<?php

class Classes_Password
{
    /**
     * Reference to database connection
     *
     * @var object Zend_DB
     */
    protected $_db = null;

    /**
     * Hashing algorithm to use
     *
     * @var string
     */
    protected $_hashAlgorithm = 'tiger192,4';

    private $_passwordHash = null;

    public function __construct()
    {
        // Assign reference to database connection
        $this->_db = Zend_Registry::get('db');
    }

    /**
     * Create password hash
     *
     * - Create a salt by hashing time() as random string
     * - Take the first 24 characters of the salt for use later
     * - Create encryption of the password by hashing the concatenation of the first 24 characters of the salt and the password
     * - Take the first 24 characters of the encryption for use later
     * - Hash to store in the database is the concatenation of the first 24 characters of the salt and the first 24 characters of the encryption
     *
     * @param string Password
     * @return string Encryption string
     */
    public function encrypt( $password )
    {
        // Create a salt by hashing time() as random string
        $salt = hash( $this->_hashAlgorithm, time() );

        // Take the first 24 characters of the salt for use later
        $halfSalt = substr( $salt, 0, 24 );

        // Create encryption of the password by hashing the concatenation of the first 24 characters of the salt and the password
        $encryption = hash( $this->_hashAlgorithm, $halfSalt.$password );

        // Take the first 24 characters of the encryption for use later
        $halfEncryption = substr( $encryption, 0, 24 );

        return $halfSalt.$halfEncryption;
    }

    /**
     * Determine whether provided password is valid or not
     *
     * @param string Password
     * @return boolean true|false
     */
    public function isValid( $encryptionString, $password )
    {
        $halfSalt = substr( $encryptionString, 0, 24 );
        $halfEncryption = substr( $encryptionString, 24 );

        return ( $halfEncryption == substr( hash( $this->_hashAlgorithm, $halfSalt.$password ), 0, 24 ) ) ? true : false;
    }

    public function getEncryptionSalt( $username )
    {
        if ( ! isset( $this->_passwordHash ) )
        {
            $this->_passwordHash = substr( $this->_getPasswordHash($username), 0, 24 );
        }

        return $this->_passwordHash;
    }

    public function getEncryptionString( $username, $password )
    {
        $encryptionString = $this->getEncryptionSalt($username) . substr( hash( $this->_hashAlgorithm, $this->getEncryptionSalt($username).$password ), 0, 24 );

        return $encryptionString;
    }

    protected function _getPasswordHash( $username )
    {
        $result = $this->_db->fetchRow("
            SELECT
                password
            FROM
                credentials
            WHERE
                username = '" . $username . "'
        ");

        return $result->password;
    }
}