import XCTest
@testable import MCT

final class LayoutEngineTests: XCTestCase {
    let screenBounds = CGRect(x: 0, y: 0, width: 1920, height: 1080)

    // MARK: - Helpers

    private func makeWindow(
        id: CGWindowID,
        title: String,
        appName: String,
        bundleID: String
    ) -> WindowInfo {
        WindowInfo(
            windowID: id,
            title: title,
            appName: appName,
            appBundleID: bundleID,
            appIcon: nil,
            frame: CGRect(x: 0, y: 0, width: 800, height: 600),
            pid: pid_t(id),
            isOnScreen: true,
            thumbnail: nil
        )
    }

    private func makeSnapshot(windows: [WindowInfo]) -> WindowSnapshot {
        let groups = WindowEnumerator.groupWindows(windows)
        return WindowSnapshot(groups: groups)
    }

    // MARK: - Grouping Tests

    func testGroupingByApp() {
        let windows = [
            makeWindow(id: 1, title: "Doc 1", appName: "Safari", bundleID: "com.apple.Safari"),
            makeWindow(id: 2, title: "Doc 2", appName: "Safari", bundleID: "com.apple.Safari"),
            makeWindow(id: 3, title: "Main", appName: "Xcode", bundleID: "com.apple.dt.Xcode"),
        ]

        let groups = WindowEnumerator.groupWindows(windows)
        XCTAssertEqual(groups.count, 2)
        // Safari has frontmost window (index 0), so it should be first
        XCTAssertEqual(groups[0].appBundleID, "com.apple.Safari")
        XCTAssertEqual(groups[0].windows.count, 2)
        XCTAssertEqual(groups[1].appBundleID, "com.apple.dt.Xcode")
        XCTAssertEqual(groups[1].windows.count, 1)
    }

    func testGroupOrderingFrontmostFirst() {
        let windows = [
            makeWindow(id: 1, title: "Main", appName: "Xcode", bundleID: "com.apple.dt.Xcode"),
            makeWindow(id: 2, title: "Tab 1", appName: "Safari", bundleID: "com.apple.Safari"),
            makeWindow(id: 3, title: "Tab 2", appName: "Safari", bundleID: "com.apple.Safari"),
        ]

        let groups = WindowEnumerator.groupWindows(windows)
        // Xcode has the frontmost window (index 0), so it should be first
        XCTAssertEqual(groups[0].appBundleID, "com.apple.dt.Xcode")
        XCTAssertEqual(groups[1].appBundleID, "com.apple.Safari")
    }

    // MARK: - Layout Tests

    func testLayoutProducesItemsForAllWindows() {
        let windows = [
            makeWindow(id: 1, title: "W1", appName: "App", bundleID: "com.test.app"),
            makeWindow(id: 2, title: "W2", appName: "App", bundleID: "com.test.app"),
            makeWindow(id: 3, title: "W3", appName: "Other", bundleID: "com.test.other"),
        ]

        let engine = LayoutEngine()
        let snapshot = makeSnapshot(windows: windows)
        let result = engine.layout(snapshot: snapshot, screenBounds: screenBounds)

        XCTAssertEqual(result.items.count, 3)
        XCTAssertEqual(result.headers.count, 2)
    }

    func testLayoutItemsWithinScreenBounds() {
        let windows = (1...6).map { i in
            makeWindow(id: CGWindowID(i), title: "Win \(i)", appName: "App", bundleID: "com.test.app")
        }

        let engine = LayoutEngine()
        let snapshot = makeSnapshot(windows: windows)
        let result = engine.layout(snapshot: snapshot, screenBounds: screenBounds)

        for item in result.items {
            XCTAssertTrue(
                screenBounds.contains(CGPoint(x: item.frame.midX, y: item.frame.midY)),
                "Item center \(item.frame) should be within screen bounds \(screenBounds)"
            )
        }
    }

    // MARK: - Fingerprint / Stability Tests

    func testSnapshotFingerprint() {
        let windows = [
            makeWindow(id: 1, title: "Doc", appName: "Safari", bundleID: "com.apple.Safari"),
            makeWindow(id: 2, title: "Main", appName: "Xcode", bundleID: "com.apple.dt.Xcode"),
        ]

        let snapshot = makeSnapshot(windows: windows)
        XCTAssertEqual(snapshot.fingerprint.count, 2)
        XCTAssertTrue(snapshot.fingerprint.contains("com.apple.Safari|Doc"))
        XCTAssertTrue(snapshot.fingerprint.contains("com.apple.dt.Xcode|Main"))
    }

    func testOverlapRatioIdentical() {
        let windows = [
            makeWindow(id: 1, title: "Doc", appName: "Safari", bundleID: "com.apple.Safari"),
        ]

        let s1 = makeSnapshot(windows: windows)
        let s2 = makeSnapshot(windows: windows)
        XCTAssertEqual(s1.overlapRatio(with: s2), 1.0)
    }

    func testOverlapRatioDisjoint() {
        let w1 = [makeWindow(id: 1, title: "A", appName: "App1", bundleID: "com.a")]
        let w2 = [makeWindow(id: 2, title: "B", appName: "App2", bundleID: "com.b")]

        let s1 = makeSnapshot(windows: w1)
        let s2 = makeSnapshot(windows: w2)
        XCTAssertEqual(s1.overlapRatio(with: s2), 0.0)
    }

    func testOverlapRatioPartial() {
        let shared = makeWindow(id: 1, title: "Shared", appName: "App", bundleID: "com.app")
        let w1 = [shared, makeWindow(id: 2, title: "Only1", appName: "X", bundleID: "com.x")]
        let w2 = [shared, makeWindow(id: 3, title: "Only2", appName: "Y", bundleID: "com.y")]

        let s1 = makeSnapshot(windows: w1)
        let s2 = makeSnapshot(windows: w2)
        // intersection = 1 (shared), union = 3 (shared, Only1, Only2)
        XCTAssertEqual(s1.overlapRatio(with: s2), 1.0 / 3.0, accuracy: 0.001)
    }

    // MARK: - Stability Tests

    func testStableLayoutSameWindows() {
        let windows = [
            makeWindow(id: 1, title: "W1", appName: "App", bundleID: "com.test"),
            makeWindow(id: 2, title: "W2", appName: "App", bundleID: "com.test"),
        ]

        let engine = LayoutEngine()
        let snapshot = makeSnapshot(windows: windows)

        let result1 = engine.layout(snapshot: snapshot, screenBounds: screenBounds)
        let result2 = engine.layout(snapshot: snapshot, screenBounds: screenBounds)

        // Same windows should produce same positions
        for (item1, item2) in zip(result1.items, result2.items) {
            XCTAssertEqual(item1.frame.origin.x, item2.frame.origin.x, accuracy: 1.0)
            XCTAssertEqual(item1.frame.origin.y, item2.frame.origin.y, accuracy: 1.0)
        }
    }

    // MARK: - Geometry Tests

    func testThumbnailSizeFitsOnScreen() {
        let (size, cols) = LayoutGeometry.uniformThumbnailSize(
            groupWindowCounts: [4, 4, 4, 4, 4],
            availableWidth: 1920 - LayoutGeometry.margin * 2,
            availableHeight: 1080 - LayoutGeometry.margin * 2
        )
        XCTAssertGreaterThan(size.width, 0)
        XCTAssertGreaterThan(cols, 0)
    }

    func testAspectFit() {
        let fitted = LayoutGeometry.aspectFit(
            source: CGSize(width: 1600, height: 900),
            target: CGSize(width: 320, height: 200)
        )
        XCTAssertLessThanOrEqual(fitted.width, 320)
        XCTAssertLessThanOrEqual(fitted.height, 200)
        // Aspect ratio should be preserved
        let sourceRatio = 1600.0 / 900.0
        let fittedRatio = fitted.width / fitted.height
        XCTAssertEqual(sourceRatio, fittedRatio, accuracy: 0.01)
    }
}