Tiny networking revisited

main.swift

import Result
import Unbox

public enum Method: String { // Bluntly stolen from Alamofire
    case OPTIONS = "OPTIONS"
    case GET = "GET"
    case HEAD = "HEAD"
    case POST = "POST"
    case PUT = "PUT"
    case PATCH = "PATCH"
    case DELETE = "DELETE"
    case TRACE = "TRACE"
    case CONNECT = "CONNECT"
}

public struct Resource<A> {
    let path: String
    let method : Method
    let parameters: [String: AnyObject]?
    let headers : [String: String]
    let transform: NSData -> Result<A, NSError>
}

public class Error: Unboxable {
    let code: String
    let message: String

    required public init(unboxer: Unboxer) {
        self.code = unboxer.unbox("error.code", isKeyPath: true)
        self.message = unboxer.unbox("error.message", isKeyPath: true)
    }
}


public enum HTTPFailureReason {
    case NoData
    case NoSuccessStatusCode(statusCode: Int, error: Error?)
    case Other(NSError)
}

extension HTTPFailureReason: ErrorType { }

public protocol Cancellable {
    func cancel()
}
extension NSURLSessionTask: Cancellable {}

public func apiRequest<A>(baseURL: NSURL, resource: Resource<A>, completion: Result<A, HTTPFailureReason> -> ()) -> Cancellable {

    let session = NSURLSession.sharedSession()
    let url = baseURL.URLByAppendingPathComponent(resource.path)
    let request = NSMutableURLRequest(URL: url)
    request.HTTPMethod = resource.method.rawValue

    //do not attach nil parameters
    //do not createrequest prior to getting param type
    if resource.method == .GET {
        let comps = NSURLComponents(URL: url, resolvingAgainstBaseURL: false)!
        comps.queryItems = (resource.parameters ?? [:]).map { NSURLQueryItem(name: $0.0, value: "\($0.1)") }
        request.URL = comps.URL
    } else {
        request.HTTPBody = encodeJSON(resource.parameters ?? [:])
    }

    for (key,value) in resource.headers {
        request.setValue(value, forHTTPHeaderField: key)
    }

    let task = session.dataTaskWithRequest(request) { (data, response, error) in
        guard let httpResponse = response as? NSHTTPURLResponse else {
            return completion(Result(error: .Other(error!))) // remove !
        }

        guard let responseData = data else {
            return completion(Result(error: .NoData))
        }

        guard 200..<300 ~= httpResponse.statusCode else {
            return completion(Result(error:.NoSuccessStatusCode(statusCode: httpResponse.statusCode, error: Unbox(responseData))))
        }

        completion(resource.transform(responseData).mapError { .Other($0) })
    }

    task.resume()

    return task
}

func encodeJSON(dict: JSONDictionary) -> NSData? {
    //TODO: do not swallow error
    return dict.count > 0 ? try? NSJSONSerialization.dataWithJSONObject(dict, options: NSJSONWritingOptions()) : nil
}

public typealias JSONDictionary = [String:AnyObject]

public func jsonResource<A where A: Unboxable>(path: String, method: Method, parameters: [String: AnyObject]? = nil, headers: [String: String]? = nil) -> Resource<A> {
    var allHeaders = ["Content-Type": "application/json"]
// ??[:] is ugly
    for (key, value) in headers ?? [:] {
        allHeaders[key] = value
    }
    let transform: NSData -> Result<A, NSError> = { data in  materialize { try UnboxOrThrow(data) } }
    return Resource(path: path, method: method, parameters: parameters, headers: allHeaders, transform: transform)
}

// Specific


public func getProductCategories() -> Resource<Collection<ShopCategory>> {
    return jsonResource("v1/categories", method: .GET, parameters: ["per_page" : 100])
}

public func getProduct(ID: Int) -> Resource<Product> {
    return jsonResource("v1/products/\(ID)", method: .GET)
}

public func login(login: String, password: String) -> Resource<User> {
    let params = ["login": login, "password": password]
    return jsonResource("v1/users/login", method: .POST, parameters: params)
}

public func getCards() -> Resource<Collection<Card>> {
    return secureJsonResource("v1/users/cards", method: .GET, parameters: ["per_page" : 100])
}

public func createCard(token: String) -> Resource<Card> {
    return secureJsonResource("v1/users/cards", method: .POST, parameters: ["token": token])
}

public func removeCard(ID: Int) -> Resource<OperationStatus> {
    return secureJsonResource("v1/users/cards/\(ID)", method: .DELETE)
}

func secureJsonResource<A where A: Unboxable>(path: String, method: Method, parameters: [String: AnyObject]? = nil) -> Resource<A> {
    guard let token = SwiftGift.token else { preconditionFailure("Token expected to be set before secure request.") }

    return jsonResource(path, method: method, parameters: parameters, headers: ["X-Access-Token": token])
}

public enum SwiftGiftError {
    case HTTP(NSError)
    case API(Error)
    case Other
}

extension SwiftGiftError: ErrorType {}

public struct SwiftGift {
    static var token: String? = nil

    static public func request<A>(resource: Resource<A>, completion: Result<A, SwiftGiftError> -> ()) -> Cancellable {
        return apiRequest(NSURL(string: "https://example.com")!, resource: resource) { result in

            //swallow cancelled requests
            if case let .Other(e)? = result.error where e.isCancelled {
                return
            }

            completion(result.mapError(promoteHTTPErrorToAppError))
        }
    }

    private static func promoteHTTPErrorToAppError(error: HTTPFailureReason) -> SwiftGiftError {
        switch error {
        case let .NoSuccessStatusCode(_, error: apiError?):
            return .API(apiError)
        case let .Other(error):
            return .HTTP(error)
        default:
            return .Other
        }
    }
}

private extension NSError {
    var isCancelled: Bool {
        return domain == NSURLErrorDomain && code == NSURLErrorCancelled
    }
}

//model

public struct OperationStatus: Unboxable {
    public init(unboxer: Unboxer) {

    }
}

public class ShopCategory: Unboxable {
    public let ID: Int
    public let imageUrl: String?

    required public init(unboxer: Unboxer) {
        self.ID = unboxer.unbox("id")
        self.imageUrl = unboxer.unbox("image_url")
    }
}

public struct Collection<A where A: Unboxable>: Unboxable {
    let items: [A]

    public init(unboxer: Unboxer) {
        items = unboxer.unbox("collection")
    }
}

public class Product: NSObject, Unboxable {
    let name: String

    public required init(unboxer: Unboxer) {
        name = unboxer.unbox("name")
    }
}

public class User: NSObject, Unboxable {
    let email: String
    let token: Token
    public required init(unboxer: Unboxer) {
        email = unboxer.unbox("email")
        token = unboxer.unbox("token")
    }
}

public struct Token: Unboxable {

    let token: String
    let refreshToken: String
    let expires: NSTimeInterval

    public init(unboxer: Unboxer) {
        token = unboxer.unbox("value")
        refreshToken = unboxer.unbox("refresh_token")
        expires = unboxer.unbox("expires")
    }
}

public struct Card: Unboxable {

    let ID: Int
    let stripeID: String
    let last4: String
    let vendor: String
    let expirationMonth: Int
    let expirationYear: Int

    public init(unboxer: Unboxer) {
        ID = unboxer.unbox("id")
        stripeID = unboxer.unbox("card_id")
        last4 = unboxer.unbox("last4")
        vendor = unboxer.unbox("type")
        expirationMonth = unboxer.unbox("expiration_month")
        expirationYear = unboxer.unbox("expiration_year")
    }
}

usage.swift

SwiftGift.request(getProductCategories()) { result in
  print(result)
}

let token = SwiftGift.request(login("[email protected]", password: "notabc23")) { result in

  
}
token.cancel()