Use sets for filters

Instead of filtering by a single value,
use sets for each category.
Display results iff they match any set element
in all non-empty sets.

src/main/webapp/app/search/search.component.ts

@@ -37,9 +37,9 @@ export class SearchComponent implements OnInit, OnDestroy {
   gitFilesAggregation?: IGitFilesAggregation;
 
   private filterSelectionSubscription: Subscription = new Subscription();
-  private selectedRepository: string | null = null;
-  private selectedUniversity: string | null = null;
-  private selectedFileFormat: string | null = null;
+  private selectedRepositories = new Set();
+  private selectedUniversities = new Set();
+  private selectedFileFormats = new Set();
 
   public paramGroup: QueryParamGroup;
   private componentDestroyed$ = new Subject<void>();
@@ -157,18 +157,20 @@ export class SearchComponent implements OnInit, OnDestroy {
   // this function is called.
   // It updates the local filters.
   // Currently, for any category (at the moment repository and file format)
-  // there is either one value all search results have to satisfy
-  // (e.g. display only files from a certain repository)
-  // or the filter is not set.
-  // Clicking a filter value which is already being applied
-  // results in this filter to be reset. (Does not filter by this category)
+  // there is a set of allowed values.
+  // If the selected item is not in the corresponding set it is added.
+  // Otherwise it is removed.
+  // If a set is empty the corresponding filter is not applied.
+  // For non-empty sets, the results which will be displayed must match one of the set's elements.
+  // (e.g. if the selectedRepositories set contains "foo" and "bar",
+  // only results from these two repos will be shown.)
   public updateSearchInfoFilter(selection: IMetadataSelection): void {
     switch (selection.category) {
       case 'repository': {
-        if (this.selectedRepository === selection.value) {
-          this.selectedRepository = null;
+        if (this.selectedRepositories.has(selection.value)) {
+          this.selectedRepositories.delete(selection.value);
         } else {
-          this.selectedRepository = selection.value;
+          this.selectedRepositories.add(selection.value);
         }
         break;
       }
@@ -176,18 +178,18 @@ export class SearchComponent implements OnInit, OnDestroy {
         // University seems to be a derived attribute.
         // Currently not implemented.
         alert('Filtering by university is not supported at the moment. Cause: University is not in the interface IGitFiles.');
-        /* if (this.selectedUniversity === selection.value) {
-          this.selectedUniversity = null;
+        /* if (this.selectedUniversities.has(selection.value)) {
+          this.selectedUniversities.delete(selection.value);
         } else {
-          this.selectedUniversity = selection.value;
+          this.selectedUniversities.add(selection.value);
         } */
         break;
       }
       case 'fileFormat': {
-        if (this.selectedFileFormat === selection.value) {
-          this.selectedFileFormat = null;
+        if (this.selectedFileFormats.has(selection.value)) {
+          this.selectedFileFormats.delete(selection.value);
         } else {
-          this.selectedFileFormat = selection.value;
+          this.selectedFileFormats.add(selection.value);
         }
         break;
       }
@@ -197,13 +199,13 @@ export class SearchComponent implements OnInit, OnDestroy {
 
   // Checks if a given file matches the local filters.
   matchesSelection(file: IGitFiles): boolean {
-    if (this.selectedRepository && file.repository !== this.selectedRepository) {
+    if (this.selectedRepositories.size > 0 && !this.selectedRepositories.has(file.repository)) {
       return false;
     }
-    /* if (this.selectedUniversity && file.university !== this.selectedUniversity) {
-      return false;
-    } */
-    if (this.selectedFileFormat && file.fileFormat !== this.selectedFileFormat) {
+    /* if (this.selectedUniversities.size > 0 && !this.selectedUniversities.has(file.university)) {
+       return false;
+     } */
+    if (this.selectedFileFormats.size > 0 && !this.selectedFileFormats.has(file.fileFormat)) {
       return false;
     }
     return true;