/*

  * Licensed to the Apache Software Foundation (ASF) under one or more

  * contributor license agreements.  See the NOTICE file distributed with

  * this work for additional information regarding copyright ownership.

  * The ASF licenses this file to You 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 org.apache.commons.lang3.text.translate;

 import java.io.IOException;

 import java.io.StringWriter;

 import java.io.Writer;

 import java.util.Locale;

 /**

  * An API for translating text. 

  * Its core use is to escape and unescape text. Because escaping and unescaping 

  * is completely contextual, the API does not present two separate signatures.

  * 

  * @since 3.0

  * @version $Id: CharSequenceTranslator.java 1436770 2013-01-22 07:09:45Z ggregory $

  */

 public abstract class CharSequenceTranslator {

     /**

      * Translate a set of codepoints, represented by an int index into a CharSequence, 

      * into another set of codepoints. The number of codepoints consumed must be returned, 

      * and the only IOExceptions thrown must be from interacting with the Writer so that 

      * the top level API may reliable ignore StringWriter IOExceptions. 

      *

      * @param input CharSequence that is being translated

      * @param index int representing the current point of translation

      * @param out Writer to translate the text to

      * @return int count of codepoints consumed

      * @throws IOException if and only if the Writer produces an IOException

      */

     public abstract int translate(CharSequence input, int index, Writer out) throws IOException;

     /**

      * Helper for non-Writer usage. 

      * @param input CharSequence to be translated

      * @return String output of translation

      */

     public final String translate(final CharSequence input) {

         if (input == null) {

             return null;

         }

         try {

             final StringWriter writer = new StringWriter(input.length() * 2);

             translate(input, writer);

             return writer.toString();

         } catch (final IOException ioe) {

             // this should never ever happen while writing to a StringWriter

             throw new RuntimeException(ioe);

         }

     }

     /**

      * Translate an input onto a Writer. This is intentionally final as its algorithm is 

      * tightly coupled with the abstract method of this class. 

      *

      * @param input CharSequence that is being translated

      * @param out Writer to translate the text to

      * @throws IOException if and only if the Writer produces an IOException

      */

     public final void translate(final CharSequence input, final Writer out) throws IOException {

         if (out == null) {

             throw new IllegalArgumentException("The Writer must not be null");

         }

         if (input == null) {

             return;

         }

         int pos = 0;

         final int len = input.length();

         while (pos < len) {

             final int consumed = translate(input, pos, out);

             if (consumed == 0) {

                 final char[] c = Character.toChars(Character.codePointAt(input, pos));

                 out.write(c);

                 pos+= c.length;

                 continue;

             }

 //          // contract with translators is that they have to understand codepoints 

 //          // and they just took care of a surrogate pair

             for (int pt = 0; pt < consumed; pt++) {

                 pos += Character.charCount(Character.codePointAt(input, pt));

             }

         }

     }

     /**

      * Helper method to create a merger of this translator with another set of 

      * translators. Useful in customizing the standard functionality.

      *

      * @param translators CharSequenceTranslator array of translators to merge with this one

      * @return CharSequenceTranslator merging this translator with the others

      */

     public final CharSequenceTranslator with(final CharSequenceTranslator... translators) {

         final CharSequenceTranslator[] newArray = new CharSequenceTranslator[translators.length + 1];

         newArray[0] = this;

         System.arraycopy(translators, 0, newArray, 1, translators.length);

         return new AggregateTranslator(newArray);

     }

     /**

      * <p>Returns an upper case hexadecimal <code>String</code> for the given

      * character.</p>

      *

      * @param codepoint The codepoint to convert.

      * @return An upper case hexadecimal <code>String</code>

      */

     public static String hex(final int codepoint) {

         return Integer.toHexString(codepoint).toUpperCase(Locale.ENGLISH);

     }

 }