package com.ppc.spider.fc.util;

import java.io.ByteArrayOutputStream;

import java.io.BufferedWriter;

import java.io.OutputStreamWriter;

import java.io.IOException;

import java.io.UnsupportedEncodingException;

import java.net.URLDecoder;

import java.io.CharArrayWriter;

import java.nio.charset.Charset;

import java.nio.charset.IllegalCharsetNameException;

import java.nio.charset.UnsupportedCharsetException ;

import java.util.BitSet;

import java.security.AccessController;

import sun.security.action.GetPropertyAction;

public class UrlSafeEncoder {

    static BitSet dontNeedEncoding;

    static final int caseDiff = ('a' - 'A');

    static String dfltEncName = null;

    static {

        /* The list of characters that are not encoded has been

         * determined as follows:

         *

         * RFC 2396 states:

         * -----

         * Data characters that are allowed in a URI but do not have a

         * reserved purpose are called unreserved.  These include upper

         * and lower case letters, decimal digits, and a limited set of

         * punctuation marks and symbols.

         *

         * unreserved  = alphanum | mark

         *

         * mark        = "-" | "_" | "." | "!" | "~" | "*" | "'" | "(" | ")"

         *

         * Unreserved characters can be escaped without changing the

         * semantics of the URI, but this should not be done unless the

         * URI is being used in a context that does not allow the

         * unescaped character to appear.

         * -----

         *

         * It appears that both Netscape and Internet Explorer escape

         * all special characters from this list with the exception

         * of "-", "_", ".", "*". While it is not clear why they are

         * escaping the other characters, perhaps it is safest to

         * assume that there might be contexts in which the others

         * are unsafe if not escaped. Therefore, we will use the same

         * list. It is also noteworthy that this is consistent with

         * O'Reilly's "HTML: The Definitive Guide" (page 164).

         *

         * As a last note, Intenet Explorer does not encode the "@"

         * character which is clearly not unreserved according to the

         * RFC. We are being consistent with the RFC in this matter,

         * as is Netscape.

         *

         */

        dontNeedEncoding = new BitSet(256);

        int i;

        for (i = 'a'; i <= 'z'; i++) {

            dontNeedEncoding.set(i);

        }

        for (i = 'A'; i <= 'Z'; i++) {

            dontNeedEncoding.set(i);

        }

        for (i = '0'; i <= '9'; i++) {

            dontNeedEncoding.set(i);

        }

        dontNeedEncoding.set(' '); /* encoding a space to a + is done

                                    * in the encode() method */

        dontNeedEncoding.set('-');

        dontNeedEncoding.set('_');

        dontNeedEncoding.set('.');

        dontNeedEncoding.set('*');

        dfltEncName = AccessController.doPrivileged(

            new GetPropertyAction("file.encoding")

        );

    }

    /**

     * You can't call the constructor.

     */

    private UrlSafeEncoder() { }

    /**

     * Translates a string into {@code application/x-www-form-urlencoded}

     * format using a specific encoding scheme. This method uses the

     * supplied encoding scheme to obtain the bytes for unsafe

     * characters.

     * <p>

     * <em><strong>Note:</strong> The <a href=

     * "http://www.w3.org/TR/html40/appendix/notes.html#non-ascii-chars">

     * World Wide Web Consortium Recommendation</a> states that

     * UTF-8 should be used. Not doing so may introduce

     * incompatibilities.</em>

     *

     * @param   s   {@code String} to be translated.

     * @param   enc   The name of a supported

     *    <a href="../lang/package-summary.html#charenc">character

     *    encoding</a>.

     * @return  the translated {@code String}.

     * @exception  UnsupportedEncodingException

     *             If the named encoding is not supported

     * @see URLDecoder#decode(java.lang.String, java.lang.String)

     * @since 1.4

     */

    public static String encode(String s, String enc,char safe)

        throws UnsupportedEncodingException {

        dontNeedEncoding.set(safe);

        boolean needToChange = false;

        StringBuffer out = new StringBuffer(s.length());

        Charset charset;

        CharArrayWriter charArrayWriter = new CharArrayWriter();

        if (enc == null)

            throw new NullPointerException("charsetName");

        try {

            charset = Charset.forName(enc);

        } catch (IllegalCharsetNameException e) {

            throw new UnsupportedEncodingException(enc);

        } catch (UnsupportedCharsetException e) {

            throw new UnsupportedEncodingException(enc);

        }

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

            int c = (int) s.charAt(i);

            //System.out.println("Examining character: " + c);

            if (dontNeedEncoding.get(c)) {

                if (c == ' ') {

                    c = '+';

                    needToChange = true;

                }

                //System.out.println("Storing: " + c);

                out.append((char)c);

                i++;

            } else {

                // convert to external encoding before hex conversion

                do {

                    charArrayWriter.write(c);

                    /*

                     * If this character represents the start of a Unicode

                     * surrogate pair, then pass in two characters. It's not

                     * clear what should be done if a bytes reserved in the

                     * surrogate pairs range occurs outside of a legal

                     * surrogate pair. For now, just treat it as if it were

                     * any other character.

                     */

                    if (c >= 0xD800 && c <= 0xDBFF) {

                        /*

                          System.out.println(Integer.toHexString(c)

                          + " is high surrogate");

                        */

                        if ( (i+1) < s.length()) {

                            int d = (int) s.charAt(i+1);

                            /*

                              System.out.println("\tExamining "

                              + Integer.toHexString(d));

                            */

                            if (d >= 0xDC00 && d <= 0xDFFF) {

                                /*

                                  System.out.println("\t"

                                  + Integer.toHexString(d)

                                  + " is low surrogate");

                                */

                                charArrayWriter.write(d);

                                i++;

                            }

                        }

                    }

                    i++;

                } while (i < s.length() && !dontNeedEncoding.get((c = (int) s.charAt(i))));

                charArrayWriter.flush();

                String str = new String(charArrayWriter.toCharArray());

                byte[] ba = str.getBytes(charset);

                for (int j = 0; j < ba.length; j++) {

                    out.append('%');

                    char ch = Character.forDigit((ba[j] >> 4) & 0xF, 16);

                    // converting to use uppercase letter as part of

                    // the hex value if ch is a letter.

                    if (Character.isLetter(ch)) {

                        ch -= caseDiff;

                    }

                    out.append(ch);

                    ch = Character.forDigit(ba[j] & 0xF, 16);

                    if (Character.isLetter(ch)) {

                        ch -= caseDiff;

                    }

                    out.append(ch);

                }

                charArrayWriter.reset();

                needToChange = true;

            }

        }

        return (needToChange? out.toString() : s);

    }

}