Use visitor for json creation of locations

injector/src/main/java/edu/ucr/cs/riple/injector/changes/Change.java

@@ -27,6 +27,7 @@
 import com.github.javaparser.ast.nodeTypes.NodeWithRange;
 import edu.ucr.cs.riple.injector.Helper;
 import edu.ucr.cs.riple.injector.location.Location;
+import edu.ucr.cs.riple.injector.location.LocationToJsonVisitor;
 import edu.ucr.cs.riple.injector.modifications.Modification;
 import java.util.Objects;
 import javax.annotation.Nullable;
@@ -89,7 +90,7 @@ public int hashCode() {
   @SuppressWarnings("unchecked")
   public JSONObject getJson() {
     JSONObject res = new JSONObject();
-    res.put("LOCATION", location.getJson());
+    res.put("LOCATION", LocationToJsonVisitor.INSTANCE.visit(location));
     res.put("ANNOTATION", annotation);
     return res;
   }

injector/src/main/java/edu/ucr/cs/riple/injector/location/Location.java

@@ -38,7 +38,6 @@
 import java.util.Objects;
 import java.util.function.Consumer;
 import javax.annotation.Nullable;
-import org.json.simple.JSONObject;
 
 /** Represents a location of an element in the source code. */
 public abstract class Location {
@@ -50,16 +49,6 @@ public abstract class Location {
   /** The path to the file containing the element. */
   public Path path;
 
-  /** The Keys used to represent a location in JSON format */
-  public enum KEYS {
-    VARIABLES,
-    METHOD,
-    KIND,
-    CLASS,
-    PATH,
-    INDEX
-  }
-
   /**
    * Creates an instance of {@link Location} for a given type, path and class. This constructor is a
    * base class for all subclasses and must provide these values upon instantiation.
@@ -126,13 +115,6 @@ public static Location createLocationFromArrayInfo(String[] values) {
   protected abstract Modification applyToMember(
       NodeList<BodyDeclaration<?>> members, Change change);
 
-  /**
-   * Fills the given JSON object with the information of this location.
-   *
-   * @param res The JSON object to be filled.
-   */
-  protected abstract void fillJsonInformation(JSONObject res);
-
   /**
    * Applies the change to the target element on the given compilation unit tree.
    *
@@ -152,16 +134,6 @@ public Modification apply(CompilationUnit tree, Change change) {
     return applyToMember(clazz, change);
   }
 
-  @SuppressWarnings("unchecked")
-  public JSONObject getJson() {
-    JSONObject res = new JSONObject();
-    res.put(KEYS.CLASS, clazz);
-    res.put(KEYS.KIND, type.toString());
-    res.put(KEYS.PATH, path);
-    fillJsonInformation(res);
-    return res;
-  }
-
   /**
    * If this location is of kind {@link LocationKind#METHOD}, calls the consumer on the location.
    *
@@ -268,6 +240,17 @@ public boolean equals(Object o) {
     return type == other.type && clazz.equals(other.clazz);
   }
 
+  /**
+   * Applies a visitor to this location.
+   *
+   * @param <R> the return type of the visitor's methods
+   * @param <P> the type of the additional parameter to the visitor's methods
+   * @param v the visitor operating on this type
+   * @param p additional parameter to the visitor
+   * @return a visitor-specified result
+   */
+  public abstract <R, P> R accept(LocationVisitor<R, P> v, P p);
+
   @Override
   public int hashCode() {
     return Objects.hash(type, clazz);

injector/src/main/java/edu/ucr/cs/riple/injector/location/LocationToJsonVisitor.java

@@ -0,0 +1,103 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2023 Nima Karimipour
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package edu.ucr.cs.riple.injector.location;
+
+import org.json.simple.JSONArray;
+import org.json.simple.JSONObject;
+
+/**
+ * A visitor that converts a location to a JSON object. This visitor is singleton and for all
+ * methods {@link LocationToJsonVisitor#INSTANCE} should be used.
+ */
+public class LocationToJsonVisitor implements LocationVisitor<JSONObject, Void> {
+
+  /** The Keys used to represent a location in JSON format */
+  public enum KEYS {
+    VARIABLES,
+    METHOD,
+    KIND,
+    CLASS,
+    PATH,
+    INDEX
+  }
+
+  /** A singleton instance of this visitor. */
+  public static final LocationToJsonVisitor INSTANCE = new LocationToJsonVisitor();
+
+  private LocationToJsonVisitor() {
+    // Singleton instance.
+  }
+
+  @SuppressWarnings("unchecked")
+  private JSONObject defaultAction(Location location) {
+    JSONObject res = new JSONObject();
+    res.put(KEYS.CLASS, location.clazz);
+    res.put(KEYS.KIND, location.type.toString());
+    res.put(KEYS.PATH, location.path);
+    return res;
+  }
+
+  @SuppressWarnings("unchecked")
+  @Override
+  public JSONObject visitMethod(OnMethod onMethod, Void unused) {
+    JSONObject res = defaultAction(onMethod);
+    res.put(KEYS.METHOD, onMethod.method);
+    return res;
+  }
+
+  @SuppressWarnings("unchecked")
+  @Override
+  public JSONObject visitField(OnField onField, Void unused) {
+    JSONObject res = defaultAction(onField);
+    JSONArray fields = new JSONArray();
+    fields.addAll(onField.variables);
+    res.put(KEYS.VARIABLES, fields);
+    return res;
+  }
+
+  @SuppressWarnings("unchecked")
+  @Override
+  public JSONObject visitParameter(OnParameter onParameter, Void unused) {
+    JSONObject res = defaultAction(onParameter);
+    res.put(KEYS.METHOD, onParameter.method);
+    res.put(KEYS.INDEX, onParameter.index);
+    return res;
+  }
+
+  @Override
+  public JSONObject visitClass(OnClass onClass, Void unused) {
+    return defaultAction(onClass);
+  }
+
+  /**
+   * Visits a location and returns a JSON object.
+   *
+   * @param location the location to visit
+   * @return a JSON object representing the location
+   */
+  public JSONObject visit(Location location) {
+    return location.accept(this, null);
+  }
+}

injector/src/main/java/edu/ucr/cs/riple/injector/location/LocationVisitor.java

@@ -0,0 +1,69 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2023 Nima Karimipour
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package edu.ucr.cs.riple.injector.location;
+
+/**
+ * A visitor of types, in the style of the visitor design pattern. When a visitor is passed to a
+ * location's {@link Location#accept accept} method, the <code>visit<i>Xyz</i></code> method
+ * applicable to that location is invoked.
+ */
+public interface LocationVisitor<R, P> {
+
+  /**
+   * Visits a location for a method.
+   *
+   * @param onMethod the location for a method
+   * @param p a visitor-specified parameter
+   * @return a visitor-specified result
+   */
+  R visitMethod(OnMethod onMethod, P p);
+
+  /**
+   * Visits a location for a field.
+   *
+   * @param onField the location for a field
+   * @param p a visitor-specified parameter
+   * @return a visitor-specified result
+   */
+  R visitField(OnField onField, P p);
+
+  /**
+   * Visits a location for a parameter.
+   *
+   * @param onParameter the location for a parameter
+   * @param p a visitor-specified parameter
+   * @return a visitor-specified result
+   */
+  R visitParameter(OnParameter onParameter, P p);
+
+  /**
+   * Visits a location for a class.
+   *
+   * @param onClass the location for a class
+   * @param p a visitor-specified parameter
+   * @return a visitor-specified result
+   */
+  R visitClass(OnClass onClass, P p);
+}

injector/src/main/java/edu/ucr/cs/riple/injector/location/OnClass.java

@@ -34,7 +34,6 @@
 import java.util.Optional;
 import java.util.regex.Pattern;
 import javax.annotation.Nullable;
-import org.json.simple.JSONObject;
 
 /** Represents a location for class element. This location is used to apply changes to a class. */
 public class OnClass extends Location {
@@ -77,8 +76,8 @@ public static boolean isAnonymousClassFlatName(String flatName) {
   }
 
   @Override
-  protected void fillJsonInformation(JSONObject res) {
-    // no op
+  public <R, P> R accept(LocationVisitor<R, P> v, P p) {
+    return v.visitClass(this, p);
   }
 
   @Override

injector/src/main/java/edu/ucr/cs/riple/injector/location/OnField.java

@@ -37,8 +37,6 @@
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Consumer;
 import javax.annotation.Nullable;
-import org.json.simple.JSONArray;
-import org.json.simple.JSONObject;
 
 /**
  * Represents a location for field element. This location is used to apply changes to a class field.
@@ -68,14 +66,6 @@ public OnField(String path, String clazz, Set<String> variables) {
     this(Helper.deserializePath(path), clazz, variables);
   }
 
-  @SuppressWarnings("unchecked")
-  @Override
-  protected void fillJsonInformation(JSONObject res) {
-    JSONArray fields = new JSONArray();
-    fields.addAll(variables);
-    res.put(KEYS.VARIABLES, fields);
-  }
-
   @Override
   @Nullable
   protected Modification applyToMember(NodeList<BodyDeclaration<?>> members, Change change) {
@@ -129,6 +119,11 @@ public boolean equals(Object o) {
     return super.equals(other) && !Collections.disjoint(variables, other.variables);
   }
 
+  @Override
+  public <R, P> R accept(LocationVisitor<R, P> v, P p) {
+    return v.visitField(this, p);
+  }
+
   @Override
   public int hashCode() {
     return Objects.hash(super.hashCode(), variables);

injector/src/main/java/edu/ucr/cs/riple/injector/location/OnMethod.java

@@ -35,7 +35,6 @@
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Consumer;
 import javax.annotation.Nullable;
-import org.json.simple.JSONObject;
 
 /** Represents a location for method element. This location is used to apply changes to a method. */
 public class OnMethod extends Location {
@@ -58,12 +57,6 @@ public OnMethod(String path, String clazz, String method) {
     this(Helper.deserializePath(path), clazz, method);
   }
 
-  @SuppressWarnings("unchecked")
-  @Override
-  protected void fillJsonInformation(JSONObject res) {
-    res.put(KEYS.METHOD, method);
-  }
-
   @Override
   @Nullable
   protected Modification applyToMember(NodeList<BodyDeclaration<?>> members, Change change) {
@@ -117,6 +110,11 @@ public boolean equals(Object o) {
     return super.equals(other) && method.equals(other.method);
   }
 
+  @Override
+  public <R, P> R accept(LocationVisitor<R, P> v, P p) {
+    return v.visitMethod(this, p);
+  }
+
   @Override
   public int hashCode() {
     return Objects.hash(super.hashCode(), method);

injector/src/main/java/edu/ucr/cs/riple/injector/location/OnParameter.java

@@ -37,7 +37,6 @@
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Consumer;
 import javax.annotation.Nullable;
-import org.json.simple.JSONObject;
 
 /**
  * Represents a location for parameter element. This location is used to apply changes to a
@@ -66,13 +65,6 @@ public OnParameter(String path, String clazz, String method, int index) {
     this(Helper.deserializePath(path), clazz, method, index);
   }
 
-  @SuppressWarnings("unchecked")
-  @Override
-  protected void fillJsonInformation(JSONObject res) {
-    res.put(KEYS.METHOD, method);
-    res.put(KEYS.INDEX, index);
-  }
-
   @Override
   @Nullable
   protected Modification applyToMember(NodeList<BodyDeclaration<?>> members, Change change) {
@@ -125,6 +117,11 @@ public boolean equals(Object o) {
     return super.equals(other) && method.equals(other.method) && index == other.index;
   }
 
+  @Override
+  public <R, P> R accept(LocationVisitor<R, P> v, P p) {
+    return v.visitParameter(this, p);
+  }
+
   @Override
   public int hashCode() {
     return Objects.hash(super.hashCode(), method, index);