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

#include "UIExtensionSystem.h"

#include "Blueprint/UserWidget.h"
#include "Containers/UnrealString.h"
#include "HAL/Platform.h"
#include "LogUIExtension.h"
#include "Logging/LogCategory.h"
#include "Logging/LogMacros.h"
#include "Logging/LogVerbosity.h"
#include "Misc/AssertionMacros.h"
#include "Templates/Casts.h"
#include "Templates/UnrealTemplate.h"
#include "Trace/Detail/Channel.h"
#include "UObject/Stack.h"
#include "UObject/UObjectBaseUtility.h"

class FSubsystemCollectionBase;

//=========================================================

void FUIExtensionPointHandle::Unregister()
{
	if (UUIExtensionSubsystem* ExtensionSourcePtr = ExtensionSource.Get())
	{
		ExtensionSourcePtr->UnregisterExtensionPoint(*this);
	}
}

//=========================================================

void FUIExtensionHandle::Unregister()
{
	if (UUIExtensionSubsystem* ExtensionSourcePtr = ExtensionSource.Get())
	{
		ExtensionSourcePtr->UnregisterExtension(*this);
	}
}

//=========================================================

bool FUIExtensionPoint::DoesExtensionPassContract(const FUIExtension* Extension) const
{
	if (UObject* DataPtr = Extension->Data)
	{
		const bool bMatchesContext = 
			(ContextObject.IsExplicitlyNull() && Extension->ContextObject.IsExplicitlyNull()) ||
			ContextObject == Extension->ContextObject;

		// Make sure the contexts match.
		if (bMatchesContext)
		{
			// The data can either be the literal class of the data type, or a instance of the class type.
			const UClass* DataClass = DataPtr->IsA(UClass::StaticClass()) ? Cast<UClass>(DataPtr) : DataPtr->GetClass();
			for (const UClass* AllowedDataClass : AllowedDataClasses)
			{
				if (DataClass->IsChildOf(AllowedDataClass) || DataClass->ImplementsInterface(AllowedDataClass))
				{
					return true;
				}
			}
		}
	}

	return false;
}

//=========================================================

void UUIExtensionSubsystem::AddReferencedObjects(UObject* InThis, FReferenceCollector& Collector)
{
	if (UUIExtensionSubsystem* ExtensionSubsystem = Cast<UUIExtensionSubsystem>(InThis))
	{
		for (auto MapIt = ExtensionSubsystem->ExtensionPointMap.CreateIterator(); MapIt; ++MapIt)
		{
			for (const TSharedPtr<FUIExtensionPoint>& ValueElement : MapIt.Value())
			{
				Collector.AddReferencedObjects(ValueElement->AllowedDataClasses);
			}
		}

		for (auto MapIt = ExtensionSubsystem->ExtensionMap.CreateIterator(); MapIt; ++MapIt)
		{
			for (const TSharedPtr<FUIExtension>& ValueElement : MapIt.Value())
			{
				Collector.AddReferencedObject(ValueElement->Data);
			}
		}
	}
}

void UUIExtensionSubsystem::Initialize(FSubsystemCollectionBase& Collection)
{
	Super::Initialize(Collection);
}

void UUIExtensionSubsystem::Deinitialize()
{
	Super::Deinitialize();
}

FUIExtensionPointHandle UUIExtensionSubsystem::RegisterExtensionPoint(const FGameplayTag& ExtensionPointTag, EUIExtensionPointMatch ExtensionPointTagMatchType, const TArray<UClass*>& AllowedDataClasses, FExtendExtensionPointDelegate ExtensionCallback)
{
	return RegisterExtensionPointForContext(ExtensionPointTag, nullptr, ExtensionPointTagMatchType, AllowedDataClasses, ExtensionCallback);
}

FUIExtensionPointHandle UUIExtensionSubsystem::RegisterExtensionPointForContext(const FGameplayTag& ExtensionPointTag, UObject* ContextObject, EUIExtensionPointMatch ExtensionPointTagMatchType, const TArray<UClass*>& AllowedDataClasses, FExtendExtensionPointDelegate ExtensionCallback)
{
	if (!ExtensionPointTag.IsValid())
	{
		UE_LOG(LogUIExtension, Warning, TEXT("Trying to register an invalid extension point."));
		return FUIExtensionPointHandle();
	}

	if (!ExtensionCallback.IsBound())
	{
		UE_LOG(LogUIExtension, Warning, TEXT("Trying to register an invalid extension point."));
		return FUIExtensionPointHandle();
	}

	if (AllowedDataClasses.Num() == 0)
	{
		UE_LOG(LogUIExtension, Warning, TEXT("Trying to register an invalid extension point."));
		return FUIExtensionPointHandle();
	}

	FExtensionPointList& List = ExtensionPointMap.FindOrAdd(ExtensionPointTag);

	TSharedPtr<FUIExtensionPoint>& Entry = List.Add_GetRef(MakeShared<FUIExtensionPoint>());
	Entry->ExtensionPointTag = ExtensionPointTag;
	Entry->ContextObject = ContextObject;
	Entry->ExtensionPointTagMatchType = ExtensionPointTagMatchType;
	Entry->AllowedDataClasses = AllowedDataClasses;
	Entry->Callback = MoveTemp(ExtensionCallback);

	UE_LOG(LogUIExtension, Verbose, TEXT("Extension Point [%s] Registered"), *ExtensionPointTag.ToString());

	NotifyExtensionPointOfExtensions(Entry);

	return FUIExtensionPointHandle(this, Entry);
}

FUIExtensionHandle UUIExtensionSubsystem::RegisterExtensionAsWidget(const FGameplayTag& ExtensionPointTag, TSubclassOf<UUserWidget> WidgetClass, int32 Priority)
{
	return RegisterExtensionAsData(ExtensionPointTag, nullptr, WidgetClass, Priority);
}

FUIExtensionHandle UUIExtensionSubsystem::RegisterExtensionAsWidgetForContext(const FGameplayTag& ExtensionPointTag, UObject* ContextObject, TSubclassOf<UUserWidget> WidgetClass, int32 Priority)
{
	return RegisterExtensionAsData(ExtensionPointTag, ContextObject, WidgetClass, Priority);
}

FUIExtensionHandle UUIExtensionSubsystem::RegisterExtensionAsData(const FGameplayTag& ExtensionPointTag, UObject* ContextObject, UObject* Data, int32 Priority)
{
	if (!ExtensionPointTag.IsValid())
	{
		UE_LOG(LogUIExtension, Warning, TEXT("Trying to register an invalid extension."));
		return FUIExtensionHandle();
	}

	if (!Data)
	{
		UE_LOG(LogUIExtension, Warning, TEXT("Trying to register an invalid extension."));
		return FUIExtensionHandle();
	}

	FExtensionList& List = ExtensionMap.FindOrAdd(ExtensionPointTag);

	TSharedPtr<FUIExtension>& Entry = List.Add_GetRef(MakeShared<FUIExtension>());
	Entry->ExtensionPointTag = ExtensionPointTag;
	Entry->ContextObject = ContextObject;
	Entry->Data = Data;
	Entry->Priority = Priority;

	if (ContextObject)
	{
		UE_LOG(LogUIExtension, Verbose, TEXT("Extension [%s] @ [%s] Registered"), *GetNameSafe(Data), *ExtensionPointTag.ToString());
	}
	else
	{
		UE_LOG(LogUIExtension, Verbose, TEXT("Extension [%s] for [%s] @ [%s] Registered"), *GetNameSafe(Data), *GetNameSafe(ContextObject), *ExtensionPointTag.ToString());
	}

	NotifyExtensionPointsOfExtension(EUIExtensionAction::Added, Entry);

	return FUIExtensionHandle(this, Entry);
}

void UUIExtensionSubsystem::NotifyExtensionPointOfExtensions(TSharedPtr<FUIExtensionPoint>& ExtensionPoint)
{
	for (FGameplayTag Tag = ExtensionPoint->ExtensionPointTag; Tag.IsValid(); Tag = Tag.RequestDirectParent())
	{
		if (const FExtensionList* ListPtr = ExtensionMap.Find(Tag))
		{
			// Copy in case there are removals while handling callbacks
			FExtensionList ExtensionArray(*ListPtr);

			for (const TSharedPtr<FUIExtension>& Extension : ExtensionArray)
			{
				if (ExtensionPoint->DoesExtensionPassContract(Extension.Get()))
				{
					FUIExtensionRequest Request = CreateExtensionRequest(Extension);
					ExtensionPoint->Callback.ExecuteIfBound(EUIExtensionAction::Added, Request);
				}
			}
		}

		if (ExtensionPoint->ExtensionPointTagMatchType == EUIExtensionPointMatch::ExactMatch)
		{
			break;
		}
	}
}

void UUIExtensionSubsystem::NotifyExtensionPointsOfExtension(EUIExtensionAction Action, TSharedPtr<FUIExtension>& Extension)
{
	bool bOnInitialTag = true;
	for (FGameplayTag Tag = Extension->ExtensionPointTag; Tag.IsValid(); Tag = Tag.RequestDirectParent())
	{
		if (const FExtensionPointList* ListPtr = ExtensionPointMap.Find(Tag))
		{
			// Copy in case there are removals while handling callbacks
			FExtensionPointList ExtensionPointArray(*ListPtr);

			for (const TSharedPtr<FUIExtensionPoint>& ExtensionPoint : ExtensionPointArray)
			{
				if (bOnInitialTag || (ExtensionPoint->ExtensionPointTagMatchType == EUIExtensionPointMatch::PartialMatch))
				{
					if (ExtensionPoint->DoesExtensionPassContract(Extension.Get()))
					{
						FUIExtensionRequest Request = CreateExtensionRequest(Extension);
						ExtensionPoint->Callback.ExecuteIfBound(Action, Request);
					}
				}
			}
		}
		
		bOnInitialTag = false;
	}
}

void UUIExtensionSubsystem::UnregisterExtension(const FUIExtensionHandle& ExtensionHandle)
{
	if (ExtensionHandle.IsValid())
	{
		checkf(ExtensionHandle.ExtensionSource == this, TEXT("Trying to unregister an extension that's not from this extension subsystem."));

		TSharedPtr<FUIExtension> Extension = ExtensionHandle.DataPtr;
		if (FExtensionList* ListPtr = ExtensionMap.Find(Extension->ExtensionPointTag))
		{
			if (Extension->ContextObject.IsExplicitlyNull())
			{
				UE_LOG(LogUIExtension, Verbose, TEXT("Extension [%s] @ [%s] Unregistered"), *GetNameSafe(Extension->Data), *Extension->ExtensionPointTag.ToString());
			}
			else
			{
				UE_LOG(LogUIExtension, Verbose, TEXT("Extension [%s] for [%s] @ [%s] Unregistered"), *GetNameSafe(Extension->Data), *GetNameSafe(Extension->ContextObject.Get()), *Extension->ExtensionPointTag.ToString());
			}

			NotifyExtensionPointsOfExtension(EUIExtensionAction::Removed, Extension);

			ListPtr->RemoveSwap(Extension);
			
			if (ListPtr->Num() == 0)
			{
				ExtensionMap.Remove(Extension->ExtensionPointTag);
			}
		}
	}
	else
	{
		UE_LOG(LogUIExtension, Warning, TEXT("Trying to unregister an invalid Handle."));
	}
}

void UUIExtensionSubsystem::UnregisterExtensionPoint(const FUIExtensionPointHandle& ExtensionPointHandle)
{
	if (ExtensionPointHandle.IsValid())
	{
		check(ExtensionPointHandle.ExtensionSource == this);

		const TSharedPtr<FUIExtensionPoint> ExtensionPoint = ExtensionPointHandle.DataPtr;
		if (FExtensionPointList* ListPtr = ExtensionPointMap.Find(ExtensionPoint->ExtensionPointTag))
		{
			UE_LOG(LogUIExtension, Verbose, TEXT("Extension Point [%s] Unregistered"), *ExtensionPoint->ExtensionPointTag.ToString());

			ListPtr->RemoveSwap(ExtensionPoint);
			if (ListPtr->Num() == 0)
			{
				ExtensionPointMap.Remove(ExtensionPoint->ExtensionPointTag);
			}
		}
	}
	else
	{
		UE_LOG(LogUIExtension, Warning, TEXT("Trying to unregister an invalid Handle."));
	}
}

FUIExtensionRequest UUIExtensionSubsystem::CreateExtensionRequest(const TSharedPtr<FUIExtension>& Extension)
{
	FUIExtensionRequest Request;
	Request.ExtensionHandle = FUIExtensionHandle(this, Extension);
	Request.ExtensionPointTag = Extension->ExtensionPointTag;
	Request.Priority = Extension->Priority;
	Request.Data = Extension->Data;
	Request.ContextObject = Extension->ContextObject.Get();

	return Request;
}

FUIExtensionPointHandle UUIExtensionSubsystem::K2_RegisterExtensionPoint(FGameplayTag ExtensionPointTag, EUIExtensionPointMatch ExtensionPointTagMatchType, const TArray<UClass*>& AllowedDataClasses, FExtendExtensionPointDynamicDelegate ExtensionCallback)
{
	return RegisterExtensionPoint(ExtensionPointTag, ExtensionPointTagMatchType, AllowedDataClasses, FExtendExtensionPointDelegate::CreateWeakLambda(ExtensionCallback.GetUObject(), [this, ExtensionCallback](EUIExtensionAction Action, const FUIExtensionRequest& Request) {
		ExtensionCallback.ExecuteIfBound(Action, Request);
	}));
}

FUIExtensionHandle UUIExtensionSubsystem::K2_RegisterExtensionAsWidget(FGameplayTag ExtensionPointTag, TSubclassOf<UUserWidget> WidgetClass, int32 Priority)
{
	return RegisterExtensionAsWidget(ExtensionPointTag, WidgetClass, Priority);
}

FUIExtensionHandle UUIExtensionSubsystem::K2_RegisterExtensionAsWidgetForContext(FGameplayTag ExtensionPointTag, TSubclassOf<UUserWidget> WidgetClass, UObject* ContextObject, int32 Priority)
{
	if (ContextObject)
	{
		return RegisterExtensionAsWidgetForContext(ExtensionPointTag, ContextObject, WidgetClass, Priority);
	}
	else
	{
		FFrame::KismetExecutionMessage(TEXT("A null ContextObject was passed to Register Extension (Widget For Context)"), ELogVerbosity::Error);
		return FUIExtensionHandle();
	}
}

FUIExtensionHandle UUIExtensionSubsystem::K2_RegisterExtensionAsData(FGameplayTag ExtensionPointTag, UObject* Data, int32 Priority)
{
	return RegisterExtensionAsData(ExtensionPointTag, nullptr, Data, Priority);
}

FUIExtensionHandle UUIExtensionSubsystem::K2_RegisterExtensionAsDataForContext(FGameplayTag ExtensionPointTag, UObject* ContextObject, UObject* Data, int32 Priority)
{
	if (ContextObject)
	{
		return RegisterExtensionAsData(ExtensionPointTag, ContextObject, Data, Priority);
	}
	else
	{
		FFrame::KismetExecutionMessage(TEXT("A null ContextObject was passed to Register Extension (Data For Context)"), ELogVerbosity::Error);
		return FUIExtensionHandle();
	}
}

//=========================================================

void UUIExtensionHandleFunctions::Unregister(FUIExtensionHandle& Handle)
{
	Handle.Unregister();
}

bool UUIExtensionHandleFunctions::IsValid(FUIExtensionHandle& Handle)
{
	return Handle.IsValid();
}

//=========================================================

void UUIExtensionPointHandleFunctions::Unregister(FUIExtensionPointHandle& Handle)
{
	Handle.Unregister();
}

bool UUIExtensionPointHandleFunctions::IsValid(FUIExtensionPointHandle& Handle)
{
	return Handle.IsValid();
}