@using System
@using Sandbox.UI
@namespace Sandbox
@inherits Panel

<root>

    @if ( !_isSubmenu )
    {
        <div class="background" @onmousedown=@Close @onclick=@Close></div>
    }

    <div class="inner @( _submenuOpensLeft && _options.Any( o => o.SubmenuBuilder != null ) ? "opens-left" : "" )">

        @foreach ( var option in _options )
        {
            if ( option.IsSpacer )
            {
                <div class="spacer"></div>
                continue;
            }

            var opt = option;

            <div class="option @( opt.SubmenuBuilder != null ? "has-submenu" : "" )"
                 @onclick="@(() => OnOptionClick( opt ))"
                 @onmouseover="@(() => OnOptionHover( opt ))">

                <div class="icon">@opt.Icon</div>
                <div class="text">@opt.Text</div>

                @if ( opt.SubmenuBuilder != null )
                {
                    <div class="submenu-arrow">@( _submenuOpensLeft ? "◀" : "▶" )</div>
                }

            </div>
        }

    </div>

</root>

@code
{
    record MenuOption( string Icon, string Text, Action Action, Action<MenuPanel> SubmenuBuilder = null )
    {
        public bool IsSpacer => Icon == "__spacer__";
    }

    readonly List<MenuOption> _options = new();
    MenuPanel _openSubmenu;
    MenuOption? _activeSubmenuOption;
    bool _isSubmenu;
    bool _openLeft;
    float _parentLeft;
    bool _submenuOpensLeft;
    Rect _layoutRect;
    Panel _source;

    public static MenuPanel Open( Panel source )
    {
        var root = source.FindRootPanel();
        var menu = root.AddChild<MenuPanel>();
        menu._source = source;
        menu.Style.Left = root.MousePosition.x * root.ScaleFromScreen;
        menu.Style.Top = root.MousePosition.y * root.ScaleFromScreen;
        menu.PlaySound( "sounds/kenney/ui/ui.navigate.forward.sound" );
        return menu;
    }

    public override void Tick()
    {
        base.Tick();

        if ( _isSubmenu ) return;
        if ( !_source.IsValid() ) { Close(); return; }

        // Walk the source ancestor chain — if any panel becomes invisible, close the menu
        if ( _source.AncestorsAndSelf.Any( p => !p.IsVisible ) )
            Close();
    }

    public void AddOption( string icon, string text, Action action )
    {
        _options.Add( new MenuOption( icon, text, action ) );
    }

    public void AddSubmenu( string icon, string text, Action<MenuPanel> builder )
    {
        _options.Add( new MenuOption( icon, text, null, builder ) );
    }

    public void AddSpacer()
    {
        _options.Add( new MenuOption( "__spacer__", "", null ) );
    }

    void OnOptionClick( MenuOption option )
    {
        if ( option.SubmenuBuilder != null )
            OnOptionHover( option );
        else
            SelectOption( option );
    }

    void OnOptionHover( MenuOption option )
    {
        if ( _activeSubmenuOption == option ) return;
        _activeSubmenuOption = option;

        CloseSubmenu();

        if ( option.SubmenuBuilder == null ) return;

        const int minWidth = 200;
        const int gap = 4;
        const int padding = 10;

        bool hasRoomRight = Box.Right + gap + minWidth < Screen.Width - padding;

        var root = FindRootPanel();
        var submenu = root.AddChild<MenuPanel>();
        submenu._isSubmenu = true;
        submenu._openLeft = !hasRoomRight;
        submenu._parentLeft = Box.Left;
        submenu.Style.Left = hasRoomRight ? Box.Right + gap : Box.Left - gap - minWidth;
        submenu.Style.Top = root.MousePosition.y * root.ScaleFromScreen - gap;

        option.SubmenuBuilder( submenu );
        submenu.StateHasChanged();
        _openSubmenu = submenu;
    }

    void CloseSubmenu()
    {
        if ( _openSubmenu == null ) return;
        _openSubmenu.Delete( false );
        _openSubmenu = null;
    }

    void SelectOption( MenuOption option )
    {
        CloseAll( this );
        option.Action?.Invoke();
    }

    public void Close()
    {
        CloseAll( this );
    }

    static void CloseAll( Panel source )
    {
        var root = source.FindRootPanel();
        foreach ( var menu in root.Children.OfType<MenuPanel>().ToList() )
            menu.Delete( false );
    }

    public override void OnLayout( ref Rect layoutRect )
    {
        const int padding = 10;
        const int gap = 4;

        if ( _openLeft )
        {
            var w = layoutRect.Width;
            layoutRect.Right = _parentLeft - gap;
            layoutRect.Left = layoutRect.Right - w;
        }

        if ( layoutRect.Right > Screen.Width - padding )
        {
            layoutRect.Left -= layoutRect.Right - ( Screen.Width - padding );
            layoutRect.Right = Screen.Width - padding;
        }

        if ( layoutRect.Bottom > Screen.Height - padding )
        {
            layoutRect.Top -= layoutRect.Bottom - ( Screen.Height - padding );
            layoutRect.Bottom = Screen.Height - padding;
        }

        _layoutRect = layoutRect;
        _submenuOpensLeft = !_isSubmenu && !( layoutRect.Right + 4 + 200 < Screen.Width - 10 );
    }
}