/// Manage labels: create, nest, and delete.
library;

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

import '../models/transaction_meta.dart';
import '../providers/tx_meta_provider.dart';
import '../widgets/label_parent_picker.dart';
import '../widgets/responsive_body.dart';

class LabelsScreen extends StatelessWidget {
  const LabelsScreen({super.key});

  Future<void> _create(
    BuildContext context, {
    String? parentId,
  }) async {
    final meta = context.read<TxMetaController>();
    final result = await showCreateLabelDialog(
      context,
      parents: meta.allLabels,
      initialParentId: parentId,
    );
    if (result == null || !context.mounted) return;
    await meta.createLabel(result.name, parentId: result.parentId);
    if (!context.mounted) return;
    ScaffoldMessenger.of(context).showSnackBar(
      SnackBar(content: Text('Created “${result.name}”')),
    );
  }

  Future<void> _delete(BuildContext context, TxLabel label) async {
    final ok = await showDialog<bool>(
      context: context,
      builder: (dialogContext) {
        return AlertDialog(
          title: Text('Remove “${label.name}”?'),
          content: const Text(
            'This deletes the label. Transactions keep any other labels. '
            'Sub-labels move up one level.',
          ),
          actions: [
            TextButton(
              onPressed: () => Navigator.pop(dialogContext, false),
              child: const Text('Cancel'),
            ),
            FilledButton(
              onPressed: () => Navigator.pop(dialogContext, true),
              child: const Text('Remove'),
            ),
          ],
        );
      },
    );
    if (ok != true || !context.mounted) return;
    await context.read<TxMetaController>().removeLabel(label.id);
    if (!context.mounted) return;
    ScaffoldMessenger.of(context).showSnackBar(
      SnackBar(content: Text('Removed “${label.name}”')),
    );
  }

  @override
  Widget build(BuildContext context) {
    final meta = context.watch<TxMetaController>();
    final theme = Theme.of(context);
    final colors = theme.colorScheme;
    final entries = meta.labelsInTreeOrder();

    return Scaffold(
      appBar: AppBar(
        title: const Text('Labels'),
        actions: [
          IconButton(
            tooltip: 'New label',
            onPressed: () => _create(context),
            icon: const Icon(Icons.add),
          ),
        ],
      ),
      floatingActionButton: FloatingActionButton.extended(
        onPressed: () => _create(context),
        icon: const Icon(Icons.add),
        label: const Text('New label'),
      ),
      body: ResponsiveBody(
        child: entries.isEmpty
            ? ListView(
                children: [
                  const SizedBox(height: 48),
                  Icon(
                    Icons.label_outline,
                    size: 48,
                    color: colors.outline,
                  ),
                  const SizedBox(height: 12),
                  Text(
                    'No labels yet',
                    textAlign: TextAlign.center,
                    style: theme.textTheme.titleMedium,
                  ),
                  const SizedBox(height: 8),
                  Text(
                    'Create labels to categorize spending.',
                    textAlign: TextAlign.center,
                    style: theme.textTheme.bodyMedium,
                  ),
                ],
              )
            : ListView.separated(
                padding: const EdgeInsets.fromLTRB(0, 8, 0, 88),
                itemCount: entries.length + 1,
                separatorBuilder: (_, _) => const Divider(height: 1),
                itemBuilder: (context, index) {
                  if (index == 0) {
                    return Padding(
                      padding: const EdgeInsets.fromLTRB(4, 4, 4, 12),
                      child: Text(
                        'Create, nest under another label, or delete custom '
                        'ones. Built-in labels can be moved but not deleted.',
                        style: theme.textTheme.bodyMedium,
                      ),
                    );
                  }
                  final entry = entries[index - 1];
                  final label = entry.label;
                  final parentId = meta.parentIdOf(label.id);
                  final parent = parentId == null ? null : meta.labelById(parentId);
                  return ListTile(
                    contentPadding: EdgeInsets.fromLTRB(
                      8 + entry.depth * 16.0,
                      0,
                      4,
                      0,
                    ),
                    leading: Icon(label.icon, color: label.color),
                    title: Text(label.name),
                    subtitle: Text(
                      [
                        if (label.custom) 'Custom' else 'Built-in',
                        if (parent != null) 'under ${parent.name}',
                      ].join(' · '),
                    ),
                    trailing: PopupMenuButton<String>(
                      tooltip: 'Actions',
                      onSelected: (value) async {
                        switch (value) {
                          case 'sub':
                            await _create(context, parentId: label.id);
                          case 'move':
                            await showMoveLabelDialog(context, label: label);
                          case 'delete':
                            await _delete(context, label);
                        }
                      },
                      itemBuilder: (context) => [
                        if (meta.depthOf(label.id) < kMaxLabelDepth)
                          const PopupMenuItem(
                            value: 'sub',
                            child: ListTile(
                              dense: true,
                              contentPadding: EdgeInsets.zero,
                              leading: Icon(Icons.subdirectory_arrow_right),
                              title: Text('Add sub-label'),
                            ),
                          ),
                        const PopupMenuItem(
                          value: 'move',
                          child: ListTile(
                            dense: true,
                            contentPadding: EdgeInsets.zero,
                            leading: Icon(Icons.account_tree_outlined),
                            title: Text('Move under…'),
                          ),
                        ),
                        if (label.custom)
                          PopupMenuItem(
                            value: 'delete',
                            child: ListTile(
                              dense: true,
                              contentPadding: EdgeInsets.zero,
                              leading: Icon(
                                Icons.delete_outline,
                                color: colors.error,
                              ),
                              title: Text(
                                'Delete',
                                style: TextStyle(color: colors.error),
                              ),
                            ),
                          ),
                      ],
                    ),
                  );
                },
              ),
      ),
    );
  }
}