/*
 *  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 java.net;

import java.io.ByteArrayOutputStream;
import java.io.UnsupportedEncodingException;

import org.apache.harmony.luni.util.Msg;
import org.apache.harmony.luni.util.Util;

/**
 * This class is used to decode a string which is encoded in the {@code
 * application/x-www-form-urlencoded} MIME content type.
 * 
 * @since Android 1.0
 */
public class URLDecoder {

    /**
     * Decodes the argument which is assumed to be encoded in the {@code
     * x-www-form-urlencoded} MIME content type.
     * <p>
     *'+' will be converted to space, '%' and two following hex digit
     * characters are converted to the equivalent byte value. All other
     * characters are passed through unmodified. For example "A+B+C %24%25" ->
     * "A B C $%".
     * </p>
     * 
     * @param s
     *            the encoded string.
     * @return the decoded clear-text representation of the given string.
     * @deprecated use {@link #decode(String, String)} instead.
     * @since Android 1.0
     */
    @Deprecated
    public static String decode(String s) {
        return Util.decode(s, true);
    }
    
    /**
     * Decodes the argument which is assumed to be encoded in the {@code
     * x-www-form-urlencoded} MIME content type using the specified encoding
     * scheme.
     * <p>
     *'+' will be converted to space, '%' and two following hex digit
     * characters are converted to the equivalent byte value. All other
     * characters are passed through unmodified. For example "A+B+C %24%25" ->
     * "A B C $%".
     * </p>
     * 
     * @param s
     *            the encoded string.
     * @param enc
     *            the encoding scheme to be used.
     * @return the decoded clear-text representation of the given string.
     * @throws UnsupportedEncodingException
     *             if the specified encoding scheme is invalid.
     * @since Android 1.0
     */
    public static String decode(String s, String enc)
            throws UnsupportedEncodingException {

        if (enc == null) {
            throw new NullPointerException();
        }

        // If the given encoding is an empty string throw an exception.
        if (enc.length() == 0) {
            throw new UnsupportedEncodingException(Msg
                    .getString("K00a5", "enc")); //$NON-NLS-1$ //$NON-NLS-2$
        }

        StringBuffer result = new StringBuffer(s.length());
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        for (int i = 0; i < s.length();) {
            char c = s.charAt(i);
            if (c == '+') {
                result.append(' ');
            } else if (c == '%') {
                out.reset();
                do {
                    if (i + 2 >= s.length()) {
                        throw new IllegalArgumentException(Msg.getString(
                                "K01fe", i)); //$NON-NLS-1$
                    }
                    int d1 = Character.digit(s.charAt(i + 1), 16);
                    int d2 = Character.digit(s.charAt(i + 2), 16);
                    if (d1 == -1 || d2 == -1) {
                        throw new IllegalArgumentException(Msg.getString(
                                "K01ff", //$NON-NLS-1$
                                s.substring(i, i + 3), String.valueOf(i)));
                    }
                    out.write((byte) ((d1 << 4) + d2));
                    i += 3;
                } while (i < s.length() && s.charAt(i) == '%');
                result.append(out.toString(enc));
                continue;
            } else {
                result.append(c);
            }
            i++;
        }
        return result.toString();
    }
}