#include "Std140Buffer.h"

#include <cstring>
#include <iostream>
#include <vector>

namespace
{
int gFailures = 0;

void Expect(bool condition, const char* message)
{
	if (condition)
		return;

	std::cerr << "FAIL: " << message << "\n";
	++gFailures;
}

float ReadFloat(const std::vector<unsigned char>& buffer, std::size_t offset)
{
	float value = 0.0f;
	std::memcpy(&value, buffer.data() + offset, sizeof(float));
	return value;
}

int ReadInt(const std::vector<unsigned char>& buffer, std::size_t offset)
{
	int value = 0;
	std::memcpy(&value, buffer.data() + offset, sizeof(int));
	return value;
}

void TestScalarPacking()
{
	std::vector<unsigned char> buffer;
	AppendStd140Float(buffer, 1.25f);
	AppendStd140Int(buffer, 7);

	Expect(buffer.size() == 8, "scalar values pack tightly on 4-byte alignment");
	Expect(ReadFloat(buffer, 0) == 1.25f, "float value is written at offset 0");
	Expect(ReadInt(buffer, 4) == 7, "int value is written at offset 4");
}

void TestVectorAlignment()
{
	std::vector<unsigned char> buffer;
	AppendStd140Float(buffer, 1.0f);
	AppendStd140Vec2(buffer, 2.0f, 3.0f);
	AppendStd140Vec4(buffer, 4.0f, 5.0f, 6.0f, 7.0f);

	Expect(buffer.size() == 32, "vec2 aligns to 8 bytes and vec4 aligns to 16 bytes");
	Expect(ReadFloat(buffer, 8) == 2.0f, "vec2 x value is aligned");
	Expect(ReadFloat(buffer, 12) == 3.0f, "vec2 y value follows x");
	Expect(ReadFloat(buffer, 16) == 4.0f, "vec4 x value is aligned");
	Expect(ReadFloat(buffer, 28) == 7.0f, "vec4 w value is written");
}
}

int main()
{
	TestScalarPacking();
	TestVectorAlignment();

	if (gFailures != 0)
	{
		std::cerr << gFailures << " Std140Buffer test failure(s).\n";
		return 1;
	}

	std::cout << "Std140Buffer tests passed.\n";
	return 0;
}