Agenda view sorting based on custom property

[Haakon HR <haakonhr@gmail.com>]

Hi all,

I'm trying to hack together a custom agenda view where I want to sort
the entries by a custom property, let's call it :CUSTOM:. So the entries
in question would look like this:

* TODO Buy cheese
  :PROPERTIES
  :CUSTOM: 2
  :END:

I have tried a few approaches but I'm a bit stuck. My first approach was
to use the variable `org-agenda-cmp-user-defined' and implement a
comparison function based on the already existing ones like
`org-cmp-alpha' or `org-cmp-effort'. However, I'm not able to extract
the custom property from the kind of entry that is passed into the
comparison function, which seem to rely on `text-properties'. Is it
possible to somehow make custom properties available as a text property,
similar to things like 'todo-state, 'tags and so on?

My second approach was to try to use the org parsing capabilities. I can
get the AST by parsing the buffers of interest containing entries I want
to sort. I'm for example able to get the list of :CUSTOM: with this
snippet:

`(org-element-map (org-element-parse-buffer) '(headline) (lambda (hl)
  (org-element-property :RELEVANCE hl)))'

Then I imagine I can manipulate the AST into the order I want and then
use `org-element-interpret-data' to create a new buffer w/ the desired
sorting. However, I haven't found a way to actually create a buffer
containing all the information from the interpreted AST as some
information seem to get lost. The end goal in this case is also an
agenda view where I can build on top of all the agenda capabilities, but
using this custom sorting. Is there a way to start from an AST and
transform it into an agenda view?

Thanks for any help or tips,
Haakon