How do I process metadata on titles in asciidoctor? - asciidoctor

Question

I'm using asciidoctor to generate a static site for an upcoming event in my hometown, and we have a list of hotels and places of interest for out of town guests. Each location has a position on the map, a type (hotel, restaurant, ect.) and whether their a sponsor of the event.
I've read the docs on Block Processors and this seems to be the best way to do it, but I can't figure out how to tag a title with metadata that can be processed this way.
Currently, we have the descriptions of each location in the document like this
== Locations
[[Fancy_Hotel]]
=== Fancy Hotel
[location, 55, 73, hotel, sponsor]
A nice hotel in the middle of town
[[Chain_Restaurant]]
=== Chain Breakfast Restaurant
[location, 98, 16, restaurant]
A good place for food
and I read the metadata when building the page, then populate the map with clickable links which navigate to the appropriate entry. The following code works, but I'd like to move the metadata above the title if possible, so I'm not relying on parent so aggressively.
require 'asciidoctor'
require 'asciidoctor/extensions'
$Locations = Array.new
def make_map_svg locs
# Do some magic here
locs.each {|a| puts a}
end
class LocationBlock < Asciidoctor::Extensions::BlockProcessor
use_dsl
named :location
on_context :paragraph
name_positional_attributes ['x', 'y', 'type', 'sponsor']
def process parent, reader, attrs
x = ((attrs.delete 'x') || 0).to_i
y = ((attrs.delete 'y') || 0).to_i
type = attrs.delete 'type'
sponsor = (attrs.delete 'sponsor') == 'sponsor'
$Locations.push({
x:x,
y:y,
type:type,
sponsor:sponsor,
title:parent.title,
parent.id
})
create_paragraph parent, reader.lines, attrs, {}
end
end
Asciidoctor::Extensions.register do
block LocationBlock
end
Asciidoctor.convert_file "./Locations.adoc"
make_map_svg $Locations
The make_map_svg function works fine, the issue is figuring out how to make the metadata entries less hacky.

Answer 1

You might think of the location data as metadata, but processing it with a block processor implies that it is not metadata; blocks occupy a location in Asciidoctor's AST and are expected to occupy a position in the output; there should be something rendered at that location.
Titles are special in that they define both the text of the section/document title, but also a container for the title and the section's child elements. If you use a block processor, it must follow the title, or it is not enclosed in the container with the title and other child elements. Navigating the element structure from your [location ...] block to the entitled section would be more challenging than just using parent.
If the location data is truly metadata, in that you do not expect anything to render where [location ...] exists, you might consider implementing your logic as a preprocessor, which could read the location information from a comment in the lines of your source.
One advantage of using the preprocessor approach to parse comments is that anyone using your Asciidoctor source would see the same rendering (aside from CSS), whether they had your extension installed/active or not.