facets: add collection facet

cds/config.py

@@ -812,6 +812,21 @@ def _parse_env_bool(var_name, default=None):
             "language": {
                 "terms": {"field": "language.untouched"},
             },
+            "collections": {
+                "terms": {
+                    "field": "collections",
+                    "size": 50,
+                    "order": {"_key": "asc"},
+                    # Include if the collection term contains '::'.
+                    **(
+                        {"include": r".*::.*"}
+                    ),
+                    # Exclude if the collection term contains two '::' (3-level paths like A::B::C).
+                    **(
+                        {"exclude": r".*::.*::.*"}
+                    ),
+                },
+            },
             "years": {
                 "date_histogram": {
                     "field": "date",
@@ -826,6 +841,7 @@ def _parse_env_bool(var_name, default=None):
             "category": terms_filter("category.untouched"),
             "type": terms_filter("type.untouched"),
             "language": terms_filter("language"),
+            "collections": terms_filter("collections"),
             "years": range_filter("date", format="yyyy", end_date_math="/y"),
         },
     }

cds/modules/search_ui/static/templates/cds_search_ui/facets.html

@@ -8,7 +8,11 @@ <h2 class="text-capitalize f8 mt-5"><b>{{ key }}</b></h2>
             class="cds-facets-item-link"
             ng-class="{'cds-facets-item-link-checked': values.indexOf(item.key) > -1}"
             ng-click="handleClick(key, item.key)">
-              {{ (key === 'language') ? (item.key | isoToLanguage) : item.key }}
+              {{
+                (key === 'language') ? (item.key | isoToLanguage) :
+                (key === 'collections') ? (item.key | collectionLabel) :
+                item.key
+              }}
               <span class="cds-facets-item-link-counter pull-right fw-b">
                 <span ng-show="values.indexOf(item.key) > -1">
                   <i class="fa fa-remove"></i>

cds/modules/theme/assets/bootstrap3/js/cds/module.js

@@ -643,6 +643,15 @@ app.filter("isoToLanguage", [
   },
 ]);
 
+// Filter to translate collection keys to display labels
+app.filter("collectionLabel", function () {
+  return function (key) {
+    if (!key) return key;
+    const strKey = String(key);
+    return strKey.includes("::") ? strKey.split("::").pop() : strKey;
+  };
+});
+
 app.filter("format_relation_resource_type", function () {
   return function (input) {
     if (!input) return "";