SwiftUI helpers to make dealing with ImmsersiveSpaces less annoying.

ImmersiveSpaceHelper.swift

/// Create an ``ImmersiveSpaceState`` in your view, wrap it with `@State` and modify your view content with ``immersiveSpaceHelper()``.
/// Example:
/// ```swift
/// struct MyView: View {
///     @State
///     var immersiveSpaceState = ImmersiveSpaceState(id: "my-immersive-space-id")
///
///     var body: some View {
///         Toggle("Show/Hide Immersive Space", isOn: $immersiveSpaceState.show)
///         .immersiveSpaceHelper($immersiveSpaceState)
///     }
/// }
/// ```

public struct ImmersiveSpaceState {
    public fileprivate(set) var id: String

    /// The actual (read-only) visible state of the immersive space.
    public fileprivate(set) var shown: Bool = false
    
    /// The desired visible state of the immersive space. Set/reset this to open/dismiss the immersive state.
    public var show: Bool = false

    /// Call to (try to) open the immersive space.
    public fileprivate(set) var open: () async -> Bool = { fatalError() }

    /// Call to dismiss the immersive space.
    public fileprivate(set) var dismiss: () async -> Void = { fatalError() }

    public init(id: String) {
        self.id = id
    }
}

public struct ImmersiveSpaceStateModifier: ViewModifier {
    @Binding
    var immersiveSpaceState: ImmersiveSpaceState
  
    @Environment(\.openImmersiveSpace)
    var openImmersiveSpace

    @Environment(\.dismissImmersiveSpace)
    var dismissImmersiveSpace

    public func body(content: Content) -> some View {
        content
        .onAppear {
            immersiveSpaceState.open = {
                switch await openImmersiveSpace(id: immersiveSpaceState.id) {
                case .opened:
                    immersiveSpaceState.shown = true
                    immersiveSpaceState.show = true
                case .error:
                    logger?.error("Failed to open immersive space (we don't know what the error is because, API)")
                    immersiveSpaceState.shown = false
                    immersiveSpaceState.show = false
                case .userCancelled:
                    logger?.error("User cancelled immersive space open.")
                    immersiveSpaceState.shown = false
                    immersiveSpaceState.show = false
                @unknown default:
                    fatalError("Immsersive space entered unknown state.")
                }
                return immersiveSpaceState.shown
            }
            immersiveSpaceState.dismiss = {
                await dismissImmersiveSpace()
                immersiveSpaceState.shown = false
            }
        }
        .onChange(of: immersiveSpaceState.show) { oldValue, newValue in
            guard oldValue != newValue else {
                return
            }
            switch (newValue, immersiveSpaceState.shown) {
           case (true, false):
               Task {
                   await immersiveSpaceState.open()
               }
           case (false, true):
               Task {
                   await immersiveSpaceState.dismiss()
               }
           default:
               logger?.log("Request to change state to same state ignored.")
           }
        }
    }
}

public extension View {
    func immersiveSpaceHelper(_ state: Binding<ImmersiveSpaceState>) -> some View {
        modifier(ImmersiveSpaceStateModifier(immersiveSpaceState: state))
    }
}