/*
 * Copyright Red Hat, Inc. and/or its affiliates
 * and other contributors as indicated by the @author tags and
 * the COPYRIGHT.txt file distributed with this work.
 *
 * Licensed 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.teiid.core.util;

import java.util.Arrays;

/**
 * <p>Encodes and decodes to and from Base64 notation.</p>
 * <p>Homepage: <a href="http://iharder.net/base64">http://iharder.net/base64</a>.</p>
 *
 * <p>The <tt>options</tt> parameter, which appears in a few places, is used to pass 
 * several pieces of information to the encoder. In the "higher level" methods such as 
 * encodeBytes( bytes, options ) the options parameter can be used to indicate such 
 * things as first gzipping the bytes before encoding them, not inserting linefeeds 
 * (though that breaks strict Base64 compatibility), and encoding using the URL-safe 
 * and Ordered dialects.</p>
 *
 * <p>The constants defined in Base64 can be OR-ed together to combine options, so you 
 * might make a call like this:</p>
 *
 * <code>String encoded = Base64.encodeBytes( mybytes, Base64.GZIP | Base64.DONT_BREAK_LINES );</code>
 *
 * <p>to compress the data before encoding it and then making the output have no newline characters.</p>
 *
 *
 * <p>
 * Change Log:
 * </p>
 * <ul>
 *  <li>v2.2.2 - Fixed encodeFileToFile and decodeFileToFile to use the
 *   Base64.InputStream class to encode and decode on the fly which uses
 *   less memory than encoding/decoding an entire file into memory before writing.</li>
 *  <li>v2.2.1 - Fixed bug using URL_SAFE and ORDERED encodings. Fixed bug
 *   when using very small files (~< 40 bytes).</li>
 *  <li>v2.2 - Added some helper methods for encoding/decoding directly from
 *   one file to the next. Also added a main() method to support command line
 *   encoding/decoding from one file to the next. Also added these Base64 dialects:
 *   <ol>
 *   <li>The default is RFC3548 format.</li>
 *   <li>Calling Base64.setFormat(Base64.BASE64_FORMAT.URLSAFE_FORMAT) generates
 *   URL and file name friendly format as described in Section 4 of RFC3548.
 *   http://www.faqs.org/rfcs/rfc3548.html</li>
 *   <li>Calling Base64.setFormat(Base64.BASE64_FORMAT.ORDERED_FORMAT) generates
 *   URL and file name friendly format that preserves lexical ordering as described
 *   in http://www.faqs.org/qa/rfcc-1940.html</li>
 *   </ol>
 *   Special thanks to Jim Kellerman at <a href="http://www.powerset.com/">http://www.powerset.com/</a>
 *   for contributing the new Base64 dialects.
 *  </li>
 * 
 *  <li>v2.1 - Cleaned up javadoc comments and unused variables and methods. Added
 *   some convenience methods for reading and writing to and from files.</li>
 *  <li>v2.0.2 - Now specifies UTF-8 encoding in places where the code fails on systems
 *   with other encodings (like EBCDIC).</li>
 *  <li>v2.0.1 - Fixed an error when decoding a single byte, that is, when the
 *   encoded data was a single byte.</li>
 *  <li>v2.0 - I got rid of methods that used booleans to set options. 
 *   Now everything is more consolidated and cleaner. The code now detects
 *   when data that's being decoded is gzip-compressed and will decompress it
 *   automatically. Generally things are cleaner. You'll probably have to
 *   change some method calls that you were making to support the new
 *   options format (<tt>int</tt>s that you "OR" together).</li>
 *  <li>v1.5.1 - Fixed bug when decompressing and decoding to a             
 *   byte[] using <tt>decode( String s, boolean gzipCompressed )</tt>.      
 *   Added the ability to "suspend" encoding in the Output Stream so        
 *   you can turn on and off the encoding if you need to embed base64       
 *   data in an otherwise "normal" stream (like an XML file).</li>  
 *  <li>v1.5 - Output stream pases on flush() command but doesn't do anything itself.
 *      This helps when using GZIP streams.
 *      Added the ability to GZip-compress objects before encoding them.</li>
 *  <li>v1.4 - Added helper methods to read/write files.</li>
 *  <li>v1.3.6 - Fixed OutputStream.flush() so that 'position' is reset.</li>
 *  <li>v1.3.5 - Added flag to turn on and off line breaks. Fixed bug in input stream
 *      where last buffer being read, if not completely full, was not returned.</li>
 *  <li>v1.3.4 - Fixed when "improperly padded stream" error was thrown at the wrong time.</li>
 *  <li>v1.3.3 - Fixed I/O streams which were totally messed up.</li>
 * </ul>
 *
 * <p>
 * I am placing this code in the Public Domain. Do with it as you will.
 * This software comes with no guarantees or warranties but with
 * plenty of well-wishing instead!
 * Please visit <a href="http://iharder.net/base64">http://iharder.net/base64</a>
 * periodically to check for updates or to contribute improvements.
 * </p>
 *
 * @author Robert Harder
 * @author rob@iharder.net
 * @version 2.2.2
 */
public class Base64
{
    
/* ********  P R I V A T E   F I E L D S  ******** */  
    
    
    /** Maximum line length (76) of Base64 output. */
    private final static int MAX_LINE_LENGTH = 76;
    
    
    /** The equals sign (=) as a byte. */
    private final static byte EQUALS_SIGN = (byte)'=';
    
    
    /** The new line character (\n) as a byte. */
    private final static byte NEW_LINE = (byte)'\n';
    
    
    /** Preferred encoding. */
    private final static String PREFERRED_ENCODING = "UTF-8"; //$NON-NLS-1$
    
	
    private final static byte WHITE_SPACE_ENC = -5; // Indicates white space in encoding
    private final static byte EQUALS_SIGN_ENC = -1; // Indicates equals sign in encoding
	
	
/* ********  S T A N D A R D   B A S E 6 4   A L P H A B E T  ******** */	
    
    /** The 64 valid Base64 values. */
	/* Host platform me be something funny like EBCDIC, so we hardcode these values. */
	private final static byte[] _STANDARD_ALPHABET =
    {
        (byte)'A', (byte)'B', (byte)'C', (byte)'D', (byte)'E', (byte)'F', (byte)'G',
        (byte)'H', (byte)'I', (byte)'J', (byte)'K', (byte)'L', (byte)'M', (byte)'N',
        (byte)'O', (byte)'P', (byte)'Q', (byte)'R', (byte)'S', (byte)'T', (byte)'U', 
        (byte)'V', (byte)'W', (byte)'X', (byte)'Y', (byte)'Z',
        (byte)'a', (byte)'b', (byte)'c', (byte)'d', (byte)'e', (byte)'f', (byte)'g',
        (byte)'h', (byte)'i', (byte)'j', (byte)'k', (byte)'l', (byte)'m', (byte)'n',
        (byte)'o', (byte)'p', (byte)'q', (byte)'r', (byte)'s', (byte)'t', (byte)'u', 
        (byte)'v', (byte)'w', (byte)'x', (byte)'y', (byte)'z',
        (byte)'0', (byte)'1', (byte)'2', (byte)'3', (byte)'4', (byte)'5', 
        (byte)'6', (byte)'7', (byte)'8', (byte)'9', (byte)'+', (byte)'/'
    };
	
    
    /** 
     * Translates a Base64 value to either its 6-bit reconstruction value
     * or a negative number indicating some other meaning.
     **/
    private final static byte[] _STANDARD_DECODABET =
    {   
        -9,-9,-9,-9,-9,-9,-9,-9,-9,                 // Decimal  0 -  8
        -5,-5,                                      // Whitespace: Tab and Linefeed
        -9,-9,                                      // Decimal 11 - 12
        -5,                                         // Whitespace: Carriage Return
        -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,     // Decimal 14 - 26
        -9,-9,-9,-9,-9,                             // Decimal 27 - 31
        -5,                                         // Whitespace: Space
        -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,              // Decimal 33 - 42
        62,                                         // Plus sign at decimal 43
        -9,-9,-9,                                   // Decimal 44 - 46
        63,                                         // Slash at decimal 47
        52,53,54,55,56,57,58,59,60,61,              // Numbers zero through nine
        -9,-9,-9,                                   // Decimal 58 - 60
        -1,                                         // Equals sign at decimal 61
        -9,-9,-9,                                      // Decimal 62 - 64
        0,1,2,3,4,5,6,7,8,9,10,11,12,13,            // Letters 'A' through 'N'
        14,15,16,17,18,19,20,21,22,23,24,25,        // Letters 'O' through 'Z'
        -9,-9,-9,-9,-9,-9,                          // Decimal 91 - 96
        26,27,28,29,30,31,32,33,34,35,36,37,38,     // Letters 'a' through 'm'
        39,40,41,42,43,44,45,46,47,48,49,50,51,     // Letters 'n' through 'z'
        -9,-9,-9,-9                                 // Decimal 123 - 126
        /*,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,     // Decimal 127 - 139
        -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,     // Decimal 140 - 152
        -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,     // Decimal 153 - 165
        -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,     // Decimal 166 - 178
        -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,     // Decimal 179 - 191
        -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,     // Decimal 192 - 204
        -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,     // Decimal 205 - 217
        -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,     // Decimal 218 - 230
        -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,     // Decimal 231 - 243
        -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9         // Decimal 244 - 255 */
    };
	    
    /** Defeats instantiation. */
    private Base64(){}
    

/* ********  E N C O D I N G   M E T H O D S  ******** */    
    
    
    /**
     * <p>Encodes up to three bytes of the array <var>source</var>
     * and writes the resulting four Base64 bytes to <var>destination</var>.
     * The source and destination arrays can be manipulated
     * anywhere along their length by specifying 
     * <var>srcOffset</var> and <var>destOffset</var>.
     * This method does not check to make sure your arrays
     * are large enough to accomodate <var>srcOffset</var> + 3 for
     * the <var>source</var> array or <var>destOffset</var> + 4 for
     * the <var>destination</var> array.
     * The actual number of significant bytes in your array is
     * given by <var>numSigBytes</var>.</p>
	 * <p>This is the lowest level of the encoding methods with
	 * all possible parameters.</p>
     *
     * @param source the array to convert
     * @param srcOffset the index where conversion begins
     * @param numSigBytes the number of significant bytes in your array
     * @param destination the array to hold the conversion
     * @param destOffset the index where output will be put
     * @return the <var>destination</var> array
     * @since 1.3
     */
    private static byte[] encode3to4( 
     byte[] source, int srcOffset, int numSigBytes,
     byte[] destination, int destOffset )
    {
		byte[] ALPHABET = _STANDARD_ALPHABET;
	
        //           1         2         3  
        // 01234567890123456789012345678901 Bit position
        // --------000000001111111122222222 Array position from threeBytes
        // --------|    ||    ||    ||    | Six bit groups to index ALPHABET
        //          >>18  >>12  >> 6  >> 0  Right shift necessary
        //                0x3f  0x3f  0x3f  Additional AND
        
        // Create buffer with zero-padding if there are only one or two
        // significant bytes passed in the array.
        // We have to shift left 24 in order to flush out the 1's that appear
        // when Java treats a value as negative that is cast from a byte to an int.
        int inBuff =   ( numSigBytes > 0 ? ((source[ srcOffset     ] << 24) >>>  8) : 0 )
                     | ( numSigBytes > 1 ? ((source[ srcOffset + 1 ] << 24) >>> 16) : 0 )
                     | ( numSigBytes > 2 ? ((source[ srcOffset + 2 ] << 24) >>> 24) : 0 );

        switch( numSigBytes )
        {
            case 3:
                destination[ destOffset     ] = ALPHABET[ (inBuff >>> 18)        ];
                destination[ destOffset + 1 ] = ALPHABET[ (inBuff >>> 12) & 0x3f ];
                destination[ destOffset + 2 ] = ALPHABET[ (inBuff >>>  6) & 0x3f ];
                destination[ destOffset + 3 ] = ALPHABET[ (inBuff       ) & 0x3f ];
                return destination;
                
            case 2:
                destination[ destOffset     ] = ALPHABET[ (inBuff >>> 18)        ];
                destination[ destOffset + 1 ] = ALPHABET[ (inBuff >>> 12) & 0x3f ];
                destination[ destOffset + 2 ] = ALPHABET[ (inBuff >>>  6) & 0x3f ];
                destination[ destOffset + 3 ] = EQUALS_SIGN;
                return destination;
                
            case 1:
                destination[ destOffset     ] = ALPHABET[ (inBuff >>> 18)        ];
                destination[ destOffset + 1 ] = ALPHABET[ (inBuff >>> 12) & 0x3f ];
                destination[ destOffset + 2 ] = EQUALS_SIGN;
                destination[ destOffset + 3 ] = EQUALS_SIGN;
                return destination;
                
            default:
                return destination;
        }   // end switch
    }   // end encode3to4
    
    
    
    /**
     * Encodes a byte array into Base64 notation.
     * Does not GZip-compress data.
     *
     * @param source The data to convert
     * @since 1.4
     */
    public static String encodeBytes( byte[] source )
    {
        // Convert option to boolean in way that code likes it.
        boolean breakLines = false;
        int len = source.length;
        int    len43   = len * 4 / 3;
        byte[] outBuff = new byte[   ( len43 )                      // Main 4:3
                                   + ( (len % 3) > 0 ? 4 : 0 )      // Account for padding
                                   + (breakLines ? ( len43 / MAX_LINE_LENGTH ) : 0) ]; // New lines      
        int d = 0;
        int e = 0;
        int len2 = len - 2;
        int lineLength = 0;
        for( ; d < len2; d+=3, e+=4 )
        {
            encode3to4( source, d, 3, outBuff, e );

            lineLength += 4;
            if( breakLines && lineLength == MAX_LINE_LENGTH )
            {   
                outBuff[e+4] = NEW_LINE;
                e++;
                lineLength = 0;
            }   // end if: end of line
        }   // en dfor: each piece of array

        if( d < len )
        {
            encode3to4( source, d, len - d, outBuff, e );
            e += 4;
        }   // end if: some padding needed

        
        // Return value according to relevant encoding.
        try
        {
            return new String( outBuff, 0, e, PREFERRED_ENCODING );
        }   // end try
        catch (java.io.UnsupportedEncodingException uue)
        {
            return new String( outBuff, 0, e );
        }   // end catch
        
    }   // end else: don't compress
    
    
/* ********  D E C O D I N G   M E T H O D S  ******** */
    
    
    /**
     * Decodes four bytes from array <var>source</var>
     * and writes the resulting bytes (up to three of them)
     * to <var>destination</var>.
     * The source and destination arrays can be manipulated
     * anywhere along their length by specifying 
     * <var>srcOffset</var> and <var>destOffset</var>.
     * This method does not check to make sure your arrays
     * are large enough to accomodate <var>srcOffset</var> + 4 for
     * the <var>source</var> array or <var>destOffset</var> + 3 for
     * the <var>destination</var> array.
     * This method returns the actual number of bytes that 
     * were converted from the Base64 encoding.
	 * <p>This is the lowest level of the decoding methods with
	 * all possible parameters.</p>
     * 
     *
     * @param source the array to convert
     * @param srcOffset the index where conversion begins
     * @param destination the array to hold the conversion
	 * @param options alphabet type is pulled from this (standard, url-safe, ordered)
     * @return the number of decoded bytes converted
     * @since 1.3
     */
    private static int decode4to3( byte[] source, int srcOffset, byte[] destination, int destOffset )
    {
		byte[] DECODABET = _STANDARD_DECODABET; 
	
        // Example: Dk==
        if( source[ srcOffset + 2] == EQUALS_SIGN )
        {
            // Two ways to do the same thing. Don't know which way I like best.
            //int outBuff =   ( ( DECODABET[ source[ srcOffset    ] ] << 24 ) >>>  6 )
            //              | ( ( DECODABET[ source[ srcOffset + 1] ] << 24 ) >>> 12 );
            int outBuff =   ( ( DECODABET[ source[ srcOffset    ] ] & 0xFF ) << 18 )
                          | ( ( DECODABET[ source[ srcOffset + 1] ] & 0xFF ) << 12 );
            
            destination[ destOffset ] = (byte)( outBuff >>> 16 );
            return 1;
        }
        
        // Example: DkL=
        else if( source[ srcOffset + 3 ] == EQUALS_SIGN )
        {
            // Two ways to do the same thing. Don't know which way I like best.
            //int outBuff =   ( ( DECODABET[ source[ srcOffset     ] ] << 24 ) >>>  6 )
            //              | ( ( DECODABET[ source[ srcOffset + 1 ] ] << 24 ) >>> 12 )
            //              | ( ( DECODABET[ source[ srcOffset + 2 ] ] << 24 ) >>> 18 );
            int outBuff =   ( ( DECODABET[ source[ srcOffset     ] ] & 0xFF ) << 18 )
                          | ( ( DECODABET[ source[ srcOffset + 1 ] ] & 0xFF ) << 12 )
                          | ( ( DECODABET[ source[ srcOffset + 2 ] ] & 0xFF ) <<  6 );
            
            destination[ destOffset     ] = (byte)( outBuff >>> 16 );
            destination[ destOffset + 1 ] = (byte)( outBuff >>>  8 );
            return 2;
        }
        
        // Example: DkLE
        else
        {
            // Two ways to do the same thing. Don't know which way I like best.
            //int outBuff =   ( ( DECODABET[ source[ srcOffset     ] ] << 24 ) >>>  6 )
            //              | ( ( DECODABET[ source[ srcOffset + 1 ] ] << 24 ) >>> 12 )
            //              | ( ( DECODABET[ source[ srcOffset + 2 ] ] << 24 ) >>> 18 )
            //              | ( ( DECODABET[ source[ srcOffset + 3 ] ] << 24 ) >>> 24 );
            int outBuff =   ( ( DECODABET[ source[ srcOffset     ] ] & 0xFF ) << 18 )
                          | ( ( DECODABET[ source[ srcOffset + 1 ] ] & 0xFF ) << 12 )
                          | ( ( DECODABET[ source[ srcOffset + 2 ] ] & 0xFF ) <<  6)
                          | ( ( DECODABET[ source[ srcOffset + 3 ] ] & 0xFF )      );

            
            destination[ destOffset     ] = (byte)( outBuff >> 16 );
            destination[ destOffset + 1 ] = (byte)( outBuff >>  8 );
            destination[ destOffset + 2 ] = (byte)( outBuff       );

            return 3;
        }
    }   // end decodeToBytes
    
    /**
     * Decodes data from Base64 notation.
     *
     * @param s the string to decode
     * @return the decoded data
     * @since 1.4
     */
    public static byte[] decode( CharSequence s )
	{
        if (s.length() % 4 != 0) {
        	throw new IllegalArgumentException("Source bytes are not valid"); //$NON-NLS-1$
        }
        byte[] DECODABET = _STANDARD_DECODABET;
    	int len = s.length();
        byte[] outBuff = new byte[ len * 3 / 4 ]; // Upper limit on size of output
        int    outBuffPosn = 0;
        
        byte[] b4        = new byte[4];
        int    b4Posn    = 0;
        int    i         = 0;
        byte   sbiCrop   = 0;
        byte   sbiDecode = 0;
        for( i = 0; i < len; i++ )
        {
            sbiCrop = (byte)(s.charAt(i) & 0x7f); // Only the low seven bits
            sbiDecode = DECODABET[ sbiCrop ];
            
            if( sbiDecode >= WHITE_SPACE_ENC ) // White space, Equals sign or better
            {
                if( sbiDecode >= EQUALS_SIGN_ENC )
                {
                    b4[ b4Posn++ ] = sbiCrop;
                    if( b4Posn > 3 )
                    {
                        outBuffPosn += decode4to3( b4, 0, outBuff, outBuffPosn );
                        b4Posn = 0;
                        
                        // If that was the equals sign, break out of 'for' loop
                        if( sbiCrop == EQUALS_SIGN )
                            break;
                    }   // end if: quartet built
                    
                }   // end if: equals sign or better
                
            }   // end if: white space, equals sign or better
            else
            {
                throw new IllegalArgumentException("Source bytes are not valid"); //$NON-NLS-1$
            }   // end else: 
        }   // each input character
                                   
        byte[] out = new byte[ outBuffPosn ];
        System.arraycopy( outBuff, 0, out, 0, outBuffPosn ); 
        return out;
    }   // end decode
    
    public static String encodeUrlSafe(byte[] data) {
        byte[] encode = encodeBytes(data).getBytes();
        for (int i = 0; i < encode.length; i++) {
            if (encode[i] == '+') {
                encode[i] = '-';
            } else if (encode[i] == '/') {
                encode[i] = '_';
            }
        }
        return new String(encode);
    }

    public static byte[] decodeUrlSafe(CharSequence data) {
        StringBuilder encode = new StringBuilder();
        for (int i = 0; i < data.length(); i++) {
            char c = data.charAt(i);
            if ( c == '-') {
                encode.append('+');
            } else if (c == '_') {
                encode.append('/');
            } else {
                encode.append(c);
            }
        }
        return decode(encode.toString());
    }    
    
}   // end class Base64
