//  ScreenGeometry.swift
//  GreenshotMac
//
//  Conversions between AppKit's bottom-left global space and CoreGraphics'
//  top-left global space, plus display lookups.

import AppKit

enum ScreenGeometry {

    /// Height of the primary display, the anchor for both coordinate systems.
    static var primaryHeight: CGFloat {
        NSScreen.screens.first(where: { $0.frame.origin == .zero })?.frame.height
            ?? NSScreen.screens.first?.frame.height
            ?? 0
    }

    /// AppKit global rect (bottom-left origin) to CoreGraphics global rect (top-left origin).
    static func cgRect(fromAppKit rect: CGRect) -> CGRect {
        CGRect(x: rect.origin.x,
               y: primaryHeight - rect.origin.y - rect.height,
               width: rect.width,
               height: rect.height)
    }

    /// CoreGraphics global rect (top-left origin) to AppKit global rect (bottom-left origin).
    static func appKitRect(fromCG rect: CGRect) -> CGRect {
        CGRect(x: rect.origin.x,
               y: primaryHeight - rect.origin.y - rect.height,
               width: rect.width,
               height: rect.height)
    }

    static func displayID(for screen: NSScreen) -> CGDirectDisplayID? {
        screen.deviceDescription[NSDeviceDescriptionKey("NSScreenNumber")] as? CGDirectDisplayID
    }

    static func screen(for displayID: CGDirectDisplayID) -> NSScreen? {
        NSScreen.screens.first { ScreenGeometry.displayID(for: $0) == displayID }
    }

    static func screen(containing point: CGPoint) -> NSScreen? {
        NSScreen.screens.first { $0.frame.contains(point) } ?? NSScreen.main
    }

    /// Crops a CGImage using a rect expressed in points relative to the image's top-left corner.
    static func crop(_ image: CGImage, toPointRect rect: CGRect, scale: CGFloat) -> CGImage? {
        let pixelRect = CGRect(x: (rect.origin.x * scale).rounded(.down),
                               y: (rect.origin.y * scale).rounded(.down),
                               width: (rect.width * scale).rounded(),
                               height: (rect.height * scale).rounded())
            .intersection(CGRect(x: 0, y: 0, width: CGFloat(image.width), height: CGFloat(image.height)))
        guard pixelRect.width >= 1, pixelRect.height >= 1 else { return nil }
        return image.cropping(to: pixelRect)
    }
}