/*
 * Copyright 2006 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.gwt.core.ext;

/**
 * Generates source code for subclasses during deferred binding requests.
 * Subclasses must be thread-safe.
 */
public abstract class Generator {

  /**
   * Escapes string content to be a valid string literal.
   * 
   * @return an escaped version of <code>unescaped</code>, suitable for being
   *         enclosed in double quotes in Java source
   */
  public static String escape(String unescaped) {
    int extra = 0;
    for (int in = 0, n = unescaped.length(); in < n; ++in) {
      switch (unescaped.charAt(in)) {
        case '\0':
        case '\n':
        case '\r':
        case '\"':
        case '\\':
          ++extra;
          break;
      }
    }

    if (extra == 0) {
      return unescaped;
    }

    char[] oldChars = unescaped.toCharArray();
    char[] newChars = new char[oldChars.length + extra];
    for (int in = 0, out = 0, n = oldChars.length; in < n; ++in, ++out) {
      char c = oldChars[in];
      switch (c) {
        case '\0':
          newChars[out++] = '\\';
          c = '0';
          break;
        case '\n':
          newChars[out++] = '\\';
          c = 'n';
          break;
        case '\r':
          newChars[out++] = '\\';
          c = 'r';
          break;
        case '\"':
          newChars[out++] = '\\';
          c = '"';
          break;
        case '\\':
          newChars[out++] = '\\';
          c = '\\';
          break;
      }
      newChars[out] = c;
    }

    return String.valueOf(newChars);
  }

  /**
   * Generate a default constructible subclass of the requested type. The
   * generator throws <code>UnableToCompleteException</code> if for any reason
   * it cannot provide a substitute class
   * 
   * @return the name of a subclass to substitute for the requested class, or
   *         return <code>null</code> to cause the requested type itself to be
   *         used
   * 
   */
  public abstract String generate(TreeLogger logger, GeneratorContext context,
      String typeName) throws UnableToCompleteException;
}