// ----------------------------------------------------------------------------
// -                        Open3D: www.open3d.org                            -
// ----------------------------------------------------------------------------
// Copyright (c) 2018-2023 www.open3d.org
// SPDX-License-Identifier: MIT
// ----------------------------------------------------------------------------

#pragma once

#include <memory>

#include "open3d/visualization/gui/Events.h"

namespace open3d {
namespace visualization {
namespace gui {

struct DrawContext;
struct Theme;

/// The menu item action is handled by Window, rather than by registering a
/// a callback function with (non-existent) Menu::SetOnClicked(). This is
/// because on macOS the menubar is global over all application windows, so any
/// callback would need to go find the data object corresponding to the active
/// window.
class MenuBase {
public:
    using ItemId = int;
    static constexpr ItemId NO_ITEM = -1;

    MenuBase() {}
    virtual ~MenuBase() {}

    virtual void AddItem(const char* name,
                         ItemId item_id = NO_ITEM,
                         KeyName key = KEY_NONE) = 0;
    virtual void AddMenu(const char* name,
                         std::shared_ptr<MenuBase> submenu) = 0;
    virtual void AddSeparator() = 0;

    virtual void InsertItem(int index,
                            const char* name,
                            ItemId item_id = NO_ITEM,
                            KeyName key = KEY_NONE) = 0;
    virtual void InsertMenu(int index,
                            const char* name,
                            std::shared_ptr<MenuBase> submenu) = 0;
    virtual void InsertSeparator(int index) = 0;

    virtual int GetNumberOfItems() const = 0;

    /// Searches the menu hierarchy down from this menu to find the item
    /// and returns true if the item is enabled.
    virtual bool IsEnabled(ItemId item_id) const = 0;
    /// Searches the menu hierarchy down from this menu to find the item
    /// and set it enabled according to \p enabled.
    virtual void SetEnabled(ItemId item_id, bool enabled) = 0;

    virtual bool IsChecked(ItemId item_id) const = 0;
    virtual void SetChecked(ItemId item_id, bool checked) = 0;

    virtual int CalcHeight(const Theme& theme) const = 0;

    /// Returns true if submenu visibility changed on last call to DrawMenuBar
    virtual bool CheckVisibilityChange() const = 0;

    virtual ItemId DrawMenuBar(const DrawContext& context, bool is_enabled) = 0;
    virtual ItemId Draw(const DrawContext& context,
                        const char* name,
                        bool is_enabled) = 0;

    virtual void* GetNativePointer() = 0;  // nullptr if not using native menus
};

}  // namespace gui
}  // namespace visualization
}  // namespace open3d