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/status_badge.dart';
import '../../core/widgets/error_view.dart';
import 'tasks_provider.dart';

class TaskDetailScreen extends ConsumerStatefulWidget {
  final int id;
  const TaskDetailScreen({super.key, required this.id});

  @override
  ConsumerState<TaskDetailScreen> createState() => _TaskDetailScreenState();
}

class _TaskDetailScreenState extends ConsumerState<TaskDetailScreen> {
  final _commentCtrl = TextEditingController();
  bool _sendingComment = false;

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

  Future<void> _sendComment() async {
    if (_commentCtrl.text.trim().isEmpty) return;
    setState(() => _sendingComment = true);
    try {
      await addComment(widget.id, _commentCtrl.text.trim());
      _commentCtrl.clear();
      ref.invalidate(taskDetailProvider(widget.id));
    } catch (e) {
      if (mounted) ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(content: Text(e.toString()), backgroundColor: AppColors.danger));
    } finally {
      if (mounted) setState(() => _sendingComment = false);
    }
  }

  Future<void> _updateStatus(String newStatus) async {
    try {
      await updateTask(widget.id, {'status': newStatus});
      ref.invalidate(taskDetailProvider(widget.id));
      ref.read(tasksProvider.notifier).load();
    } catch (e) {
      if (mounted) ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(content: Text(e.toString()), backgroundColor: AppColors.danger));
    }
  }

  Future<void> _delete() async {
    final confirm = await showDialog<bool>(context: context, builder: (_) => AlertDialog(
      title: const Text('Delete Task'),
      content: const Text('This task will be permanently deleted.'),
      actions: [
        TextButton(onPressed: () => Navigator.pop(context, false), child: const Text('Cancel')),
        TextButton(onPressed: () => Navigator.pop(context, true),
            child: const Text('Delete', style: TextStyle(color: AppColors.danger))),
      ],
    ));
    if (confirm != true) return;
    try {
      await deleteTask(widget.id);
      if (mounted) { context.pop(); ref.read(tasksProvider.notifier).load(); }
    } catch (e) {
      if (mounted) ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(content: Text(e.toString()), backgroundColor: AppColors.danger));
    }
  }

  @override
  Widget build(BuildContext context) {
    final async = ref.watch(taskDetailProvider(widget.id));

    return async.when(
      loading: () => const Scaffold(body: Center(child: CircularProgressIndicator())),
      error: (e, _) => Scaffold(
        appBar: AppBar(),
        body: ErrorView(message: e.toString(), onRetry: () => ref.invalidate(taskDetailProvider(widget.id))),
      ),
      data: (task) => Scaffold(
        appBar: AppBar(
          title: const Text('Task Detail'),
          actions: [
            IconButton(
              icon: const Icon(Icons.edit_outlined),
              onPressed: () async {
                await context.push('/tasks/${task.id}/edit');
                ref.invalidate(taskDetailProvider(widget.id));
              },
            ),
            IconButton(
              icon: const Icon(Icons.delete_outline, color: AppColors.danger),
              onPressed: _delete,
            ),
          ],
        ),
        body: Column(
          children: [
            Expanded(
              child: ListView(
                padding: const EdgeInsets.all(16),
                children: [
                  // Header card
                  _card(Column(
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: [
                      Row(children: [
                        Expanded(child: Text(task.title,
                            style: const TextStyle(fontSize: 16, fontWeight: FontWeight.w700, color: AppColors.text))),
                        const SizedBox(width: 8),
                        StatusBadge(task.status),
                      ]),
                      const SizedBox(height: 16),
                      _infoRow(Icons.person_outline, 'Assignee', task.assignedUsername ?? '-'),
                      _infoRow(Icons.person_outlined, 'Created by', task.createdByUsername),
                      if (task.dueDate != null)
                        _infoRow(Icons.calendar_today_outlined, 'Deadline',
                            DateFormat('d MMMM yyyy').format(task.dueDate!),
                            color: task.isOverdue ? AppColors.danger : null),
                      if (task.completedAt != null)
                        _infoRow(Icons.check_circle_outline, 'Completed',
                            DateFormat('d MMM yyyy HH:mm').format(task.completedAt!)),
                    ],
                  )),
                  const SizedBox(height: 12),

                  // Status update
                  _card(Column(
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: [
                      const Text('Update Status', style: TextStyle(fontWeight: FontWeight.w700, fontSize: 13)),
                      const SizedBox(height: 10),
                      Row(
                        children: [
                          for (final s in ['todo', 'in_progress', 'done'])
                            Expanded(child: Padding(
                              padding: const EdgeInsets.only(right: 6),
                              child: OutlinedButton(
                                style: OutlinedButton.styleFrom(
                                  backgroundColor: task.status == s ? AppColors.primary : null,
                                  foregroundColor: task.status == s ? Colors.white : AppColors.text,
                                  side: BorderSide(color: task.status == s ? AppColors.primary : AppColors.border),
                                  minimumSize: const Size(0, 36),
                                  textStyle: const TextStyle(fontSize: 11, fontWeight: FontWeight.w600),
                                  padding: EdgeInsets.zero,
                                ),
                                onPressed: task.status == s ? null : () => _updateStatus(s),
                                child: Text(s == 'in_progress' ? 'Progress' : s.capitalize()),
                              ),
                            )),
                        ],
                      ),
                    ],
                  )),
                  const SizedBox(height: 12),

                  // Subtasks
                  if (task.subtasks.isNotEmpty) ...[
                    _card(Column(
                      crossAxisAlignment: CrossAxisAlignment.start,
                      children: [
                        Text('Subtasks (${task.subtasks.length})',
                            style: const TextStyle(fontWeight: FontWeight.w700, fontSize: 13)),
                        const SizedBox(height: 10),
                        ...task.subtasks.map((s) => ListTile(
                          contentPadding: EdgeInsets.zero,
                          dense: true,
                          leading: StatusBadge(s.status, small: true),
                          title: Text(s.title, style: const TextStyle(fontSize: 13)),
                          onTap: () async {
                            await context.push('/tasks/${task.id}/subtasks/${s.id}');
                            ref.invalidate(taskDetailProvider(widget.id));
                          },
                        )),
                      ],
                    )),
                    const SizedBox(height: 12),
                  ],

                  // Comments
                  _card(Column(
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: [
                      Text('Comments (${task.comments.length})',
                          style: const TextStyle(fontWeight: FontWeight.w700, fontSize: 13)),
                      if (task.comments.isEmpty)
                        const Padding(
                          padding: EdgeInsets.symmetric(vertical: 12),
                          child: Text('No comments yet', style: TextStyle(color: AppColors.textSub, fontSize: 13)),
                        ),
                      ...task.comments.map((c) => Padding(
                        padding: const EdgeInsets.only(top: 12),
                        child: Row(
                          crossAxisAlignment: CrossAxisAlignment.start,
                          children: [
                            CircleAvatar(
                              radius: 16,
                              backgroundColor: AppColors.primaryLight,
                              child: Text(c.username.isNotEmpty ? c.username[0].toUpperCase() : '?',
                                  style: const TextStyle(color: AppColors.primary, fontSize: 12, fontWeight: FontWeight.w700)),
                            ),
                            const SizedBox(width: 10),
                            Expanded(child: Column(
                              crossAxisAlignment: CrossAxisAlignment.start,
                              children: [
                                Row(children: [
                                  Text(c.username, style: const TextStyle(fontWeight: FontWeight.w600, fontSize: 13)),
                                  const SizedBox(width: 8),
                                  Text(DateFormat('d MMM HH:mm').format(c.createdAt),
                                      style: const TextStyle(fontSize: 11, color: AppColors.textSub)),
                                ]),
                                const SizedBox(height: 4),
                                Text(c.body, style: const TextStyle(fontSize: 13, color: AppColors.text)),
                              ],
                            )),
                          ],
                        ),
                      )),
                    ],
                  )),
                  const SizedBox(height: 16),
                ],
              ),
            ),
            // Sticky comment bar
            Container(
              padding: EdgeInsets.only(
                left: 16, right: 16, top: 12,
                bottom: MediaQuery.of(context).viewInsets.bottom + 12,
              ),
              decoration: const BoxDecoration(
                color: AppColors.surface,
                border: Border(top: BorderSide(color: AppColors.border)),
              ),
              child: Row(
                children: [
                  Expanded(
                    child: TextField(
                      controller: _commentCtrl,
                      decoration: const InputDecoration(hintText: 'Write a comment...', isDense: true),
                      textInputAction: TextInputAction.send,
                      onSubmitted: (_) => _sendComment(),
                    ),
                  ),
                  const SizedBox(width: 8),
                  IconButton(
                    onPressed: _sendingComment ? null : _sendComment,
                    icon: _sendingComment
                        ? const SizedBox(width: 20, height: 20, child: CircularProgressIndicator(strokeWidth: 2))
                        : const Icon(Icons.send, color: AppColors.primary),
                  ),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }

  Widget _card(Widget child) => Container(
    padding: const EdgeInsets.all(14),
    decoration: BoxDecoration(
      color: AppColors.surface,
      borderRadius: BorderRadius.circular(12),
      border: Border.all(color: AppColors.border),
    ),
    child: child,
  );

  Widget _infoRow(IconData icon, String label, String value, {Color? color}) => Padding(
    padding: const EdgeInsets.only(bottom: 8),
    child: Row(children: [
      Icon(icon, size: 15, color: AppColors.textSub),
      const SizedBox(width: 8),
      Text('$label: ', style: const TextStyle(fontSize: 13, color: AppColors.textSub)),
      Expanded(child: Text(value, style: TextStyle(fontSize: 13, fontWeight: FontWeight.w600, color: color ?? AppColors.text))),
    ]),
  );
}

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