import AppKit
import Darwin
import Foundation
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)
            }
        }
    }

    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)
        exit(0)
    }

    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)
    }
}