/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.shiro.samples.spring.realm;

import org.apache.shiro.authc.AccountException;
import org.apache.shiro.authc.AuthenticationException;
import org.apache.shiro.authc.AuthenticationInfo;
import org.apache.shiro.authc.AuthenticationToken;
import org.apache.shiro.authc.SimpleAuthenticationInfo;
import org.apache.shiro.authc.UnknownAccountException;
import org.apache.shiro.authc.UsernamePasswordToken;
import org.apache.shiro.realm.jdbc.JdbcRealm;
import org.apache.shiro.lang.util.ByteSource;
import org.apache.shiro.util.JdbcUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

/**
 * Realm that exists to support salted credentials.  The JdbcRealm implementation needs to be updated in a future
 * Shiro release to handle this.
 */
public class SaltAwareJdbcRealm extends JdbcRealm {

    private static final Logger LOGGER = LoggerFactory.getLogger(SaltAwareJdbcRealm.class);

    @Override
    protected AuthenticationInfo doGetAuthenticationInfo(AuthenticationToken token) throws AuthenticationException {
        UsernamePasswordToken upToken = (UsernamePasswordToken) token;
        String username = upToken.getUsername();

        // Null username is invalid
        if (username == null) {
            throw new AccountException("Null usernames are not allowed by this realm.");
        }

        Connection conn = null;
        AuthenticationInfo info = null;
        try {
            conn = dataSource.getConnection();

            String password = getPasswordForUser(conn, username);

            if (password == null) {
                throw new UnknownAccountException("No account found for user [" + username + "]");
            }

            SimpleAuthenticationInfo saInfo = new SimpleAuthenticationInfo(username, password, getName());
            /**
             * This (very bad) example uses the username as the salt in this sample app.  DON'T DO THIS IN A REAL APP!
             *
             * Salts should not be based on anything that a user could enter (attackers can exploit this).  Instead
             * they should ideally be cryptographically-strong randomly generated numbers.
             */
            saInfo.setCredentialsSalt(ByteSource.Util.bytes(username));

            info = saInfo;

        } catch (SQLException e) {
            final String message = "There was a SQL error while authenticating user [" + username + "]";
            if (LOGGER.isErrorEnabled()) {
                LOGGER.error(message, e);
            }

            // Rethrow any SQL errors as an authentication exception
            throw new AuthenticationException(message, e);
        } finally {
            JdbcUtils.closeConnection(conn);
        }

        return info;
    }

    private String getPasswordForUser(Connection conn, String username) throws SQLException {

        PreparedStatement ps = null;
        ResultSet rs = null;
        String password = null;
        try {
            ps = conn.prepareStatement(authenticationQuery);
            ps.setString(1, username);

            // Execute query
            rs = ps.executeQuery();

            // Loop over results - although we are only expecting one result, since usernames should be unique
            boolean foundResult = false;
            while (rs.next()) {

                // Check to ensure only one row is processed
                if (foundResult) {
                    throw new AuthenticationException("More than one user row found for user ["
                            + username + "]. Usernames must be unique.");
                }

                password = rs.getString(1);

                foundResult = true;
            }
        } finally {
            JdbcUtils.closeResultSet(rs);
            JdbcUtils.closeStatement(ps);
        }

        return password;
    }

}
