AR15 PDW Weapon Light

I would love to build my own weapon light verses purchasing something overpriced for my next build.

I have some loose requirements and having never built up a flashlight yet am open to parts to build this to meet said requirements.

Emitter: Cree XM-L
Drive Modes: Minumium two; max three. Basic low/med/high - no strobe or sos
Body type: 1” Body
Battery: 18650
Beam Pattern:?? Suggestions. Likely non adjustable but not sure.

A pressure switch is a must.

Thanks for any ideas/suggestions!