[operators]feat: Add operation expr interface and operator kind enum

src/main/java/com/google/api/generator/engine/ast/OperationExpr.java

@@ -0,0 +1,24 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.api.generator.engine.ast;
+
+public interface OperationExpr extends Expr {
+
+  OperatorKind operatorKind();
+
+  TypeNode type();
+
+  void accept(AstNodeVisitor visitor);
+}

src/main/java/com/google/api/generator/engine/ast/OperatorKind.java

@@ -0,0 +1,32 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.api.generator.engine.ast;
+
+import java.util.EnumSet;
+
+public enum OperatorKind {
+  ARITHMETIC_ADDITION,
+  RELATIONAL_EQUAL_TO,
+  RELATIONAL_NOT_EQUAL_TO,
+  UNARY_LOGICAL_NOT,
+  UNARY_POST_INCREMENT;
+
+  private static final EnumSet<OperatorKind> PREFIX_OPERATORS_SET =
+      EnumSet.of(OperatorKind.UNARY_LOGICAL_NOT);
+
+  public boolean isPrefixOperator() {
+    return PREFIX_OPERATORS_SET.contains(this);
+  }
+}

src/main/java/com/google/api/generator/engine/writer/JavaWriterVisitor.java

@@ -35,6 +35,7 @@
 import com.google.api.generator.engine.ast.MethodDefinition;
 import com.google.api.generator.engine.ast.MethodInvocationExpr;
 import com.google.api.generator.engine.ast.NewObjectExpr;
+import com.google.api.generator.engine.ast.OperatorKind;
 import com.google.api.generator.engine.ast.ReferenceConstructorExpr;
 import com.google.api.generator.engine.ast.ReturnExpr;
 import com.google.api.generator.engine.ast.ScopeNode;
@@ -100,6 +101,13 @@ public class JavaWriterVisitor implements AstNodeVisitor {
   private static final String VOLATILE = "volatile";
   private static final String WHILE = "while";
 
+  // Operators
+  private static final String OPERATOR_ADDITION = "+";
+  private static final String OPERATOR_EQUAL_TO = "==";
+  private static final String OPERATOR_NOT_EQUAL_TO = "!=";
+  private static final String OPERATOR_INCREMENT = "++";
+  private static final String OPERATOR_LOGICAL_NOT = "!";
+
   private final StringBuffer buffer = new StringBuffer();
   private final ImportWriterVisitor importWriterVisitor = new ImportWriterVisitor();
 
@@ -822,4 +830,24 @@ private void rightBrace() {
   private void semicolon() {
     buffer.append(SEMICOLON);
   }
+
+  private void operator(OperatorKind kind) {
+    switch (kind) {
+      case RELATIONAL_EQUAL_TO:
+        buffer.append(OPERATOR_EQUAL_TO);
+        break;
+      case RELATIONAL_NOT_EQUAL_TO:
+        buffer.append(OPERATOR_NOT_EQUAL_TO);
+        break;
+      case UNARY_POST_INCREMENT:
+        buffer.append(OPERATOR_INCREMENT);
+        break;
+      case UNARY_LOGICAL_NOT:
+        buffer.append(OPERATOR_LOGICAL_NOT);
+        break;
+      case ARITHMETIC_ADDITION:
+        buffer.append(OPERATOR_ADDITION);
+        break;
+    }
+  }
 }