/*

 * 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.Writer;

/**

 * Translate escaped octal Strings back to their octal values.

 *

 * For example, "\45" should go back to being the specific value (a %).

 *

 * Note that this currently only supports the viable range of octal for Java; namely

 * 1 to 377. This is because parsing Java is the main use case.

 *

 * @since 3.0

 * @deprecated as of 3.6, use commons-text

 * <a href="https://commons.apache.org/proper/commons-text/javadocs/api-release/org/apache/commons/text/translate/OctalUnescaper.html">

 * OctalUnescaper</a> instead

 */

@Deprecated

public class OctalUnescaper extends CharSequenceTranslator {

    /**

     * {@inheritDoc}

     */

    @Override

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

        final int remaining = input.length() - index - 1; // how many characters left, ignoring the first \

        final StringBuilder builder = new StringBuilder();

        if (input.charAt(index) == '\\' && remaining > 0 && isOctalDigit(input.charAt(index + 1)) ) {

            final int next = index + 1;

            final int next2 = index + 2;

            final int next3 = index + 3;

            // we know this is good as we checked it in the if block above

            builder.append(input.charAt(next));

            if (remaining > 1 && isOctalDigit(input.charAt(next2))) {

                builder.append(input.charAt(next2));

                if (remaining > 2 && isZeroToThree(input.charAt(next)) && isOctalDigit(input.charAt(next3))) {

                    builder.append(input.charAt(next3));

                }

            }

            out.write( Integer.parseInt(builder.toString(), 8) );

            return 1 + builder.length();

        }

        return 0;

    }

    /**

     * Checks if the given char is an octal digit. Octal digits are the character representations of the digits 0 to 7.

     * @param ch the char to check

     * @return true if the given char is the character representation of one of the digits from 0 to 7

     */

    private boolean isOctalDigit(final char ch) {

        return ch >= '0' && ch <= '7';

    }

    /**

     * Checks if the given char is the character representation of one of the digit from 0 to 3.

     * @param ch the char to check

     * @return true if the given char is the character representation of one of the digits from 0 to 3

     */

    private boolean isZeroToThree(final char ch) {

        return ch >= '0' && ch <= '3';

    }

}