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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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/*
 *
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (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.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Rhino code, released
 * May 6, 1999.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1997-1999
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Bob Jervis
 *   Google Inc.
 *
 * Alternatively, the contents of this file may be used under the terms of
 * the GNU General Public License Version 2 or later (the "GPL"), in which
 * case the provisions of the GPL are applicable instead of those above. If
 * you wish to allow use of your version of this file only under the terms of
 * the GPL and not to allow others to use your version of this file under the
 * MPL, indicate your decision by deleting the provisions above and replacing
 * them with the notice and other provisions required by the GPL. If you do
 * not delete the provisions above, a recipient may use your version of this
 * file under either the MPL or the GPL.
 *
 * ***** END LICENSE BLOCK ***** */

package com.google.javascript.rhino.jstype;

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

/**
 * A builder for the Rhino Node representing Function parameters.
 * @author [email protected] (Nick Santos)
 */
public class FunctionParamBuilder {

  private final JSTypeRegistry registry;
  private final Node root = new Node(Token.PARAM_LIST);

  public FunctionParamBuilder(JSTypeRegistry registry) {
    this.registry = registry;
  }

  /**
   * Add parameters of the given type to the end of the param list.
   * @return False if this is called after optional params are added.
   */
  public boolean addRequiredParams(JSType ...types) {
    if (hasOptionalOrVarArgs()) {
      return false;
    }

    for (JSType type : types) {
      newParameter(type);
    }
    return true;
  }

  /**
   * Add optional parameters of the given type to the end of the param list.
   * @param types Types for each optional parameter. The builder will make them
   *     undefine-able.
   * @return False if this is called after var args are added.
   */
  public boolean addOptionalParams(JSType ...types) {
    if (hasVarArgs()) {
      return false;
    }

    for (JSType type : types) {
      newParameter(registry.createOptionalType(type)).setOptionalArg(true);
    }
    return true;
  }

  /**
   * Add variable arguments to the end of the parameter list.
   * @return False if this is called after var args are added.
   */
  public boolean addVarArgs(JSType type) {
    if (hasVarArgs()) {
      return false;
    }

    // There are two types of variable argument functions:
    // 1) Programmer-defined var args
    // 2) Native bottom types that can accept any argument.
    // For the first one, "undefined" is a valid value for all arguments.
    // For the second, we do not want to cast it up to undefined.
    if (!type.isEmptyType()) {
      type = registry.createOptionalType(type);
    }
    newParameter(type).setVarArgs(true);
    return true;
  }

  /**
   * Copies the parameter specification from the given node.
   */
  public Node newParameterFromNode(Node n) {
    Node newParam = newParameter(n.getJSType());
    newParam.setVarArgs(n.isVarArgs());
    newParam.setOptionalArg(n.isOptionalArg());
    return newParam;
  }

  /**
   * Copies the parameter specification from the given node,
   * but makes sure it's optional.
   */
  public Node newOptionalParameterFromNode(Node n) {
    Node newParam = newParameterFromNode(n);
    if (!newParam.isVarArgs() && !newParam.isOptionalArg()) {
      newParam.setOptionalArg(true);
    }
    return newParam;
  }

  // Add a parameter to the list with the given type.
  private Node newParameter(JSType type) {
    Node paramNode = Node.newString(Token.NAME, "");
    paramNode.setJSType(type);
    root.addChildToBack(paramNode);
    return paramNode;
  }

  public Node build() {
    return root;
  }

  private boolean hasOptionalOrVarArgs() {
    Node lastChild = root.getLastChild();
    return lastChild != null &&
        (lastChild.isOptionalArg() || lastChild.isVarArgs());
  }

  public boolean hasVarArgs() {
    Node lastChild = root.getLastChild();
    return lastChild != null && lastChild.isVarArgs();
  }
}