#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec2 aTexCoord;
layout (location = 2) in int aTileIndex;
layout (location = 3) in mat4 aModel;

uniform int tilesPerRow;
uniform mat4 proj;
uniform mat4 view;

out vec2 texCoord;
out int tileIndex;

void main()
{
	tileIndex = aTileIndex;
	gl_Position = proj * view * aModel * vec4(aPos, 1.0);
	if (tileIndex != 0) 
	{
		int index = tileIndex - 1;
		float tileSize = 1.0 / float(tilesPerRow);

		int row = index / tilesPerRow;
		int col = index % tilesPerRow;

		float offsetX = float(col) * tileSize;
		float offsetY = float(row) * tileSize;

		texCoord.x = (aTexCoord.x + col) * tileSize;
		texCoord.y = (aTexCoord.y + row) * tileSize;
	}
	else
	{
		texCoord.x = 0.0;
		texCoord.y = 0.0;
	}
}