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Closure Compiler is a JavaScript optimizing compiler. It parses your JavaScript, analyzes it, removes dead code and rewrites and minimizes what's left. It also checks syntax, variable references, and types, and warns about common JavaScript pitfalls. It is used in many of Google's JavaScript apps, including Gmail, Google Web Search, Google Maps, and Google Docs.

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/*
 * Copyright 2004 The Closure Compiler Authors.
 *
 * 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.javascript.jscomp;

import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.TokenStream;

/**
 * Utility class that extracts the qualified name out of a node.
 * Useful when trying to get a human-friendly string representation of
 * a property node that can be used to describe the node or name
 * related nodes based on it (as done by the NameAnonymousFunctions
 * compiler pass).
 */
class NodeNameExtractor {
  private final char delimiter;
  private int nextUniqueInt = 0;

  NodeNameExtractor(char delimiter) {
    this.delimiter = delimiter;
  }

  /**
   * Returns a qualified name of the specified node. Dots and brackets
   * are changed to the delimiter passed in when constructing the
   * NodeNameExtractor object.  We also replace ".prototype" with the
   * delimiter to keep names short, while still differentiating them
   * from static properties.  (Prototype properties will end up
   * looking like "a$b$$c" if this.delimiter = '$'.)
   */
  String getName(Node node) {
    switch (node.getToken()) {
      case CLASS:
      case FUNCTION:
        return NodeUtil.getName(node);
      case GETPROP:
        Node lhsOfDot = node.getFirstChild();
        Node rhsOfDot = lhsOfDot.getNext();
        String lhsOfDotName = getName(lhsOfDot);
        String rhsOfDotName = getName(rhsOfDot);
        if ("prototype".equals(rhsOfDotName)) {
          return lhsOfDotName + delimiter;
        } else {
          return lhsOfDotName + delimiter + rhsOfDotName;
        }
      case GETELEM:
        Node outsideBrackets = node.getFirstChild();
        Node insideBrackets = outsideBrackets.getNext();
        String nameOutsideBrackets = getName(outsideBrackets);
        String nameInsideBrackets = getName(insideBrackets);
        if ("prototype".equals(nameInsideBrackets)) {
          return nameOutsideBrackets + delimiter;
        } else {
          return nameOutsideBrackets + delimiter + nameInsideBrackets;
        }
      case NAME:
        return node.getString();
      case STRINGLIT:
      case STRING_KEY:
      case MEMBER_FUNCTION_DEF:
        return TokenStream.isJSIdentifier(node.getString()) ?
            node.getString() : ("__" + nextUniqueInt++);
      case NUMBER:
        return NodeUtil.getStringValue(node);
      case THIS:
        return "this";
      case CALL:
      case COMPUTED_PROP:
        return getName(node.getFirstChild());
      default:
        StringBuilder sb = new StringBuilder();
        for (Node child = node.getFirstChild(); child != null;
             child = child.getNext()) {
          if (sb.length() > 0) {
            sb.append(delimiter);
          }
          sb.append(getName(child));
        }
        return sb.toString();
    }
  }
}