import XCTest
@testable import LCFeatureControl
@testable import LCEssentials

final class FeatureControlExposureTests: 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 makeManager() -> FeatureControlManager {
        let config = FeatureControlConfiguration(baseURL: "https://api.example.com",
                                                 environment: "production",
                                                 auth: FeatureControlHeaderAuth(headers: [:]))
        return FeatureControlManager(configuration: config, api: api)
    }

    private func event(_ index: Int) -> FeatureControlExposureEvent {
        FeatureControlExposureEvent(featureKey: "fc.checkout_v2", variant: "on",
                                    subjectType: .customer, storeId: "store_\(index)")
    }

    func testFlushSendsSingleBatchUnderLimit() async {
        StubURLProtocol.setStub(.init(statusCode: 200, body: Data(#"{"error":false,"code":"OK"}"#.utf8)))
        let manager = makeManager()
        for i in 0..<10 { await manager.recordExposure(event(i)) }

        await manager.flushExposures()

        XCTAssertEqual(StubURLProtocol.requestCount, 1)
    }

    func testFlushSplitsIntoMultipleBatchesOverLimit() async {
        StubURLProtocol.setStub(.init(statusCode: 200, body: Data(#"{"error":false,"code":"OK"}"#.utf8)))
        let manager = makeManager()
        for i in 0..<130 { await manager.recordExposure(event(i)) }

        await manager.flushExposures()

        XCTAssertEqual(StubURLProtocol.requestCount, 2)
    }

    func testFailedBatchIsDroppedNotRetriedIndefinitely() async {
        StubURLProtocol.setStub(.init(statusCode: 500, body: Data()))
        let manager = makeManager()
        for i in 0..<10 { await manager.recordExposure(event(i)) }

        await manager.flushExposures() // must not throw, must not hang

        XCTAssertEqual(StubURLProtocol.requestCount, 1)

        // buffer was cleared even though the batch failed — a second flush sends nothing new
        StubURLProtocol.reset()
        StubURLProtocol.setStub(.init(statusCode: 200, body: Data(#"{"error":false,"code":"OK"}"#.utf8)))
        await manager.flushExposures()
        XCTAssertEqual(StubURLProtocol.requestCount, 0)
    }
}