Try looking into the light info node. Also search the maya docs for "Use the Light Info utility". You can get the light direction for any point on a texture. Some simple trig might be necessary, but if you need help on that, just ask.

Edit: Actually thinking about it more, that wouldn't necessarily give you the surface normal, so what you could do is use the Sampler Info node, specifically the facing ratio, and just look through the light (use it as a camera).