// Copyright Epic Games, Inc. All Rights Reserved.

#pragma once

#include "CoreMinimal.h"
#include "Tickable.h"

/**
 * This class provides common registration for gamethread editor only tickable objects. It is an
 * abstract base class requiring you to implement the GetStatId, IsTickable, and Tick methods.
 * If you need a class that can tick in both the Editor and at Runtime then use FTickableGameObject
 * instead, overriding the IsTickableInEditor() function instead.
 */
class UNREALED_API FTickableEditorObject: public FTickableObjectBase
{
public:
    static void TickObjects(const float DeltaSeconds)
    {
        TArray<FTickableEditorObject*>& PendingTickableObjects = GetPendingTickableObjects();
        TArray<FTickableObjectEntry>& TickableObjects          = GetTickableObjects();

        for (FTickableEditorObject* PendingTickable: PendingTickableObjects)
        {
            AddTickableObject(TickableObjects, PendingTickable);
        }
        PendingTickableObjects.Empty();

        if (TickableObjects.Num() > 0)
        {
            check(!bIsTickingObjects);
            bIsTickingObjects  = true;

            bool bNeedsCleanup = false;

            for (const FTickableObjectEntry& TickableEntry: TickableObjects)
            {
                if (FTickableObjectBase* TickableObject = TickableEntry.TickableObject)
                {
                    if ((TickableEntry.TickType == ETickableTickType::Always) || TickableObject->IsTickable())
                    {
                        ObjectBeingTicked = TickableObject;
                        TickableObject->Tick(DeltaSeconds);
                        ObjectBeingTicked = nullptr;
                    }

                    // In case it was removed during tick
                    if (TickableEntry.TickableObject == nullptr)
                    {
                        bNeedsCleanup = true;
                    }
                }
                else
                {
                    bNeedsCleanup = true;
                }
            }

            if (bNeedsCleanup)
            {
                TickableObjects.RemoveAll([](const FTickableObjectEntry& Entry)
                                          {
                                              return (Entry.TickableObject == nullptr);
                                          });
            }

            bIsTickingObjects = false;
        }
    }

    /** Registers this instance with the static array of tickable objects. */
    FTickableEditorObject()
    {
        ensure(IsInGameThread() || IsInAsyncLoadingThread());
        check(!GetPendingTickableObjects().Contains(this));
        check(!GetTickableObjects().Contains(this));
        GetPendingTickableObjects().Add(this);
    }

    /** Removes this instance from the static array of tickable objects. */
    virtual ~FTickableEditorObject()
    {
        ensureMsgf(ObjectBeingTicked != this, TEXT("Detected possible memory stomp. We are in the Tickable objects Tick function but hit its deconstructor, the 'this' pointer for the Object will now be invalid"));

        ensure(IsInGameThread() || IsInAsyncLoadingThread());
        if (bCollectionIntact && GetPendingTickableObjects().Remove(this) == 0)
        {
            RemoveTickableObject(GetTickableObjects(), this, bIsTickingObjects);
        }
    }

private:
    /**
     * Class that avoids crashes when unregistering a tickable editor object too late.
     *
     * Some tickable objects can outlive the collection
     * (global/static destructor order is unpredictable).
     */
    class TTickableObjectsCollection: public TArray<FTickableObjectEntry>
    {
    public:
        ~TTickableObjectsCollection()
        {
            FTickableEditorObject::bCollectionIntact = false;
        }
    };

    friend class TTickableObjectsCollection;

    /** True if collection of tickable objects is still intact. */
    static bool bCollectionIntact;
    /** True if currently ticking of tickable editor objects. */
    static bool bIsTickingObjects;

    /** Set if we are in the Tick function for an editor tickable object */
    static FTickableObjectBase* ObjectBeingTicked;

    static TArray<FTickableObjectEntry>& GetTickableObjects();

    static TArray<FTickableEditorObject*>& GetPendingTickableObjects();
};