Refactor expression visitor (#2808)

* Refactoring Expression Visitor so all expression types have visit methods.

* Added BooleanExpression class

elide-core/src/main/java/com/yahoo/elide/core/security/permissions/expressions/AnyFieldExpression.java

@@ -32,7 +32,7 @@ public ExpressionResult evaluate(EvaluationMode mode) {
 
     @Override
     public <T> T accept(ExpressionVisitor<T> visitor) {
-        return visitor.visitExpression(this);
+        return visitor.visitAnyFieldExpression(this);
     }
 
     @Override

elide-core/src/main/java/com/yahoo/elide/core/security/permissions/expressions/BooleanExpression.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2022, Yahoo Inc.
+ * Licensed under the Apache License, Version 2.0
+ * See LICENSE file in project root for terms.
+ */
+
+package com.yahoo.elide.core.security.permissions.expressions;
+
+import static org.fusesource.jansi.Ansi.ansi;
+
+import com.yahoo.elide.core.security.permissions.ExpressionResult;
+import org.fusesource.jansi.Ansi;
+
+/**
+ * Expression that returns always true (PASS) or false (FAILURE).
+ */
+public class BooleanExpression implements Expression {
+    private boolean value;
+    public BooleanExpression(boolean value) {
+        this.value = value;
+    }
+    @Override
+    public ExpressionResult evaluate(EvaluationMode mode) {
+        if (value == true) {
+            return ExpressionResult.PASS;
+        }
+        return ExpressionResult.FAIL;
+    }
+
+    @Override
+    public <T> T accept(ExpressionVisitor<T> visitor) {
+        return visitor.visitBooleanExpression(this);
+    }
+
+    @Override
+    public String toString() {
+        Ansi.Color color = value ? Ansi.Color.GREEN : Ansi.Color.RED;
+        String label = value ? "SUCCESS" : "FAILURE";
+        return ansi().fg(color).a(label).reset().toString();
+    }
+}

elide-core/src/main/java/com/yahoo/elide/core/security/permissions/expressions/Expression.java

@@ -5,9 +5,7 @@
  */
 package com.yahoo.elide.core.security.permissions.expressions;
 
-import static org.fusesource.jansi.Ansi.ansi;
 import com.yahoo.elide.core.security.permissions.ExpressionResult;
-import org.fusesource.jansi.Ansi;
 
 /**
  * Interface describing an expression.
@@ -37,37 +35,7 @@ public enum EvaluationMode {
      * Static Expressions that return PASS or FAIL.
      */
     public static class Results {
-        public static final Expression SUCCESS = new Expression() {
-            @Override
-            public ExpressionResult evaluate(EvaluationMode ignored) {
-                return ExpressionResult.PASS;
-            }
-
-            @Override
-            public <T> T accept(ExpressionVisitor<T> visitor) {
-                return visitor.visitExpression(this);
-            }
-
-            @Override
-            public String toString() {
-                return ansi().fg(Ansi.Color.GREEN).a("SUCCESS").reset().toString();
-            }
-        };
-        public static final Expression FAILURE = new Expression() {
-            @Override
-            public ExpressionResult evaluate(EvaluationMode ignored) {
-                return ExpressionResult.FAIL;
-            }
-
-            @Override
-            public <T> T accept(ExpressionVisitor<T> visitor) {
-                return visitor.visitExpression(this);
-            }
-
-            @Override
-            public String toString() {
-                return ansi().fg(Ansi.Color.RED).a("FAILURE").reset().toString();
-            }
-        };
+        public static final Expression SUCCESS = new BooleanExpression(true);
+        public static final Expression FAILURE = new BooleanExpression(false);
     }
 }

elide-core/src/main/java/com/yahoo/elide/core/security/permissions/expressions/ExpressionVisitor.java

@@ -11,7 +11,9 @@
  * @param <T> The return type of the visitor
  */
 public interface ExpressionVisitor<T> {
-    T visitExpression(Expression expression);
+    T visitSpecificFieldExpression(SpecificFieldExpression expression);
+    T visitAnyFieldExpression(AnyFieldExpression expression);
+    T visitBooleanExpression(BooleanExpression expression);
     T visitCheckExpression(CheckExpression checkExpression);
     T visitAndExpression(AndExpression andExpression);
     T visitOrExpression(OrExpression orExpression);

elide-core/src/main/java/com/yahoo/elide/core/security/permissions/expressions/SpecificFieldExpression.java

@@ -41,7 +41,7 @@ public ExpressionResult evaluate(EvaluationMode mode) {
 
     @Override
     public <T> T accept(ExpressionVisitor<T> visitor) {
-        return visitor.visitExpression(this);
+        return visitor.visitSpecificFieldExpression(this);
     }
 
 

elide-core/src/main/java/com/yahoo/elide/core/security/visitors/PermissionExpressionNormalizationVisitor.java

@@ -6,19 +6,24 @@
 
 package com.yahoo.elide.core.security.visitors;
 
-import com.yahoo.elide.core.security.permissions.expressions.AndExpression;
-import com.yahoo.elide.core.security.permissions.expressions.CheckExpression;
-import com.yahoo.elide.core.security.permissions.expressions.Expression;
-import com.yahoo.elide.core.security.permissions.expressions.ExpressionVisitor;
-import com.yahoo.elide.core.security.permissions.expressions.NotExpression;
-import com.yahoo.elide.core.security.permissions.expressions.OrExpression;
+import com.yahoo.elide.core.security.permissions.expressions.*;
 
 /**
  * Expression Visitor to normalize Permission expression.
  */
 public class PermissionExpressionNormalizationVisitor implements ExpressionVisitor<Expression> {
     @Override
-    public Expression visitExpression(Expression expression) {
+    public Expression visitSpecificFieldExpression(SpecificFieldExpression expression) {
+        return expression;
+    }
+
+    @Override
+    public Expression visitAnyFieldExpression(AnyFieldExpression expression) {
+        return expression;
+    }
+
+    @Override
+    public Expression visitBooleanExpression(BooleanExpression expression) {
         return expression;
     }
 

elide-core/src/main/java/com/yahoo/elide/core/security/visitors/PermissionToFilterExpressionVisitor.java

@@ -18,12 +18,7 @@
 import com.yahoo.elide.core.security.checks.Check;
 import com.yahoo.elide.core.security.checks.FilterExpressionCheck;
 import com.yahoo.elide.core.security.checks.UserCheck;
-import com.yahoo.elide.core.security.permissions.expressions.AndExpression;
-import com.yahoo.elide.core.security.permissions.expressions.CheckExpression;
-import com.yahoo.elide.core.security.permissions.expressions.Expression;
-import com.yahoo.elide.core.security.permissions.expressions.ExpressionVisitor;
-import com.yahoo.elide.core.security.permissions.expressions.NotExpression;
-import com.yahoo.elide.core.security.permissions.expressions.OrExpression;
+import com.yahoo.elide.core.security.permissions.expressions.*;
 import com.yahoo.elide.core.type.Type;
 
 import java.util.Objects;
@@ -199,7 +194,17 @@ private Operator operator(FilterExpression expression) {
     }
 
     @Override
-    public FilterExpression visitExpression(Expression expression) {
+    public FilterExpression visitSpecificFieldExpression(SpecificFieldExpression expression) {
+        return NO_EVALUATION_EXPRESSION;
+    }
+
+    @Override
+    public FilterExpression visitAnyFieldExpression(AnyFieldExpression expression) {
+        return NO_EVALUATION_EXPRESSION;
+    }
+
+    @Override
+    public FilterExpression visitBooleanExpression(BooleanExpression expression) {
         return NO_EVALUATION_EXPRESSION;
     }
 }

elide-core/src/test/java/com/yahoo/elide/parsers/expression/PermissionExpressionVisitorTest.java

@@ -158,7 +158,7 @@ public ExpressionResult evaluate(EvaluationMode ignored) {
 
         @Override
         public <T> T accept(ExpressionVisitor<T> visitor) {
-            return visitor.visitExpression(this);
+            return null;
         }
     }
 }