feat: Add extended CEL Libraries

build.gradle

@@ -33,7 +33,7 @@ lombok {
 }
 
 group 'com.gotocompany'
-version '0.10.5'
+version '0.10.6'
 
 def projName = "firehose"
 

docs/docs/sinks/grpc-sink.md

@@ -42,14 +42,23 @@ Note - final metadata will be generated with merging metadata and the kafka reco
 
     message GenericPayload {
       string field = "field_name";
-      string field_two = "field_two";
+      string field_two = "FIELD_two";
       string id = "123";
       int code = 400;
     }
   ```
-  Example config : `$com.goto.company.GenericPayload.field: $(com.goto.company.GenericPayload.field_two + '_' + string(com.goto.company.GenericPayload.code))`
+  Example config : `$com.goto.company.GenericPayload.field: $(com.goto.company.GenericPayload.field_two.lowerAscii() + '_' + string(com.goto.company.GenericPayload.code))`
   This would result in : `field_name:field_two_400`
-
+- CEL Extended Libraries : 
+  - String operations (https://github.com/google/cel-java/blob/main/extensions/src/main/java/dev/cel/extensions/README.md#strings)
+    - Add the capabilities of performing typical string operations such as up/lower casting, trimming, replacement, etc.
+    - Example : `com.goto.company.GenericPayload.field_two.lowerAscii()`, `com.goto.company.GenericPayload.field_two.upperAscii()`
+  - Math Operations (https://github.com/google/cel-java/blob/main/extensions/src/main/java/dev/cel/extensions/README.md#math)
+    - Currently only support finding greatest and least of numerical inputs
+    - Example : `math.greatest(com.goto.company.GenericPayload.code, 999), math.least(com.goto.company.GenericPayload.code, 999)`
+  - Binding Operations (https://github.com/google/cel-java/blob/main/extensions/src/main/java/dev/cel/extensions/README.md#celbind)
+    - Add the capabilities of binding a CEL Expression into variables and reusing them in the subsequent expression
+    - Example : `cel.bind(stringifiedCode, string(com.goto.company.GenericPayload.code), stringifiedCode + '_' + com.goto.company.GenericPayload.id)`
 
 ### `SINK_GRPC_RESPONSE_SCHEMA_PROTO_CLASS`
 

src/main/java/com/gotocompany/firehose/evaluator/GrpcResponseCelPayloadEvaluator.java

@@ -6,7 +6,6 @@
 import dev.cel.common.types.CelKind;
 import dev.cel.compiler.CelCompiler;
 import dev.cel.runtime.CelRuntime;
-import dev.cel.runtime.CelRuntimeFactory;
 import lombok.extern.slf4j.Slf4j;
 
 /**
@@ -52,8 +51,7 @@ public boolean evaluate(Message payload) {
      */
     private void buildCelEnvironment(String celExpression) {
         CelCompiler celCompiler = CelUtils.initializeCelCompiler(this.descriptor);
-        CelRuntime celRuntime = CelRuntimeFactory.standardCelRuntimeBuilder()
-                .build();
+        CelRuntime celRuntime = CelUtils.initializeCelRuntime();
         this.celProgram = CelUtils.initializeCelProgram(celExpression, celRuntime, celCompiler,
                 celType -> celType.kind().equals(CelKind.BOOL));
     }

src/main/java/com/gotocompany/firehose/proto/ProtoToMetadataMapper.java

@@ -8,7 +8,6 @@
 import com.gotocompany.firehose.utils.CelUtils;
 import dev.cel.compiler.CelCompiler;
 import dev.cel.runtime.CelRuntime;
-import dev.cel.runtime.CelRuntimeFactory;
 import io.grpc.Metadata;
 import org.apache.commons.collections.MapUtils;
 
@@ -102,7 +101,7 @@ private Object evaluateExpression(String input, Message message) {
      * @return a map of CEL expressions to their corresponding programs
      */
     private Map<String, CelRuntime.Program> initializeCelPrograms() {
-        CelRuntime celRuntime = CelRuntimeFactory.standardCelRuntimeBuilder().build();
+        CelRuntime celRuntime = CelUtils.initializeCelRuntime();
         CelCompiler celCompiler = CelUtils.initializeCelCompiler(this.descriptor);
         return this.metadataTemplate.entrySet()
                 .stream()

src/main/java/com/gotocompany/firehose/utils/CelUtils.java

@@ -3,16 +3,18 @@
 import com.google.protobuf.Descriptors;
 import com.google.protobuf.Message;
 import dev.cel.common.CelAbstractSyntaxTree;
+import dev.cel.common.CelOptions;
 import dev.cel.common.CelValidationException;
 import dev.cel.common.types.CelType;
 import dev.cel.common.types.StructTypeReference;
 import dev.cel.compiler.CelCompiler;
 import dev.cel.compiler.CelCompilerFactory;
+import dev.cel.extensions.CelExtensions;
 import dev.cel.parser.CelStandardMacro;
 import dev.cel.runtime.CelEvaluationException;
 import dev.cel.runtime.CelRuntime;
-import org.aeonbits.owner.util.Collections;
-
+import dev.cel.runtime.CelRuntimeFactory;
+import java.util.Collections;
 import java.util.function.Predicate;
 
 /**
@@ -28,7 +30,7 @@ public class CelUtils {
      */
     public static Object evaluate(CelRuntime.Program program, Message payload) {
         try {
-            return program.eval(Collections.map(payload.getDescriptorForType().getFullName(), payload));
+            return program.eval(Collections.singletonMap(payload.getDescriptorForType().getFullName(), payload));
         } catch (CelEvaluationException e) {
             throw new IllegalArgumentException("Could not evaluate Cel expression", e);
         }
@@ -43,10 +45,22 @@ public static CelCompiler initializeCelCompiler(Descriptors.Descriptor descripto
         return CelCompilerFactory.standardCelCompilerBuilder()
                 .setStandardMacros(CelStandardMacro.values())
                 .addVar(descriptor.getFullName(), StructTypeReference.create(descriptor.getFullName()))
+                .addLibraries(CelExtensions.strings(), CelExtensions.bindings(), CelExtensions.math(CelOptions.DEFAULT))
                 .addMessageTypes(descriptor)
                 .build();
     }
 
+    /**
+     * Initializes the CEL runtime with extended libraries.
+     *
+     * @return the initialized CEL runtime
+     */
+    public static CelRuntime initializeCelRuntime() {
+        return CelRuntimeFactory.standardCelRuntimeBuilder()
+                .addLibraries(CelExtensions.strings(), CelExtensions.math(CelOptions.DEFAULT))
+                .build();
+    }
+
     /**
      * Initializes a CEL program for a given expression.
      *

src/test/java/com/gotocompany/firehose/proto/ProtoToMetadataMapperTest.java

@@ -18,10 +18,13 @@ public class ProtoToMetadataMapperTest {
     public void setup() {
         Map<String, String> template = new HashMap<>();
         template.put("$GenericResponse.detail", "$GenericResponse.success");
+        template.put("detail", "$GenericResponse.detail.lowerAscii()");
         template.put("someField", "someValue");
         template.put("$GenericResponse.success", "staticValue");
         template.put("staticKey", "$(GenericResponse.errors[0].cause + '-' + GenericResponse.errors[0].code + '-' + string(GenericResponse.code))");
         template.put("entity", "$GenericResponse.errors[0].entity");
+        template.put("binding", "$cel.bind(code, GenericResponse.code, code + 100)");
+        template.put("math", "$math.greatest(GenericResponse.code, 200)");
         this.protoToMetadataMapper = new ProtoToMetadataMapper(
                 GenericResponse.getDescriptor(),
                 template
@@ -32,7 +35,7 @@ public void setup() {
     public void shouldBuildDynamicMetadataWithCorrectPlaceholders() {
         GenericResponse payload = GenericResponse.newBuilder()
                 .setSuccess(false)
-                .setDetail("detail_of_error")
+                .setDetail("Detail_Of_Error")
                 .setCode(100)
                 .addErrors(GenericError.newBuilder()
                         .setCode("404")
@@ -44,6 +47,8 @@ public void shouldBuildDynamicMetadataWithCorrectPlaceholders() {
 
         Assertions.assertTrue(metadata.containsKey(Metadata.Key.of("detail_of_error", Metadata.ASCII_STRING_MARSHALLER)));
         Assertions.assertEquals("false", metadata.get(Metadata.Key.of("detail_of_error", Metadata.ASCII_STRING_MARSHALLER)));
+        Assertions.assertTrue(metadata.containsKey(Metadata.Key.of("detail", Metadata.ASCII_STRING_MARSHALLER)));
+        Assertions.assertEquals("detail_of_error", metadata.get(Metadata.Key.of("detail", Metadata.ASCII_STRING_MARSHALLER)));
         Assertions.assertTrue(metadata.containsKey(Metadata.Key.of("statickey", Metadata.ASCII_STRING_MARSHALLER)));
         Assertions.assertEquals("not_found-404-100", metadata.get(Metadata.Key.of("statickey", Metadata.ASCII_STRING_MARSHALLER)));
         Assertions.assertTrue(metadata.containsKey(Metadata.Key.of("somefield", Metadata.ASCII_STRING_MARSHALLER)));
@@ -52,6 +57,10 @@ public void shouldBuildDynamicMetadataWithCorrectPlaceholders() {
         Assertions.assertEquals("", metadata.get(Metadata.Key.of("entity", Metadata.ASCII_STRING_MARSHALLER)));
         Assertions.assertTrue(metadata.containsKey(Metadata.Key.of("false", Metadata.ASCII_STRING_MARSHALLER)));
         Assertions.assertEquals("staticValue", metadata.get(Metadata.Key.of("false", Metadata.ASCII_STRING_MARSHALLER)));
+        Assertions.assertTrue(metadata.containsKey(Metadata.Key.of("binding", Metadata.ASCII_STRING_MARSHALLER)));
+        Assertions.assertEquals("200", metadata.get(Metadata.Key.of("binding", Metadata.ASCII_STRING_MARSHALLER)));
+        Assertions.assertTrue(metadata.containsKey(Metadata.Key.of("math", Metadata.ASCII_STRING_MARSHALLER)));
+        Assertions.assertEquals("200", metadata.get(Metadata.Key.of("math", Metadata.ASCII_STRING_MARSHALLER)));
     }
 
     @Test