Networking in iOS: URLSession Deep Dive

func fetchUsers() async throws -> [User] {
    let url = URL(string: "https://api.example.com/users")!
    let (data, response) = try await URLSession.shared.data(from: url)
    
    guard let httpResponse = response as? HTTPURLResponse,
          (200...299).contains(httpResponse.statusCode) else {
        throw NetworkError.invalidResponse
    }
    
    let decoder = JSONDecoder()
    decoder.dateDecodingStrategy = .iso8601
    return try decoder.decode([User].self, from: data)
}

func createUser(name: String, email: String) async throws -> User {
    let url = URL(string: "https://api.example.com/users")!
    var request = URLRequest(url: url)
    request.httpMethod = "POST"
    request.setValue("application/json", forHTTPHeaderField: "Content-Type")
    
    let payload = CreateUserRequest(name: name, email: email)
    request.httpBody = try JSONEncoder().encode(payload)
    
    let (data, response) = try await URLSession.shared.data(for: request)
    
    guard let httpResponse = response as? HTTPURLResponse,
          (200...299).contains(httpResponse.statusCode) else {
        throw NetworkError.invalidResponse
    }
    
    return try JSONDecoder().decode(User.self, from: data)
}

let configuration = URLSessionConfiguration.default
configuration.timeoutIntervalForRequest = 30
configuration.timeoutIntervalForResource = 60
configuration.waitsForConnectivity = true

let session = URLSession(configuration: configuration)

func uploadImage(data: Data, progress: @escaping (Double) -> Void) async throws -> String {
    let url = URL(string: "https://api.example.com/upload")!
    var request = URLRequest(url: url)
    request.httpMethod = "POST"
    
    let boundary = UUID().uuidString
    request.setValue("multipart/form-data; boundary=\(boundary)", forHTTPHeaderField: "Content-Type")
    
    let (responseData, response) = try await session.upload(for: request, from: data)
    
    guard let httpResponse = response as? HTTPURLResponse,
          (200...299).contains(httpResponse.statusCode) else {
        throw NetworkError.uploadFailed
    }
    
    let result = try JSONDecoder().decode(UploadResponse.self, from: responseData)
    return result.url
}

enum NetworkError: Error {
    case invalidURL
    case invalidResponse
    case httpError(Int)
    case decodingError
    case noData
    case timeout
    case noConnection
    
    var localizedDescription: String {
        switch self {
        case .invalidURL: return "Invalid URL"
        case .invalidResponse: return "Invalid response from server"
        case .httpError(let code): return "HTTP error: \(code)"
        case .decodingError: return "Failed to decode response"
        case .noData: return "No data received"
        case .timeout: return "Request timed out"
        case .noConnection: return "No internet connection"
        }
    }
}