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

#include <zencore/iohash.h>

#include <zencore/blake3.h>
#include <zencore/compositebuffer.h>
#include <zencore/filesystem.h>
#include <zencore/string.h>
#include <zencore/testing.h>

#include <gsl/gsl-lite.hpp>

namespace zen {

const IoHash IoHash::Zero{};  // Initialized to all zeros

IoHash
IoHash::HashBuffer(const void* data, size_t byteCount)
{
	BLAKE3 b3 = BLAKE3::HashMemory(data, byteCount);

	IoHash io;
	memcpy(io.Hash, b3.Hash, sizeof io.Hash);

	return io;
}

IoHash
IoHash::HashBuffer(const CompositeBuffer& Buffer)
{
	IoHashStream Hasher;

	for (const SharedBuffer& Segment : Buffer.GetSegments())
	{
		size_t				  SegmentSize	= Segment.GetSize();
		static const uint64_t BufferingSize = 256u * 1024u;

		IoBufferFileReference FileRef;
		if (SegmentSize >= (BufferingSize + BufferingSize / 2) && Segment.GetFileReference(FileRef))
		{
			ScanFile(FileRef.FileHandle,
					 FileRef.FileChunkOffset,
					 FileRef.FileChunkSize,
					 BufferingSize,
					 [&Hasher](const void* Data, size_t Size) { Hasher.Append(Data, Size); });
		}
		else
		{
			Hasher.Append(Segment.GetData(), SegmentSize);
		}
	}

	return Hasher.GetHash();
}

IoHash
IoHash::HashBuffer(const IoBuffer& Buffer)
{
	IoHashStream Hasher;

	size_t				  BufferSize	= Buffer.GetSize();
	static const uint64_t BufferingSize = 256u * 1024u;
	IoBufferFileReference FileRef;
	if (BufferSize >= (BufferingSize + BufferingSize / 2) && Buffer.GetFileReference(FileRef))
	{
		ScanFile(FileRef.FileHandle,
				 FileRef.FileChunkOffset,
				 FileRef.FileChunkSize,
				 BufferingSize,
				 [&Hasher](const void* Data, size_t Size) { Hasher.Append(Data, Size); });
	}
	else
	{
		Hasher.Append(Buffer.GetData(), BufferSize);
	}

	return Hasher.GetHash();
}

IoHash
IoHash::FromHexString(const char* string)
{
	return FromHexString({string, sizeof(IoHash::Hash) * 2});
}

IoHash
IoHash::FromHexString(std::string_view string)
{
	ZEN_ASSERT(string.size() == 2 * sizeof(IoHash::Hash));

	IoHash io;

	ParseHexBytes(string.data(), string.size(), io.Hash);

	return io;
}

const char*
IoHash::ToHexString(char* outString /* 40 characters + NUL terminator */) const
{
	ToHexBytes(Hash, sizeof(IoHash), outString);
	outString[2 * sizeof(IoHash)] = '\0';

	return outString;
}

StringBuilderBase&
IoHash::ToHexString(StringBuilderBase& outBuilder) const
{
	String_t Str;
	ToHexString(Str);

	outBuilder.AppendRange(Str, &Str[StringLength]);

	return outBuilder;
}

std::string
IoHash::ToHexString() const
{
	String_t Str;
	ToHexString(Str);

	return Str;
}

}  // namespace zen