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

import '../../core/constants.dart';
import '../../core/exceptions.dart';
import '../../core/theme.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;
  final int? initialProjectId;
  const TaskEditScreen({super.key, this.taskId, this.initialProjectId});

  @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;
  List<Task> _subTasks = [];

  late final Future<void> _initFuture;

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

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

  Future<void> _loadExisting() async {
    final repo = ref.read(tasksRepositoryProvider);
    final task = await repo.getOne(widget.taskId!);
    _titleController.text = task.title;
    _descController.text = task.description ?? '';
    _status = task.status;
    _priority = task.priority;
    _dueDate = task.dueDate;
    _projectId = task.projectId;
    // Fetch sub-tasks
    final api = ref.read(tasksApiProvider);
    final subs = await api.getSubTasks(widget.taskId!);
    setState(() => _subTasks = subs);
  }

  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),
              style: TextButton.styleFrom(
                foregroundColor: Theme.of(dialogContext).extension<ActionColors>()!.destructive,
              ),
              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);
  }

  Future<void> _addSubTask() async {
    final titleCtrl = TextEditingController();
    final result = await showDialog<String>(
      context: context,
      builder: (ctx) => AlertDialog(
        title: const Text('Add sub-task'),
        content: TextField(
          controller: titleCtrl,
          autofocus: true,
          decoration: const InputDecoration(
            labelText: 'Title',
            border: OutlineInputBorder(),
          ),
          textInputAction: TextInputAction.done,
          onSubmitted: (v) => Navigator.pop(ctx, v.trim()),
        ),
        actions: [
          TextButton(
              onPressed: () => Navigator.pop(ctx),
              child: const Text('Cancel')),
          FilledButton(
              onPressed: () =>
                  Navigator.pop(ctx, titleCtrl.text.trim()),
              child: const Text('Add')),
        ],
      ),
    );
    titleCtrl.dispose();
    if (result == null || result.isEmpty || !mounted) return;
    try {
      final api = ref.read(tasksApiProvider);
      final sub = await api.create(
        title: result,
        status: TaskStatus.todo,
        priority: TaskPriority.none,
        projectId: _projectId,
        parentId: widget.taskId,
      );
      ref.invalidate(tasksProvider);
      setState(() => _subTasks = [..._subTasks, sub]);
    } on AppException catch (e) {
      if (mounted) {
        ScaffoldMessenger.of(context)
            .showSnackBar(SnackBar(content: Text(e.message)));
      }
    }
  }

  @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(LucideIcons.trash2),
                  onPressed: _delete,
                ),
              IconButton(
                icon: _saving
                    ? const SizedBox(
                        width: 20,
                        height: 20,
                        child: CircularProgressIndicator(strokeWidth: 2),
                      )
                    : const Icon(LucideIcons.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>(
                            // ignore: deprecated_member_use
                            value: _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>(
                            // ignore: deprecated_member_use
                            value: _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(LucideIcons.calendarDays),
                            trailing: _dueDate != null
                                ? IconButton(
                                    icon: const Icon(LucideIcons.x),
                                    onPressed: () =>
                                        setState(() => _dueDate = null),
                                  )
                                : null,
                            onTap: _pickDate,
                          ),
                          const SizedBox(height: 16),
                          ProjectSelector(
                            value: _projectId,
                            onChanged: (id) =>
                                setState(() => _projectId = id),
                          ),
                          // Sub-tasks (only when editing an existing task)
                          if (widget.taskId != null) ...[
                            const SizedBox(height: 24),
                            _SubTasksSection(
                              subTasks: _subTasks,
                              onAdd: _addSubTask,
                            ),
                          ],
                        ],
                      ),
                    ),
                  ),
                ),
        );
      },
    );
  }
}

// ─── Sub-tasks section ─────────────────────────────────────────────────────────

class _SubTasksSection extends ConsumerWidget {
  final List<Task> subTasks;
  final VoidCallback onAdd;
  const _SubTasksSection({required this.subTasks, required this.onAdd});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final colorScheme = Theme.of(context).colorScheme;
    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        Row(
          children: [
            Text(
              'Sub-tasks',
              style: Theme.of(context).textTheme.titleSmall?.copyWith(
                    color: colorScheme.onSurfaceVariant,
                  ),
            ),
            const Spacer(),
            TextButton.icon(
              onPressed: onAdd,
              icon: const Icon(LucideIcons.plus, size: 16),
              label: const Text('Add'),
              style: TextButton.styleFrom(
                foregroundColor: colorScheme.primary,
                padding:
                    const EdgeInsets.symmetric(horizontal: 8, vertical: 4),
                textStyle: const TextStyle(fontSize: 13),
              ),
            ),
          ],
        ),
        if (subTasks.isEmpty)
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 8),
            child: Text(
              'No sub-tasks yet.',
              style: Theme.of(context).textTheme.bodySmall?.copyWith(
                    color: colorScheme.outline,
                  ),
            ),
          )
        else
          ...subTasks.map((sub) => _SubTaskTile(task: sub, ref: ref)),
      ],
    );
  }
}

class _SubTaskTile extends StatelessWidget {
  final Task task;
  final WidgetRef ref;
  const _SubTaskTile({required this.task, required this.ref});

  @override
  Widget build(BuildContext context) {
    final isDone = task.status == TaskStatus.done;
    return ListTile(
      dense: true,
      contentPadding: EdgeInsets.zero,
      leading: Checkbox(
        value: isDone,
        onChanged: (_) async {
          final newStatus =
              isDone ? TaskStatus.todo : TaskStatus.done;
          await ref.read(tasksProvider.notifier).updateTask(
              task.id, {'status': newStatus.value});
        },
      ),
      title: Text(
        task.title,
        style: TextStyle(
          decoration: isDone ? TextDecoration.lineThrough : null,
          color: isDone
              ? Theme.of(context).colorScheme.outline
              : null,
        ),
      ),
      onTap: () => context.push(
        Routes.taskEdit.replaceFirst(':id', '${task.id}'),
      ),
    );
  }
}