// Distributed under the MIT License (MIT) (see accompanying LICENSE file)

#pragma once

#include <Core.h>


/**
 * Delegates to ImGui debug events called. World delegates are called once per frame to draw debug for owning world
 * and are automatically cleared when that world becomes invalid. Multi-context delegates are called once for every
 * world that needs to be debugged.
 * In engine version 4.18 or later delegates are called during OnWorldPostActorTick event while in older versions
 * 4.18 during OnWorldTickStart event. Calling behaviours can be changed in build configuration.
 */
class IMGUI_API FImGuiDelegates
{
public:

	/**
	 * Get a delegate to ImGui world debug event for current world (GWorld).
	 * @returns Simple multicast delegate to debug events called once per frame to debug current world
	 */
	static FSimpleMulticastDelegate& OnWorldDebug();

	/**
	 * Get a delegate to ImGui world debug event for given world.
	 * @param World - World for which we need a delegate
	 * @returns Simple multicast delegate to debug events called once per frame to debug given world
	 */
	static FSimpleMulticastDelegate& OnWorldDebug(UWorld* World);

	/**
	 * Get a delegate to ImGui multi-context debug event.
	 * @returns Simple multicast delegate to debug events called once per frame for every world to debug
	 */
	static FSimpleMulticastDelegate& OnMultiContextDebug();
};


/** Enable to support legacy ImGui delegates API. */
#define IMGUI_WITH_OBSOLETE_DELEGATES 1

#if IMGUI_WITH_OBSOLETE_DELEGATES

/** Delegate that allows to subscribe for ImGui events.  */
typedef FSimpleMulticastDelegate::FDelegate FImGuiDelegate;

/**
 * Handle to ImGui delegate. Contains additional information locating delegates in different contexts.
 */
class FImGuiDelegateHandle
{
public:

	FImGuiDelegateHandle() = default;

	bool IsValid() const
	{
		return Handle.IsValid();
	}

	void Reset()
	{
		Handle.Reset();
		Index = 0;
	}

private:

	FImGuiDelegateHandle(const FDelegateHandle& InHandle, int32 InCategory, int32 InIndex = 0)
		: Handle(InHandle)
		, Category(InCategory)
		, Index(InIndex)
	{
	}

	friend bool operator==(const FImGuiDelegateHandle& Lhs, const FImGuiDelegateHandle& Rhs)
	{
		return Lhs.Handle == Rhs.Handle && Lhs.Category == Rhs.Category && Lhs.Index == Rhs.Index;
	}

	friend bool operator!=(const FImGuiDelegateHandle& Lhs, const FImGuiDelegateHandle& Rhs)
	{
		return !(Lhs == Rhs);
	}

	FDelegateHandle Handle;
	int32 Category = 0;
	int32 Index = 0;

	friend class FImGuiModule;
};

#endif // IMGUI_WITH_OBSOLETE_DELEGATES