URLSession

// # not executed here: Swift 6.3.3 toolchain is unavailable.
import Foundation

final class StubProtocol: URLProtocol {
    override class func canInit(with request: URLRequest) -> Bool { true }
    override class func canonicalRequest(for request: URLRequest) -> URLRequest { request }

    override func startLoading() {
        let response = HTTPURLResponse(
            url: request.url!, statusCode: 200,
            httpVersion: "HTTP/1.1", headerFields: ["Content-Type": "application/json"]
        )!
        let data = Data(#"{"id":7,"name":"Mina"}"#.utf8)
        client?.urlProtocol(self, didReceive: response, cacheStoragePolicy: .notAllowed)
        client?.urlProtocol(self, didLoad: data)
        client?.urlProtocolDidFinishLoading(self)
    }

    override func stopLoading() {}
}

struct User: Decodable { let id: Int; let name: String }
enum ClientError: Error { case nonHTTP; case status(Int) }

let configuration = URLSessionConfiguration.ephemeral
configuration.protocolClasses = [StubProtocol.self]
let session = URLSession(configuration: configuration)
let request = URLRequest(url: URL(string: "https://api.example.test/users/7")!)
let (data, response) = try await session.data(for: request)

guard let http = response as? HTTPURLResponse else { throw ClientError.nonHTTP }
guard (200...299).contains(http.statusCode) else {
    throw ClientError.status(http.statusCode)
}

let user = try JSONDecoder().decode(User.self, from: data)
print("\(user.id): \(user.name)")

// # not executed here: Swift 6.3.3 toolchain is unavailable.
import Foundation

let configuration = URLSessionConfiguration.ephemeral
configuration.timeoutIntervalForRequest = 12
configuration.timeoutIntervalForResource = 45
configuration.waitsForConnectivity = true
configuration.allowsExpensiveNetworkAccess = false
configuration.httpAdditionalHeaders = [
    "Accept": "application/json",
    "User-Agent": "CatalogApp/1.0",
]

let session = URLSession(configuration: configuration)
configuration.timeoutIntervalForRequest = 99

print(session.configuration.timeoutIntervalForRequest)
print(session.configuration.timeoutIntervalForResource)
print(session.configuration.allowsExpensiveNetworkAccess)
session.invalidateAndCancel()

// # not executed here: Swift 6.3.3 toolchain is unavailable.
import Foundation

struct RetryPolicy {
    let maximumAttempts = 3
    let transientStatuses: Set<Int> = [408, 429, 500, 502, 503, 504]

    func permits(_ request: URLRequest, status: Int, attempt: Int) -> Bool {
        guard attempt < maximumAttempts else { return false }
        guard transientStatuses.contains(status) else { return false }
        return request.httpMethod == "GET" || request.httpMethod == "HEAD"
    }

    func fallbackDelay(after attempt: Int) -> TimeInterval {
        min(pow(2, Double(attempt - 1)), 8)
    }
}

let policy = RetryPolicy()
var get = URLRequest(url: URL(string: "https://api.example.com/items")!)
get.httpMethod = "GET"
var post = get
post.httpMethod = "POST"

print(policy.permits(get, status: 503, attempt: 1))
print(policy.permits(post, status: 503, attempt: 1))
print(policy.permits(get, status: 404, attempt: 1))
print(policy.fallbackDelay(after: 3))