adwaita-swift/Sources/Adwaita/View/NavigationView+.swift

//
//  NavigationView+.swift
//  Adwaita
//
//  Created by david-swift on 17.02.24.
//

import CAdw

extension NavigationView {

    /// The ID for the component field in a content storage.
    static var componentID: String { "component" }

    /// Initialize a navigation view.
    /// - Parameters:
    ///   - stack: The navigation stack for pushing and popping.
    ///   - initialTitle: The title of the initial view.
    ///   - content: The view for a path component.
    ///   - initialView: The view that is displayed when the path is empty.
    public init<Component>(
        _ stack: Binding<NavigationStack<Component>>,
        _ initialTitle: String,
        @ViewBuilder content: @escaping (Component) -> Body,
        @ViewBuilder initialView: @escaping () -> Body
    ) {
        self.init()
        appearFunctions.append { storage, data in
            let initialStorage = initialView().storage(data: data, type: AdwaitaMainView.self)
            storage.fields[.mainContent] = [initialStorage]
            adw_navigation_view_push(
                storage.opaquePointer,
                adw_navigation_page_new(initialStorage.opaquePointer?.cast(), initialTitle)
            )
            storage.connectSignal(name: "popped", id: "components", argCount: 1) { args in
                guard var storages = storage.fields[.mainContent] as? [ViewStorage],
                let arg = args.first as? UnsafeRawPointer else {
                    return
                }
                if storages.last?.opaquePointer == adw_navigation_page_get_child(OpaquePointer(arg).cast())?.opaque() {
                    storages.removeLast()
                    storage.fields[.mainContent] = storages
                }
            }
        }
        updateFunctions.append { [self] storage, data, updateProperties in
            updateFunction(
                storage: storage,
                data: data,
                stack: stack,
                views: (content, initialView()),
                updateProperties: updateProperties
            )
        }
    }

    /// A stack controls a navigation view.
    public struct NavigationStack<Component> where Component: CustomStringConvertible {

        /// The action to run at the next view update, if any.
        var action: Action<Component>?

        /// Initialize a navigation stack.
        public init() { }

        /// Remove the last item from the navigation view.
        public mutating func pop() {
            action = .pop
        }

        /// Add a new item to the navigation view.
        /// - Parameter component: The component's value.
        public mutating func push(_ component: Component) {
            action = .push(component: component)
        }

    }

    /// An action to run on a view update.
    enum Action<Component> {

        /// Remove the last item.
        case pop
        /// Add a new item.
        case push(component: Component)

    }

    /// Update a navigation view.
    /// - Parameters:
    ///   - storage: The view storage.
    ///   - modifiers: The view modifiers.
    ///   - stack: The navigation stack for pushing and popping.
    ///   - views: The views.
    ///   - updateProperties: Whether to update properties.
    func updateFunction<Component>(
        storage: ViewStorage,
        data: WidgetData,
        stack: Binding<NavigationStack<Component>>,
        views: ((Component) -> Body, Body),
        updateProperties: Bool
    ) {
        guard var storages = storage.fields[.mainContent] as? [ViewStorage] else {
            return
        }
        switch stack.wrappedValue.action {
        case .pop:
            if storages.count > 1 {
                adw_navigation_view_pop(storage.opaquePointer)
                storages.removeLast()
            } else { print("Warning: removing the initial view is not allowed.") }
        case let .push(component):
            let contentStorage = views.0(component).storage(data: data, type: AdwaitaMainView.self)
            contentStorage.fields[Self.componentID] = component
            storages.append(contentStorage)
            adw_navigation_view_push(
                storage.opaquePointer,
                adw_navigation_page_new(contentStorage.opaquePointer?.cast(), component.description)
            )
        default:
            break
        }
        StateManager.blockUpdates = true; stack.wrappedValue.action = nil; StateManager.blockUpdates = false
        storage.fields[.mainContent] = storages
        for storage in storages {
            if let component = storage.fields[Self.componentID] as? Component {
                views.0(component)
                    .updateStorage(
                        storage,
                        data: data,
                        updateProperties: updateProperties,
                        type: AdwaitaMainView.self
                    )
            } else {
                views.1
                    .updateStorage(
                        storage,
                        data: data,
                        updateProperties: updateProperties,
                        type: AdwaitaMainView.self
                    )
            }
        }
    }

}

/// A stack controls a navigation view.
public typealias NavigationStack = NavigationView.NavigationStack