environment_monitoring_app/lib/services/retry_service.dart

// lib/services/retry_service.dart

import 'dart:convert';
import 'dart:io';
import 'package:flutter/foundation.dart';
import 'package:environment_monitoring_app/services/api_service.dart';
import 'package:environment_monitoring_app/services/base_api_service.dart';
import 'package:environment_monitoring_app/services/ftp_service.dart';

/// A dedicated service to manage the queue of failed API and FTP requests
/// for manual resubmission.
class RetryService {
  // Use singleton instances to avoid re-creating services unnecessarily.
  final DatabaseHelper _dbHelper = DatabaseHelper();
  final BaseApiService _baseApiService = BaseApiService();
  final FtpService _ftpService = FtpService();

  /// Adds a failed API request to the local database queue.
  Future<void> addApiToQueue({
    required String endpoint,
    required String method, // e.g., 'POST' or 'POST_MULTIPART'
    Map<String, dynamic>? body,
    Map<String, String>? fields,
    Map<String, File>? files,
  }) async {
    // We must convert File objects to their string paths before saving to JSON.
    final serializableFiles = files?.map((key, value) => MapEntry(key, value.path));

    final payload = {
      'method': method,
      'body': body,
      'fields': fields,
      'files': serializableFiles,
    };

    await _dbHelper.queueFailedRequest({
      'type': 'api',
      'endpoint_or_path': endpoint,
      'payload': jsonEncode(payload),
      'timestamp': DateTime.now().toIso8601String(),
      'status': 'pending',
    });
    debugPrint("API request for endpoint '$endpoint' has been queued for retry.");
  }

  /// Adds a failed FTP upload to the local database queue.
  Future<void> addFtpToQueue({
    required String localFilePath,
    required String remotePath,
  }) async {
    final payload = {'localFilePath': localFilePath};
    await _dbHelper.queueFailedRequest({
      'type': 'ftp',
      'endpoint_or_path': remotePath,
      'payload': jsonEncode(payload),
      'timestamp': DateTime.now().toIso8601String(),
      'status': 'pending',
    });
    debugPrint("FTP upload for file '$localFilePath' has been queued for retry.");
  }

  /// Retrieves all tasks currently in the 'pending' state from the queue.
  Future<List<Map<String, dynamic>>> getPendingTasks() {
    return _dbHelper.getPendingRequests();
  }

  /// Attempts to re-execute a single failed task from the queue.
  /// Returns `true` on success, `false` on failure.
  Future<bool> retryTask(int taskId) async {
    final task = await _dbHelper.getRequestById(taskId);
    if (task == null) {
      debugPrint("Retry failed: Task with ID $taskId not found in the queue.");
      return false;
    }

    bool success = false;
    final payload = jsonDecode(task['payload'] as String);

    try {
      if (task['type'] == 'api') {
        final endpoint = task['endpoint_or_path'] as String;
        final method = payload['method'] as String;

        debugPrint("Retrying API task $taskId: $method to $endpoint");
        Map<String, dynamic> result;

        if (method == 'POST_MULTIPART') {
          // Reconstruct fields and files from the stored payload
          final Map<String, String> fields = Map<String, String>.from(payload['fields'] ?? {});
          final Map<String, File> files = (payload['files'] as Map<String, dynamic>?)
              ?.map((key, value) => MapEntry(key, File(value as String))) ?? {};

          result = await _baseApiService.postMultipart(endpoint: endpoint, fields: fields, files: files);
        } else { // Assume 'POST'
          final Map<String, dynamic> body = Map<String, dynamic>.from(payload['body'] ?? {});
          result = await _baseApiService.post(endpoint, body);
        }

        success = result['success'];

      } else if (task['type'] == 'ftp') {
        final remotePath = task['endpoint_or_path'] as String;
        final localFile = File(payload['localFilePath'] as String);

        debugPrint("Retrying FTP task $taskId: Uploading ${localFile.path} to $remotePath");

        // Ensure the file still exists before attempting to re-upload
        if (await localFile.exists()) {
          final result = await _ftpService.uploadFile(localFile, remotePath);
          // The FTP service already queues on failure, so we only care about success here.
          success = result['success'];
        } else {
          debugPrint("Retry failed for FTP task $taskId: Source file no longer exists at ${localFile.path}");
          success = false;
        }
      }
    } catch (e) {
      debugPrint("A critical error occurred while retrying task $taskId: $e");
      success = false;
    }

    if (success) {
      debugPrint("Task $taskId completed successfully. Removing from queue.");
      await _dbHelper.deleteRequestFromQueue(taskId);
    } else {
      debugPrint("Retry attempt for task $taskId failed. It will remain in the queue.");
    }

    return success;
  }
}