anonymizer - add rex for anonymizer and test

Signed-off-by: Jialiang Liang <jiallian@amazon.com>

Author: RyanL1997

ppl/src/main/java/org/opensearch/sql/ppl/utils/PPLQueryDataAnonymizer.java

@@ -76,6 +76,7 @@
 import org.opensearch.sql.ast.tree.Relation;
 import org.opensearch.sql.ast.tree.Rename;
 import org.opensearch.sql.ast.tree.Reverse;
+import org.opensearch.sql.ast.tree.Rex;
 import org.opensearch.sql.ast.tree.Sort;
 import org.opensearch.sql.ast.tree.SpanBin;
 import org.opensearch.sql.ast.tree.SubqueryAlias;
@@ -419,6 +420,32 @@ public String visitReverse(Reverse node, String context) {
     return StringUtils.format("%s | reverse", child);
   }
 
+  @Override
+  public String visitRex(Rex node, String context) {
+    String child = node.getChild().get(0).accept(this, context);
+    String field = visitExpression(node.getField());
+    String pattern = "\"" + node.getPattern().toString() + "\"";
+    StringBuilder command = new StringBuilder();
+
+    // Build the base command
+    if (node.getMode() == Rex.RexMode.SED) {
+      command.append(String.format("%s | rex field=%s mode=sed %s", child, field, pattern));
+    } else {
+      command.append(String.format("%s | rex field=%s %s", child, field, pattern));
+    }
+
+    // Add optional parameters
+    if (node.getMaxMatch().isPresent()) {
+      command.append(" max_match=").append(node.getMaxMatch().get());
+    }
+
+    if (node.getOffsetField().isPresent()) {
+      command.append(" offset_field=").append(node.getOffsetField().get());
+    }
+
+    return command.toString();
+  }
+
   @Override
   public String visitParse(Parse node, String context) {
     String child = node.getChild().get(0).accept(this, context);
@@ -734,5 +761,11 @@ public String visitCast(Cast node, String context) {
       String expr = analyze(node.getExpression(), context);
       return StringUtils.format("cast(%s as %s)", expr, node.getConvertedType().toString());
     }
+
+    @Override
+    public String visitQualifiedName(
+        org.opensearch.sql.ast.expression.QualifiedName node, String context) {
+      return String.join(".", node.getParts());
+    }
   }
 }

ppl/src/test/java/org/opensearch/sql/ppl/utils/PPLQueryDataAnonymizerTest.java

@@ -511,6 +511,37 @@ public void testPatterns() {
                 + " variable_count_threshold=5"));
   }
 
+  @Test
+  public void testRexCommand() {
+    assertEquals(
+        "source=t | rex field=message \"(?<user>[A-Z]+)\"",
+        anonymize("source=t | rex field=message \"(?<user>[A-Z]+)\""));
+    assertEquals(
+        "source=t | rex field=lastname \"(?<initial>^[A-Z])\" | fields + lastname,initial",
+        anonymize(
+            "source=t | rex field=lastname \"(?<initial>^[A-Z])\" | fields lastname, initial"));
+    assertEquals(
+        "source=t | rex field=name \"(?<first>[A-Z])\" max_match=3",
+        anonymize("source=t | rex field=name \"(?<first>[A-Z])\" max_match=3"));
+  }
+
+  @Test
+  public void testRexSedMode() {
+    assertEquals(
+        "source=t | rex field=lastname mode=sed \"s/^[A-Z]/X/\"",
+        anonymize("source=t | rex field=lastname mode=sed \"s/^[A-Z]/X/\""));
+    assertEquals(
+        "source=t | rex field=data mode=sed \"s/sensitive/clean/g\" | fields + data",
+        anonymize("source=t | rex field=data mode=sed \"s/sensitive/clean/g\" | fields data"));
+  }
+
+  @Test
+  public void testRexWithOffsetField() {
+    assertEquals(
+        "source=t | rex field=message \"(?<word>[a-z]+)\" offset_field=pos",
+        anonymize("source=t | rex field=message \"(?<word>[a-z]+)\" offset_field=pos"));
+  }
+
   private String anonymize(String query) {
     AstBuilder astBuilder = new AstBuilder(query, settings);
     return anonymize(astBuilder.visit(parser.parse(query)));