package org.spongycastle.cms.bc;

import java.io.OutputStream;
import java.security.SecureRandom;
import java.util.HashMap;
import java.util.Map;

import org.spongycastle.asn1.ASN1ObjectIdentifier;
import org.spongycastle.asn1.x509.AlgorithmIdentifier;
import org.spongycastle.cms.CMSAlgorithm;
import org.spongycastle.cms.CMSException;
import org.spongycastle.crypto.BufferedBlockCipher;
import org.spongycastle.crypto.CipherKeyGenerator;
import org.spongycastle.crypto.StreamCipher;
import org.spongycastle.crypto.io.CipherOutputStream;
import org.spongycastle.crypto.params.KeyParameter;
import org.spongycastle.operator.GenericKey;
import org.spongycastle.operator.OutputEncryptor;
import org.spongycastle.util.Integers;

public class BcCMSContentEncryptorBuilder
{
    private static Map keySizes = new HashMap();

    static
    {
        keySizes.put(CMSAlgorithm.AES128_CBC, Integers.valueOf(128));
        keySizes.put(CMSAlgorithm.AES192_CBC, Integers.valueOf(192));
        keySizes.put(CMSAlgorithm.AES256_CBC, Integers.valueOf(256));

        keySizes.put(CMSAlgorithm.CAMELLIA128_CBC, Integers.valueOf(128));
        keySizes.put(CMSAlgorithm.CAMELLIA192_CBC, Integers.valueOf(192));
        keySizes.put(CMSAlgorithm.CAMELLIA256_CBC, Integers.valueOf(256));
    }

    private static int getKeySize(ASN1ObjectIdentifier oid)
    {
        Integer size = (Integer)keySizes.get(oid);

        if (size != null)
        {
            return size.intValue();
        }

        return -1;
    }

    private ASN1ObjectIdentifier encryptionOID;
    private int                  keySize;

    private EnvelopedDataHelper helper = new EnvelopedDataHelper();
    private SecureRandom random;

    public BcCMSContentEncryptorBuilder(ASN1ObjectIdentifier encryptionOID)
    {
        this(encryptionOID, getKeySize(encryptionOID));
    }

    public BcCMSContentEncryptorBuilder(ASN1ObjectIdentifier encryptionOID, int keySize)
    {
        this.encryptionOID = encryptionOID;
        this.keySize = keySize;
    }

    public BcCMSContentEncryptorBuilder setSecureRandom(SecureRandom random)
    {
        this.random = random;

        return this;
    }

    public OutputEncryptor build()
        throws CMSException
    {
        return new CMSOutputEncryptor(encryptionOID, keySize, random);
    }

    private class CMSOutputEncryptor
        implements OutputEncryptor
    {
        private KeyParameter encKey;
        private AlgorithmIdentifier algorithmIdentifier;
        private Object             cipher;

        CMSOutputEncryptor(ASN1ObjectIdentifier encryptionOID, int keySize, SecureRandom random)
            throws CMSException
        {
            if (random == null)
            {
                random = new SecureRandom();
            }

            CipherKeyGenerator keyGen = helper.createKeyGenerator(encryptionOID, random);

            encKey = new KeyParameter(keyGen.generateKey());

            algorithmIdentifier = helper.generateAlgorithmIdentifier(encryptionOID, encKey, random);

            cipher = helper.createContentCipher(true, encKey, algorithmIdentifier);
        }

        public AlgorithmIdentifier getAlgorithmIdentifier()
        {
            return algorithmIdentifier;
        }

        public OutputStream getOutputStream(OutputStream dOut)
        {
            if (cipher instanceof BufferedBlockCipher)
            {
                return new CipherOutputStream(dOut, (BufferedBlockCipher)cipher);
            }
            else
            {
                return new CipherOutputStream(dOut, (StreamCipher)cipher);
            }
        }

        public GenericKey getKey()
        {
            return new GenericKey(algorithmIdentifier, encKey.getKey());
        }
    }
}
