import XCTest
@testable import NetworkCityCore

final class TrafficDifferTests: XCTestCase {

    private func conn(_ host: String, in bIn: UInt64, out bOut: UInt64) -> Connection {
        Connection(
            proto: .tcp4,
            local: Endpoint(host: "192.168.1.2", port: 5000),
            remote: Endpoint(host: host, port: 443),
            bytesIn: bIn, bytesOut: bOut,
            processName: "test", pid: 1
        )
    }

    func testFirstSnapshotYieldsNoDeltas() {
        let differ = TrafficDiffer()
        let t0 = Date(timeIntervalSince1970: 1000)
        let deltas = differ.ingest(ConnectionSnapshot(timestamp: t0, connections: [conn("1.1.1.1", in: 100, out: 50)]))
        XCTAssertTrue(deltas.isEmpty)   // need two readings to know a rate
    }

    func testComputesDeltaAndRate() {
        let differ = TrafficDiffer()
        let t0 = Date(timeIntervalSince1970: 1000)
        let t1 = Date(timeIntervalSince1970: 1002)   // +2s
        _ = differ.ingest(ConnectionSnapshot(timestamp: t0, connections: [conn("1.1.1.1", in: 100, out: 50)]))
        let deltas = differ.ingest(ConnectionSnapshot(timestamp: t1, connections: [conn("1.1.1.1", in: 1124, out: 50)]))

        XCTAssertEqual(deltas.count, 1)
        XCTAssertEqual(deltas[0].bytesInDelta, 1024)
        XCTAssertEqual(deltas[0].bytesOutDelta, 0)
        XCTAssertEqual(deltas[0].inBytesPerSec, 512, accuracy: 0.001)   // 1024 / 2s
    }

    func testCounterResetTreatedAsZero() {
        let differ = TrafficDiffer()
        let t0 = Date(timeIntervalSince1970: 1000)
        let t1 = Date(timeIntervalSince1970: 1002)
        _ = differ.ingest(ConnectionSnapshot(timestamp: t0, connections: [conn("1.1.1.1", in: 9999, out: 0)]))
        let deltas = differ.ingest(ConnectionSnapshot(timestamp: t1, connections: [conn("1.1.1.1", in: 10, out: 0)]))
        XCTAssertTrue(deltas.isEmpty)   // reused tuple, counter dropped -> no phantom delta
    }
}