import XCTest
import Foundation
import ForgeGrade
import ForgeColor
@testable import ForgeCamera

/// Counts pushes with timestamps.
actor CountingDriver: CameraDriver {
    nonisolated let capabilities = CameraCapabilities(
        vendor: .simulated, supportsNativeCDL: true, lut3dSizes: [17, 33], metadataFields: [])

    private(set) var pushes = [(look: FlattenedLook, at: ContinuousClock.Instant)]()

    nonisolated var state: AsyncStream<CameraState> {
        AsyncStream { _ in }
    }

    func connect() async throws {}
    func disconnect() async {}
    func push(look: FlattenedLook) async throws {
        pushes.append((look, ContinuousClock.now))
    }
}

final class DebouncedPushTests: XCTestCase {

    func grade(slope: Float) -> GradeStack {
        GradeStack(nodes: [GradeNode(kind: .cdl(CDL(
            slope: SIMD3(repeating: slope), offset: .zero, power: .one, saturation: 1)))])
    }

    // Rapid updates coalesce: >= 1 push, far fewer than updates, trailing value wins.
    func testCoalescing() async throws {
        let driver = CountingDriver()
        let pusher = DebouncedPusher(driver: driver, interval: .milliseconds(50), latticeSize: 17)

        // 30 rapid updates (panel spin).
        for i in 0..<30 {
            await pusher.update(grade: grade(slope: 1.0 + Float(i) * 0.01))
            try await Task.sleep(for: .milliseconds(2))
        }
        // Allow trailing push to flush.
        try await Task.sleep(for: .milliseconds(150))

        let pushes = await driver.pushes
        XCTAssertGreaterThanOrEqual(pushes.count, 1)
        XCTAssertLessThan(pushes.count, 10, "expected coalescing, got \(pushes.count) pushes for 30 updates")
        // Trailing edge: final pushed look reflects last update (slope 1.29).
        let lastCDL = pushes.last!.look.cdl
        XCTAssertEqual(lastCDL?.slope.x ?? 0, 1.29, accuracy: 1e-4)
        await pusher.stop()
    }

    // Single update pushes exactly once.
    func testSingleUpdateSinglePush() async throws {
        let driver = CountingDriver()
        let pusher = DebouncedPusher(driver: driver, interval: .milliseconds(30), latticeSize: 17)
        await pusher.update(grade: grade(slope: 1.5))
        try await Task.sleep(for: .milliseconds(120))
        let pushes = await driver.pushes
        XCTAssertEqual(pushes.count, 1)
        await pusher.stop()
    }

    // Pushes respect min interval spacing.
    func testMinIntervalRespected() async throws {
        let driver = CountingDriver()
        let pusher = DebouncedPusher(driver: driver, interval: .milliseconds(60), latticeSize: 17)
        for i in 0..<20 {
            await pusher.update(grade: grade(slope: 1.0 + Float(i) * 0.01))
            try await Task.sleep(for: .milliseconds(10))
        }
        try await Task.sleep(for: .milliseconds(200))
        let pushes = await driver.pushes
        for pair in zip(pushes, pushes.dropFirst()) {
            let gap = pair.0.at.duration(to: pair.1.at)
            XCTAssertGreaterThanOrEqual(gap, .milliseconds(55), "pushes too close: \(gap)")
        }
        await pusher.stop()
    }

    // Independent pushers per camera: no cross-interference.
    func testPerCameraIndependence() async throws {
        let driverA = CountingDriver()
        let driverB = CountingDriver()
        let pusherA = DebouncedPusher(driver: driverA, interval: .milliseconds(30), latticeSize: 17)
        let pusherB = DebouncedPusher(driver: driverB, interval: .milliseconds(30), latticeSize: 17)

        await pusherA.update(grade: grade(slope: 1.1))
        // B gets nothing.
        try await Task.sleep(for: .milliseconds(120))
        let pushesA = await driverA.pushes
        let pushesB = await driverB.pushes
        XCTAssertEqual(pushesA.count, 1)
        XCTAssertEqual(pushesB.count, 0)
        await pusherA.stop()
        await pusherB.stop()
    }

    // stop() cancels pending trailing push.
    func testStopCancelsPending() async throws {
        let driver = CountingDriver()
        let pusher = DebouncedPusher(driver: driver, interval: .milliseconds(100), latticeSize: 17)
        await pusher.update(grade: grade(slope: 1.2))
        await pusher.update(grade: grade(slope: 1.3)) // pending trailing
        await pusher.stop()
        try await Task.sleep(for: .milliseconds(200))
        let pushes = await driver.pushes
        // First push may have fired immediately; trailing must not after stop.
        XCTAssertLessThanOrEqual(pushes.count, 1)
    }
}