Re: Lua filter for section numbers in internal references

[Albert Krewinkel <albert+pandoc-9EawChwDxG8hFhg+JK9F0w@public.gmane.org>]

be...-GbY3e145aRm8w6eVIr4Tmg@public.gmane.org <berg-GbY3e145aRm8w6eVIr4Tmg@public.gmane.org> writes:

> I am trying to make a Lua filter that will replace the normal link text in
> internal links with section numbers. I want to use internal links in my
> markdown document like this:
>
>   See the [Quick introduction].
>
> So, the links are given by the full title of the respective section they
> refer to.

Here's a quick rewrite of my old code that should do it.
If there are internal links that should not be modified, simply add a
title or a class to that link, and the filter will leave it alone.

``` lua
local sections = {}

function populate_section_numbers (doc)
  function populate (blocks)
    for _, div in pairs(blocks) do
      if div.t == 'Div' and div.attributes.number then
        local header = div.content[1]
        if header and header.t == 'Header' then
          sections['#' .. div.attr.identifier] = {
            number = div.attributes.number,
          }
          populate(div.content)
        end
      end
    end
  end
  populate(pandoc.utils.make_sections(true, nil, doc.blocks))
end

function resolve_section_ref (link)
  -- don't edit non-internal links or those with a title or a class.
  if link.target:sub(1, 1) ~= '#' or #link.classes > 0 or #link.title > 0 then
    return nil
  end
  local section = sections[link.target]
  if section then
    link.content = {pandoc.Str(section.number .. '\u{A0}')} .. link.content
    return link
  end
end

return {
  {Pandoc = populate_section_numbers},
  {Link = resolve_section_ref}
}
```


--
Albert Krewinkel
GPG: 8eed e3e2 e8c5 6f18 81fe  e836 388d c0b2 1f63 1124