//
//  AppearObserver.swift
//  Adwaita
//
//  Created by david-swift on 29.11.23.
//

import CAdw

/// A widget which executes a custom code when being rendered for the first time.
struct AppearObserver: Widget {

    /// The function.
    var onAppear: (ViewStorage) -> Void
    /// The content.
    var content: View

    /// Get the content's container.
    /// - Parameter modifiers: Modify views before being updated.
    /// - Returns: The content's container.
    func container(modifiers: [(View) -> View]) -> ViewStorage {
        let storage = content.storage(modifiers: modifiers)
        onAppear(storage)
        return storage
    }

    /// Update the content.
    /// - Parameters:
    ///     - storage: The content's storage.
    ///     - modifiers: Modify views before being updated.
    ///     - updateProperties: Whether to update properties.
    func update(_ storage: ViewStorage, modifiers: [(View) -> View], updateProperties: Bool) {
        content.updateStorage(storage, modifiers: modifiers, updateProperties: updateProperties)
    }

}

extension View {

    /// Run a function on the widget when it appears for the first time.
    /// - Parameter closure: The function.
    /// - Returns: A view.
    public func inspectOnAppear(_ closure: @escaping (ViewStorage) -> Void) -> View {
        AppearObserver(onAppear: closure, content: self)
    }

    /// Run a function when the view appears for the first time.
    /// - Parameter closure: The function.
    /// - Returns: A view.
    public func onAppear(_ closure: @escaping () -> Void) -> View {
        inspectOnAppear { _ in closure() }
    }

    /// Run a function when the widget gets clicked.
    /// - Parameter handler: The function.
    /// - Returns: A view.
    public func onClick(handler: @escaping () -> Void) -> View {
        inspectOnAppear { storage in
            let controller = ViewStorage(gtk_gesture_click_new())
            gtk_widget_add_controller(storage.pointer?.cast(), controller.pointer)
            storage.fields["controller"] = controller
            let argCount = 3
            controller.connectSignal(name: "released", argCount: argCount, handler: handler)
        }
    }

    /// Add CSS classes to the app as soon as the view appears.
    /// - Parameter getString: Get the CSS.
    /// - Returns: A view.
    public func css(_ getString: @escaping () -> String) -> View {
        inspectOnAppear { _ in
            let provider = gtk_css_provider_new()
            gtk_css_provider_load_from_string(
                provider,
                getString()
            )
            let display = gdk_display_get_default()
            gtk_style_context_add_provider_for_display(
                display,
                provider?.opaque(),
                .init(GTK_STYLE_PROVIDER_PRIORITY_APPLICATION)
            )
        }
    }

}