.clear),
                                onPressed: () =>
                                    setState(() => _dueDate = null),
                              )
                            : null,
                        onTap: _pickDate,
                      ),
                      const SizedBox(height: 16),
                      ProjectSelector(
                        value: _projectId,
                        onChanged: (id) => setState(() => _projectId = id),
                      ),
                    ],
                  ),
                ),
                  ),
                ),
        );
      },
    );
  }
}