macbackend/Sources/Core/Model/SwiftUI/SwiftUIWidget.swift

//
//  SwiftUIWidget.swift
//  MacBackend
//
//  Created by david-swift on 25.11.2024.
//

import LevenshteinTransformations
import SwiftUI

/// Wrap a SwiftUI widget to be used inside a `MacBackend` view.
public protocol SwiftUIWidget: MacWidget {

    /// The content SwiftUI view.
    associatedtype Content: SwiftUI.View

    /// The wrapped views.
    var wrappedViews: [String: Meta.AnyView] { get }

    /// Get the SwiftUI view.
    /// - Parameter properties: The widget data.
    /// - Returns: The SwiftUI view.
    @SwiftUI.ViewBuilder
    static func view(properties: Self) -> Content

}

extension SwiftUIWidget {

    /// The wrapped views.
    public var wrappedViews: [String: Meta.AnyView] {
        [:]
    }

    /// The view storage.
    /// - Parameters:
    ///     - data: Modify views before being updated.
    ///     - type: The view render data type.
    /// - Returns: The view storage.
    public func container<Data>(
        data: WidgetData,
        type: Data.Type
    ) -> ViewStorage where Data: ViewRenderData {
        internalContainer(data: data, type: type)
    }

    /// The view storage.
    /// - Parameters:
    ///     - data: Modify views before being updated.
    ///     - type: The view render data type.
    /// - Returns: The view storage.
    func internalContainer<Data>(
        data: WidgetData,
        type: Data.Type
    ) -> ViewStorage where Data: ViewRenderData {
        let id = UUID().uuidString
        let updater = SwiftUIUpdater.updater
        updater.state[id] = self
        let wrappedStorages = wrappedViews.reduce(into: [String: ViewStorage]()) { partialResult, element in
            partialResult[element.key] = element.value.storage(data: data, type: type)
        }
        let storage: ViewStorage = .init(nil)
        storage.fields["child-storages"] = wrappedStorages
        let view = NSHostingView(
            rootView: SwiftUIWrapperView(updater: updater, id: id, data: data) { value in
                if let value = value as? Self {
                    Self.view(properties: value)
                        .environment(\.views, storage.fields["child-storages"] as? [String: ViewStorage])
                }
            }
        )
        storage.pointer = view
        storage.fields["updater-id"] = id
        return storage
    }

    /// Update the stored content.
    /// - Parameters:
    ///     - storage: The storage to update.
    ///     - data: Modify views before being updated
    ///     - updateProperties: Whether to update the view's properties.
    ///     - type: The view render data type.
    public func update<Data>(
        _ storage: ViewStorage,
        data: WidgetData,
        updateProperties: Bool,
        type: Data.Type
    ) where Data: ViewRenderData {
        internalUpdate(storage, data: data, updateProperties: updateProperties, type: type)
    }

    /// Update the stored content.
    /// - Parameters:
    ///     - storage: The storage to update.
    ///     - data: Modify views before being updated
    ///     - updateProperties: Whether to update the view's properties.
    ///     - type: The view render data type.
    func internalUpdate<Data>(
        _ storage: ViewStorage,
        data: WidgetData,
        updateProperties: Bool,
        type: Data.Type
    ) where Data: ViewRenderData {
        if updateProperties, let id = storage.fields["updater-id"] as? String {
            Task { @MainActor in
                SwiftUIUpdater.updater.state[id] = self
            }
        }
        var children = storage.fields["child-storages"] as? [String: ViewStorage] ?? [:]
        for view in wrappedViews where !children.contains(where: { $0.key == view.key }) {
            children[view.key] = view.value.storage(data: data, type: type)
        }
        for view in children where !wrappedViews.contains(where: { $0.key == view.key }) {
            children[view.key] = nil
        }
        storage.fields["child-storages"] = children
        for (key, storage) in children {
            wrappedViews[key]?.updateStorage(storage, data: data, updateProperties: updateProperties, type: type)
        }
    }

}

/// A SwiftUI view which can be displayed and updated inside a `MacBackend` widget.
struct SwiftUIWrapperView<Content>: SwiftUI.View where Content: SwiftUI.View {

    /// The updater observable object.
    @ObservedObject var updater: SwiftUIUpdater
    /// The identifier.
    var id: String
    /// The widget data.
    var data: WidgetData
    /// The wrapped view.
    var view: (Any) -> Content

    /// The SwiftUI view content.
    var body: some SwiftUI.View {
        if let state = updater.state[id] {
            view(state)
        }
    }

    /// Initialize the SwiftUI wrapper view.
    /// - Parameters:
    ///   - updater: The updater observable object.
    ///   - id: The identifier.
    ///   - data: The widget data.
    ///   - view: The wrapped view.
    init(updater: SwiftUIUpdater, id: String, data: WidgetData, @SwiftUI.ViewBuilder view: @escaping (Any) -> Content) {
        self.updater = updater
        self.id = id
        self.view = view
        self.data = data
    }

}

extension EnvironmentValues {

    /// The views environment value.
    @Entry var views: [String: ViewStorage]?

}

/// The SwiftUI updater object.
class SwiftUIUpdater: ObservableObject {

    /// The updater.
    static var updater: SwiftUIUpdater = .init()

    /// The state for SwiftUI views.
    @Published var state: [String: Any] = [:]

    /// Initialize an updater.
    init() { }

}