//
//  ViewStack.swift
//  Adwaita
//
//  Created by david-swift on 30.12.23.
//

import Libadwaita

/// A widget holding multiple children but only displaying one.
public struct ViewStack: Widget {

    /// The stack's active content.
    var content: Body
    /// The stack's active identifier.
    var id: CustomStringConvertible

    /// Initialize the stack.
    /// - Parameters:
    ///     - id: The identifier of the current view.
    ///     - view: The current view.
    public init<Identifier>(
        id: Identifier,
        @ViewBuilder view: @escaping (Identifier) -> Body
    ) where Identifier: CustomStringConvertible {
        content = view(id)
        self.id = id
    }

    /// Initialize the stack.
    /// - Parameters:
    ///     - element: The current identifiable element.
    ///     - view: The current view.
    public init<Element>(
        element: Element,
        @ViewBuilder view: @escaping (Element) -> Body
    ) where Element: Identifiable, Element.ID: CustomStringConvertible {
        content = view(element)
        self.id = element.id
    }

    /// Get a stack's view storage.
    /// - Parameter modifiers: Modify views before being updated.
    /// - Returns: The stack's view storage.
    public func container(modifiers: [(View) -> View]) -> ViewStorage {
        let stack = Stack()
        let storage = ViewStorage(stack)
        update(storage, modifiers: modifiers)
        return storage
    }

    /// Update a stack's view storage.
    /// - Parameters:
    ///     - storage: The view storage.
    ///     - modifiers: Modify views before being updated.
    public func update(_ storage: ViewStorage, modifiers: [(View) -> View]) {
        if let stack = storage.view as? Stack {
            let widget = content.widget(modifiers: modifiers)
            if let view = storage.content[id.description]?.first {
                widget.updateStorage(view, modifiers: modifiers)
            } else {
                let view = widget.storage(modifiers: modifiers)
                _ = stack.append(view.view)
                storage.content[id.description] = [view]
            }
            if let visibleView = storage.content[id.description]?.first?.view {
                _ = stack.setVisible(visibleView, transition: visibleView.fields[.transition] as? Transition)
            }
        }
    }

}