package org.bouncycastle.asn1;

import java.io.IOException;

import org.bouncycastle.util.Arrays;

/**
 * DER UniversalString object - encodes UNICODE (ISO 10646) characters using 32-bit format. In Java we
 * have no way of representing this directly so we rely on byte arrays to carry these.
 */
public class DERUniversalString
    extends ASN1Primitive
    implements ASN1String
{
    private static final char[]  table = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
    private final byte[] string;
    
    /**
     * Return a Universal String from the passed in object.
     *
     * @param obj a DERUniversalString or an object that can be converted into one.
     * @exception IllegalArgumentException if the object cannot be converted.
     * @return a DERUniversalString instance, or null
     */
    public static DERUniversalString getInstance(
        Object  obj)
    {
        if (obj == null || obj instanceof DERUniversalString)
        {
            return (DERUniversalString)obj;
        }

        if (obj instanceof byte[])
        {
            try
            {
                return (DERUniversalString)fromByteArray((byte[])obj);
            }
            catch (Exception e)
            {
                throw new IllegalArgumentException("encoding error getInstance: " + e.toString());
            }
        }

        throw new IllegalArgumentException("illegal object in getInstance: " + obj.getClass().getName());
    }

    /**
     * Return a Universal String from a tagged object.
     *
     * @param obj the tagged object holding the object we want
     * @param explicit true if the object is meant to be explicitly
     *              tagged false otherwise.
     * @exception IllegalArgumentException if the tagged object cannot
     *               be converted.
     * @return a DERUniversalString instance, or null
     */
    public static DERUniversalString getInstance(
        ASN1TaggedObject obj,
        boolean          explicit)
    {
        ASN1Primitive o = obj.getObject();

        if (explicit || o instanceof DERUniversalString)
        {
            return getInstance(o);
        }
        else
        {
            return new DERUniversalString(ASN1OctetString.getInstance(o).getOctets());
        }
    }

    /**
     * Basic constructor - byte encoded string.
     *
     * @param string the byte encoding of the string to be carried in the UniversalString object,
     */
    public DERUniversalString(
        byte[]   string)
    {
        this.string = Arrays.clone(string);
    }

    public String getString()
    {
        StringBuffer buf = new StringBuffer("#");

        byte[] string;
        try
        {
            string = getEncoded();
        }
        catch (IOException e)
        {
           throw new ASN1ParsingException("internal error encoding UniversalString");
        }

        for (int i = 0; i != string.length; i++)
        {
            buf.append(table[(string[i] >>> 4) & 0xf]);
            buf.append(table[string[i] & 0xf]);
        }
        
        return buf.toString();
    }

    public String toString()
    {
        return getString();
    }

    public byte[] getOctets()
    {
        return Arrays.clone(string);
    }

    boolean isConstructed()
    {
        return false;
    }

    int encodedLength()
    {
        return 1 + StreamUtil.calculateBodyLength(string.length) + string.length;
    }

    void encode(ASN1OutputStream out, boolean withTag) throws IOException
    {
        out.writeEncoded(withTag, BERTags.UNIVERSAL_STRING, string);
    }

    boolean asn1Equals(
        ASN1Primitive o)
    {
        if (!(o instanceof DERUniversalString))
        {
            return false;
        }

        return Arrays.areEqual(string, ((DERUniversalString)o).string);
    }
    
    public int hashCode()
    {
        return Arrays.hashCode(string);
    }
}