import SwiftUI

// All backport view/scene modifiers go as an extension on this. We use this
// so we can easily track and centralize all backports.
struct Backport<Content> {
    let content: Content
}

extension View {
    var backport: Backport<Self> { Backport(content: self) }
}

extension Scene {
    var backport: Backport<Self> { Backport(content: self) }
}

extension Backport where Content: Scene {
    // None currently
}

/// Result type for backported onKeyPress handler
enum BackportKeyPressResult {
    case handled
    case ignored
}

extension Backport where Content: View {
    func pointerVisibility(_ v: BackportVisibility) -> some View {
        #if canImport(AppKit)
        if #available(macOS 15, *) {
            return content.pointerVisibility(v.official)
        } else {
            return content
        }
        #else
        return content
        #endif
    }

    func pointerStyle(_ style: BackportPointerStyle?) -> some View {
        #if canImport(AppKit)
        if #available(macOS 15, *) {
            return content.pointerStyle(style?.official)
        } else {
            return content
        }
        #else
        return content
        #endif
    }

    /// Backported onKeyPress that works on macOS 14+ and is a no-op on macOS 13.
    func onKeyPress(_ key: KeyEquivalent, action: @escaping (EventModifiers) -> BackportKeyPressResult) -> some View {
        #if canImport(AppKit)
        if #available(macOS 14, *) {
            return content.onKeyPress(key, phases: .down, action: { keyPress in
                switch action(keyPress.modifiers) {
                case .handled: return .handled
                case .ignored: return .ignored
                }
            })
        } else {
            return content
        }
        #else
        return content
        #endif
    }
}

enum BackportVisibility {
    case automatic
    case visible
    case hidden

    @available(macOS 15, *)
    var official: Visibility {
        switch self {
        case .automatic: return .automatic
        case .visible: return .visible
        case .hidden: return .hidden
        }
    }
}

enum BackportPointerStyle {
    case `default`
    case grabIdle
    case grabActive
    case horizontalText
    case verticalText
    case link
    case resizeLeft
    case resizeRight
    case resizeUp
    case resizeDown
    case resizeUpDown
    case resizeLeftRight

    #if canImport(AppKit)
    @available(macOS 15, *)
    var official: PointerStyle {
        switch self {
        case .default: return .default
        case .grabIdle: return .grabIdle
        case .grabActive: return .grabActive
        case .horizontalText: return .horizontalText
        case .verticalText: return .verticalText
        case .link: return .link
        case .resizeLeft: return .frameResize(position: .trailing, directions: [.inward])
        case .resizeRight: return .frameResize(position: .leading, directions: [.inward])
        case .resizeUp: return .frameResize(position: .bottom, directions: [.inward])
        case .resizeDown: return .frameResize(position: .top, directions: [.inward])
        case .resizeUpDown: return .frameResize(position: .top)
        case .resizeLeftRight: return .frameResize(position: .trailing)
        }
    }
    #endif
}

enum BackportNSGlassStyle {
    case regular, clear

    #if canImport(AppKit)
    @available(macOS 26, *)
    var official: NSGlassEffectView.Style {
        switch self {
        case .regular: return .regular
        case .clear: return .clear
        }
    }
    #endif
}
