google/escapevelocity/TokenNode.java

/*
 * Copyright (C) 2018 Google, Inc.
 *
 * 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.escapevelocity;

import com.google.common.collect.ImmutableList;
import java.util.List;

/**
 * A parsing node that will be deleted during the construction of the parse tree, to be replaced
 * by a higher-level construct such as {@link DirectiveNode.IfNode}. See {@link Parser#parse()}
 * for a description of the way these tokens work.
 *
 * @author emcmanus@google.com (Éamonn McManus)
 */
abstract class TokenNode extends Node {
  TokenNode(String resourceName, int lineNumber) {
    super(resourceName, lineNumber);
  }

  /**
   * This method always throws an exception because a node like this should never be found in the
   * final parse tree.
   */
  @Override Object evaluate(EvaluationContext vars) {
    throw new UnsupportedOperationException(getClass().getName());
  }

  /**
   * The name of the token, for use in parse error messages.
   */
  abstract String name();

  /**
   * A synthetic node that represents the end of the input. This node is the last one in the
   * initial token string and also the last one in the parse tree.
   */
  static final class EofNode extends TokenNode {
    EofNode(String resourceName, int lineNumber) {
      super(resourceName, lineNumber);
    }

    @Override
    String name() {
      return "end of file";
    }
  }

  static final class EndTokenNode extends TokenNode {
    EndTokenNode(String resourceName, int lineNumber) {
      super(resourceName, lineNumber);
    }

    @Override String name() {
      return "#end";
    }
  }

  /**
   * A node in the parse tree representing a comment. Comments are introduced by {@code ##} and
   * extend to the end of the line. The only reason for recording comment nodes is so that we can
   * skip space between a comment and a following {@code #set}, to be compatible with Velocity
   * behaviour.
   */
  static class CommentTokenNode extends TokenNode {
    CommentTokenNode(String resourceName, int lineNumber) {
      super(resourceName, lineNumber);
    }

    @Override String name() {
      return "##";
    }
  }

  abstract static class IfOrElseIfTokenNode extends TokenNode {
    final ExpressionNode condition;

    IfOrElseIfTokenNode(ExpressionNode condition) {
      super(condition.resourceName, condition.lineNumber);
      this.condition = condition;
    }
  }

  static final class IfTokenNode extends IfOrElseIfTokenNode {
    IfTokenNode(ExpressionNode condition) {
      super(condition);
    }

    @Override String name() {
      return "#if";
    }
  }

  static final class ElseIfTokenNode extends IfOrElseIfTokenNode {
    ElseIfTokenNode(ExpressionNode condition) {
      super(condition);
    }

    @Override String name() {
      return "#elseif";
    }
  }

  static final class ElseTokenNode extends TokenNode {
    ElseTokenNode(String resourceName, int lineNumber) {
      super(resourceName, lineNumber);
    }

    @Override String name() {
      return "#else";
    }
  }

  static final class ForEachTokenNode extends TokenNode {
    final String var;
    final ExpressionNode collection;

    ForEachTokenNode(String var, ExpressionNode collection) {
      super(collection.resourceName, collection.lineNumber);
      this.var = var;
      this.collection = collection;
    }

    @Override String name() {
      return "#foreach";
    }
  }

  static final class NestedTokenNode extends TokenNode {
    final ImmutableList<Node> nodes;

    NestedTokenNode(String resourceName, ImmutableList<Node> nodes) {
      super(resourceName, 1);
      this.nodes = nodes;
    }

    @Override String name() {
      return "#parse(\"" + resourceName + "\")";
    }
  }

  static final class MacroDefinitionTokenNode extends TokenNode {
    final String name;
    final ImmutableList<String> parameterNames;

    MacroDefinitionTokenNode(
        String resourceName, int lineNumber, String name, List<String> parameterNames) {
      super(resourceName, lineNumber);
      this.name = name;
      this.parameterNames = ImmutableList.copyOf(parameterNames);
    }

    @Override String name() {
      return "#macro(" + name + ")";
    }
  }
}