/*
 *  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 org.apache.tomcat.util.buf;

import java.io.CharConversionException;
import java.io.IOException;

/** 
 *  All URL decoding happens here. This way we can reuse, review, optimize
 *  without adding complexity to the buffers.
 *
 *  The conversion will modify the original buffer.
 * 
 *  @author Costin Manolache
 */
public final class UDecoder {
    
    private static org.apache.juli.logging.Log log=
        org.apache.juli.logging.LogFactory.getLog(UDecoder.class );
    
    public UDecoder() 
    {
    }

    /** URLDecode, will modify the source.  Includes converting
     *  '+' to ' '.
     */
    public void convert( ByteChunk mb )
        throws IOException
    {
        convert(mb, true);
    }

    /** URLDecode, will modify the source.
     */
    public void convert( ByteChunk mb, boolean query )
	throws IOException
    {
	int start=mb.getOffset();
	byte buff[]=mb.getBytes();
	int end=mb.getEnd();

	int idx= ByteChunk.indexOf( buff, start, end, '%' );
        int idx2=-1;
        if( query )
            idx2= ByteChunk.indexOf( buff, start, end, '+' );
	if( idx<0 && idx2<0 ) {
	    return;
	}

	// idx will be the smallest positive inxes ( first % or + )
	if( idx2 >= 0 && idx2 < idx ) idx=idx2;
	if( idx < 0 ) idx=idx2;

	for( int j=idx; j<end; j++, idx++ ) {
	    if( buff[ j ] == '+' && query) {
		buff[idx]= (byte)' ' ;
	    } else if( buff[ j ] != '%' ) {
		buff[idx]= buff[j];
	    } else {
		// read next 2 digits
		if( j+2 >= end ) {
		    throw new CharConversionException("EOF");
		}
		byte b1= buff[j+1];
		byte b2=buff[j+2];
		if( !isHexDigit( b1 ) || ! isHexDigit(b2 ))
		    throw new CharConversionException( "isHexDigit");
		
		j+=2;
		int res=x2c( b1, b2 );
		buff[idx]=(byte)res;
	    }
	}

	mb.setEnd( idx );
	
	return;
    }

    // -------------------- Additional methods --------------------
    // XXX What do we do about charset ????

    /** In-buffer processing - the buffer will be modified
     *  Includes converting  '+' to ' '.
     */
    public void convert( CharChunk mb )
	throws IOException
    {
        convert(mb, true);
    }

    /** In-buffer processing - the buffer will be modified
     */
    public void convert( CharChunk mb, boolean query )
	throws IOException
    {
	//	log( "Converting a char chunk ");
	int start=mb.getOffset();
	char buff[]=mb.getBuffer();
	int cend=mb.getEnd();

	int idx= CharChunk.indexOf( buff, start, cend, '%' );
        int idx2=-1;
        if( query )
            idx2= CharChunk.indexOf( buff, start, cend, '+' );
	if( idx<0 && idx2<0 ) {
	    return;
	}
	
	if( idx2 >= 0 && idx2 < idx ) idx=idx2; 
	if( idx < 0 ) idx=idx2;

	for( int j=idx; j<cend; j++, idx++ ) {
	    if( buff[ j ] == '+' && query ) {
		buff[idx]=( ' ' );
	    } else if( buff[ j ] != '%' ) {
		buff[idx]=buff[j];
	    } else {
		// read next 2 digits
		if( j+2 >= cend ) {
		    // invalid
		    throw new CharConversionException("EOF");
		}
		char b1= buff[j+1];
		char b2=buff[j+2];
		if( !isHexDigit( b1 ) || ! isHexDigit(b2 ))
		    throw new CharConversionException("isHexDigit");
		
		j+=2;
		int res=x2c( b1, b2 );
		buff[idx]=(char)res;
	    }
	}
	mb.setEnd( idx );
    }

    /** URLDecode, will modify the source
     *  Includes converting  '+' to ' '.
     */
    public void convert(MessageBytes mb)
	throws IOException
    {
        convert(mb, true);
    }

    /** URLDecode, will modify the source
     */
    public void convert(MessageBytes mb, boolean query)
	throws IOException
    {
	
	switch (mb.getType()) {
	case MessageBytes.T_STR:
	    String strValue=mb.toString();
	    if( strValue==null ) return;
	    mb.setString( convert( strValue, query ));
	    break;
	case MessageBytes.T_CHARS:
	    CharChunk charC=mb.getCharChunk();
	    convert( charC, query );
	    break;
	case MessageBytes.T_BYTES:
	    ByteChunk bytesC=mb.getByteChunk();
	    convert( bytesC, query );
	    break;
	}
    }

    // XXX Old code, needs to be replaced !!!!
    // 
    public final String convert(String str)
    {
        return convert(str, true);
    }

    public final String convert(String str, boolean query)
    {
        if (str == null)  return  null;
	
	if( (!query || str.indexOf( '+' ) < 0) && str.indexOf( '%' ) < 0 )
	    return str;
	
        StringBuffer dec = new StringBuffer();    // decoded string output
        int strPos = 0;
        int strLen = str.length();

        dec.ensureCapacity(str.length());
        while (strPos < strLen) {
            int laPos;        // lookahead position

            // look ahead to next URLencoded metacharacter, if any
            for (laPos = strPos; laPos < strLen; laPos++) {
                char laChar = str.charAt(laPos);
                if ((laChar == '+' && query) || (laChar == '%')) {
                    break;
                }
            }

            // if there were non-metacharacters, copy them all as a block
            if (laPos > strPos) {
                dec.append(str.substring(strPos,laPos));
                strPos = laPos;
            }

            // shortcut out of here if we're at the end of the string
            if (strPos >= strLen) {
                break;
            }

            // process next metacharacter
            char metaChar = str.charAt(strPos);
            if (metaChar == '+') {
                dec.append(' ');
                strPos++;
                continue;
            } else if (metaChar == '%') {
		// We throw the original exception - the super will deal with
		// it
		//                try {
		dec.append((char)Integer.
			   parseInt(str.substring(strPos + 1, strPos + 3),16));
                strPos += 3;
            }
        }

        return dec.toString();
    }



    private static boolean isHexDigit( int c ) {
	return ( ( c>='0' && c<='9' ) ||
		 ( c>='a' && c<='f' ) ||
		 ( c>='A' && c<='F' ));
    }
    
    private static int x2c( byte b1, byte b2 ) {
	int digit= (b1>='A') ? ( (b1 & 0xDF)-'A') + 10 :
	    (b1 -'0');
	digit*=16;
	digit +=(b2>='A') ? ( (b2 & 0xDF)-'A') + 10 :
	    (b2 -'0');
	return digit;
    }

    private static int x2c( char b1, char b2 ) {
	int digit= (b1>='A') ? ( (b1 & 0xDF)-'A') + 10 :
	    (b1 -'0');
	digit*=16;
	digit +=(b2>='A') ? ( (b2 & 0xDF)-'A') + 10 :
	    (b2 -'0');
	return digit;
    }

    private final static int debug=0;
    private static void log( String s ) {
        if (log.isDebugEnabled())
            log.debug("URLDecoder: " + s );
    }

}
