/* Copyright 2004, 2005, 2006 Acegi Technology Pty Limited
 *
 * Licensed 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.springframework.security.providers.encoding;

/**
 * <p>Convenience base for all password encoders.</p>
 *
 * @author Ben Alex
 * @version $Id$
 */
public abstract class BasePasswordEncoder implements PasswordEncoder {
    //~ Methods ========================================================================================================

    /**
     * Used by subclasses to extract the password and salt from a merged <code>String</code> created using
     * {@link #mergePasswordAndSalt(String,Object,boolean)}.<p>The first element in the returned array is the
     * password. The second element is the salt. The salt array element will always be present, even if no salt was
     * found in the <code>mergedPasswordSalt</code> argument.</p>
     *
     * @param mergedPasswordSalt as generated by <code>mergePasswordAndSalt</code>
     *
     * @return an array, in which the first element is the password and the second the salt
     *
     * @throws IllegalArgumentException if mergedPasswordSalt is null or empty.
     */
    protected String[] demergePasswordAndSalt(String mergedPasswordSalt) {
        if ((mergedPasswordSalt == null) || "".equals(mergedPasswordSalt)) {
            throw new IllegalArgumentException("Cannot pass a null or empty String");
        }

        String password = mergedPasswordSalt;
        String salt = "";

        int saltBegins = mergedPasswordSalt.lastIndexOf("{");

        if ((saltBegins != -1) && ((saltBegins + 1) < mergedPasswordSalt.length())) {
            salt = mergedPasswordSalt.substring(saltBegins + 1, mergedPasswordSalt.length() - 1);
            password = mergedPasswordSalt.substring(0, saltBegins);
        }

        return new String[] {password, salt};
    }

    /**
     * Used by subclasses to generate a merged password and salt <code>String</code>.<P>The generated password
     * will be in the form of <code>password{salt}</code>.</p>
     *  <p>A <code>null</code> can be passed to either method, and will be handled correctly. If the
     * <code>salt</code> is <code>null</code> or empty, the resulting generated password will simply be the passed
     * <code>password</code>. The <code>toString</code> method of the <code>salt</code> will be used to represent the
     * salt.</p>
     *
     * @param password the password to be used (can be <code>null</code>)
     * @param salt the salt to be used (can be <code>null</code>)
     * @param strict ensures salt doesn't contain the delimiters
     *
     * @return a merged password and salt <code>String</code>
     *
     * @throws IllegalArgumentException if the salt contains '{' or '}' characters.
     */
    protected String mergePasswordAndSalt(String password, Object salt, boolean strict) {
        if (password == null) {
            password = "";
        }

        if (strict && (salt != null)) {
            if ((salt.toString().lastIndexOf("{") != -1) || (salt.toString().lastIndexOf("}") != -1)) {
                throw new IllegalArgumentException("Cannot use { or } in salt.toString()");
            }
        }

        if ((salt == null) || "".equals(salt)) {
            return password;
        } else {
            return password + "{" + salt.toString() + "}";
        }
    }
}
