// 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 {

static const uint8_t MaxData[20] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
									0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff};

const IoHash IoHash::Max = IoHash::MakeFrom(MaxData);  // Initialized to all 0xff
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, std::atomic<uint64_t>* ProcessedBytes)
{
	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, ProcessedBytes](const void* Data, size_t Size) {
						 Hasher.Append(Data, Size);
						 if (ProcessedBytes != nullptr)
						 {
							 ProcessedBytes->fetch_add(Size);
						 }
					 });
		}
		else
		{
			Hasher.Append(Segment.GetData(), SegmentSize);
			if (ProcessedBytes != nullptr)
			{
				ProcessedBytes->fetch_add(SegmentSize);
			}
		}
	}

	return Hasher.GetHash();
}

IoHash
IoHash::HashBuffer(const IoBuffer& Buffer, std::atomic<uint64_t>* ProcessedBytes)
{
	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, ProcessedBytes](const void* Data, size_t Size) {
					 Hasher.Append(Data, Size);
					 if (ProcessedBytes != nullptr)
					 {
						 ProcessedBytes->fetch_add(Size);
					 }
				 });
	}
	else
	{
		Hasher.Append(Buffer.GetData(), BufferSize);
		if (ProcessedBytes != nullptr)
		{
			ProcessedBytes->fetch_add(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;
}

bool
IoHash::TryParse(std::string_view Str, IoHash& Hash)
{
	using namespace std::literals;

	if (Str.size() == IoHash::StringLength)
	{
		return ParseHexBytes(Str.data(), Str.size(), Hash.Hash);
	}

	if (Str.starts_with("0x"sv))
	{
		return TryParse(Str.substr(2), Hash);
	}

	return false;
}

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