Need an "ordered channel number".

[brettviren]

In WCT the "channel number" or "channel identifier" is an "opaque" value. WCT does not care what the number is as long as it is unique. Ultimately the channel numbering is set by the "WCT wire file" (see wirecell-util make-wires or wirecell-util convert-oneside-wires for an example that makes a "wire file").

However, there are times where one must know the channels in some kind of ordering. In particular, for the signal processing one must be able to order them to match the order of field response functions.

For MB, this "accidentally" is almost satisfied. The conventional MB channel number ordering following that of the wires exactly (up to a per-plane offset). This nice degeneracy of two different concepts is heavily violated in DUNE where wrapped wires and the ADC channel "shuffle" destroy any hope of sequential channel numbers having any meaningful pattern.

DUNE does have the concept of "wire attachment number" which runs 1-400 (U/V) or 1-480 (W) along the top of an APA face. However, this is not right either as "the other side" U/V wires need to be included.

So, some concept needs to be invented, a mapping from channel to this new number made for each detector, and any existing code which assumes the degeneracy needs to be fixed.