mana-swift-core/Sources/ManaTokens/Themes/View+ManaTheme.swift

import SwiftUI

private struct ManaThemeEnvironmentKey: EnvironmentKey {
    static let defaultValue: ManaTheme = .mana
}

public extension EnvironmentValues {
    /// Aktuell aktive Theme-Variant. Default: ``ManaTheme/mana``.
    var manaTheme: ManaTheme {
        get { self[ManaThemeEnvironmentKey.self] }
        set { self[ManaThemeEnvironmentKey.self] = newValue }
    }
}

public extension View {
    /// Setzt die aktive Theme-Variant für diesen View-Subtree.
    ///
    /// Apps mit fixer Identität setzen das an der App-Root:
    ///
    /// ```swift
    /// @main
    /// struct CardsApp: App {
    ///     var body: some Scene {
    ///         WindowGroup {
    ///             ContentView()
    ///                 .manaTheme(.forest)
    ///         }
    ///     }
    /// }
    /// ```
    ///
    /// Apps mit User-Theme-Switching binden den Wert an `@AppStorage`
    /// oder eine Settings-Source und re-rendern bei Wechsel automatisch.
    func manaTheme(_ theme: ManaTheme) -> some View {
        environment(\.manaTheme, theme)
    }
}