====== Server Print Templates ======

===== What's the Problem? =====

  * Templates whose syntax depends on the UI framework creates inconsistency and is not sustainable.
  * Angular templates must be pre-compiled.
    * Template modification requires local install and use of 'ng build'.
  * Current template editing could be more secure (scrubbing scripts, etc.)

==== Proposal: Server Templates ====

  * Templates are configured and stored in the database, similar to Action/Trigger templates, using Template Toolkit.
  * Modifying templates requires permissions.
  * Print templates can be saved per-org (and potentially per workstation if needed).
  * Print templates are managed via admin UI.
  * Support per-locale templates.
  * Templates can produce different content types
  * Templates are compiled for printing on the server
    * At print time, the caller passes template data, template name, etc. to the server and receives a compiled (text, html, etc.) response.
  * Template content can be scrubbed on the server for added security.
    * We could use something like https://metacpan.org/pod/HTML::Restrict to remove all but an anointed set of HTML tags and attributes (for text/html templates)
  * Note we are already using server-managed templates for self-checkout receipts, some ACQ interfaces, and various others, so the general concept is not new.

==== Proof of Concept ====

https://git.evergreen-ils.org/?p=working/Evergreen.git;a=shortlog;h=refs/heads/user/berick/server-print-templates

This creates a purpose-built template processor instead of using Action/Trigger for several reasons:

  * A/T has a lot of moving parts which are not needed
    * Printing needs to be as streamlined as possible to avoid slowing staff work flow.
    * There is no environment building, etc.
  * Provides an opportunity to add locale, content type, etc. support.
  * Uses a mod_perl front-end so template content can be returned as-is (i.e. a text/html page) avoiding the unnecessary opensrf packaging.

==== Offline Caveat ====

The staff client offline interface will still require a small set of pre-compiled templates that live within the application, since it will not be able to call out for template compilation.