import AppKit
import CoreGraphics
import Darwin
import Foundation
import ImageIO
import ShotdeckCore

/// In-process self-test for the region picker, driven by `SHOTDECK_PICKER_SELFTEST`.
/// Posts synthetic mouse events through `NSApp.postEvent` only — never CGEventPost/taps.
@MainActor
enum PickerSelfTest {
    private static let pointA = NSPoint(x: 200, y: 300)
    private static let pointB = NSPoint(x: 600, y: 600)
    private static let dragSteps = 6

    /// Called from `main.swift` before `ShotdeckApp.main()`. Returns immediately when the
    /// env var is unset; otherwise waits for launch, drives the production picker, and `exit`s.
    static func runIfRequested() {
        guard let raw = ProcessInfo.processInfo.environment["SHOTDECK_PICKER_SELFTEST"],
              !raw.isEmpty
        else { return }

        let output = URL(fileURLWithPath: raw, isDirectory: true)
        // Hop onto a plain main-queue turn after NSApp starts. Nested run loops
        // from a Swift Task do not drain NSApp's event queue.
        DispatchQueue.main.async {
            MainActor.assumeIsolated {
                execute(outputDirectory: output)
            }
        }
    }

    /// Standalone HISTORY phase when `SHOTDECK_HISTORY_SELFTEST` is set without
    /// the picker chain. Waits for NSApp like the other phases, then exits.
    static func runHistoryIfRequested() {
        guard let raw = ProcessInfo.processInfo.environment["SHOTDECK_HISTORY_SELFTEST"],
              !raw.isEmpty
        else { return }
        _ = raw
        DispatchQueue.main.async {
            MainActor.assumeIsolated {
                runHistoryPhase()
            }
        }
    }

    private static func execute(outputDirectory: URL) {
        do {
            try FileManager.default.createDirectory(
                at: outputDirectory,
                withIntermediateDirectories: true
            )
        } catch {
            fail(expected: expectedLabel(), got: "could not create output dir: \(error)")
        }

        guard let screen = NSScreen.screens.first(where: { $0.frame.contains(pointA) })
            ?? NSScreen.screens.first
        else {
            fail(expected: expectedLabel(), got: "no NSScreen")
        }

        let appKitRect = CGRect(
            x: min(pointA.x, pointB.x),
            y: min(pointA.y, pointB.y),
            width: abs(pointB.x - pointA.x),
            height: abs(pointB.y - pointA.y)
        ).intersection(screen.frame)
        let expected = CaptureRegion.fromAppKit(rect: appKitRect, on: screen)

        let picker = RegionPickerController()
        var result: CaptureRegion??
        picker.pick { region in
            result = .some(region)
        }

        guard let overlay = overlayWindow(containing: pointA) else {
            fail(expected: format(expected.rect), got: "no overlay window after pick()")
        }
        overlay.makeKey()

        var eventNumber = 1
        func post(_ type: NSEvent.EventType, at screenPoint: NSPoint, clickCount: Int) {
            let locationInWindow = overlay.convertPoint(fromScreen: screenPoint)
            guard let event = NSEvent.mouseEvent(
                with: type,
                location: locationInWindow,
                modifierFlags: [],
                timestamp: ProcessInfo.processInfo.systemUptime,
                windowNumber: overlay.windowNumber,
                context: nil,
                eventNumber: eventNumber,
                clickCount: clickCount,
                pressure: 1
            ) else {
                fail(expected: format(expected.rect), got: "NSEvent.mouseEvent(\(type.rawValue)) returned nil")
            }
            eventNumber += 1
            NSApp.postEvent(event, atStart: false)
            // Local monitors run during NSApp.sendEvent (production dispatch),
            // not during nextEvent dequeue. Drive that same path here.
            NSApp.sendEvent(event)
        }

        post(.leftMouseDown, at: pointA, clickCount: 1)
        for step in 1...(dragSteps / 2) {
            post(.leftMouseDragged, at: interpolate(step), clickCount: 0)
        }

        writeOverlayBitmap(overlay, to: outputDirectory.appendingPathComponent("overlay-middrag.png"))

        for step in ((dragSteps / 2) + 1)...dragSteps {
            post(.leftMouseDragged, at: interpolate(step), clickCount: 0)
        }
        post(.leftMouseUp, at: pointB, clickCount: 1)

        guard let wrapped = result else {
            fail(expected: format(expected.rect), got: "completion never fired")
        }
        guard let got = wrapped else {
            fail(expected: format(expected.rect), got: "nil")
        }

        if got.rect != expected.rect {
            fail(expected: format(expected.rect), got: format(got.rect))
        }

        print("PICKER-SELFTEST PASS rect=\(format(got.rect))")
        fflush(stdout)

        runRegionPersistPhase()
        // Hop off this MainActor job so the SEND-TRUTH Task can run; do not
        // exit(0) here — runSendTruthPhase prints its own PASS/FAIL, then
        // chains to HISTORY, then UPDATE-SELFTEST (or exits if that phase is
        // not requested).
        runSendTruthPhase()
    }

    /// Phase 2: writes a known region under `CaptureRegion.defaultsKey`, reloads it through
    /// `AppModel.loadPersistedRegion()` (the same path init uses), then restores whatever
    /// value was stored before so a real picked region is untouched.
    private static func runRegionPersistPhase() {
        let defaults = UserDefaults.standard
        let previous = defaults.data(forKey: CaptureRegion.defaultsKey)

        let known = CaptureRegion(
            displayID: CGMainDisplayID(),
            rect: CGRect(x: 10, y: 10, width: 100, height: 100),
            capturedScale: 2.0
        )
        var failure: String?
        if let encoded = try? JSONEncoder().encode(known) {
            defaults.set(encoded, forKey: CaptureRegion.defaultsKey)
            if let loaded = AppModel.loadPersistedRegion() {
                if loaded.rect != known.rect {
                    failure = "expected=\(format(known.rect)) got=\(format(loaded.rect))"
                }
            } else {
                failure = "loadPersistedRegion returned nil"
            }
        } else {
            failure = "could not encode CaptureRegion"
        }

        if let previous {
            defaults.set(previous, forKey: CaptureRegion.defaultsKey)
        } else {
            defaults.removeObject(forKey: CaptureRegion.defaultsKey)
        }

        if let failure {
            print("REGION-PERSIST FAIL \(failure)")
            fflush(stdout)
            exit(1)
        }
        print("REGION-PERSIST PASS")
        fflush(stdout)
    }

    /// Phase 3: drive SendController's share-outcome seams with no AirDrop sheet.
    /// Fail path must leave the session open in the temp spool; success path archives
    /// and mints a fresh empty session. Scheduled as a new MainActor job because this
    /// function is called from inside `execute()` — a nested run-loop wait would never
    /// let the Task start. On success, chains to HISTORY instead of exiting.
    private static func runSendTruthPhase() {
        Task { @MainActor in
            do {
                try await executeSendTruth()
                print("SEND-TRUTH PASS")
                fflush(stdout)
            } catch {
                print("SEND-TRUTH FAIL \(error)")
                fflush(stdout)
                exit(1)
            }
            runHistoryPhase()
        }
    }

    /// Phase 4: drive HistoryStore record/prune in a temp root. Env-gated by
    /// `SHOTDECK_HISTORY_SELFTEST` the same way UPDATE is gated, and also runs
    /// whenever the picker self-test chain is already in flight so a full
    /// self-test prints HISTORY PASS|FAIL. Chains to UPDATE-SELFTEST (or exits).
    private static func runHistoryPhase() {
        let historyRequested = ProcessInfo.processInfo.environment["SHOTDECK_HISTORY_SELFTEST"]
        let pickerRequested = ProcessInfo.processInfo.environment["SHOTDECK_PICKER_SELFTEST"]
        let shouldRun = (historyRequested.map { !$0.isEmpty } ?? false)
            || (pickerRequested.map { !$0.isEmpty } ?? false)
        guard shouldRun else {
            if !startUpdateSelfTestIfRequested() {
                exit(0)
            }
            return
        }

        Task { @MainActor in
            do {
                try await executeHistorySelfTest()
                print("HISTORY PASS")
                fflush(stdout)
                if !startUpdateSelfTestIfRequested() {
                    exit(0)
                }
            } catch {
                print("HISTORY FAIL \(error)")
                fflush(stdout)
                exit(1)
            }
        }
    }

    private static func executeHistorySelfTest() async throws {
        let fm = FileManager.default
        let root = fm.temporaryDirectory
            .appendingPathComponent("shotdeck-history-selftest-\(UUID().uuidString)", isDirectory: true)
        defer { try? fm.removeItem(at: root) }

        let paths = try AppSupportPaths(
            root: root.appendingPathComponent("root", isDirectory: true),
            outbox: root.appendingPathComponent("outbox", isDirectory: true),
            watchFolder: root.appendingPathComponent("watch", isDirectory: true)
        )
        let store = try HistoryStore(paths: paths)
        let sources = root.appendingPathComponent("user-sources", isDirectory: true)
        try fm.createDirectory(at: sources, withIntermediateDirectories: true)

        var recorded: [HistoryEntry] = []
        for i in 0..<12 {
            let source = sources.appendingPathComponent("source-\(i).pdf")
            try Data("%PDF-1.4\n%hist-\(i)\n%%EOF\n".utf8).write(to: source)
            let entry = try await store.recordSentPDF(
                sourceURL: source,
                sessionID: UUID(),
                pageCount: 1,
                sentAt: Date(timeIntervalSince1970: 1_800_000_000 + TimeInterval(i))
            )
            recorded.append(entry)
            let onDisk = try Data(contentsOf: source)
            guard onDisk == Data("%PDF-1.4\n%hist-\(i)\n%%EOF\n".utf8) else {
                throw HistorySelfTestError.detail("user source PDF was modified: \(source.path)")
            }
        }

        let listed = await store.listPDFs()
        guard listed.count == 10 else {
            throw HistorySelfTestError.detail("listPDFs count \(listed.count) want 10")
        }
        let wantNewest = Array(recorded.suffix(10).reversed())
        guard listed.map(\.id) == wantNewest.map(\.id) else {
            throw HistorySelfTestError.detail("listPDFs did not return the 10 newest")
        }
        let pdfsDir = paths.root.appendingPathComponent("history/pdfs", isDirectory: true)
        for entry in recorded.prefix(2) {
            let gone = pdfsDir.appendingPathComponent(entry.fileName)
            guard !fm.fileExists(atPath: gone.path) else {
                throw HistorySelfTestError.detail("oldest PDF still on disk: \(gone.path)")
            }
        }

        let same = sources.appendingPathComponent("same.pdf")
        try Data("%PDF-1.4\n%same\n%%EOF\n".utf8).write(to: same)
        let first = try await store.recordSentPDF(
            sourceURL: same, sessionID: nil, pageCount: 1,
            sentAt: Date(timeIntervalSince1970: 1_800_000_100)
        )
        let second = try await store.recordSentPDF(
            sourceURL: same, sessionID: nil, pageCount: 1,
            sentAt: Date(timeIntervalSince1970: 1_800_000_101)
        )
        guard first.id != second.id, first.fileURL.path != second.fileURL.path,
              fm.fileExists(atPath: first.fileURL.path),
              fm.fileExists(atPath: second.fileURL.path),
              fm.fileExists(atPath: same.path)
        else {
            throw HistorySelfTestError.detail("re-record same source did not produce two distinct copies")
        }

        let spool = try SpoolStore(paths: paths)
        let png = try makeTinyPNGData()
        let base = Date(timeIntervalSince1970: 1_800_100_000)
        var n = 0
        var oldestSessionID: UUID?
        for count in [5, 15, 15] {
            if n == 0 {
                oldestSessionID = try await spool.currentSession().id
            }
            for _ in 0..<count {
                _ = try await spool.append(
                    pngData: png, pixelWidth: 64, pixelHeight: 48, scale: 1,
                    capturedAt: base.addingTimeInterval(TimeInterval(n))
                )
                n += 1
            }
            _ = try await spool.archiveCurrent(pdfFileName: "Redline-hist-\(n).pdf")
        }
        let openCapture = try await spool.append(
            pngData: png, pixelWidth: 64, pixelHeight: 48, scale: 1,
            capturedAt: Date(timeIntervalSince1970: 1_900_000_000)
        )
        let openSession = try await spool.currentSession()
        let openPNG = paths.sessionDirectory(openSession.id).appendingPathComponent(openCapture.fileName)
        let openBytes = try Data(contentsOf: openPNG)

        try await store.pruneImages()

        let images = try await store.listImages(limit: 50)
        guard images.count == 30 else {
            throw HistorySelfTestError.detail("listImages count \(images.count) want 30")
        }
        if let oldestSessionID {
            let oldDir = paths.archiveDirectory(oldestSessionID)
            guard !fm.fileExists(atPath: oldDir.path) else {
                throw HistorySelfTestError.detail("emptied archive session still on disk")
            }
        }
        guard fm.fileExists(atPath: openPNG.path), try Data(contentsOf: openPNG) == openBytes else {
            throw HistorySelfTestError.detail("open session PNG was touched")
        }
        let remainingOpen = try await spool.currentSession()
        guard remainingOpen.id == openSession.id,
              remainingOpen.captures.map(\.id) == [openCapture.id]
        else {
            throw HistorySelfTestError.detail("open session manifest was touched")
        }
    }

    private static func executeSendTruth() async throws {
        let fm = FileManager.default
        let root = fm.temporaryDirectory
            .appendingPathComponent("shotdeck-send-truth-\(UUID().uuidString)", isDirectory: true)
        defer { try? fm.removeItem(at: root) }

        let paths = try AppSupportPaths(
            root: root,
            outbox: root.appendingPathComponent("outbox", isDirectory: true),
            watchFolder: root.appendingPathComponent("watch", isDirectory: true)
        )
        let ledger = try ReturnLedger(paths: paths)
        let model = try AppModel(
            paths: paths,
            spool: try SpoolStore(paths: paths),
            composer: PDFComposer(),
            capturer: ScreenCapturer(),
            hotkeys: HotkeyCenter(),
            picker: RegionPickerController(),
            ledger: ledger,
            watcher: ReturnWatcher(paths: paths, ledger: ledger)
        )
        model.setFolderURLs(outbox: paths.outbox, watch: paths.watchFolder)

        let png = try makeTinyPNGData()
        _ = try await model.spool.append(
            pngData: png,
            pixelWidth: 64,
            pixelHeight: 48,
            scale: 1,
            capturedAt: Date()
        )
        model.replaceSession(try await model.spool.currentSession())
        let openID = model.session.id
        guard !model.session.isEmpty else {
            sendTruthFail("seeded session was empty")
        }

        let pending = try await model.composePDFForSend()
        guard fm.fileExists(atPath: pending.fileURL.path) else {
            sendTruthFail("PDF was not written")
        }

        model.handleDidFailToShareItems(fileName: pending.fileName)
        let still = try await model.spool.currentSession()
        guard still.id == openID, !still.isEmpty, still.state == .open else {
            sendTruthFail("fail path archived or replaced the session")
        }
        let spoolDir = paths.sessionDirectory(openID)
        guard fm.fileExists(atPath: spoolDir.path) else {
            sendTruthFail("fail path: session missing from temp spool")
        }
        guard let status = model.statusLine, status.contains("nothing was sent") else {
            sendTruthFail("fail path status missing 'nothing was sent': \(model.statusLine ?? "nil")")
        }

        await model.handleDidShareItems(fileName: pending.fileName, pageCount: pending.pageCount)
        let fresh = try await model.spool.currentSession()
        guard fresh.isEmpty, fresh.id != openID, fresh.state == .open else {
            sendTruthFail("success path did not mint a fresh empty session")
        }
        let archived = try await model.spool.archivedSessions()
        guard archived.contains(where: { $0.id == openID && $0.state == .archived }) else {
            sendTruthFail("success path did not archive the session")
        }
        let archiveDir = paths.archiveDirectory(openID)
        guard fm.fileExists(atPath: archiveDir.path) else {
            sendTruthFail("success path: archive dir missing")
        }
        guard !fm.fileExists(atPath: spoolDir.path) else {
            sendTruthFail("success path: session still in spool")
        }
    }

    private static func makeTinyPNGData() throws -> Data {
        let width = 64
        let height = 48
        let colorSpace = CGColorSpaceCreateDeviceRGB()
        guard let context = CGContext(
            data: nil,
            width: width,
            height: height,
            bitsPerComponent: 8,
            bytesPerRow: width * 4,
            space: colorSpace,
            bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue
        ) else {
            sendTruthFail("could not create PNG context")
        }
        context.setFillColor(red: 0.2, green: 0.4, blue: 0.8, alpha: 1)
        context.fill(CGRect(x: 0, y: 0, width: width, height: height))
        guard let image = context.makeImage() else {
            sendTruthFail("could not make CGImage")
        }
        let buffer = NSMutableData()
        guard let destination = CGImageDestinationCreateWithData(
            buffer,
            "public.png" as CFString,
            1,
            nil
        ) else {
            sendTruthFail("could not create PNG destination")
        }
        CGImageDestinationAddImage(destination, image, nil)
        guard CGImageDestinationFinalize(destination) else {
            sendTruthFail("could not finalize PNG")
        }
        return buffer as Data
    }

    private static func sendTruthFail(_ reason: String) -> Never {
        print("SEND-TRUTH FAIL \(reason)")
        fflush(stdout)
        exit(1)
    }

    /// Phase 5: builds a fake 99.0.0 bundle, serves a local appcast, stages via
    /// `checkNow`, then `installStaged` into the env dir — never `/Applications`.
    /// Returns true when the async phase was scheduled (it calls `exit` itself).
    @discardableResult
    private static func startUpdateSelfTestIfRequested() -> Bool {
        guard let raw = ProcessInfo.processInfo.environment["SHOTDECK_UPDATE_SELFTEST"],
              !raw.isEmpty
        else { return false }

        let output = URL(fileURLWithPath: raw, isDirectory: true)
        Task { @MainActor in
            do {
                try await runUpdateSelfTest(outputDirectory: output)
                print("UPDATE-SELFTEST PASS version=99.0.0")
                fflush(stdout)
                exit(0)
            } catch let error as UpdateSelfTestError {
                updateFail(error.description)
            } catch {
                updateFail(String(describing: error))
            }
        }
        return true
    }

    private static func runUpdateSelfTest(outputDirectory: URL) async throws {
        let fm = FileManager.default
        try fm.createDirectory(at: outputDirectory, withIntermediateDirectories: true)

        guard let sourceApp = ownAppBundleURL() else {
            throw UpdateSelfTestError.detail("own bundle is not a .app (\(Bundle.main.bundleURL.path))")
        }

        let payload = outputDirectory.appendingPathComponent("payload", isDirectory: true)
        if fm.fileExists(atPath: payload.path) {
            try fm.removeItem(at: payload)
        }
        try fm.createDirectory(at: payload, withIntermediateDirectories: true)
        let fakeApp = payload.appendingPathComponent("Redline.app")
        try fm.copyItem(at: sourceApp, to: fakeApp)

        let plistURL = fakeApp.appendingPathComponent("Contents/Info.plist")
        let plistData = try Data(contentsOf: plistURL)
        guard var plist = try PropertyListSerialization.propertyList(from: plistData, format: nil) as? [String: Any] else {
            throw UpdateSelfTestError.detail("could not parse copied Info.plist")
        }
        plist["CFBundleShortVersionString"] = "99.0.0"
        let rewritten = try PropertyListSerialization.data(fromPropertyList: plist, format: .xml, options: 0)
        try rewritten.write(to: plistURL)

        let zipURL = outputDirectory.appendingPathComponent("Redline-99.0.0.zip")
        if fm.fileExists(atPath: zipURL.path) {
            try fm.removeItem(at: zipURL)
        }
        try runDitto(arguments: ["-c", "-k", payload.path, zipURL.path])

        let zipData = try Data(contentsOf: zipURL)
        let hex = UpdateChecker.sha256Hex(zipData)

        let appcastURL = outputDirectory.appendingPathComponent("appcast.json")
        let appcast: [String: String] = [
            "version": "99.0.0",
            "zipURL": zipURL.absoluteString,
            "sha256": hex,
            "notes": "UPDATE-SELFTEST",
        ]
        let appcastData = try JSONSerialization.data(withJSONObject: appcast, options: [.sortedKeys])
        try appcastData.write(to: appcastURL)

        let defaults = UserDefaults.standard
        let previous = defaults.string(forKey: UpdateChecker.appcastURLDefaultsKey)
        defaults.set(appcastURL.absoluteString, forKey: UpdateChecker.appcastURLDefaultsKey)
        defer {
            if let previous {
                defaults.set(previous, forKey: UpdateChecker.appcastURLDefaultsKey)
            } else {
                defaults.removeObject(forKey: UpdateChecker.appcastURLDefaultsKey)
            }
        }

        let (model, isolatedRoot) = try makeIsolatedUpdateModel()
        defer { try? fm.removeItem(at: isolatedRoot) }

        await model.updateChecker.checkNow()

        guard model.updateAvailable?.version == "99.0.0" else {
            throw UpdateSelfTestError.detail(
                "updateAvailable=\(model.updateAvailable?.version ?? "nil")"
            )
        }
        guard let staged = model.updateChecker.stagedAppURL else {
            throw UpdateSelfTestError.detail("staged payload missing")
        }
        guard staged.lastPathComponent == "Redline.app" else {
            throw UpdateSelfTestError.detail("staged name \(staged.lastPathComponent)")
        }
        let stagedExe = staged.appendingPathComponent("Contents/MacOS/Shotdeck")
        guard fm.fileExists(atPath: stagedExe.path) else {
            throw UpdateSelfTestError.detail("staged Contents/MacOS/Shotdeck missing")
        }

        let targetRoot = outputDirectory.appendingPathComponent("target", isDirectory: true)
        if fm.fileExists(atPath: targetRoot.path) {
            try fm.removeItem(at: targetRoot)
        }
        let target = targetRoot.appendingPathComponent("Redline.app")
        model.updateChecker.installStaged(to: target)

        let installedPlist = target.appendingPathComponent("Contents/Info.plist")
        guard let installed = NSDictionary(contentsOf: installedPlist) as? [String: Any],
              let installedVersion = installed["CFBundleShortVersionString"] as? String
        else {
            throw UpdateSelfTestError.detail("installed Info.plist unreadable")
        }
        guard installedVersion == "99.0.0" else {
            throw UpdateSelfTestError.detail("installed version \(installedVersion)")
        }
    }

    private static func ownAppBundleURL() -> URL? {
        let bundle = Bundle.main.bundleURL
        if bundle.pathExtension == "app" { return bundle }
        let up3 = bundle
            .deletingLastPathComponent()
            .deletingLastPathComponent()
            .deletingLastPathComponent()
        if up3.pathExtension == "app" { return up3 }
        return nil
    }

    private static func makeIsolatedUpdateModel() throws -> (AppModel, URL) {
        let root = FileManager.default.temporaryDirectory
            .appendingPathComponent("shotdeck-update-selftest-\(UUID().uuidString)", isDirectory: true)
        let paths = try AppSupportPaths(
            root: root,
            outbox: root.appendingPathComponent("outbox", isDirectory: true),
            watchFolder: root.appendingPathComponent("watch", isDirectory: true)
        )
        let ledger = try ReturnLedger(paths: paths)
        let model = try AppModel(
            paths: paths,
            spool: try SpoolStore(paths: paths),
            composer: PDFComposer(),
            capturer: ScreenCapturer(),
            hotkeys: HotkeyCenter(),
            picker: RegionPickerController(),
            ledger: ledger,
            watcher: ReturnWatcher(paths: paths, ledger: ledger)
        )
        return (model, root)
    }

    private static func runDitto(arguments: [String]) throws {
        let process = Process()
        process.executableURL = URL(fileURLWithPath: "/usr/bin/ditto")
        process.arguments = arguments
        let err = Pipe()
        process.standardError = err
        process.standardOutput = Pipe()
        try process.run()
        process.waitUntilExit()
        guard process.terminationStatus == 0 else {
            let message = String(data: err.fileHandleForReading.readDataToEndOfFile(), encoding: .utf8) ?? ""
            throw UpdateSelfTestError.detail("ditto failed: \(message)")
        }
    }

    private static func updateFail(_ detail: String) -> Never {
        print("UPDATE-SELFTEST FAIL \(detail)")
        fflush(stdout)
        exit(1)
    }

    private static func interpolate(_ step: Int) -> NSPoint {
        let t = CGFloat(step) / CGFloat(dragSteps)
        return NSPoint(
            x: pointA.x + (pointB.x - pointA.x) * t,
            y: pointA.y + (pointB.y - pointA.y) * t
        )
    }

    private static func overlayWindow(containing point: NSPoint) -> RegionPickerWindow? {
        let overlays = NSApp.windows.compactMap { $0 as? RegionPickerWindow }
        return overlays.first(where: { $0.coveringScreen.frame.contains(point) }) ?? overlays.first
    }

    private static func writeOverlayBitmap(_ overlay: RegionPickerWindow, to url: URL) {
        guard let view = overlay.contentView else {
            fail(expected: expectedLabel(), got: "overlay has no contentView")
        }
        overlay.layoutIfNeeded()
        view.layoutSubtreeIfNeeded()
        view.display()
        let bounds = view.bounds
        guard let rep = view.bitmapImageRepForCachingDisplay(in: bounds) else {
            fail(expected: expectedLabel(), got: "bitmapImageRepForCachingDisplay failed")
        }
        view.cacheDisplay(in: bounds, to: rep)
        guard let png = rep.representation(using: .png, properties: [:]) else {
            fail(expected: expectedLabel(), got: "PNG encode failed")
        }
        do {
            try png.write(to: url)
        } catch {
            fail(expected: expectedLabel(), got: "could not write \(url.path): \(error)")
        }
        print(url.path)
        fflush(stdout)
    }

    private static func expectedLabel() -> String {
        format(CGRect(
            x: min(pointA.x, pointB.x),
            y: min(pointA.y, pointB.y),
            width: abs(pointB.x - pointA.x),
            height: abs(pointB.y - pointA.y)
        ))
    }

    private static func format(_ rect: CGRect) -> String {
        "(\(rect.origin.x), \(rect.origin.y), \(rect.width), \(rect.height))"
    }

    private static func fail(expected: String, got: String) -> Never {
        print("PICKER-SELFTEST FAIL expected=\(expected) got=\(got)")
        fflush(stdout)
        exit(1)
    }
}

private enum UpdateSelfTestError: Error, CustomStringConvertible {
    case detail(String)
    var description: String {
        switch self {
        case .detail(let s): return s
        }
    }
}

private enum HistorySelfTestError: Error, CustomStringConvertible {
    case detail(String)
    var description: String {
        switch self {
        case .detail(let s): return s
        }
    }
}