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

#include "CoreMinimal.h"
#include "Misc/Guid.h"
#include "Serialization/CustomVersion.h"
#include "UObject/UObjectBaseUtility.h"
#include "UObject/Package.h"
#include "UObject/LinkerLoad.h"

/**
 * Returns the UE4 version of the linker for this object.
 *
 * @return	the UE4 version of the engine's package file when this object
 *			was last saved, or GPackageFileUE4Version (current version) if
 *			this object does not have a linker, which indicates that
 *			a) this object is a native only class, or
 *			b) this object's linker has been detached, in which case it is already fully loaded
 */
int32 UObjectBaseUtility::GetLinkerUE4Version() const
{
    FLinkerLoad* Loader = GetLinker();

    // No linker.
    if (Loader == nullptr)
    {
        // the _Linker reference is never set for the top-most UPackage of a package (the linker root), so if this object
        // is the linker root, find our loader in the global list.
        if (GetOutermost() == this)
        {
            Loader = FLinkerLoad::FindExistingLinkerForPackage(const_cast<UPackage*>(CastChecked<UPackage>((const UObject*)this)));
        }
    }

    if (Loader != nullptr)
    {
        // We have a linker so we can return its version.
        return Loader->UE4Ver();
    }
    else if (GetOutermost())
    {
        // Get the linker version associated with the package this object lives in
        return GetOutermost()->LinkerPackageVersion;
    }
    else
    {
        // We don't have a linker associated as we e.g. might have been saved or had loaders reset, ...
        return GPackageFileUE4Version;
    }
}

int32 UObjectBaseUtility::GetLinkerCustomVersion(FGuid CustomVersionKey) const
{
    FLinkerLoad* Loader = GetLinker();

    // No linker.
    if (Loader == NULL)
    {
        // the _Linker reference is never set for the top-most UPackage of a package (the linker root), so if this object
        // is the linker root, find our loader in the global list.
        if (GetOutermost() == this)
        {
            Loader = FLinkerLoad::FindExistingLinkerForPackage(const_cast<UPackage*>(CastChecked<UPackage>((const UObject*)this)));
        }
    }

    if (Loader != NULL)
    {
        // We have a linker so we can return its version.
        const FCustomVersion* CustomVersion = Loader->Summary.GetCustomVersionContainer().GetVersion(CustomVersionKey);
        return CustomVersion ? CustomVersion->Version : -1;
    }
    else if (GetOutermost() && GetOutermost()->LinkerCustomVersion.GetAllVersions().Num())
    {
        // Get the linker version associated with the package this object lives in
        const FCustomVersion* CustomVersion = GetOutermost()->LinkerCustomVersion.GetVersion(CustomVersionKey);
        return CustomVersion ? CustomVersion->Version : -1;
    }
    // We don't have a linker associated as we e.g. might have been saved or had loaders reset, ...
    // We must have a current version for this tag.
    return FCurrentCustomVersions::Get(CustomVersionKey).GetValue().Version;
}

/**
 * Returns the licensee version of the linker for this object.
 *
 * @return	the licensee version of the engine's package file when this object
 *			was last saved, or GPackageFileLicenseeVersion (current version) if
 *			this object does not have a linker, which indicates that
 *			a) this object is a native only class, or
 *			b) this object's linker has been detached, in which case it is already fully loaded
 */
int32 UObjectBaseUtility::GetLinkerLicenseeUE4Version() const
{
    FLinkerLoad* Loader = GetLinker();

    // No linker.
    if (Loader == NULL)
    {
        // the _Linker reference is never set for the top-most UPackage of a package (the linker root), so if this object
        // is the linker root, find our loader in the global list.
        if (GetOutermost() == this)
        {
            Loader = FLinkerLoad::FindExistingLinkerForPackage(const_cast<UPackage*>(CastChecked<UPackage>((const UObject*)this)));
        }
    }

    if (Loader != NULL)
    {
        // We have a linker so we can return its version.
        return Loader->LicenseeUE4Ver();
    }
    else if (GetOutermost())
    {
        // Get the linker version associated with the package this object lives in
        return GetOutermost()->LinkerLicenseeVersion;
    }
    else
    {
        // We don't have a linker associated as we e.g. might have been saved or had loaders reset, ...
        return GPackageFileLicenseeUE4Version;
    }
}