We only allow a single tax of each class in products and invoices,
because it does not make sense to add two different VAT to the same
product, for instance.
We will only allow to select a tax from each of the tax classes, but
the user needs to know what class each tax belongs to, and grouping
the taxes by class in the select helps with that.
Apparently, in older version of WeasyPrint it was possible to output
either PNG or PDF, so they had that parameter. In more recent versions,
the only acceptable is PDF, but they removed the fucking parameter
between versions 51 and 52, to it _will_ fail in recent version of
WeasyPrint.
For now, i am using the same version that Debian 11 does, and let’s
hope it stays like this a long time. (It won’t, of course, but well….)
Although it is possible to just print the invoice from the browser, many
people will not even try an assume that they can not create a PDF for
the invoice.
I thought of using Groff or TeX to create the PDF, but it would mean
maintaining two templates in two different systems (HTML and whatever i
would use), and would probably look very different, because i do not
know Groff or TeX that well.
I wish there was a way to tell the browser to print to PDF, and it can
be done, but only with the Chrome Protocol to a server-side running
Chrome instance. This works, but i would need a Chrome running as a
daemon.
I also wrote a Qt application that uses QWebEngine to print the PDF,
much like wkhtmltopdf, but with support for more recent HTML and CSS
standards. Unfortunately, Qt 6.4’s embedded Chromium does not follow
break-page-inside as well as WeasyPrint does.
To use WeasyPrint, at first i wanted to reach the same URL as the user,
passing the cookie to WeasyPrint so that i can access the same invoice
as the user, something that can be done with wkhtmltopdf, but WeasyPrint
does not have such option. I did it with a custom Python script, but
then i need to package and install that script, that is not that much
work, but using the Debian-provided script is even less work, and less
likely to drift when WeasyPrint changes API.
Also, it is unnecessary to do a network round-trip from Go to Python
back to Go, because i can already write the invoice HTML as is to
WeasyPrint’s stdin.
Had to group name and description rows in tbody because i do not want
to break them on pagination.
I also could not use tfoot for subtotal, taxes, and total because then
they appear on every page.
The disclaimer should appear only at the very bottom of the last page,
but i do not know how to do that; using position fixed shows it on
every page.
They are not functions because i need to join them with the main
invoice relation, and although possible is a bit more awkward with
functions.
The taxes have their own relation because i will need them grouped by
their name in the PDF, so it will probably be a select for that
relation.
When updating the product list, i forgot to change the index in the
product field’s names and, therefore, i created invoices with only the
products until the first gap.
I have moved everything into a different file, even though it is related
to “db”, because it was starting to get a bit ugly.
Apparently i was doing too much work and had to read the code to
understand what i was supposed to do, because pgtypes’ documentation,
as all other projects from the same author, is almost non-existent.
I needed to add binary encoding function for the new_invoice_product
type, and currently it is not correct: i hardcoded the OID values, but
they are going to be different on a different database.
They are to complete the invoice, so it can be in an invalid date, but
we do not want to force people to finish all required inputs before they
can add products or update quantities, do we?
Now had to add the empty option label for customer in all cases, because
it could be empty, although that should be done regardless in case
someone has a browser that does not validate fields.
I have seen that pgx has the CollectRows function to do the same job as
that function. I can not use CollectRows because it uses generics and
requires Go 1.18, but i have adopted the same nomenclature they use.
Apparently, url.Values.Has and math.MaxInt was added to Go 1.17,
but on Debian Bullseye there is only Go 1.16. I do not want to
install a new version of Go to the server unless there is an
overwhelming reason, and a couple of methods are not. Thus, now i use
Go 1.16 too on my development machine, to avoid situations like this.
jordi fita mas