package org.bouncycastle.asn1.x509;

import java.io.IOException;

import org.bouncycastle.asn1.ASN1InputStream;
import org.bouncycastle.asn1.ASN1ObjectIdentifier;
import org.bouncycastle.asn1.ASN1Primitive;
import org.bouncycastle.asn1.DERPrintableString;
import org.bouncycastle.util.Strings;

It turns out that the number of standard ways the fields in a DN should be 
encoded into their ASN.1 counterparts is rapidly approaching the
number of machines on the internet. By default the X509Name class 
will produce UTF8Strings in line with the current recommendations (RFC 3280).

An example of an encoder look like below:
public class X509DirEntryConverter
    extends X509NameEntryConverter
{
    public ASN1Primitive getConvertedValue(
        ASN1ObjectIdentifier  oid,
        String               value)
    {
        if (str.length() != 0 && str.charAt(0) == '#')
        {
            return convertHexEncoded(str, 1);
        }
        if (oid.equals(EmailAddress))
        {
            return new DERIA5String(str);
        }
        else if (canBePrintable(str))
        {
            return new DERPrintableString(str);
        }
        else if (canBeUTF8(str))
        {
            return new DERUTF8String(str);
        }
        else
        {
            return new DERBMPString(str);
        }
    }
}

/**
 * It turns out that the number of standard ways the fields in a DN should be 
 * encoded into their ASN.1 counterparts is rapidly approaching the
 * number of machines on the internet. By default the X509Name class 
 * will produce UTF8Strings in line with the current recommendations (RFC 3280).
 * <p>
 * An example of an encoder look like below:
 * <pre>
 * public class X509DirEntryConverter
 *     extends X509NameEntryConverter
 * {
 *     public ASN1Primitive getConvertedValue(
 *         ASN1ObjectIdentifier  oid,
 *         String               value)
 *     {
 *         if (str.length() != 0 &amp;&amp; str.charAt(0) == '#')
 *         {
 *             return convertHexEncoded(str, 1);
 *         }
 *         if (oid.equals(EmailAddress))
 *         {
 *             return new DERIA5String(str);
 *         }
 *         else if (canBePrintable(str))
 *         {
 *             return new DERPrintableString(str);
 *         }
 *         else if (canBeUTF8(str))
 *         {
 *             return new DERUTF8String(str);
 *         }
 *         else
 *         {
 *             return new DERBMPString(str);
 *         }
 *     }
 * }
 * </pre>
 */
public abstract class X509NameEntryConverter
{
    
Convert an inline encoded hex string rendition of an ASN.1
object back into its corresponding ASN.1 object.
Params:
str – the hex encoded object
off – the index at which the encoding starts
Returns:
the decoded object/**
     * Convert an inline encoded hex string rendition of an ASN.1
     * object back into its corresponding ASN.1 object.
     * 
     * @param str the hex encoded object
     * @param off the index at which the encoding starts
     * @return the decoded object
     */
    protected ASN1Primitive convertHexEncoded(
        String  str,
        int     off)
        throws IOException
    {
        str = Strings.toLowerCase(str);
        byte[] data = new byte[(str.length() - off) / 2];
        for (int index = 0; index != data.length; index++)
        {
            char left = str.charAt((index * 2) + off);
            char right = str.charAt((index * 2) + off + 1);
            
            if (left < 'a')
            {
                data[index] = (byte)((left - '0') << 4);
            }
            else
            {
                data[index] = (byte)((left - 'a' + 10) << 4);
            }
            if (right < 'a')
            {
                data[index] |= (byte)(right - '0');
            }
            else
            {
                data[index] |= (byte)(right - 'a' + 10);
            }
        }

        ASN1InputStream aIn = new ASN1InputStream(data);
                                            
        return aIn.readObject();
    }
    
    
return true if the passed in String can be represented without
loss as a PrintableString, false otherwise.
/**
     * return true if the passed in String can be represented without
     * loss as a PrintableString, false otherwise.
     */
    protected boolean canBePrintable(
        String  str)
    {
        return DERPrintableString.isPrintableString(str);
    }
    
    
Convert the passed in String value into the appropriate ASN.1
encoded object.
Params:
oid – the oid associated with the value in the DN.
value – the value of the particular DN component.
Returns:
the ASN.1 equivalent for the value./**
     * Convert the passed in String value into the appropriate ASN.1
     * encoded object.
     * 
     * @param oid the oid associated with the value in the DN.
     * @param value the value of the particular DN component.
     * @return the ASN.1 equivalent for the value.
     */
    public abstract ASN1Primitive getConvertedValue(ASN1ObjectIdentifier oid, String value);
}