#include <sp/common/VarInt.h>

#include <sp/common/DataBuffer.h>
#include <sp/common/DataBufferOperators.h>
#include <stdexcept>

namespace sp {

static constexpr int SEGMENT_BITS = (1 << 7) - 1;
static constexpr int CONTINUE_BIT = 1 << 7;

std::size_t VarInt::GetSerializedLength() const {
	DataBuffer buffer;
	buffer << *this;
	return buffer.GetSize();
}

DataBuffer& operator<<(DataBuffer& out, const VarInt& var) {
	std::uint64_t value = var.m_Value;
	while (true) {
		if ((value & ~static_cast<std::uint64_t>(SEGMENT_BITS)) == 0) {
			out << static_cast<std::uint8_t>(value);
			return out;
		}

		out << static_cast<std::uint8_t>((value & SEGMENT_BITS) | CONTINUE_BIT);

		value >>= 7;
	}
}

DataBuffer& operator>>(DataBuffer& in, VarInt& var) {
	var.Read([&in](std::uint8_t& data){
		in.ReadSome(&data, 1);
	});
	return in;
}

void VarInt::Read(const ReadFunc& read) {
	m_Value = 0;
	unsigned int position = 0;
	std::uint8_t currentByte;

	while (true) {
		read(currentByte);
		m_Value |= static_cast<std::uint64_t>(currentByte & SEGMENT_BITS) << position;

		if ((currentByte & CONTINUE_BIT) == 0)
			break;

		position += 7;

		if (position >= 8 * sizeof(m_Value))
			throw std::runtime_error("VarInt is too big");
	}
}

}  // namespace sp