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

#include "DerivedDataLegacyCacheStore.h"

#include "Algo/AllOf.h"
#include "DerivedDataBackendInterface.h"
#include "DerivedDataCacheInterface.h"
#include "Misc/Crc.h"
#include "Misc/ScopeRWLock.h"
#include "Misc/SecureHash.h"
#include "Misc/StringBuilder.h"
#include "ProfilingDebugging/CpuProfilerTrace.h"
#include "String/BytesToHex.h"

namespace UE::DerivedData
{

void ILegacyCacheStore::LegacyPut(
	const TConstArrayView<FLegacyCachePutRequest> Requests,
	IRequestOwner& Owner,
	FOnLegacyCachePutComplete&& OnComplete)
{
	struct FKeyWithUserData
	{
		FLegacyCacheKey Key;
		uint64 UserData;
	};

	TArray<FKeyWithUserData, TInlineAllocator<1>> LegacyRequests;
	TArray<FCachePutValueRequest, TInlineAllocator<1>> ValueRequests;
	LegacyRequests.Reserve(Requests.Num());
	ValueRequests.Reserve(Requests.Num());

	uint64 RequestIndex = 0;
	for (const FLegacyCachePutRequest& Request : Requests)
	{
		LegacyRequests.Add({Request.Key, Request.UserData});
		ValueRequests.Add({Request.Name, Request.Key.GetKey(), Request.Value.GetValue(), Request.Policy, RequestIndex++});
	}

	PutValue(ValueRequests, Owner, [LegacyRequests = MoveTemp(LegacyRequests), OnComplete = MoveTemp(OnComplete)](FCachePutValueResponse&& Response)
	{
		const FKeyWithUserData& LegacyRequest = LegacyRequests[int32(Response.UserData)];
		OnComplete({Response.Name, LegacyRequest.Key, LegacyRequest.UserData, Response.Status});
	});
}

void ILegacyCacheStore::LegacyGet(
	const TConstArrayView<FLegacyCacheGetRequest> Requests,
	IRequestOwner& Owner,
	FOnLegacyCacheGetComplete&& OnComplete)
{
	struct FKeyWithUserData
	{
		FLegacyCacheKey Key;
		uint64 UserData;
	};

	TArray<FKeyWithUserData, TInlineAllocator<1>> LegacyRequests;
	TArray<FCacheGetValueRequest, TInlineAllocator<1>> ValueRequests;
	LegacyRequests.Reserve(Requests.Num());
	ValueRequests.Reserve(Requests.Num());

	uint64 RequestIndex = 0;
	for (const FLegacyCacheGetRequest& Request : Requests)
	{
		LegacyRequests.Add({Request.Key, Request.UserData});
		ValueRequests.Add({Request.Name, Request.Key.GetKey(), Request.Policy, RequestIndex++});
	}

	GetValue(ValueRequests, Owner, [LegacyRequests = MoveTemp(LegacyRequests), OnComplete = MoveTemp(OnComplete)](FCacheGetValueResponse&& Response)
	{
		const FKeyWithUserData& LegacyRequest = LegacyRequests[int32(Response.UserData)];
		OnComplete({Response.Name, LegacyRequest.Key, FLegacyCacheValue(Response.Value), LegacyRequest.UserData, Response.Status});
	});
}

void ILegacyCacheStore::LegacyDelete(
	const TConstArrayView<FLegacyCacheDeleteRequest> Requests,
	IRequestOwner& Owner,
	FOnLegacyCacheDeleteComplete&& OnComplete)
{
	CompleteWithStatus(Requests, OnComplete, EStatus::Error);
}

Private::FLegacyCacheKeyShared::FLegacyCacheKeyShared(const FStringView InFullKey, const int32 InMaxKeyLength)
	: FullKey(InFullKey)
	, MaxKeyLength(InMaxKeyLength)
{
}

const FSharedString& Private::FLegacyCacheKeyShared::GetShortKey()
{
	if (FReadScopeLock ReadLock(Lock); !ShortKey.IsEmpty())
	{
		return ShortKey;
	}

	TRACE_CPUPROFILER_EVENT_SCOPE(FLegacyCacheKey::GetShortKey);

	FWriteScopeLock WriteLock(Lock);
	if (!ShortKey.IsEmpty())
	{
		return ShortKey;
	}

	const FStringView LocalFullKey = FullKey;
	checkf(Algo::AllOf(LocalFullKey, FDerivedDataCacheInterface::IsValidCacheChar),
		TEXT("Invalid characters in cache key %s. Use SanitizeCacheKey or BuildCacheKey to create valid keys."), *FullKey);

	if (LocalFullKey.Len() <= MaxKeyLength)
	{
		ShortKey = FullKey;
		return ShortKey;
	}

	const auto FullKeyUCS2 = StringCast<UCS2CHAR>(LocalFullKey.GetData(), LocalFullKey.Len());
	const int32 FullKeyLength = FullKeyUCS2.Length();
	const uint32 CRCofPayload(FCrc::MemCrc32(FullKeyUCS2.Get(), FullKeyLength * sizeof(UCS2CHAR)));

	uint8 Hash[FSHA1::DigestSize];
	FSHA1 HashState;
	HashState.Update((const uint8*)&FullKeyLength, sizeof(int32));
	HashState.Update((const uint8*)&CRCofPayload, sizeof(uint32));
	HashState.Update((const uint8*)FullKeyUCS2.Get(), FullKeyLength * sizeof(UCS2CHAR));
	HashState.Final();
	HashState.GetHash(Hash);

	TStringBuilder<256> ShortKeyBuilder;
	ShortKeyBuilder << LocalFullKey.Left(MaxKeyLength - FSHA1::DigestSize * 2 - 2) << TEXT("__");
	String::BytesToHex(Hash, ShortKeyBuilder);

	check(ShortKeyBuilder.Len() == MaxKeyLength && ShortKeyBuilder.Len() > 0);
	ShortKey = ShortKeyBuilder;
	return ShortKey;
}

FLegacyCacheKey::FLegacyCacheKey(const FStringView FullKey, const int32 MaxKeyLength)
	: Key(ConvertLegacyCacheKey(FullKey))
	, Shared(new Private::FLegacyCacheKeyShared(FullKey, MaxKeyLength))
{
}

bool FLegacyCacheKey::ReadValueTrailer(FCompositeBuffer& Value) const
{
	if (HasShortKey())
	{
		FUtf8StringBuilderBase FullKey;
		FullKey << GetFullKey();
		const FMemoryView CompareKey(*FullKey, (FullKey.Len() + 1) * sizeof(UTF8CHAR));
		if (Value.GetSize() < CompareKey.GetSize())
		{
			UE_LOG(LogDerivedDataCache, Display, TEXT("FLegacyCacheKey: Hash collision or short value for key %s."), *GetFullKey());
			return false;
		}
		FUniqueBuffer CopyBuffer;
		const uint64 KeyOffset = Value.GetSize() - CompareKey.GetSize();
		const FMemoryView ValueKey = Value.ViewOrCopyRange(KeyOffset, CompareKey.GetSize(), CopyBuffer);
		if (!CompareKey.EqualBytes(ValueKey))
		{
			UE_LOG(LogDerivedDataCache, Display, TEXT("FLegacyCacheKey: Hash collision for key %s."), *GetFullKey());
			return false;
		}
		Value = Value.Mid(0, KeyOffset);
	}
	return true;
}

void FLegacyCacheKey::WriteValueTrailer(FCompositeBuffer& Value) const
{
	if (HasShortKey())
	{
		FUtf8StringBuilderBase FullKey;
		FullKey << GetFullKey();
		Value = FCompositeBuffer(Value, FSharedBuffer::Clone(*FullKey, (FullKey.Len() + 1) * sizeof(UTF8CHAR)));
	}
}

FLegacyCacheValue::FLegacyCacheValue(const FValue& Value)
{
	if (Value.HasData() || !Value.GetRawHash().IsZero())
	{
		Shared = new Private::FLegacyCacheValueShared(Value);
	}
}

FLegacyCacheValue::FLegacyCacheValue(const FCompositeBuffer& RawData)
{
	if (RawData)
	{
		Shared = new Private::FLegacyCacheValueShared(RawData);
	}
}

Private::FLegacyCacheValueShared::FLegacyCacheValueShared(const FValue& InValue)
	: Value(InValue)
{
}

Private::FLegacyCacheValueShared::FLegacyCacheValueShared(const FCompositeBuffer& InRawData)
	: RawData(InRawData.MakeOwned())
{
}

const FValue& Private::FLegacyCacheValueShared::GetValue()
{
	FWriteScopeLock WriteLock(Lock);
	if (!Value.HasData() && !RawData.IsNull())
	{
		Value = FValue::Compress(RawData);
	}
	return Value;
}

const FCompositeBuffer& Private::FLegacyCacheValueShared::GetRawData()
{
	FWriteScopeLock WriteLock(Lock);
	if (RawData.IsNull() && Value.HasData())
	{
		RawData = Value.GetData().DecompressToComposite();
	}
	return RawData;
}

FIoHash Private::FLegacyCacheValueShared::GetRawHash() const
{
	return Value.HasData() ? Value.GetRawHash() : FIoHash::HashBuffer(RawData);
}

uint64 Private::FLegacyCacheValueShared::GetRawSize() const
{
	return Value.HasData() ? Value.GetRawSize() : RawData.GetSize();
}

FLegacyCachePutResponse FLegacyCachePutRequest::MakeResponse(const EStatus Status) const
{
	return {Name, Key, UserData, Status};
}

FLegacyCacheGetResponse FLegacyCacheGetRequest::MakeResponse(const EStatus Status) const
{
	return {Name, Key, {}, UserData, Status};
}

FLegacyCacheDeleteResponse FLegacyCacheDeleteRequest::MakeResponse(const EStatus Status) const
{
	return {Name, Key, UserData, Status};
}

} // UE::DerivedData