local gpuobj
local function putpixel(obj)
	gpuobj.setColor(obj.r,obj.g,obj.b)
	gpuobj.plot(obj.x,obj.y)
end

local function copy(orig)
    local orig_type = type(orig)
    local copy
    if orig_type == 'table' then
        copy = {}
        for orig_key, orig_value in pairs(orig) do
            copy[orig_key] = orig_value
        end
    else -- number, string, boolean, etc
        copy = orig
    end
    return copy
end

function gouraud(gpu,x1,y1,x2,y2,x3,y3,r1,g1,b1,r2,g2,b2,r3,g3,b3)
	gpuobj = gpu
	A = {x = x1,y = y1,r = r1,g = g1,b = b1}
	B = {x = x2,y = y2,r = r2,g = g2,b = b2}
	C = {x = x3,y = y3,r = r3,g = g3,b = b3}
	if B.y > C.y then
		B,C = C,B
	end
	if A.y > B.y then
		A,B = B,A
	end
	if A.y > C.y then
		A,C = C,A
	end
	if (B.y-A.y > 0) then
		dx1=(B.x-A.x)/(B.y-A.y);
		dr1=(B.r-A.r)/(B.y-A.y);
		dg1=(B.g-A.g)/(B.y-A.y);
		db1=(B.b-A.b)/(B.y-A.y);
	else
		dx1,dr1,dg1,db1=0,0,0,0;
	end

	if (C.y-A.y > 0) then
		dx2=(C.x-A.x)/(C.y-A.y);
		dr2=(C.r-A.r)/(C.y-A.y);
		dg2=(C.g-A.g)/(C.y-A.y);
		db2=(C.b-A.b)/(C.y-A.y);
	else
		dx2,dr2,dg2,db2=0,0,0,0;
	end

	if (C.y-B.y > 0) then
		dx3=(C.x-B.x)/(C.y-B.y);
		dr3=(C.r-B.r)/(C.y-B.y);
		dg3=(C.g-B.g)/(C.y-B.y);
		db3=(C.b-B.b)/(C.y-B.y);
	else
		dx3,dr3,dg3,db3=0,0,0,0;
	end

	E=copy(A);
	S=copy(E);
	if (dx1 > dx2) then
		while (S.y<=B.y) do
			if (E.x-S.x > 0) then
				dr=(E.r-S.r)/(E.x-S.x);
				dg=(E.g-S.g)/(E.x-S.x);
				db=(E.b-S.b)/(E.x-S.x);
			else
				dr,dg,db=0,0,0;
			end
			P=copy(S);
			while (P.x < E.x) do
				putpixel(P);
				P.r=P.r+dr; P.g=P.g+dg; P.b=P.b+db;
				P.x = P.x + 1
			end
			S.x=S.x+dx2; S.r=S.r+dr2; S.g=S.g+dg2; S.b=S.b+db2;
			E.x=E.x+dx1; E.r=E.r+dr1; E.g=E.g+dg1; E.b=E.b+db1;
			S.y = S.y + 1
			E.y = E.y + 1
		end

		E=copy(B);
		while (S.y<=C.y) do
			if (E.x-S.x > 0) then
				dr=(E.r-S.r)/(E.x-S.x);
				dg=(E.g-S.g)/(E.x-S.x);
				db=(E.b-S.b)/(E.x-S.x);
			else
				dr,dg,db=0,0,0;
			end
			P=copy(S);
			while (P.x < E.x) do
				putpixel(P);
				P.r=P.r+dr; P.g=P.g+dg; P.b=P.b+db;
				P.x = P.x + 1
			end
			S.x=S.x+dx2; S.r=S.r+dr2; S.g=S.g+dg2; S.b=S.b+db2;
			E.x=E.x+dx3; E.r=E.r+dr3; E.g=E.g+dg3; E.b=E.b+db3;
			S.y = S.y + 1
			E.y = E.y + 1
		end
	else
		while (S.y<=B.y) do
			if (E.x-S.x > 0) then
				dr=(E.r-S.r)/(E.x-S.x);
				dg=(E.g-S.g)/(E.x-S.x);
				db=(E.b-S.b)/(E.x-S.x);
			else
				dr,dg,db=0,0,0;
			end

			P=copy(S);
			while (P.x < E.x) do
				putpixel(P);
				P.r=P.r+dr; P.g=P.g+dg; P.b=P.b+db;
				P.x = P.x + 1
			end
			S.x=S.x+dx1; S.r=S.r+dr1; S.g=S.g+dg1; S.b=S.b+db1;
			E.x=E.x+dx2; E.r=E.r+dr2; E.g=E.g+dg2; E.b=E.b+db2;
			S.y = S.y + 1
			E.y = E.y + 1
		end

		S=copy(B);
		while (S.y<=C.y) do
			if (E.x-S.x > 0) then
				dr=(E.r-S.r)/(E.x-S.x);
				dg=(E.g-S.g)/(E.x-S.x);
				db=(E.b-S.b)/(E.x-S.x);
			else
				dr,dg,db=0,0,0;
			end

			P=copy(S);
			while (P.x < E.x) do
				putpixel(P);
				P.r=P.r+dr; P.g=P.g+dg; P.b=P.b+db;
				P.x = P.x + 1
			end
			S.x=S.x+dx3; S.r=S.r+dr3; S.g=S.g+dg3; S.b=S.b+db3;
			E.x=E.x+dx2; E.r=E.r+dr2; E.g=E.g+dg2; E.b=E.b+db2;
			S.y = S.y + 1
			E.y = E.y + 1
		end
	end
end