Adding query fuzziness validation

CHANGELOG.md

@@ -95,6 +95,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Increasing timeout of testQuorumRecovery to 90 seconds from 30 ([#5651](https://github.com/opensearch-project/OpenSearch/pull/5651))
 - [Segment Replication] Fix for peer recovery ([#5344](https://github.com/opensearch-project/OpenSearch/pull/5344))
 - [Test] Renaming PIT tests to IT to fix intermittent test failures ([#5750](https://github.com/opensearch-project/OpenSearch/pull/5750))
+- Fix fuzziness validation ([#5805](https://github.com/opensearch-project/OpenSearch/pull/5805))
 
 ### Security
 

server/src/main/java/org/opensearch/common/unit/Fuzziness.java

@@ -189,7 +189,12 @@ public static Fuzziness parse(XContentParser parser) throws IOException {
                             return build(fuzziness);
                     }
                 } catch (NumberFormatException ex) {
-                    return build(fuzziness);
+                    try {
+                        final float minimumSimilarity = Float.parseFloat(fuzziness);
+                        return build(fuzziness);
+                    } catch (NumberFormatException e) {
+                        throw new IllegalArgumentException("Invalid fuzziness value: " + fuzziness);
+                    }
                 }
 
             default:
@@ -225,7 +230,7 @@ public float asFloat() {
         if (this.equals(AUTO) || isAutoWithCustomValues()) {
             return 1f;
         }
-        return Float.parseFloat(fuzziness.toString());
+        return Float.parseFloat(fuzziness);
     }
 
     private int termLen(String text) {
@@ -234,9 +239,9 @@ private int termLen(String text) {
 
     public String asString() {
         if (isAutoWithCustomValues()) {
-            return fuzziness.toString() + ":" + lowDistance + "," + highDistance;
+            return fuzziness + ":" + lowDistance + "," + highDistance;
         }
-        return fuzziness.toString();
+        return fuzziness;
     }
 
     private boolean isAutoWithCustomValues() {

server/src/test/java/org/opensearch/common/unit/FuzzinessTests.java

@@ -31,6 +31,7 @@
 
 package org.opensearch.common.unit;
 
+import org.opensearch.OpenSearchParseException;
 import org.opensearch.common.io.stream.BytesStreamOutput;
 import org.opensearch.common.io.stream.StreamInput;
 import org.opensearch.common.xcontent.XContentBuilder;
@@ -41,6 +42,7 @@
 
 import static org.opensearch.common.xcontent.XContentFactory.jsonBuilder;
 import static org.hamcrest.CoreMatchers.anyOf;
+import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.CoreMatchers.sameInstance;
 
@@ -138,6 +140,26 @@ public void testParseFromXContent() throws IOException {
 
     }
 
+    public void testFuzzinessValidationWithStrings() throws IOException {
+        String[] invalidStrings = new String[] { "+++", "asdfghjkl", "2k23" };
+        XContentBuilder json = jsonBuilder().startObject().field(Fuzziness.X_FIELD_NAME, randomFrom(invalidStrings)).endObject();
+        try (XContentParser parser = createParser(json)) {
+            assertThat(parser.nextToken(), equalTo(XContentParser.Token.START_OBJECT));
+            assertThat(parser.nextToken(), equalTo(XContentParser.Token.FIELD_NAME));
+            assertThat(parser.nextToken(), equalTo(XContentParser.Token.VALUE_STRING));
+            IllegalArgumentException e = expectThrows(IllegalArgumentException.class, () -> Fuzziness.parse(parser));
+            assertThat(e.getMessage(), containsString("Invalid fuzziness value:"));
+        }
+        json = jsonBuilder().startObject().field(Fuzziness.X_FIELD_NAME, "AUTO:").endObject();
+        try (XContentParser parser = createParser(json)) {
+            assertThat(parser.nextToken(), equalTo(XContentParser.Token.START_OBJECT));
+            assertThat(parser.nextToken(), equalTo(XContentParser.Token.FIELD_NAME));
+            assertThat(parser.nextToken(), equalTo(XContentParser.Token.VALUE_STRING));
+            OpenSearchParseException e = expectThrows(OpenSearchParseException.class, () -> Fuzziness.parse(parser));
+            assertThat(e.getMessage(), containsString("failed to find low and high distance values"));
+        }
+    }
+
     public void testAuto() {
         assertThat(Fuzziness.AUTO.asFloat(), equalTo(1f));
     }