#pragma once

#include "Async/Future.h"
#include "Containers/Array.h"
#include "Containers/UnrealString.h"
#include "PixelFormat.h"
#include "Templates/Function.h"
#include "UObject/Object.h"
#include "ImageLoader.generated.h"

// Forward declarations
class UTexture2D;

/**
Utility class for asynchronously loading an image into a texture.
Allows Blueprint scripts to request asynchronous loading of an image and be notified when loading is complete.
*/
UCLASS( BlueprintType )
class UImageLoader : public UObject
{
    GENERATED_BODY()

public:
    /**
    Loads an image file from disk into a texture on a worker thread. This will not block the calling thread.
    @return An image loader object with an OnLoadCompleted event that users can bind to, to get notified when loading is done.
    */
    UFUNCTION( BlueprintCallable, Category = ImageLoader, meta = ( HidePin = "Outer", DefaultToSelf = "Outer" ) )
    static UImageLoader* LoadImageFromDiskAsync( UObject* Outer, const FString& ImagePath );

    /**
    Loads an image file from disk into a texture on a worker thread. This will not block the calling thread.
    @return A future object which will hold the image texture once loading is done.
    */
    static TFuture< UTexture2D* > LoadImageFromDiskAsync( UObject* Outer, const FString& ImagePath, TFunction< void() > CompletionCallback );

    /**
    Loads an image file from disk into a texture. This will block the calling thread until completed.
    @return A texture created from the loaded image file.
    */
    UFUNCTION( BlueprintCallable, Category = ImageLoader, meta = ( HidePin = "Outer", DefaultToSelf = "Outer" ) )
    static UTexture2D* LoadImageFromDisk( UObject* Outer, const FString& ImagePath );

public:
    /**
    Declare a broadcast-style delegate type, which is used for the load completed event.
    Dynamic multicast delegates are the only type of event delegates that Blueprint scripts can bind to.
    */
    DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam( FOnImageLoadCompleted, UTexture2D*, Texture );

    /** This accessor function allows C++ code to bind to the event. */
    FOnImageLoadCompleted& OnLoadCompleted()
    {
        return LoadCompleted;
    }

private:
    /** Helper function that initiates the loading operation and fires the event when loading is done. */
    void LoadImageAsync( UObject* Outer, const FString& ImagePath );

    /** Helper function to dynamically create a new texture from raw pixel data. */
    static UTexture2D* CreateTexture(
        UObject* Outer, const TArray< uint8 >& PixelData, int32 InSizeX, int32 InSizeY, EPixelFormat PixelFormat = EPixelFormat::PF_B8G8R8A8, FName BaseName = NAME_None );

private:
    /**
    Holds the load completed event delegate.
    Giving Blueprint access to this private variable allows Blueprint scripts to bind to the event.
    */
    UPROPERTY( BlueprintAssignable, Category = ImageLoader, meta = ( AllowPrivateAccess = true ) )
    FOnImageLoadCompleted LoadCompleted;

    /** Holds the future value which represents the asynchronous loading operation. */
    TFuture< UTexture2D* > Future;
};