Enable users to simultaneously search all SearchBasedFetchers

CHANGELOG.md

@@ -24,6 +24,7 @@ Note that this project **does not** adhere to [Semantic Versioning](http://semve
 - We fixed the bug when strike the delete key in the text field. [#6421](https://github.com/JabRef/jabref/issues/6421)
 - We added a BibTex key modifier for truncating strings. [#3915](https://github.com/JabRef/jabref/issues/3915)
 - We added support for jumping to target entry when typing letter/digit after sorting a column in maintable [#6146](https://github.com/JabRef/jabref/issues/6146)
+- We added a new fetcher to enable users to search all available E-Libraries simultaneously. [#369](https://github.com/koppor/jabref/issues/369)
 
 ### Changed
 

src/main/java/org/jabref/logic/importer/WebFetchers.java

@@ -12,6 +12,7 @@
 import org.jabref.logic.importer.fetcher.ArXiv;
 import org.jabref.logic.importer.fetcher.AstrophysicsDataSystem;
 import org.jabref.logic.importer.fetcher.CiteSeer;
+import org.jabref.logic.importer.fetcher.CompositeSearchBasedFetcher;
 import org.jabref.logic.importer.fetcher.CrossRef;
 import org.jabref.logic.importer.fetcher.DBLPFetcher;
 import org.jabref.logic.importer.fetcher.DOAJFetcher;
@@ -101,6 +102,7 @@ public static SortedSet<SearchBasedFetcher> getSearchBasedFetchers(ImportFormatP
         set.add(new DOAJFetcher(importFormatPreferences));
         set.add(new IEEE(importFormatPreferences));
         set.add(new GrobidCitationFetcher(importFormatPreferences));
+        set.add(new CompositeSearchBasedFetcher(set));
         return set;
     }
 

src/main/java/org/jabref/logic/importer/fetcher/CompositeSearchBasedFetcher.java

@@ -0,0 +1,51 @@
+package org.jabref.logic.importer.fetcher;
+
+import java.util.List;
+import java.util.Optional;
+import java.util.Set;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import org.jabref.logic.help.HelpFile;
+import org.jabref.logic.importer.FetcherException;
+import org.jabref.logic.importer.SearchBasedFetcher;
+import org.jabref.model.entry.BibEntry;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class CompositeSearchBasedFetcher implements SearchBasedFetcher {
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(CompositeSearchBasedFetcher.class);
+
+    private final Set<SearchBasedFetcher> fetchers;
+
+    public CompositeSearchBasedFetcher(Set<SearchBasedFetcher> searchBasedFetchers) {
+        // Remove the Composite Fetcher instance from its own fetcher set to prevent a StackOverflow
+        this.fetchers = searchBasedFetchers.stream()
+                .filter(searchBasedFetcher -> searchBasedFetcher != this)
+                .collect(Collectors.toSet());
+    }
+
+    @Override
+    public List<BibEntry> performSearch(String query) {
+        return fetchers.stream().flatMap(searchBasedFetcher -> {
+            try {
+                return searchBasedFetcher.performSearch(query).stream();
+            } catch (FetcherException e) {
+                LOGGER.warn(String.format("%s API request failed", searchBasedFetcher.getName()), e);
+                return Stream.empty();
+            }
+        }).parallel().collect(Collectors.toList());
+    }
+
+    @Override
+    public String getName() {
+        return "SearchAll";
+    }
+
+    @Override
+    public Optional<HelpFile> getHelpPage() {
+        return Optional.empty();
+    }
+}

src/test/java/org/jabref/logic/importer/fetcher/CompositeSearchBasedFetcherTest.java

@@ -0,0 +1,50 @@
+package org.jabref.logic.importer.fetcher;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import org.jabref.logic.importer.FetcherException;
+import org.jabref.logic.importer.ImportFormatPreferences;
+import org.jabref.logic.importer.SearchBasedFetcher;
+import org.jabref.logic.importer.SearchBasedParserFetcher;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.mockito.Mockito.mock;
+
+public class CompositeSearchBasedFetcherTest {
+
+    private CompositeSearchBasedFetcher finder;
+    private SearchBasedFetcher searchBasedFetcher;
+    private SearchBasedParserFetcher searchBasedParserFetcher;
+
+    @BeforeEach
+    public void setUp() {
+        ImportFormatPreferences importFormatPreferences = mock(ImportFormatPreferences.class);
+
+        Set<SearchBasedFetcher> setOfSearchBasedFetchers = new HashSet<>();
+        // Add one searchBasedFetcher and one searchBasedParserFetcher
+        searchBasedFetcher = new ArXiv(importFormatPreferences);
+        searchBasedParserFetcher = new CiteSeer();
+        setOfSearchBasedFetchers.add(searchBasedFetcher);
+        setOfSearchBasedFetchers.add(searchBasedParserFetcher);
+        finder = new CompositeSearchBasedFetcher(setOfSearchBasedFetchers);
+    }
+
+    @Test
+    public void performSearchOnEmptyQuery() {
+        Assertions.assertTrue(finder.performSearch("").isEmpty());
+    }
+
+    @Test
+    public void performSearchContainsResultsOfSearchBasedFetcher() throws FetcherException {
+        Assertions.assertTrue(finder.performSearch("quantum").containsAll(searchBasedFetcher.performSearch("quantum")));
+    }
+
+    @Test
+    public void performSearchContainsResultsOfSearchBasedParserFetcher() throws FetcherException {
+        Assertions.assertTrue(finder.performSearch("quantum").containsAll(searchBasedParserFetcher.performSearch("quantum")));
+    }
+}