import AppKit
import SwiftUI

/// Manages the app icon color, allowing users to customize the Dock icon tint.
/// Persists selection to UserDefaults and applies it via NSApplication.shared.applicationIconImage.
final class AppIconConfig: ObservableObject {
    static let shared = AppIconConfig()

    /// Available icon color options, matching the iOS app.
    struct IconColorOption: Identifiable {
        let id: String // name
        let name: String
        let color: Color
        let nsColor: NSColor

        init(_ name: String, _ color: Color, _ nsColor: NSColor) {
            self.id = name
            self.name = name
            self.color = color
            self.nsColor = nsColor
        }
    }

    static let iconColors: [IconColorOption] = [
        IconColorOption("Default", .green, NSColor(red: 0.35, green: 0.85, blue: 0.25, alpha: 1)),
        IconColorOption("Green", Color(red: 0.35, green: 0.85, blue: 0.25), NSColor(red: 0.35, green: 0.85, blue: 0.25, alpha: 1)),
        IconColorOption("Lime", Color(red: 0.55, green: 0.95, blue: 0.15), NSColor(red: 0.55, green: 0.95, blue: 0.15, alpha: 1)),
        IconColorOption("Cyan", Color(red: 0.15, green: 0.85, blue: 0.85), NSColor(red: 0.15, green: 0.85, blue: 0.85, alpha: 1)),
        IconColorOption("Blue", Color(red: 0.25, green: 0.45, blue: 0.95), NSColor(red: 0.25, green: 0.45, blue: 0.95, alpha: 1)),
        IconColorOption("Purple", Color(red: 0.6, green: 0.3, blue: 0.9), NSColor(red: 0.6, green: 0.3, blue: 0.9, alpha: 1)),
        IconColorOption("Pink", Color(red: 0.95, green: 0.3, blue: 0.6), NSColor(red: 0.95, green: 0.3, blue: 0.6, alpha: 1)),
        IconColorOption("Red", Color(red: 0.95, green: 0.25, blue: 0.25), NSColor(red: 0.95, green: 0.25, blue: 0.25, alpha: 1)),
        IconColorOption("Orange", Color(red: 0.95, green: 0.55, blue: 0.15), NSColor(red: 0.95, green: 0.55, blue: 0.15, alpha: 1)),
        IconColorOption("Gold", Color(red: 0.95, green: 0.8, blue: 0.15), NSColor(red: 0.95, green: 0.8, blue: 0.15, alpha: 1)),
        IconColorOption("White", Color(red: 0.9, green: 0.9, blue: 0.92), NSColor(red: 0.9, green: 0.9, blue: 0.92, alpha: 1)),
    ]

    @Published var selectedColorName: String {
        didSet {
            UserDefaults.standard.set(selectedColorName, forKey: "appIconColorName")
            applyIcon()
        }
    }

    private init() {
        self.selectedColorName = UserDefaults.standard.string(forKey: "appIconColorName") ?? "Default"
    }

    /// The currently selected color option.
    var selectedOption: IconColorOption {
        Self.iconColors.first(where: { $0.name == selectedColorName }) ?? Self.iconColors[0]
    }

    /// Apply the selected icon color to the Dock icon.
    func applyIcon() {
        if selectedColorName == "Default" {
            // Reset to the bundle icon
            NSApplication.shared.applicationIconImage = nil
            return
        }

        guard let option = Self.iconColors.first(where: { $0.name == selectedColorName }) else { return }
        guard let tintedIcon = generateTintedIcon(color: option.nsColor) else { return }
        NSApplication.shared.applicationIconImage = tintedIcon
    }

    /// Generate the app icon tinted with the given color.
    /// Loads the default icon from the bundle, desaturates it, and applies the new color.
    private func generateTintedIcon(color: NSColor) -> NSImage? {
        // Load the high-res icon from the asset catalog
        guard let bundleIcon = loadBundleIcon() else { return nil }
        guard let cgImage = bundleIcon.cgImage(forProposedRect: nil, context: nil, hints: nil) else { return nil }

        let width = cgImage.width
        let height = cgImage.height

        guard let context = CGContext(
            data: nil,
            width: width,
            height: height,
            bitsPerComponent: 8,
            bytesPerRow: 0,
            space: CGColorSpaceCreateDeviceRGB(),
            bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue
        ) else { return nil }

        let rect = CGRect(x: 0, y: 0, width: width, height: height)

        // 1) Draw the original icon (to get its luminance structure)
        context.draw(cgImage, in: rect)

        // 2) Apply color overlay with .color blend mode (preserves luminance, applies hue+saturation)
        context.setBlendMode(.color)
        context.setFillColor(color.cgColor)
        context.fill(rect)

        // 3) Clip to original alpha by drawing original with .destinationIn
        context.setBlendMode(.destinationIn)
        context.draw(cgImage, in: rect)

        guard let resultCG = context.makeImage() else { return nil }
        let result = NSImage(cgImage: resultCG, size: NSSize(width: width, height: height))
        return result
    }

    /// Load the 1024px icon from the app bundle's asset catalog.
    private func loadBundleIcon() -> NSImage? {
        // Try loading from bundle resources directly
        if let url = Bundle.main.url(forResource: "icon_1024", withExtension: "png"),
           let img = NSImage(contentsOf: url) {
            return img
        }
        // Fallback: use the app icon from the bundle
        if let iconName = Bundle.main.infoDictionary?["CFBundleIconFile"] as? String,
           let img = NSImage(named: iconName) {
            return img
        }
        // Final fallback: NSApp icon
        return NSApp.applicationIconImage
    }
}