LCEssentials/Tests/LCEssentialsTests/APIRequestTests.swift

import XCTest
@testable import LCEssentials

private struct Echo: Decodable, Sendable, Equatable {
    let id: Int
    let name: String
}

private struct CreateDTO: Encodable, Sendable {
    let name: String
}

final class APIRequestTests: XCTestCase {

    private var api: API!

    override func setUp() {
        super.setUp()
        let cfg = URLSessionConfiguration.ephemeral
        cfg.protocolClasses = [StubURLProtocol.self]
        api = API(testConfiguration: cfg)
    }

    override func tearDown() {
        StubURLProtocol.reset()
        api = nil
        super.tearDown()
    }

    func testJSONBodyRequestSendsEncodedBodyAndDecodesResponse() async throws {
        var stub = StubURLProtocol.Stub()
        stub.statusCode = 200
        stub.body = Data(#"{"id":10,"name":"x"}"#.utf8)
        StubURLProtocol.setStub(stub)

        let result: Echo = try await api.request(
            url: "https://api.example.com/users",
            method: .post,
            body: jsonBody(CreateDTO(name: "x"))
        )

        XCTAssertEqual(result, Echo(id: 10, name: "x"))
        let sent = StubURLProtocol.capturedRequests.first
        XCTAssertEqual(sent?.httpMethod, "POST")
        XCTAssertEqual(sent?.value(forHTTPHeaderField: "Content-Type"), "application/json; charset=UTF-8")
        XCTAssertEqual(StubURLProtocol.lastCapturedBody, Data(#"{"name":"x"}"#.utf8))
    }

    func testCustomHeaderOverridesDefault() async throws {
        StubURLProtocol.setStub(.init(statusCode: 200, body: Data(#"{"id":1,"name":"a"}"#.utf8)))

        let _: Echo = try await api.request(
            url: "https://api.example.com/x",
            method: .get,
            headers: ["Accept": "application/xml"]
        )

        XCTAssertEqual(StubURLProtocol.capturedRequests.first?.value(forHTTPHeaderField: "Accept"),
                       "application/xml")
    }

    func testPathParamsSubstitution() async throws {
        StubURLProtocol.setStub(.init(statusCode: 200, body: Data(#"{"id":42,"name":"a"}"#.utf8)))

        let _: Echo = try await api.request(
            url: "https://api.example.com/users/{id}/posts",
            method: .get,
            pathParams: ["id": "42"]
        )

        XCTAssertEqual(StubURLProtocol.capturedRequests.first?.url?.absoluteString,
                       "https://api.example.com/users/42/posts")
    }

    func testStringResponsePassthroughSkipsJSONDecoding() async throws {
        StubURLProtocol.setStub(.init(statusCode: 200,
                                      headers: ["Content-Type": "text/plain"],
                                      body: Data("plain hello".utf8)))

        let text: String = try await api.request(url: "https://api.example.com/ping", method: .get)
        XCTAssertEqual(text, "plain hello")
    }

    func testClientErrorThrowsNSErrorWithStatusAndBody() async {
        StubURLProtocol.setStub(.init(statusCode: 422,
                                      body: Data(#"{"error":"invalid"}"#.utf8)))

        do {
            let _: Echo = try await api.request(url: "https://api.example.com/x", method: .post,
                                                body: jsonBody(CreateDTO(name: "")))
            XCTFail("expected throw")
        } catch let error as NSError {
            XCTAssertEqual(error.code, 422)
            XCTAssertTrue(error.localizedFailureReason?.contains("invalid") ?? false,
                          "reason: \(error.localizedFailureReason ?? "nil")")
        }
    }

    func testPersistConnectionRetriesButIsBoundedOnPermanentClientError() async {
        StubURLProtocol.setStub(.init(statusCode: 400, body: Data(#"{"error":"nope"}"#.utf8)))

        do {
            let _: Echo = try await api.request(url: "https://api.example.com/x",
                                                method: .get, persistConnection: true)
            XCTFail("expected throw after retries exhausted")
        } catch let error as NSError {
            XCTAssertEqual(error.code, 400)
        } catch {
            XCTFail("unexpected error type: \(error)")
        }

        // retried, but did NOT loop forever
        XCTAssertGreaterThanOrEqual(StubURLProtocol.requestCount, 2)
        XCTAssertLessThanOrEqual(StubURLProtocol.requestCount, API.maxPersistRetries + 1)
    }

    func testNoPersistConnectionDoesNotRetry() async {
        StubURLProtocol.setStub(.init(statusCode: 400, body: Data(#"{"error":"nope"}"#.utf8)))
        let _: Echo? = try? await api.request(url: "https://api.example.com/x", method: .get)
        XCTAssertEqual(StubURLProtocol.requestCount, 1)
    }
}