/*
 *  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.UnsupportedEncodingException;

/** This class is used to encode a string using the format required by {@code application/x-www-form-urlencoded} MIME content
 * type. */
public class URLEncoder {

	static final String digits = "0123456789ABCDEF";

	/** Prevents this class from being instantiated. */
	private URLEncoder () {
	}

	/** Encodes a given string {@code s} in a x-www-form-urlencoded string using the specified encoding scheme {@code enc}.
	 * <p>
	 * All characters except letters ('a'..'z', 'A'..'Z') and numbers ('0'..'9') and characters '.', '-', '*', '_' are converted
	 * into their hexadecimal value prepended by '%'. For example: '#' -> %23. In addition, spaces are substituted by '+'
	 *
	 * @param s the string to be encoded.
	 * @return the encoded string.
	 * @deprecated use {@link #encode(String, String)} instead. */
	@Deprecated
	public static String encode (String s) {
		// Guess a bit bigger for encoded form
		StringBuilder buf = new StringBuilder(s.length() + 16);
		for (int i = 0; i < s.length(); i++) {
			char ch = s.charAt(i);
			if ((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z') || (ch >= '0' && ch <= '9') || ".-*_".indexOf(ch) > -1) {
				buf.append(ch);
			} else if (ch == ' ') {
				buf.append('+');
			} else {
				byte[] bytes = new String(new char[] {ch}).getBytes();
				for (int j = 0; j < bytes.length; j++) {
					buf.append('%');
					buf.append(digits.charAt((bytes[j] & 0xf0) >> 4));
					buf.append(digits.charAt(bytes[j] & 0xf));
				}
			}
		}
		return buf.toString();
	}

	/** Encodes the given string {@code s} in a x-www-form-urlencoded string using the specified encoding scheme {@code enc}.
	 * <p>
	 * All characters except letters ('a'..'z', 'A'..'Z') and numbers ('0'..'9') and characters '.', '-', '*', '_' are converted
	 * into their hexadecimal value prepended by '%'. For example: '#' -> %23. In addition, spaces are substituted by '+'
	 *
	 * @param s the string to be encoded.
	 * @param enc the encoding scheme to be used.
	 * @return the encoded string.
	 * @throws UnsupportedEncodingException if the specified encoding scheme is invalid. */
	public static String encode (String s, String enc) throws UnsupportedEncodingException {
		if (s == null || enc == null) {
			throw new NullPointerException();
		}
		// check for UnsupportedEncodingException
		"".getBytes(enc);

		// Guess a bit bigger for encoded form
		StringBuilder buf = new StringBuilder(s.length() + 16);
		int start = -1;
		for (int i = 0; i < s.length(); i++) {
			char ch = s.charAt(i);
			if ((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z') || (ch >= '0' && ch <= '9') || " .-*_".indexOf(ch) > -1) {
				if (start >= 0) {
					convert(s.substring(start, i), buf, enc);
					start = -1;
				}
				if (ch != ' ') {
					buf.append(ch);
				} else {
					buf.append('+');
				}
			} else {
				if (start < 0) {
					start = i;
				}
			}
		}
		if (start >= 0) {
			convert(s.substring(start, s.length()), buf, enc);
		}
		return buf.toString();
	}

	private static void convert (String s, StringBuilder buf, String enc) throws UnsupportedEncodingException {
		byte[] bytes = s.getBytes(enc);
		for (int j = 0; j < bytes.length; j++) {
			buf.append('%');
			buf.append(digits.charAt((bytes[j] & 0xf0) >> 4));
			buf.append(digits.charAt(bytes[j] & 0xf));
		}
	}
}
