import XCTest
@testable import LCEssentials

private struct UploadEcho: Decodable, Sendable, Equatable {
    let ok: Bool
}

/// Thread-safe sink for progress callbacks (invoked on an arbitrary queue).
private final class ProgressBox: @unchecked Sendable {
    private let lock = NSLock()
    private var storage: [Double] = []
    func record(_ value: Double) { lock.lock(); storage.append(value); lock.unlock() }
    var values: [Double] { lock.lock(); defer { lock.unlock() }; return storage }
}

final class APIUploadTests: 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()
    }

    private func tempCountInDir(_ dir: URL) -> Int {
        (try? FileManager.default.contentsOfDirectory(atPath: dir.path).filter {
            $0.hasPrefix("lce-multipart-")
        }.count) ?? -1
    }

    func testUploadSendsMultipartBodyAndDecodesResponse() async throws {
        StubURLProtocol.setStub(.init(statusCode: 200, body: Data(#"{"ok":true}"#.utf8)))

        var form = MultipartForm()
        form.field("caption", "hi")
        form.file("photo", data: Data([0x89, 0x50, 0x4E, 0x47]), filename: "p.png")
        let expectedBody = try Data(contentsOf: form.serialize().fileURL)

        let result: UploadEcho = try await api.upload(
            url: "https://api.example.com/media",
            form: form
        )

        XCTAssertEqual(result, UploadEcho(ok: true))
        let sent = StubURLProtocol.capturedRequests.first
        XCTAssertEqual(sent?.httpMethod, "POST")
        XCTAssertTrue(sent?.value(forHTTPHeaderField: "Content-Type")?
            .hasPrefix("multipart/form-data; boundary=") ?? false)
        // body framing matches a fresh serialize() (boundary differs per form
        // instance, so compare structure, not bytes, by re-serialising the SAME form)
        XCTAssertEqual(StubURLProtocol.lastCapturedBody?.count, expectedBody.count)
    }

    func testTempBodyFileRemovedAfterSuccess() async throws {
        StubURLProtocol.setStub(.init(statusCode: 200, body: Data(#"{"ok":true}"#.utf8)))
        let dir = FileManager.default.temporaryDirectory
        let before = tempCountInDir(dir)

        var form = MultipartForm()
        form.file("f", data: Data("x".utf8), filename: "a.txt")
        let _: UploadEcho = try await api.upload(url: "https://api.example.com/x", form: form)

        XCTAssertEqual(tempCountInDir(dir), before)
    }

    func testTempBodyFileRemovedAfterThrow() async {
        StubURLProtocol.setStub(.init(statusCode: 500, body: Data(#"{"error":"boom"}"#.utf8)))
        let dir = FileManager.default.temporaryDirectory
        let before = tempCountInDir(dir)

        var form = MultipartForm()
        form.file("f", data: Data("x".utf8), filename: "a.txt")
        do {
            let _: UploadEcho = try await api.upload(url: "https://api.example.com/x", form: form)
            XCTFail("expected throw")
        } catch {
            // expected
        }
        XCTAssertEqual(tempCountInDir(dir), before)
    }

    @available(iOS 15.0, *)
    func testProgressOverloadDeliversFinalCompletionAndDecodes() async throws {
        StubURLProtocol.setStub(.init(statusCode: 200, body: Data(#"{"ok":true}"#.utf8)))

        var form = MultipartForm()
        form.file("f", data: Data(repeating: 0x41, count: 4096), filename: "a.bin")

        let progressBox = ProgressBox()
        let result: UploadEcho = try await api.upload(
            url: "https://api.example.com/x",
            form: form,
            onProgress: { progressBox.record($0) }
        )

        XCTAssertEqual(result, UploadEcho(ok: true))
        let values = progressBox.values
        XCTAssertEqual(values.last, 1.0, "final progress must be 1.0")
        XCTAssertTrue(values.allSatisfy { $0 >= 0 && $0 <= 1 })
        XCTAssertEqual(values, values.sorted(), "progress must be monotonic non-decreasing")
    }

    func testUploadServerErrorThrowsWithStatus() async {
        StubURLProtocol.setStub(.init(statusCode: 413, body: Data(#"{"error":"too big"}"#.utf8)))
        var form = MultipartForm()
        form.file("f", data: Data("x".utf8), filename: "a.txt")
        do {
            let _: UploadEcho = try await api.upload(url: "https://api.example.com/x", form: form)
            XCTFail("expected throw")
        } catch let error as NSError {
            XCTAssertEqual(error.code, 413)
        } catch {
            XCTFail("wrong error: \(error)")
        }
    }
}