fix(web): fix server-side content assist filtering

3 files changed, 62 insertions, 4 deletions

diff --git a/language-ide/src/main/java/tools/refinery/language/ide/ProblemIdeModule.java b/language-ide/src/main/java/tools/refinery/language/ide/ProblemIdeModule.java
index 5327f7b4..3502c29f 100644
--- a/language-ide/src/main/java/tools/refinery/language/ide/ProblemIdeModule.java
+++ b/language-ide/src/main/java/tools/refinery/language/ide/ProblemIdeModule.java
@@ -3,16 +3,22 @@
  */
 package tools.refinery.language.ide;
 
+import org.eclipse.xtext.ide.editor.contentassist.IPrefixMatcher;
 import org.eclipse.xtext.ide.editor.syntaxcoloring.ISemanticHighlightingCalculator;
 
+import tools.refinery.language.ide.contentassist.FuzzyMatcher;
 import tools.refinery.language.ide.syntaxcoloring.ProblemSemanticHighlightingCalculator;
 
 /**
  * Use this class to register ide components.
  */
 public class ProblemIdeModule extends AbstractProblemIdeModule {
-
         public Class<? extends ISemanticHighlightingCalculator> bindISemanticHighlightingCalculator() {
                 return ProblemSemanticHighlightingCalculator.class;
         }
+        
+        @Override
+        public Class<? extends IPrefixMatcher> bindIPrefixMatcher() {
+                return FuzzyMatcher.class;
+        }
 }
diff --git a/language-ide/src/main/java/tools/refinery/language/ide/contentassist/FuzzyMatcher.java b/language-ide/src/main/java/tools/refinery/language/ide/contentassist/FuzzyMatcher.java
new file mode 100644
index 00000000..fe722ca1
--- /dev/null
+++ b/language-ide/src/main/java/tools/refinery/language/ide/contentassist/FuzzyMatcher.java
@@ -0,0 +1,44 @@
+package tools.refinery.language.ide.contentassist;
+
+import org.eclipse.xtext.ide.editor.contentassist.IPrefixMatcher;
+
+import com.google.inject.Singleton;
+
+/**
+ * Implements the candidate matching algoritm used by CodeMirror 6.
+ * 
+ * Using this class ensures that the same candidates will be returned when
+ * filtering content assist proposals on the server as on the client.
+ * 
+ * The matching is "fuzzy" (<code>fzf</code>-like), i.e., the prefix characters
+ * may occur anywhere in the name, but must be in the same order as in the
+ * prefix.
+ * 
+ * @author Kristóf Marussy
+ */
+@Singleton
+public class FuzzyMatcher implements IPrefixMatcher {
+        @Override
+        public boolean isCandidateMatchingPrefix(String name, String prefix) {
+                var nameIgnoreCase = name.toLowerCase();
+                var prefixIgnoreCase = prefix.toLowerCase();
+                int prefixLength = prefixIgnoreCase.length();
+                if (prefixLength == 0) {
+                        return true;
+                }
+                int nameLength = nameIgnoreCase.length();
+                if (prefixLength > nameLength) {
+                        return false;
+                }
+                int prefixIndex = 0;
+                for (int nameIndex = 0; nameIndex < nameLength; nameIndex++) {
+                        if (nameIgnoreCase.charAt(nameIndex) == prefixIgnoreCase.charAt(prefixIndex)) {
+                                prefixIndex++;
+                                if (prefixIndex == prefixLength) {
+                                        return true;
+                                }
+                        }
+                }
+                return false;
+        }
+}
diff --git a/language-web/src/main/js/xtext/ContentAssistService.ts b/language-web/src/main/js/xtext/ContentAssistService.ts
index ec6b80d2..8461ec7f 100644
--- a/language-web/src/main/js/xtext/ContentAssistService.ts
+++ b/language-web/src/main/js/xtext/ContentAssistService.ts
@@ -14,20 +14,28 @@ const PROPOSALS_LIMIT = 1000;
 
 const IDENTIFIER_REGEXP_STR = '[a-zA-Z0-9_]*';
 
+const HIGH_PRIORITY_KEYWORDS = ['<->'];
+
+const QUALIFIED_NAME_SEPARATOR_REGEXP = /::/g;
+
 const log = getLogger('xtext.ContentAssistService');
 
 function createCompletion(entry: IContentAssistEntry): Completion {
   let boost;
   switch (entry.kind) {
     case 'KEYWORD':
-      boost = -99;
+      // Some hard-to-type operators should be on top.
+      boost = HIGH_PRIORITY_KEYWORDS.includes(entry.proposal) ? 10 : -99;
       break;
     case 'TEXT':
     case 'SNIPPET':
       boost = -90;
       break;
-    default:
-      boost = 0;
+    default: {
+      // Penalize qualified names (vs available unqualified names).
+      const extraSegments = entry.proposal.match(QUALIFIED_NAME_SEPARATOR_REGEXP)?.length || 0;
+      boost = Math.max(-5 * extraSegments, -50);
+    }
       break;
   }
   return {