Wikidata Links in Hugo

Another step towards easier searchability of the site…

The Hugo template below is used when translating Markdown to HTML links. It uses:

Wikipedia links are enriched with the corresponding Wikidata entity identifiers via the Mediawiki API
A shot in the dark: If it is an external URL (i.e. starts with http), the Wikidata SPARQ endpoint is queried to find out whether the URL has been stored as officialWebsite (P856), officialBlog (P1581) or onlineDatabaseURL (P1316) for an entity, if so, this identifier is used.
Wikidata links marked with a CSS class (wikidata), and the identifier added
External links opened in a new tab

The file layouts/_default/_markup/render-link.html:

{{- $target := .Destination -}}
{{- $wikidataID := "" -}}
{{- if findRE `(?m)https://(.{2}).wikipedia.org/wiki/(.[^#]*)` $target -}}
  {{- $queryURL := replaceRE `(?m)https://(.{2}).wikipedia.org/wiki/(.[^#]*)` "https://$1.wikipedia.org/w/api.php?action=query&prop=pageprops&titles=$2&format=json" $target -}}
  {{- with try (resources.GetRemote $queryURL) -}}
    {{- with .Err -}}
      {{- errorf "Unable to get remote resource %s: %s"  $queryURL . -}}
    {{- else with .Value -}}
      {{- $data := .Content | transform.Unmarshal -}}
      {{ $keys := slice }}
      {{ range $k, $_ := $data.query.pages }}
        {{ $keys = $keys | append $k }}
      {{ end }}
      {{- $pageMeta := index $data.query.pages (first 1 $keys) -}}
      {{- $wikidataID = $pageMeta.pageprops.wikibase_item -}}
    {{- else -}}
      {{- errorf "Unable to get remote resource %s" $queryURL -}}
    {{- end -}}
  {{- end -}}
{{- else if hasPrefix $target "http" -}}
  {{- $queryURL := "https://query.wikidata.org/sparql" -}}
  {{- $queryOpts := dict
    "method" "get"
    "headers" (dict "Accept" "application/sparql-results+json")
  -}}
  {{- $query := printf `SELECT ?item ?itemLabel ?officialWebsite ?officialBlog ?onlineDatabaseURL WHERE {
      ?item wdt:P856 <%s> . SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en" . }
      OPTIONAL { ?item wdt:P856 ?officialWebsite . } OPTIONAL { ?item wdt:P1581 ?officialBlog . } OPTIONAL { ?item wdt:P1316 ?onlineDatabaseURL . }
    }` $target -}}
  {{- $queryURL = printf "%s?query=%s" $queryURL (urlquery $query) -}}
  {{- with try (resources.GetRemote $queryURL $queryOpts) -}}
    {{- with .Err -}}
      {{- errorf "Unable to get remote resource %s: %s"  $queryURL . -}}
    {{- else with .Value -}}
      {{- $data := .Content | transform.Unmarshal -}}
      {{- if and (reflect.IsMap $data.results) (isset $data.results "bindings") (reflect.IsSlice $data.results.bindings) (gt (len $data.results.bindings) 0) -}}
        {{- $result := index $data.results.bindings 0 -}}
        {{- $wikidataID = replaceRE `(?m)https://www.wikidata.org/entity/(.*)` "$1" $result.item.value -}}
      {{- end -}}
    {{- else -}}
      {{- errorf "Unable to get remote resource %s" $queryURL -}}
    {{- end -}}
  {{- end -}}
{{- end -}}
{{- if or (hasPrefix $target "https://www.wikidata.org/wiki/") (hasPrefix $target "https://www.wikidata.org/entity/") -}}
{{- $wikidataID = replaceRE `(?m)https://www.wikidata.org/wiki/(.*)` "$1" $target -}}
<a class="wikidata" {{ if ne $wikidataID "" }}data-wikidata-entity="{{ $wikidataID }}" {{ end }}href="{{ .Destination | safeURL }}"{{ with .Title}} title="{{ . }}"{{ end }}{{ if strings.HasPrefix .Destination "http" }} target="_blank"{{ end }}>{{ .Text | safeHTML }}</a>
{{- "" -}}
{{- else -}}
<a {{ if ne $wikidataID "" }}data-wikidata-entity="{{ $wikidataID }}" {{ end }}href="{{ .Destination | safeURL }}"{{ with .Title}} title="{{ . }}"{{ end }}{{ if strings.HasPrefix .Destination "http" }} target="_blank"{{ end }}>{{ .Text | safeHTML }}</a>
{{- "" -}}
{{- end -}}

For the SPARQL query to work, the media type must be enabled in the Hugo configuration.

The following setting (security.http) must be adjusted or added in config.toml or hugo.tml:

[security.http]
  mediaTypes = ['^application/json$', '^application/json;\s?charset=[uU][tT][fF]-8$', '^application/sparql-results\+json;\s?charset=[uU][tT][fF]-8$']

And what is it all for?

In this way, entities in the source text can simply be labelled as (markdown) links in order to then be evaluated via JavaScript during display in the browser, for example. The entities can also be helpful for indexing, e.g. to give them a higher relevance in the search.

This CSS can be used to deactivate the links:

a.wikidata {
  pointer-events: none;
  text-decoration: none;
  colour: unset;
}

Of course, the variants for :link :visited, :hover and :active also need to be adapted.

Can you see anything yet?

No (or only in the source code of the page)