SAPURLSession+Extension for SAP Blog

SAPURLSession+Extension.swift

import Foundation
import SAPFoundation
import Combine

public extension SAPURLSession {
    
    enum SAPURLError: Error {
        case requestFailed(URLError)
        case redirection(HTTPURLResponse)
        case client(response: HTTPURLResponse, payload: ODataErrorPayload?)
        case server(HTTPURLResponse)
        case unknown
        
        init(_ error: Error) {
            switch error {
            case is URLError:
                self = .requestFailed(error as! URLError)
            case is SAPURLError:
                self = error as! SAPURLError
            default:
                self = .unknown
            }
        }
    }
    
    func getImage(for url: URL) -> AnyPublisher<UIImage, SAPURLError> {
        dataTaskPublisher(for: url)
            .tryMap(mapResponseToImage)
            .mapError(SAPURLError.init)
            .eraseToAnyPublisher()
    }
    
    func getImage(for request: URLRequest) -> AnyPublisher<UIImage, SAPURLError> {
        dataTaskPublisher(for: request)
            .tryMap(mapResponseToImage)
            .mapError(SAPURLError.init)
            .eraseToAnyPublisher()
    }
}

// MARK: - Private API
private extension SAPURLSession {
    
    func mapResponseToImage(transform: (data: Data, response: URLResponse)) throws -> UIImage {
        guard let httpResponse = transform.response as? HTTPURLResponse else {
            throw SAPURLError.unknown
        }

        // 2XX Success
        if 200...299 ~= httpResponse.statusCode {
            return UIImage(data: transform.data)!
         
        // 3XX Redirection
        } else if 300...399 ~= httpResponse.statusCode {
            throw SAPURLError.redirection(httpResponse)
        
        // 4XX Client Errors
        } else if 400...499 ~= httpResponse.statusCode {
            throw SAPURLError.client(response: httpResponse, payload: decodeResponse(data: transform.data))
           
        // 5XX Server Errors
        } else if 500...599 ~= httpResponse.statusCode {
            throw SAPURLError.server(httpResponse)
            
        } else {
            throw SAPURLError.unknown
        }
    }
    
    func decodeResponse(data: Data) -> ODataErrorPayload? {
        try? JSONDecoder().decode(ODataErrorPayload.self, from: data)
    }
}

// MARK: - LocalizedError (Adapt to your needs)
extension SAPURLSession.SAPURLError: LocalizedError {
    
    public var errorDescription: String? {
        switch self {
        case .requestFailed(_):
            return "RequestError".localized()
        case .redirection(_):
            return "httpRedirectionError".localized()
        case .client(response: _, payload: let payload):
            if let payload = payload {
                return payload.error.message.value
            } else {
                return "httpClientError".localized()
            }
            
        case .server(_):
            return "httpServerError".localized()
        case .unknown:
            return "UnknownError".localized()
        }
    }
}