// ================
// Vertex shader:
// ================
#version 330 core
layout (location = 0) in vec2 position;
layout (location = 1) in vec3 color;

out VS_OUT {
    vec3 color;
} vs_out;

void main()
{
    gl_Position = vec4(position.x, position.y, 0.0f, 1.0f); 
    vs_out.color = color;
}


// ================
// Fragment shader:
// ================
#version 330 core
in vec3 fColor;
out vec4 color;

void main()
{
    color = vec4(fColor, 1.0f);   
}


// ================
// Geometry shader:
// ================
#version 330 core
layout (points) in;
layout (triangle_strip, max_vertices = 5) out;

in VS_OUT {
    vec3 color;
} gs_in[];

out vec3 fColor;

void build_house(vec4 position)
{    
    fColor = gs_in[0].color; // gs_in[0] since there's only one input vertex
    gl_Position = position + vec4(-0.2f, -0.2f, 0.0f, 0.0f);    // 1:bottom-left   
    EmitVertex();   
    gl_Position = position + vec4( 0.2f, -0.2f, 0.0f, 0.0f);    // 2:bottom-right
    EmitVertex();
    gl_Position = position + vec4(-0.2f,  0.2f, 0.0f, 0.0f);    // 3:top-left
    EmitVertex();
    gl_Position = position + vec4( 0.2f,  0.2f, 0.0f, 0.0f);    // 4:top-right
    EmitVertex();
    gl_Position = position + vec4( 0.0f,  0.4f, 0.0f, 0.0f);    // 5:top
    fColor = vec3(1.0f, 1.0f, 1.0f);
    EmitVertex();
    EndPrimitive();
}

void main() {    
    build_house(gl_in[0].gl_Position);
}