import SwiftUI
import WebKit
import CoreText

#if os(macOS)
import AppKit
typealias AeselImage = NSImage
typealias AeselColor = NSColor
typealias AeselFont = NSFont

/// Keep WebKit setup and coordinators shared; only the SwiftUI adapter differs.
protocol AeselWebViewRepresentable: NSViewRepresentable where NSViewType == WKWebView {
    func makeWebView(context: Context) -> WKWebView
    func updateWebView(_ view: WKWebView, context: Context)
    static func dismantleWebView(_ view: WKWebView, coordinator: Coordinator)
}
extension AeselWebViewRepresentable {
    func makeNSView(context: Context) -> WKWebView { makeWebView(context: context) }
    func updateNSView(_ view: WKWebView, context: Context) { updateWebView(view, context: context) }
    static func dismantleNSView(_ view: WKWebView, coordinator: Coordinator) { dismantleWebView(view, coordinator: coordinator) }
    static func dismantleWebView(_ view: WKWebView, coordinator: Coordinator) {}
}
#else
import UIKit
typealias AeselImage = UIImage
typealias AeselColor = UIColor
typealias AeselFont = UIFont

protocol AeselWebViewRepresentable: UIViewRepresentable where UIViewType == WKWebView {
    func makeWebView(context: Context) -> WKWebView
    func updateWebView(_ view: WKWebView, context: Context)
    static func dismantleWebView(_ view: WKWebView, coordinator: Coordinator)
}
extension AeselWebViewRepresentable {
    func makeUIView(context: Context) -> WKWebView { makeWebView(context: context) }
    func updateUIView(_ view: WKWebView, context: Context) { updateWebView(view, context: context) }
    static func dismantleUIView(_ view: WKWebView, coordinator: Coordinator) { dismantleWebView(view, coordinator: coordinator) }
    static func dismantleWebView(_ view: WKWebView, coordinator: Coordinator) {}
}
#endif

extension Image {
    init(aeselImage: AeselImage) {
        #if os(macOS)
        self.init(nsImage: aeselImage)
        #else
        self.init(uiImage: aeselImage)
        #endif
    }
}

extension WKWebView {
    var aeselOpacity: CGFloat {
        get {
            #if os(macOS)
            alphaValue
            #else
            alpha
            #endif
        }
        set {
            #if os(macOS)
            alphaValue = newValue
            #else
            alpha = newValue
            #endif
        }
    }
}

enum ApplePlatform {
    static func setAppearance(_ view: WKWebView, colorScheme: ColorScheme) {
        #if os(macOS)
        view.appearance = NSAppearance(named: colorScheme == .dark ? .darkAqua : .aqua)
        #else
        view.overrideUserInterfaceStyle = colorScheme == .dark ? .dark : .light
        #endif
    }
    static func registerFonts() {
        #if os(macOS)
        if let url = Bundle.main.url(forResource: "ComicRelief-Bold", withExtension: "ttf") {
            CTFontManagerRegisterFontsForURL(url as CFURL, .process, nil)
        }
        #endif
    }

    static func image(size: CGSize, drawing: @escaping () -> Void) -> AeselImage {
        #if os(macOS)
        return NSImage(size: size, flipped: true) { _ in drawing(); return true }
        #else
        let format = UIGraphicsImageRendererFormat.default()
        format.opaque = false
        return UIGraphicsImageRenderer(size: size, format: format).image { _ in drawing() }
        #endif
    }

    static func cgImage(at url: URL) -> CGImage? {
        #if os(macOS)
        return NSImage(contentsOf: url)?.cgImage(forProposedRect: nil, context: nil, hints: nil)
        #else
        return UIImage(contentsOfFile: url.path)?.cgImage
        #endif
    }

    static func image(cgImage: CGImage) -> AeselImage {
        #if os(macOS)
        return NSImage(cgImage: cgImage, size: CGSize(width: cgImage.width, height: cgImage.height))
        #else
        return UIImage(cgImage: cgImage)
        #endif
    }

    static func configureEmbeddedView(_ view: WKWebView) {
        view.underPageBackgroundColor = .clear
        #if os(iOS)
        view.isOpaque = false
        view.backgroundColor = .clear
        view.scrollView.backgroundColor = .clear
        view.scrollView.isScrollEnabled = false
        view.scrollView.contentInsetAdjustmentBehavior = .never
        view.isMultipleTouchEnabled = true
        #endif
    }
}

extension View {
    @ViewBuilder func aeselKeyboardScrolling() -> some View {
        #if os(iOS)
        scrollDismissesKeyboard(.interactively)
        #else
        self
        #endif
    }
    @ViewBuilder func aeselSendLabel() -> some View {
        #if os(iOS)
        submitLabel(.send)
        #else
        self
        #endif
    }
    @ViewBuilder func aeselHelpSheet() -> some View {
        #if os(iOS)
        presentationDetents([.medium])
        #else
        frame(minWidth: 420, minHeight: 340)
        #endif
    }
    @ViewBuilder func aeselSignInSheet() -> some View {
        #if os(macOS)
        frame(minWidth: 500, minHeight: 600)
        #else
        self
        #endif
    }
}

#if os(macOS)
/// Keep native window controls over the notebook's own title strip.
private struct AeselWindowTitle: NSViewRepresentable {
    let title: String
    let paper: Color
    final class Carrier: NSView {
        var pieceTitle = ""
        var paperColor = NSColor.clear
        override func viewDidMoveToWindow() {
            super.viewDidMoveToWindow()
            DispatchQueue.main.async { [weak self] in self?.configure() }
        }
        func updateBacking() {
            guard let window else { return }
            // The window and hosting layer resize before SwiftUI's paper does.
            // Paint both backing surfaces so newly exposed pixels never flash white.
            window.backgroundColor = paperColor
            if let content = window.contentView {
                content.wantsLayer = true
                CATransaction.begin()
                CATransaction.setDisableActions(true)
                content.layer?.backgroundColor = paperColor.cgColor
                CATransaction.commit()
            }
        }
        func configure() {
            guard let window else { return }
            updateBacking()
            if window.toolbar != nil { window.toolbar = nil }
            window.toolbarStyle = .expanded
            window.styleMask.insert(.fullSizeContentView)
            window.titlebarAppearsTransparent = true
            window.titleVisibility = .hidden
            window.titlebarSeparatorStyle = .none
            if window.title != pieceTitle { window.title = pieceTitle }
        }
    }
    func makeNSView(context: Context) -> Carrier { let view = Carrier(); view.pieceTitle = title; view.paperColor = NSColor(paper); return view }
    func updateNSView(_ view: Carrier, context: Context) {
        view.pieceTitle = title
        view.paperColor = NSColor(paper)
        view.updateBacking()
        DispatchQueue.main.async { [weak view] in view?.configure() }
    }
}
#endif

extension View {
    @ViewBuilder func aeselWindowTitle(_ title: String, paper: Color) -> some View {
        #if os(macOS)
        background(AeselWindowTitle(title: title, paper: paper).frame(width: 0, height: 0))
        #else
        self
        #endif
    }
}

/// Only the empty header drags the window; document clicks belong to editing.
#if os(macOS)
struct AeselWindowDragArea: NSViewRepresentable {
    final class DragView: NSView {
        override func mouseDown(with event: NSEvent) {
            if event.clickCount == 2 { window?.zoom(nil) }
            else { window?.performDrag(with: event) }
        }
    }
    func makeNSView(context: Context) -> DragView { DragView() }
    func updateNSView(_ view: DragView, context: Context) {}
}
#else
struct AeselWindowDragArea: View {
    var body: some View { Color.clear }
}
#endif

#if os(macOS)
/// Place header controls above AppKit's title-bar event layer.
struct AeselTitlebarAccessory<Content: View>: NSViewRepresentable {
    let content: Content
    init(@ViewBuilder content: () -> Content) { self.content = content() }
    final class Carrier: NSView {
        let accessory = NSTitlebarAccessoryViewController()
        let hosting = NSHostingView(rootView: AnyView(EmptyView()))
        weak var installedWindow: NSWindow?
        var resizeObserver: NSObjectProtocol?
        override init(frame: NSRect) {
            super.init(frame: frame)
            accessory.layoutAttribute = .right
            accessory.view = hosting
        }
        required init?(coder: NSCoder) { fatalError("init(coder:) has not been implemented") }
        override func viewDidMoveToWindow() {
            super.viewDidMoveToWindow()
            DispatchQueue.main.async { [weak self] in self?.install() }
        }
        func install() {
            guard let window, installedWindow !== window else { return }
            detach()
            installedWindow = window
            resize()
            window.addTitlebarAccessoryViewController(accessory)
            resizeObserver = NotificationCenter.default.addObserver(forName: NSWindow.didResizeNotification,
                object: window, queue: .main) { [weak self] _ in self?.resize() }
        }
        func resize() {
            guard let installedWindow else { return }
            // Standard window buttons own the leftmost 64 physical points.
            hosting.setFrameSize(NSSize(width: max(0, installedWindow.frame.width - 64), height: 32))
        }
        func detach() {
            if let resizeObserver { NotificationCenter.default.removeObserver(resizeObserver) }
            resizeObserver = nil
            if let window = installedWindow,
               let index = window.titlebarAccessoryViewControllers.firstIndex(of: accessory) {
                window.removeTitlebarAccessoryViewController(at: index)
            }
            installedWindow = nil
        }
    }
    func makeNSView(context: Context) -> Carrier {
        let view = Carrier(frame: .zero)
        view.hosting.rootView = AnyView(content)
        return view
    }
    func updateNSView(_ view: Carrier, context: Context) {
        view.hosting.rootView = AnyView(content)
        view.install()
    }
    static func dismantleNSView(_ view: Carrier, coordinator: ()) { view.detach() }
}
#endif