namespace Terminal.Gui;

/// <summary>
///     <see cref="MenuBarItem"/> is a menu item on  <see cref="MenuBar"/>. MenuBarItems do not support
///     <see cref="MenuItem.Shortcut"/>.
/// </summary>
public class MenuBarItem : MenuItem
{
    /// <summary>Initializes a new <see cref="MenuBarItem"/> as a <see cref="MenuItem"/>.</summary>
    /// <param name="title">Title for the menu item.</param>
    /// <param name="help">Help text to display. Will be displayed next to the Title surrounded by parentheses.</param>
    /// <param name="action">Action to invoke when the menu item is activated.</param>
    /// <param name="canExecute">Function to determine if the action can currently be executed.</param>
    /// <param name="parent">The parent <see cref="MenuItem"/> of this if any.</param>
    public MenuBarItem (
        string title,
        string help,
        Action action,
        Func<bool> canExecute = null,
        MenuItem parent = null
    ) : base (title, help, action, canExecute, parent)
    {
        SetInitialProperties (title, null, null, true);
    }

    /// <summary>Initializes a new <see cref="MenuBarItem"/>.</summary>
    /// <param name="title">Title for the menu item.</param>
    /// <param name="children">The items in the current menu.</param>
    /// <param name="parent">The parent <see cref="MenuItem"/> of this if any.</param>
    public MenuBarItem (string title, MenuItem [] children, MenuItem parent = null) { SetInitialProperties (title, children, parent); }

    /// <summary>Initializes a new <see cref="MenuBarItem"/> with separate list of items.</summary>
    /// <param name="title">Title for the menu item.</param>
    /// <param name="children">The list of items in the current menu.</param>
    /// <param name="parent">The parent <see cref="MenuItem"/> of this if any.</param>
    public MenuBarItem (string title, List<MenuItem []> children, MenuItem parent = null) { SetInitialProperties (title, children, parent); }

    /// <summary>Initializes a new <see cref="MenuBarItem"/>.</summary>
    /// <param name="children">The items in the current menu.</param>
    public MenuBarItem (MenuItem [] children) : this ("", children) { }

    /// <summary>Initializes a new <see cref="MenuBarItem"/>.</summary>
    public MenuBarItem () : this ([]) { }

    /// <summary>
    ///     Gets or sets an array of <see cref="MenuItem"/> objects that are the children of this
    ///     <see cref="MenuBarItem"/>
    /// </summary>
    /// <value>The children.</value>
    public MenuItem [] Children { get; set; }

    internal bool IsTopLevel => Parent is null && (Children is null || Children.Length == 0) && Action != null;

    /// <summary>Get the index of a child <see cref="MenuItem"/>.</summary>
    /// <param name="children"></param>
    /// <returns>Returns a greater than -1 if the <see cref="MenuItem"/> is a child.</returns>
    public int GetChildrenIndex (MenuItem children)
    {
        var i = 0;

        if (Children is null)
        {
            return -1;
        }

        foreach (MenuItem child in Children)
        {
            if (child == children)
            {
                return i;
            }

            i++;
        }

        return -1;
    }

    /// <summary>Check if a <see cref="MenuItem"/> is a submenu of this MenuBar.</summary>
    /// <param name="menuItem"></param>
    /// <returns>Returns <c>true</c> if it is a submenu. <c>false</c> otherwise.</returns>
    public bool IsSubMenuOf (MenuItem menuItem)
    {
        return Children.Any (child => child == menuItem && child.Parent == menuItem.Parent);
    }

    /// <summary>Check if a <see cref="MenuItem"/> is a <see cref="MenuBarItem"/>.</summary>
    /// <param name="menuItem"></param>
    /// <returns>Returns a <see cref="MenuBarItem"/> or null otherwise.</returns>
    public MenuBarItem SubMenu (MenuItem menuItem) { return menuItem as MenuBarItem; }

    internal void AddShortcutKeyBindings (MenuBar menuBar)
    {
        if (Children is null)
        {
            return;
        }

        foreach (MenuItem menuItem in Children.Where (m => m is { }))
        {
            // For MenuBar only add shortcuts for submenus

            if (menuItem.Shortcut != KeyCode.Null)
            {
                KeyBinding keyBinding = new ([Command.Select], KeyBindingScope.HotKey, menuItem);
                menuBar.KeyBindings.Remove (menuItem.Shortcut);
                menuBar.KeyBindings.Add (menuItem.Shortcut, keyBinding);
            }

            SubMenu (menuItem)?.AddShortcutKeyBindings (menuBar);
        }
    }

    private void SetInitialProperties (string title, object children, MenuItem parent = null, bool isTopLevel = false)
    {
        if (!isTopLevel && children is null)
        {
            throw new ArgumentNullException (
                                             nameof (children),
                                             @"The parameter cannot be null. Use an empty array instead."
                                            );
        }

        SetTitle (title ?? "");

        if (parent is { })
        {
            Parent = parent;
        }

        switch (children)
        {
            case List<MenuItem []> childrenList:
            {
                MenuItem [] newChildren = [];

                foreach (MenuItem [] grandChild in childrenList)
                {
                    foreach (MenuItem child in grandChild)
                    {
                        SetParent (grandChild);
                        Array.Resize (ref newChildren, newChildren.Length + 1);
                        newChildren [^1] = child;
                    }
                }

                Children = newChildren;

                break;
            }
            case MenuItem [] items:
                SetParent (items);
                Children = items;

                break;
            default:
                Children = null;

                break;
        }
    }

    private void SetParent (MenuItem [] children)
    {
        foreach (MenuItem child in children)
        {
            if (child is { Parent: null })
            {
                child.Parent = this;
            }
        }
    }

    private void SetTitle (string title)
    {
        title ??= string.Empty;
        Title = title;
    }
}