opengl-compat

When using the OpenGL fixed function pipeline for vertex setup, how a fragment program looks like that is compatible to the fixed function vertex setup? I guess that usually depends on the number of light sources and texture layers etc.. So for example how does a simple non-texture one-lightsource goraud shading fragment program look like that replaces GL's fixed function shader? While Gouraud shading calculates the light in the the vertex shader, Phong shading calculates the light in the fragment shader. The standard OpenGL light model is a Gouraud shading model, with a Blinn-Phong light