Implement language detection and label service macro

Author: larsgw

scholia/app/templates/sparql-helpers.sparql

@@ -0,0 +1,33 @@
+{% macro labels(variables, languages) -%}
+  {% for variable in variables -%}
+    {% for language in languages -%}
+      OPTIONAL { {{ variable }} <http://www.w3.org/2000/01/rdf-schema#label> {{ variable }}Label_{{ language | replace("-", "_") }}. FILTER(LANG({{ variable }}Label_{{ language | replace("-", "_") }}) = "{{ language }}") }
+    {% endfor -%}
+    BIND(COALESCE(
+    {%- for language in languages -%}
+      {{ variable }}Label_{{ language | replace("-", "_") }}
+      {%- if not loop.last %}, {% endif %}
+    {%- endfor -%}
+    ) AS {{ variable }}Label)
+
+    {%- if not loop.last %}
+    {% endif %}
+  {%- endfor %}
+{%- endmacro -%}
+
+{%- macro descriptions(variables, languages) -%}
+  {% for variable in variables -%}
+    {% for language in languages -%}
+      OPTIONAL { {{ variable }} <http://schema.org/description> {{ variable }}Description_{{ language | replace("-", "_") }}. FILTER(LANG({{ variable }}Description_{{ language | replace("-", "_") }}) = "{{ language }}") }
+    {% endfor -%}
+    BIND(COALESCE(
+    {%- for language in languages -%}
+      {{ variable }}Description_{{ language | replace("-", "_") }}
+      {%- if not loop.last %}, {% endif %}
+    {%- endfor -%}
+    ) AS {{ variable }}Description)
+
+    {%- if not loop.last %}
+    {% endif %}
+  {%- endfor %}
+{%- endmacro -%}

scholia/app/views.py

@@ -3,8 +3,8 @@
 import datetime
 import re
 
-from flask import (Blueprint, current_app, redirect, render_template, request,
-                   Response, url_for)
+from flask import (Blueprint, current_app, redirect, render_template as render_template_base,
+                   request, Response, url_for)
 from jinja2 import TemplateNotFound
 from werkzeug.routing import BaseConverter
 
@@ -384,6 +384,25 @@ def get_js_config():
         config['query-server'].get('sparql_endpoint_name'),
     }
 
+def get_languages():
+    """Get language fallback chain for a given request.
+
+    Returns
+    -------
+    languages : str[]
+        Language fallback chain.
+
+    """
+    languages = [x[0] for x in request.accept_languages]
+    if 'en' not in request.accept_languages:
+        languages.append('en')
+    languages.append('mul')
+    return languages
+
+def render_template(*args, **kwargs):
+    if 'languages' not in kwargs:
+        kwargs['languages'] = get_languages()
+    return render_template_base(*args, **kwargs)
 
 @main.context_processor
 def inject_js_config():