import Gtk

/// The core protocol for declarative UI components in Portico.
///
/// Conforming types describe their visual hierarchy in `body` using the
/// ``SingleViewBuilder`` result builder. The body is evaluated exactly once at
/// mount time - Portico erases heterogeneous conditional branches to
/// ``AnyView`` while retaining its build-once, bind-live model.
@MainActor public protocol View {
    /// The type of view representing the body of this view.
    associatedtype Body: View

    /// The content and behavior of the view, composed using ``SingleViewBuilder``.
    ///
    /// The body is evaluated exactly once at mount time. Heterogeneous
    /// conditional branches are erased to ``AnyView``; Portico uses a
    /// build-once, bind-live model rather than recompute-and-diff.
    @SingleViewBuilder var body: Body { get }
}

/// Terminal conformance — `Never` has no body and terminates the
/// `View` associated-type chain.
extension Never: View {
    public var body: Never { fatalError("Never has no body") }
}