ACQ fund debit origin amount is not updated during invoicing

[Bill Erickson]

Evergreen *.*

Background:

Fund debits contain an amount in the local currency and an origin_amount to represent the amount in the currency of the debit source. E.g. A fund in CAN used to purchase items from a provider using USD. The amount would be in CAN and the origin_amount would be in USD.

Problem:

During invoicing, if the final amount for a debit is different than the original estimated price for a (e.g.) copy, the amount on the fund_debit is updated to match this new reality, however the origin_amount is not. This is confusing when reviewing fund debits under Admin -> Server Admin -> Acq -> Funds interface.

Thoughts:

In the case where the debit's origin_currency_type matches the currency of the fund, the solution is simple. We can just update the origin_amount to match the new amount.

When the currencies don't match, however, updating the origin_amount would be tricky, since the final amount is assumed by the invoicing code to be represented in the local currency and there is no way (in the interface) to specify the final amount from the origin currency. Without a UI, we would have to do the currency conversion in reverse to get the new origin_amount, but that assumes the exchange rate within Evergreen matches exactly the exchange used by the library to calculate the final invoice amount. If we do this, it seems like we may just be tracking a different, wrong number.

We could add a UI, but that would mean staff are required to enter two numbers when performing cross-currency invoicing and I'm not sure if that's a reasonable request. We could require staff to enter only the origin_amount and calculate the final amount, but then we're back to relying on the in-DB exchange rate, which may not match the externally calculated rate.

Or maybe we continue to leave the origin_amount alone during invoicing and provide better documentation for the fund UI.