// This Source Code is in the Public Domain per: http://unlicense.org
package org.litesoft.encryption.symmetric;

public interface SymmetricEncryptorManager
{
    /**
     * Adds a decryptor to the supported list
     */
    public abstract void addDecryptor( SymmetricEncryptor pSymmetricEncryptor );

    /**
     * Set the "current" Encryptor
     */
    public abstract void setSymmetricEncryptor( SymmetricEncryptor pSymmetricEncryptor );

    /**
     * @return The "current" Encryptor (the initial SE is BrainDeadSymmetricEncryptor)
     */
    public abstract SymmetricEncryptor getSymmetricEncryptor();

    /**
     * @return null if not found!
     */
    public abstract SymmetricEncryptor getSymmetricEncryptor( String pIdentifierAndVersion );

    public static class Helper
    {
        public static String fromEncrypted( SymmetricEncryptorManager pSymmetricEncryptorManager, String pEncryptedText )
        {
            if ( pEncryptedText == null )
            {
                return null;
            }

            SymmetricEncryptor zSE = pSymmetricEncryptorManager.getSymmetricEncryptor();
            String zIDnVerPrefix = zSE.getIdentifierAndVersion() + ":";
            if ( !pEncryptedText.startsWith( zIDnVerPrefix ) )
            {
                int zVerSepAt = pEncryptedText.indexOf( ':' );
                if ( zVerSepAt == -1 )
                {
                    throw new IllegalStateException( "Encrypted Field w/o Identifier And Version" );
                }
                String zIdAndVer = pEncryptedText.substring( 0, zVerSepAt );
                zSE = pSymmetricEncryptorManager.getSymmetricEncryptor( zIdAndVer );
                if ( zSE == null )
                {
                    throw new IllegalStateException( "Encrypted Field with an unsupported Identifier And Version (" + zIdAndVer + ")" );
                }
            }
            return zSE.decrypt( pEncryptedText.substring( zIDnVerPrefix.length() ) );
        }

        public static String toEncrypted( SymmetricEncryptorManager pSymmetricEncryptorManager, String pPlainText )
        {
            if ( pPlainText == null )
            {
                return null;
            }
            SymmetricEncryptor zSE = pSymmetricEncryptorManager.getSymmetricEncryptor();
            return zSE.getIdentifierAndVersion() + ":" + zSE.encrypt( pPlainText );
        }
    }
}