import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';
import 'package:intl/intl.dart';
import '../../core/theme/app_theme.dart';
import '../../core/widgets/loading_button.dart';
import '../../core/api/api_client.dart';
import '../../shared/providers/lookup_providers.dart';
import 'tasks_provider.dart';

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

  @override
  ConsumerState<TaskFormScreen> createState() => _TaskFormScreenState();
}

class _TaskFormScreenState extends ConsumerState<TaskFormScreen> {
  final _formKey = GlobalKey<FormState>();
  final _titleCtrl = TextEditingController();
  DateTime? _dueDate;
  int? _assignedTo;
  String _status = 'todo';
  bool _loading = false;
  bool _initDone = false;

  bool get isEdit => widget.editId != null;

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

  Future<void> _initEdit() async {
    if (!isEdit || _initDone) return;
    _initDone = true;
    try {
      final resp = await apiDio.get('/tasks/${widget.editId}');
      final data = resp.data as Map<String, dynamic>;
      setState(() {
        _titleCtrl.text = data['title'] ?? '';
        _status = data['status'] ?? 'todo';
        _assignedTo = data['assigned_to'];
        if (data['due_date'] != null) _dueDate = DateTime.tryParse(data['due_date']);
      });
    } catch (_) {}
  }

  Future<void> _submit() async {
    if (!_formKey.currentState!.validate()) return;
    setState(() => _loading = true);
    try {
      final data = <String, dynamic>{
        'title': _titleCtrl.text.trim(),
        'status': _status,
        if (_assignedTo != null) 'assigned_to': _assignedTo,
        if (_dueDate != null) 'due_date': DateFormat('yyyy-MM-dd').format(_dueDate!),
      };
      if (isEdit) {
        await updateTask(widget.editId!, data);
      } else {
        await createTask(data);
      }
      if (mounted) context.pop();
    } on ApiException catch (e) {
      if (mounted) ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(content: Text(e.message), backgroundColor: AppColors.danger));
    } finally {
      if (mounted) setState(() => _loading = false);
    }
  }

  Future<void> _pickDate() async {
    final picked = await showDatePicker(
      context: context,
      initialDate: _dueDate ?? DateTime.now(),
      firstDate: DateTime.now().subtract(const Duration(days: 1)),
      lastDate: DateTime.now().add(const Duration(days: 365 * 3)),
    );
    if (picked != null) setState(() => _dueDate = picked);
  }

  @override
  Widget build(BuildContext context) {
    if (isEdit) _initEdit();
    final usersAsync = ref.watch(usersProvider);

    return Scaffold(
      appBar: AppBar(title: Text(isEdit ? 'Edit Task' : 'Create Task')),
      body: Form(
        key: _formKey,
        child: ListView(
          padding: const EdgeInsets.all(16),
          children: [
            _label('Task Title'),
            TextFormField(
              controller: _titleCtrl,
              decoration: const InputDecoration(hintText: 'Enter task title'),
              validator: (v) => (v == null || v.isEmpty) ? 'Title is required' : null,
            ),
            const SizedBox(height: 16),

            _label('Status'),
            Row(
              children: [
                for (final s in ['todo', 'in_progress', 'done'])
                  Expanded(child: Padding(
                    padding: const EdgeInsets.only(right: 6),
                    child: ChoiceChip(
                      label: Text(s == 'in_progress' ? 'Progress' : s.capitalize(),
                          style: TextStyle(fontSize: 12, fontWeight: FontWeight.w600,
                              color: _status == s ? Colors.white : AppColors.textSub)),
                      selected: _status == s,
                      selectedColor: AppColors.primary,
                      onSelected: (_) => setState(() => _status = s),
                    ),
                  )),
              ],
            ),
            const SizedBox(height: 16),

            _label('Assignee (optional)'),
            usersAsync.when(
              loading: () => const LinearProgressIndicator(),
              error: (_, __) => const Text('Failed to load users'),
              data: (users) => DropdownButtonFormField<int>(
                value: _assignedTo,
                decoration: const InputDecoration(hintText: 'Select user'),
                items: [
                  const DropdownMenuItem(value: null, child: Text('Unassigned')),
                  ...users.map((u) => DropdownMenuItem(value: u.id, child: Text(u.username))),
                ],
                onChanged: (v) => setState(() => _assignedTo = v),
              ),
            ),
            const SizedBox(height: 16),

            _label('Deadline (optional)'),
            GestureDetector(
              onTap: _pickDate,
              child: Container(
                padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 14),
                decoration: BoxDecoration(
                  color: AppColors.surface,
                  border: Border.all(color: AppColors.border),
                  borderRadius: BorderRadius.circular(10),
                ),
                child: Row(children: [
                  const Icon(Icons.calendar_today_outlined, size: 16, color: AppColors.textSub),
                  const SizedBox(width: 10),
                  Text(
                    _dueDate != null ? DateFormat('d MMMM yyyy').format(_dueDate!) : 'Select date',
                    style: TextStyle(color: _dueDate != null ? AppColors.text : AppColors.textSub, fontSize: 14),
                  ),
                  const Spacer(),
                  if (_dueDate != null)
                    GestureDetector(
                      onTap: () => setState(() => _dueDate = null),
                      child: const Icon(Icons.clear, size: 16, color: AppColors.textSub),
                    ),
                ]),
              ),
            ),
            const SizedBox(height: 32),

            LoadingButton(loading: _loading, label: isEdit ? 'Save Changes' : 'Create Task', onPressed: _submit),
          ],
        ),
      ),
    );
  }

  Widget _label(String text) => Padding(
    padding: const EdgeInsets.only(bottom: 6),
    child: Text(text, style: const TextStyle(fontSize: 13, fontWeight: FontWeight.w600, color: AppColors.text)),
  );
}

extension on String {
  String capitalize() => isEmpty ? this : this[0].toUpperCase() + substring(1);
}