rely/lib/features/sync/sync_view.dart

import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:relationship_saver/core/config/app_theme.dart';
import 'package:relationship_saver/features/shared/frosted_card.dart';
import 'package:relationship_saver/integrations/backend/backend_gateway_provider.dart';
import 'package:relationship_saver/integrations/backend/models/backend_models.dart';
import 'package:uuid/uuid.dart';

class SyncView extends ConsumerStatefulWidget {
  const SyncView({super.key});

  @override
  ConsumerState<SyncView> createState() => _SyncViewState();
}

class _SyncViewState extends ConsumerState<SyncView> {
  static const Uuid _uuid = Uuid();

  bool _busy = false;
  String _status = 'Ready. Local-first mode keeps app usable without sync.';
  String? _cursor;

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.fromLTRB(28, 24, 28, 28),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          Text('Sync', style: Theme.of(context).textTheme.headlineMedium),
          const SizedBox(height: 6),
          Text(
            'Push local changes and pull remote updates when connectivity is available.',
            style: Theme.of(
              context,
            ).textTheme.bodyLarge?.copyWith(color: AppTheme.textSecondary),
          ),
          const SizedBox(height: 16),
          FrostedCard(
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: <Widget>[
                Wrap(
                  spacing: 10,
                  runSpacing: 10,
                  children: <Widget>[
                    FilledButton.icon(
                      onPressed: _busy ? null : _pushSample,
                      icon: const Icon(Icons.upload_rounded),
                      label: const Text('Push Sample Changes'),
                    ),
                    OutlinedButton.icon(
                      onPressed: _busy ? null : _pullChanges,
                      icon: const Icon(Icons.download_rounded),
                      label: const Text('Pull Changes'),
                    ),
                  ],
                ),
                const SizedBox(height: 16),
                Text(
                  'Cursor: ${_cursor ?? 'not set'}',
                  style: Theme.of(context).textTheme.bodyMedium,
                ),
                const SizedBox(height: 8),
                Text(
                  _status,
                  style: Theme.of(context).textTheme.bodyLarge?.copyWith(
                    color: AppTheme.textSecondary,
                  ),
                ),
              ],
            ),
          ),
          const SizedBox(height: 16),
          FrostedCard(
            child: Text(
              'Sync policy\n• Core usage never blocks on backend\n• Retries only for transient failures\n• Non-idempotent requests require idempotency key',
              style: Theme.of(context).textTheme.bodyLarge,
            ),
          ),
        ],
      ),
    );
  }

  Future<void> _pullChanges() async {
    setState(() {
      _busy = true;
      _status = 'Pulling changes...';
    });

    try {
      final SyncPullResult result = await ref
          .read(backendGatewayProvider)
          .pullChanges(cursor: _cursor);

      setState(() {
        _cursor = result.cursor;
        _status = 'Pulled ${result.changes.length} changes successfully.';
      });
    } catch (error) {
      setState(() {
        _status = 'Pull failed. Staying offline-safe. ($error)';
      });
    } finally {
      setState(() {
        _busy = false;
      });
    }
  }

  Future<void> _pushSample() async {
    setState(() {
      _busy = true;
      _status = 'Pushing local sample changes...';
    });

    final List<ChangeEnvelope> changes = <ChangeEnvelope>[
      ChangeEnvelope(
        schemaVersion: 1,
        entityType: 'capture',
        entityId: 'capture-${_uuid.v4()}',
        op: ChangeOperation.upsert,
        modifiedAt: DateTime.now().toUtc(),
        clientMutationId: _uuid.v4(),
        payload: const <String, dynamic>{
          'summary': 'Shared a thoughtful check-in after work.',
          'sentiment': 'positive',
        },
      ),
    ];

    try {
      final SyncPushResult result = await ref
          .read(backendGatewayProvider)
          .pushChanges(changes: changes, cursor: _cursor);

      setState(() {
        _cursor = result.cursor;
        _status =
            'Push complete. accepted=${result.accepted.length}, rejected=${result.rejected.length}';
      });
    } catch (error) {
      setState(() {
        _status = 'Push failed. Local data remains safe. ($error)';
      });
    } finally {
      setState(() {
        _busy = false;
      });
    }
  }
}