import SwiftUI

#if canImport(UIKit)
    import UIKit

    private typealias PlatformColorType = UIColor
#elseif canImport(AppKit)
    import AppKit

    private typealias PlatformColorType = NSColor
#endif

/// Paper-Variant aus `mana/packages/themes/src/variants/paper.css`.
/// Lokal in zitare-native nachgebaut, weil ManaTokens noch keine
/// Variants kennt.
///
/// Sepia, warm, lese-fokussiert — skeumorph an Druckpapier angelehnt,
/// passt zum (read)-Surface der Web-App.
enum ZitareTheme {
    /// Page-Hintergrund (warmes Off-White / dunkles Sepia)
    static let background = dynamic(light: HSL(38, 28, 95), dark: HSL(24, 14, 9))

    /// Standard-Text
    static let foreground = dynamic(light: HSL(20, 14, 16), dark: HSL(38, 24, 88))

    /// Card, Panel, Modal
    static let surface = dynamic(light: HSL(0, 0, 100), dark: HSL(24, 12, 13))

    /// Hover-State auf Surface
    static let surfaceHover = dynamic(light: HSL(38, 24, 92), dark: HSL(24, 14, 17))

    /// Disabled-Felder, Skeleton
    static let muted = dynamic(light: HSL(38, 20, 90), dark: HSL(24, 12, 18))

    /// Sekundär-Text, Placeholder
    static let mutedForeground = dynamic(light: HSL(20, 14, 50), dark: HSL(38, 12, 60))

    /// Rahmen, Trennlinien
    static let border = dynamic(light: HSL(38, 18, 80), dark: HSL(24, 10, 25))

    /// Zitare-Primary — warmes Terra/Sienna im Light, weicheres Sienna im Dark
    static let primary = dynamic(light: HSL(18, 50, 38), dark: HSL(24, 60, 65))

    /// Text auf Primary
    static let primaryForeground = dynamic(light: HSL(0, 0, 100), dark: HSL(24, 14, 9))

    static let error = dynamic(light: HSL(0, 65, 45), dark: HSL(0, 60, 55))
    static let success = dynamic(light: HSL(135, 35, 35), dark: HSL(135, 35, 55))
    static let warning = dynamic(light: HSL(38, 80, 40), dark: HSL(38, 70, 55))

    // MARK: - HSL Helper

    struct HSL {
        let hue: Double
        let saturation: Double
        let lightness: Double

        init(_ hue: Double, _ saturation: Double, _ lightness: Double) {
            self.hue = hue
            self.saturation = saturation
            self.lightness = lightness
        }

        var color: Color {
            Color(
                hue: hue / 360.0,
                saturation: saturation / 100.0,
                brightness: brightnessFromLightness(),
                opacity: 1.0
            )
        }

        /// HSL → HSB Konversion (SwiftUI Color nutzt HSB).
        private func brightnessFromLightness() -> Double {
            let l = lightness / 100.0
            let s = saturation / 100.0
            return l + s * min(l, 1 - l)
        }
    }

    private static func dynamic(light: HSL, dark: HSL) -> Color {
        #if canImport(UIKit)
            return Color(
                PlatformColorType { trait in
                    trait.userInterfaceStyle == .dark
                        ? PlatformColorType(dark.color)
                        : PlatformColorType(light.color)
                }
            )
        #elseif canImport(AppKit)
            return Color(
                PlatformColorType(name: nil) { appearance in
                    let isDark = appearance.bestMatch(
                        from: [.darkAqua, .aqua]
                    ) == .darkAqua
                    return isDark
                        ? PlatformColorType(dark.color)
                        : PlatformColorType(light.color)
                }
            )
        #else
            return light.color
        #endif
    }
}