/*

 * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package java.net;

import java.io.InputStream;

import java.io.IOException;

import java.security.AccessController;

import java.security.PrivilegedAction;

import sun.net.idn.StringPrep;

import sun.net.idn.Punycode;

import sun.text.normalizer.UCharacterIterator;

/**

 * Provides methods to convert internationalized domain names (IDNs) between

 * a normal Unicode representation and an ASCII Compatible Encoding (ACE) representation.

 * Internationalized domain names can use characters from the entire range of

 * Unicode, while traditional domain names are restricted to ASCII characters.

 * ACE is an encoding of Unicode strings that uses only ASCII characters and

 * can be used with software (such as the Domain Name System) that only

 * understands traditional domain names.

 *

 * <p>Internationalized domain names are defined in <a href="http://www.ietf.org/rfc/rfc3490.txt">RFC 3490</a>.

 * RFC 3490 defines two operations: ToASCII and ToUnicode. These 2 operations employ

 * <a href="http://www.ietf.org/rfc/rfc3491.txt">Nameprep</a> algorithm, which is a

 * profile of <a href="http://www.ietf.org/rfc/rfc3454.txt">Stringprep</a>, and

 * <a href="http://www.ietf.org/rfc/rfc3492.txt">Punycode</a> algorithm to convert

 * domain name string back and forth.

 *

 * <p>The behavior of aforementioned conversion process can be adjusted by various flags:

 *   <ul>

 *     <li>If the ALLOW_UNASSIGNED flag is used, the domain name string to be converted

 *         can contain code points that are unassigned in Unicode 3.2, which is the

 *         Unicode version on which IDN conversion is based. If the flag is not used,

 *         the presence of such unassigned code points is treated as an error.

 *     <li>If the USE_STD3_ASCII_RULES flag is used, ASCII strings are checked against <a href="http://www.ietf.org/rfc/rfc1122.txt">RFC 1122</a> and <a href="http://www.ietf.org/rfc/rfc1123.txt">RFC 1123</a>.

 *         It is an error if they don't meet the requirements.

 *   </ul>

 * These flags can be logically OR'ed together.

 *

 * <p>The security consideration is important with respect to internationalization

 * domain name support. For example, English domain names may be <i>homographed</i>

 * - maliciously misspelled by substitution of non-Latin letters.

 * <a href="http://www.unicode.org/reports/tr36/">Unicode Technical Report #36</a>

 * discusses security issues of IDN support as well as possible solutions.

 * Applications are responsible for taking adequate security measures when using

 * international domain names.

 *

 * @author Edward Wang

 * @since 1.6

 *

 */

public final class IDN {

    /**

     * Flag to allow processing of unassigned code points

     */

    public static final int ALLOW_UNASSIGNED = 0x01;

    /**

     * Flag to turn on the check against STD-3 ASCII rules

     */

    public static final int USE_STD3_ASCII_RULES = 0x02;

    /**

     * Translates a string from Unicode to ASCII Compatible Encoding (ACE),

     * as defined by the ToASCII operation of <a href="http://www.ietf.org/rfc/rfc3490.txt">RFC 3490</a>.

     *

     * <p>ToASCII operation can fail. ToASCII fails if any step of it fails.

     * If ToASCII operation fails, an IllegalArgumentException will be thrown.

     * In this case, the input string should not be used in an internationalized domain name.

     *

     * <p> A label is an individual part of a domain name. The original ToASCII operation,

     * as defined in RFC 3490, only operates on a single label. This method can handle

     * both label and entire domain name, by assuming that labels in a domain name are

     * always separated by dots. The following characters are recognized as dots:

     * \u002E (full stop), \u3002 (ideographic full stop), \uFF0E (fullwidth full stop),

     * and \uFF61 (halfwidth ideographic full stop). if dots are

     * used as label separators, this method also changes all of them to \u002E (full stop)

     * in output translated string.

     *

     * @param input     the string to be processed

     * @param flag      process flag; can be 0 or any logical OR of possible flags

     *

     * @return          the translated {@code String}

     *

     * @throws IllegalArgumentException   if the input string doesn't conform to RFC 3490 specification

     */

    public static String toASCII(String input, int flag)

    {

        int p = 0, q = 0;

        StringBuilder out = new StringBuilder();

        if (isRootLabel(input)) {

            return ".";

        }

        while (p < input.length()) {

            q = searchDots(input, p);

            out.append(toASCIIInternal(input.substring(p, q),  flag));

            if (q != (input.length())) {

               // has more labels, or keep the trailing dot as at present

               out.append('.');

            }

            p = q + 1;

        }

        return out.toString();

    }

    /**

     * Translates a string from Unicode to ASCII Compatible Encoding (ACE),

     * as defined by the ToASCII operation of <a href="http://www.ietf.org/rfc/rfc3490.txt">RFC 3490</a>.

     *

     * <p> This convenience method works as if by invoking the

     * two-argument counterpart as follows:

     * <blockquote>

     * {@link #toASCII(String, int) toASCII}(input, 0);

     * </blockquote>

     *

     * @param input     the string to be processed

     *

     * @return          the translated {@code String}

     *

     * @throws IllegalArgumentException   if the input string doesn't conform to RFC 3490 specification

     */

    public static String toASCII(String input) {

        return toASCII(input, 0);

    }

    /**

     * Translates a string from ASCII Compatible Encoding (ACE) to Unicode,

     * as defined by the ToUnicode operation of <a href="http://www.ietf.org/rfc/rfc3490.txt">RFC 3490</a>.

     *

     * <p>ToUnicode never fails. In case of any error, the input string is returned unmodified.

     *

     * <p> A label is an individual part of a domain name. The original ToUnicode operation,

     * as defined in RFC 3490, only operates on a single label. This method can handle

     * both label and entire domain name, by assuming that labels in a domain name are

     * always separated by dots. The following characters are recognized as dots:

     * \u002E (full stop), \u3002 (ideographic full stop), \uFF0E (fullwidth full stop),

     * and \uFF61 (halfwidth ideographic full stop).

     *

     * @param input     the string to be processed

     * @param flag      process flag; can be 0 or any logical OR of possible flags

     *

     * @return          the translated {@code String}

     */

    public static String toUnicode(String input, int flag) {

        int p = 0, q = 0;

        StringBuilder out = new StringBuilder();

        if (isRootLabel(input)) {

            return ".";

        }

        while (p < input.length()) {

            q = searchDots(input, p);

            out.append(toUnicodeInternal(input.substring(p, q),  flag));

            if (q != (input.length())) {

               // has more labels, or keep the trailing dot as at present

               out.append('.');

            }

            p = q + 1;

        }

        return out.toString();

    }

    /**

     * Translates a string from ASCII Compatible Encoding (ACE) to Unicode,

     * as defined by the ToUnicode operation of <a href="http://www.ietf.org/rfc/rfc3490.txt">RFC 3490</a>.

     *

     * <p> This convenience method works as if by invoking the

     * two-argument counterpart as follows:

     * <blockquote>

     * {@link #toUnicode(String, int) toUnicode}(input, 0);

     * </blockquote>

     *

     * @param input     the string to be processed

     *

     * @return          the translated {@code String}

     */

    public static String toUnicode(String input) {

        return toUnicode(input, 0);

    }

    /* ---------------- Private members -------------- */

    // ACE Prefix is "xn--"

    private static final String ACE_PREFIX = "xn--";

    private static final int ACE_PREFIX_LENGTH = ACE_PREFIX.length();

    private static final int MAX_LABEL_LENGTH   = 63;

    // single instance of nameprep

    private static StringPrep namePrep = null;

    static {

        InputStream stream = null;

        try {

            final String IDN_PROFILE = "uidna.spp";

            if (System.getSecurityManager() != null) {

                stream = AccessController.doPrivileged(new PrivilegedAction<>() {

                    public InputStream run() {

                        return StringPrep.class.getResourceAsStream(IDN_PROFILE);

                    }

                });

            } else {

                stream = StringPrep.class.getResourceAsStream(IDN_PROFILE);

            }

            namePrep = new StringPrep(stream);

            stream.close();

        } catch (IOException e) {

            // should never reach here

            assert false;

        }

    }

    /* ---------------- Private operations -------------- */

    //

    // to suppress the default zero-argument constructor

    //

    private IDN() {}

    //

    // toASCII operation; should only apply to a single label

    //

    private static String toASCIIInternal(String label, int flag)

    {

        // step 1

        // Check if the string contains code points outside the ASCII range 0..0x7c.

        boolean isASCII  = isAllASCII(label);

        StringBuffer dest;

        // step 2

        // perform the nameprep operation; flag ALLOW_UNASSIGNED is used here

        if (!isASCII) {

            UCharacterIterator iter = UCharacterIterator.getInstance(label);

            try {

                dest = namePrep.prepare(iter, flag);

            } catch (java.text.ParseException e) {

                throw new IllegalArgumentException(e);

            }

        } else {

            dest = new StringBuffer(label);

        }

        // step 8, move forward to check the smallest number of the code points

        // the length must be inside 1..63

        if (dest.length() == 0) {

            throw new IllegalArgumentException(

                        "Empty label is not a legal name");

        }

        // step 3

        // Verify the absence of non-LDH ASCII code points

        //   0..0x2c, 0x2e..0x2f, 0x3a..0x40, 0x5b..0x60, 0x7b..0x7f

        // Verify the absence of leading and trailing hyphen

        boolean useSTD3ASCIIRules = ((flag & USE_STD3_ASCII_RULES) != 0);

        if (useSTD3ASCIIRules) {

            for (int i = 0; i < dest.length(); i++) {

                int c = dest.charAt(i);

                if (isNonLDHAsciiCodePoint(c)) {

                    throw new IllegalArgumentException(

                        "Contains non-LDH ASCII characters");

                }

            }

            if (dest.charAt(0) == '-' ||

                dest.charAt(dest.length() - 1) == '-') {

                throw new IllegalArgumentException(

                        "Has leading or trailing hyphen");

            }

        }

        if (!isASCII) {

            // step 4

            // If all code points are inside 0..0x7f, skip to step 8

            if (!isAllASCII(dest.toString())) {

                // step 5

                // verify the sequence does not begin with ACE prefix

                if(!startsWithACEPrefix(dest)){

                    // step 6

                    // encode the sequence with punycode

                    try {

                        dest = Punycode.encode(dest, null);

                    } catch (java.text.ParseException e) {

                        throw new IllegalArgumentException(e);

                    }

                    dest = toASCIILower(dest);

                    // step 7

                    // prepend the ACE prefix

                    dest.insert(0, ACE_PREFIX);

                } else {

                    throw new IllegalArgumentException("The input starts with the ACE Prefix");

                }

            }

        }

        // step 8

        // the length must be inside 1..63

        if (dest.length() > MAX_LABEL_LENGTH) {

            throw new IllegalArgumentException("The label in the input is too long");

        }

        return dest.toString();

    }

    //

    // toUnicode operation; should only apply to a single label

    //

    private static String toUnicodeInternal(String label, int flag) {

        boolean[] caseFlags = null;

        StringBuffer dest;

        // step 1

        // find out if all the codepoints in input are ASCII

        boolean isASCII = isAllASCII(label);

        if(!isASCII){

            // step 2

            // perform the nameprep operation; flag ALLOW_UNASSIGNED is used here

            try {

                UCharacterIterator iter = UCharacterIterator.getInstance(label);

                dest = namePrep.prepare(iter, flag);

            } catch (Exception e) {

                // toUnicode never fails; if any step fails, return the input string

                return label;

            }

        } else {

            dest = new StringBuffer(label);

        }

        // step 3

        // verify ACE Prefix

        if(startsWithACEPrefix(dest)) {

            // step 4

            // Remove the ACE Prefix

            String temp = dest.substring(ACE_PREFIX_LENGTH, dest.length());

            try {

                // step 5

                // Decode using punycode

                StringBuffer decodeOut = Punycode.decode(new StringBuffer(temp), null);

                // step 6

                // Apply toASCII

                String toASCIIOut = toASCII(decodeOut.toString(), flag);

                // step 7

                // verify

                if (toASCIIOut.equalsIgnoreCase(dest.toString())) {

                    // step 8

                    // return output of step 5

                    return decodeOut.toString();

                }

            } catch (Exception ignored) {

                // no-op

            }

        }

        // just return the input

        return label;

    }

    //

    // LDH stands for "letter/digit/hyphen", with characters restricted to the

    // 26-letter Latin alphabet <A-Z a-z>, the digits <0-9>, and the hyphen

    // <->.

    // Non LDH refers to characters in the ASCII range, but which are not

    //

    // non-LDH = 0..0x2C, 0x2E..0x2F, 0x3A..0x40, 0x5B..0x60, 0x7B..0x7F

    //

    private static boolean isNonLDHAsciiCodePoint(int ch){

        return (0x0000 <= ch && ch <= 0x002C) ||

               (0x002E <= ch && ch <= 0x002F) ||

               (0x003A <= ch && ch <= 0x0040) ||

               (0x005B <= ch && ch <= 0x0060) ||

               (0x007B <= ch && ch <= 0x007F);

    }

    //

    // search dots in a string and return the index of that character;

    // or if there is no dots, return the length of input string

    // dots might be: \u002E (full stop), \u3002 (ideographic full stop), \uFF0E (fullwidth full stop),

    // and \uFF61 (halfwidth ideographic full stop).

    //

    private static int searchDots(String s, int start) {

        int i;

        for (i = start; i < s.length(); i++) {

            if (isLabelSeparator(s.charAt(i))) {

                break;

            }

        }

        return i;

    }

    //

    // to check if a string is a root label, ".".

    //

    private static boolean isRootLabel(String s) {

        return (s.length() == 1 && isLabelSeparator(s.charAt(0)));

    }

    //

    // to check if a character is a label separator, i.e. a dot character.

    //

    private static boolean isLabelSeparator(char c) {

        return (c == '.' || c == '\u3002' || c == '\uFF0E' || c == '\uFF61');

    }

    //

    // to check if a string only contains US-ASCII code point

    //

    private static boolean isAllASCII(String input) {

        boolean isASCII = true;

        for (int i = 0; i < input.length(); i++) {

            int c = input.charAt(i);

            if (c > 0x7F) {

                isASCII = false;

                break;

            }

        }

        return isASCII;

    }

    //

    // to check if a string starts with ACE-prefix

    //

    private static boolean startsWithACEPrefix(StringBuffer input){

        boolean startsWithPrefix = true;

        if(input.length() < ACE_PREFIX_LENGTH){

            return false;

        }

        for(int i = 0; i < ACE_PREFIX_LENGTH; i++){

            if(toASCIILower(input.charAt(i)) != ACE_PREFIX.charAt(i)){

                startsWithPrefix = false;

            }

        }

        return startsWithPrefix;

    }

    private static char toASCIILower(char ch){

        if('A' <= ch && ch <= 'Z'){

            return (char)(ch + 'a' - 'A');

        }

        return ch;

    }

    private static StringBuffer toASCIILower(StringBuffer input){

        StringBuffer dest = new StringBuffer();

        for(int i = 0; i < input.length();i++){

            dest.append(toASCIILower(input.charAt(i)));

        }

        return dest;

    }

}