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<?php
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP
 *
 * This content is released under the MIT License (MIT)
 *
 * Copyright (c) 2014 - 2018, British Columbia Institute of Technology
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * @package     CodeIgniter
 * @author      EllisLab Dev Team
 * @copyright   Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
 * @copyright   Copyright (c) 2014 - 2018, British Columbia Institute of Technology (http://bcit.ca/)
 * @license     http://opensource.org/licenses/MIT      MIT License
 * @link        https://codeigniter.com
 * @since       Version 2.0.3
 * @filesource
 */
defined('BASEPATH') OR exit('No direct script access allowed');

/**
 * SQLSRV Database Adapter Class
 *
 * Note: _DB is an extender class that the app controller
 * creates dynamically based on whether the query builder
 * class is being used or not.
 *
 * @package             CodeIgniter
 * @subpackage  Drivers
 * @category    Database
 * @author              EllisLab Dev Team
 * @link                https://codeigniter.com/user_guide/database/
 */
class CI_DB_sqlsrv_driver extends CI_DB {

        /**
         * Database driver
         *
         * @var string
         */
        public $dbdriver = 'sqlsrv';

        /**
         * Scrollable flag
         *
         * Determines what cursor type to use when executing queries.
         *
         * FALSE or SQLSRV_CURSOR_FORWARD would increase performance,
         * but would disable num_rows() (and possibly insert_id())
         *
         * @var mixed
         */
        public $scrollable;

        // --------------------------------------------------------------------

        /**
         * ORDER BY random keyword
         *
         * @var array
         */
        protected $_random_keyword = array('NEWID()', 'RAND(%d)');

        /**
         * Quoted identifier flag
         *
         * Whether to use SQL-92 standard quoted identifier
         * (double quotes) or brackets for identifier escaping.
         *
         * @var bool
         */
        protected $_quoted_identifier = TRUE;

        // --------------------------------------------------------------------

        /**
         * Class constructor
         *
         * @param       array   $params
         * @return      void
         */
        public function __construct($params)
        {
                parent::__construct($params);

                // This is only supported as of SQLSRV 3.0
                if ($this->scrollable === NULL)
                {
                        $this->scrollable = defined('SQLSRV_CURSOR_CLIENT_BUFFERED')
                                ? SQLSRV_CURSOR_CLIENT_BUFFERED
                                : FALSE;
                }
        }

        // --------------------------------------------------------------------

        /**
         * Database connection
         *
         * @param       bool    $pooling
         * @return      resource
         */
        public function db_connect($pooling = FALSE)
        {
                $charset = in_array(strtolower($this->char_set), array('utf-8', 'utf8'), TRUE)
                        ? 'UTF-8' : SQLSRV_ENC_CHAR;

                $connection = array(
                        'UID'                   => empty($this->username) ? '' : $this->username,
                        'PWD'                   => empty($this->password) ? '' : $this->password,
                        'Database'              => $this->database,
                        'ConnectionPooling'     => ($pooling === TRUE) ? 1 : 0,
                        'CharacterSet'          => $charset,
                        'Encrypt'               => ($this->encrypt === TRUE) ? 1 : 0,
                        'ReturnDatesAsStrings'  => 1
                );

                // If the username and password are both empty, assume this is a
                // 'Windows Authentication Mode' connection.
                if (empty($connection['UID']) && empty($connection['PWD']))
                {
                        unset($connection['UID'], $connection['PWD']);
                }

                if (FALSE !== ($this->conn_id = sqlsrv_connect($this->hostname, $connection)))
                {
                        // Determine how identifiers are escaped
                        $query = $this->query('SELECT CASE WHEN (@@OPTIONS | 256) = @@OPTIONS THEN 1 ELSE 0 END AS qi');
                        $query = $query->row_array();
                        $this->_quoted_identifier = empty($query) ? FALSE : (bool) $query['qi'];
                        $this->_escape_char = ($this->_quoted_identifier) ? '"' : array('[', ']');
                }

                return $this->conn_id;
        }

        // --------------------------------------------------------------------

        /**
         * Select the database
         *
         * @param       string  $database
         * @return      bool
         */
        public function db_select($database = '')
        {
                if ($database === '')
                {
                        $database = $this->database;
                }

                if ($this->_execute('USE '.$this->escape_identifiers($database)))
                {
                        $this->database = $database;
                        $this->data_cache = array();
                        return TRUE;
                }

                return FALSE;
        }

        // --------------------------------------------------------------------

        /**
         * Execute the query
         *
         * @param       string  $sql    an SQL query
         * @return      resource
         */
        protected function _execute($sql)
        {
                return ($this->scrollable === FALSE OR $this->is_write_type($sql))
                        ? sqlsrv_query($this->conn_id, $sql)
                        : sqlsrv_query($this->conn_id, $sql, NULL, array('Scrollable' => $this->scrollable));
        }

        // --------------------------------------------------------------------

        /**
         * Begin Transaction
         *
         * @return      bool
         */
        protected function _trans_begin()
        {
                return sqlsrv_begin_transaction($this->conn_id);
        }

        // --------------------------------------------------------------------

        /**
         * Commit Transaction
         *
         * @return      bool
         */
        protected function _trans_commit()
        {
                return sqlsrv_commit($this->conn_id);
        }

        // --------------------------------------------------------------------

        /**
         * Rollback Transaction
         *
         * @return      bool
         */
        protected function _trans_rollback()
        {
                return sqlsrv_rollback($this->conn_id);
        }

        // --------------------------------------------------------------------

        /**
         * Affected Rows
         *
         * @return      int
         */
        public function affected_rows()
        {
                return sqlsrv_rows_affected($this->result_id);
        }

        // --------------------------------------------------------------------

        /**
         * Insert ID
         *
         * Returns the last id created in the Identity column.
         *
         * @return      string
         */
        public function insert_id()
        {
                return $this->query('SELECT SCOPE_IDENTITY() AS insert_id')->row()->insert_id;
        }

        // --------------------------------------------------------------------

        /**
         * Database version number
         *
         * @return      string
         */
        public function version()
        {
                if (isset($this->data_cache['version']))
                {
                        return $this->data_cache['version'];
                }

                if ( ! $this->conn_id OR ($info = sqlsrv_server_info($this->conn_id)) === FALSE)
                {
                        return FALSE;
                }

                return $this->data_cache['version'] = $info['SQLServerVersion'];
        }

        // --------------------------------------------------------------------

        /**
         * List table query
         *
         * Generates a platform-specific query string so that the table names can be fetched
         *
         * @param       bool
         * @return      string  $prefix_limit
         */
        protected function _list_tables($prefix_limit = FALSE)
        {
                $sql = 'SELECT '.$this->escape_identifiers('name')
                        .' FROM '.$this->escape_identifiers('sysobjects')
                        .' WHERE '.$this->escape_identifiers('type')." = 'U'";

                if ($prefix_limit === TRUE && $this->dbprefix !== '')
                {
                        $sql .= ' AND '.$this->escape_identifiers('name')." LIKE '".$this->escape_like_str($this->dbprefix)."%' "
                                .sprintf($this->_escape_like_str, $this->_escape_like_chr);
                }

                return $sql.' ORDER BY '.$this->escape_identifiers('name');
        }

        // --------------------------------------------------------------------

        /**
         * List column query
         *
         * Generates a platform-specific query string so that the column names can be fetched
         *
         * @param       string  $table
         * @return      string
         */
        protected function _list_columns($table = '')
        {
                return 'SELECT COLUMN_NAME
                        FROM INFORMATION_SCHEMA.Columns
                        WHERE UPPER(TABLE_NAME) = '.$this->escape(strtoupper($table));
        }

        // --------------------------------------------------------------------

        /**
         * Returns an object with field data
         *
         * @param       string  $table
         * @return      array
         */
        public function field_data($table)
        {
                $sql = 'SELECT COLUMN_NAME, DATA_TYPE, CHARACTER_MAXIMUM_LENGTH, NUMERIC_PRECISION, COLUMN_DEFAULT
                        FROM INFORMATION_SCHEMA.Columns
                        WHERE UPPER(TABLE_NAME) = '.$this->escape(strtoupper($table));

                if (($query = $this->query($sql)) === FALSE)
                {
                        return FALSE;
                }
                $query = $query->result_object();

                $retval = array();
                for ($i = 0, $c = count($query); $i < $c; $i++)
                {
                        $retval[$i]                     = new stdClass();
                        $retval[$i]->name               = $query[$i]->COLUMN_NAME;
                        $retval[$i]->type               = $query[$i]->DATA_TYPE;
                        $retval[$i]->max_length         = ($query[$i]->CHARACTER_MAXIMUM_LENGTH > 0) ? $query[$i]->CHARACTER_MAXIMUM_LENGTH : $query[$i]->NUMERIC_PRECISION;
                        $retval[$i]->default            = $query[$i]->COLUMN_DEFAULT;
                }

                return $retval;
        }

        // --------------------------------------------------------------------

        /**
         * Error
         *
         * Returns an array containing code and message of the last
         * database error that has occurred.
         *
         * @return      array
         */
        public function error()
        {
                $error = array('code' => '00000', 'message' => '');
                $sqlsrv_errors = sqlsrv_errors(SQLSRV_ERR_ERRORS);

                if ( ! is_array($sqlsrv_errors))
                {
                        return $error;
                }

                $sqlsrv_error = array_shift($sqlsrv_errors);
                if (isset($sqlsrv_error['SQLSTATE']))
                {
                        $error['code'] = isset($sqlsrv_error['code']) ? $sqlsrv_error['SQLSTATE'].'/'.$sqlsrv_error['code'] : $sqlsrv_error['SQLSTATE'];
                }
                elseif (isset($sqlsrv_error['code']))
                {
                        $error['code'] = $sqlsrv_error['code'];
                }

                if (isset($sqlsrv_error['message']))
                {
                        $error['message'] = $sqlsrv_error['message'];
                }

                return $error;
        }

        // --------------------------------------------------------------------

        /**
         * Update statement
         *
         * Generates a platform-specific update string from the supplied data
         *
         * @param       string  $table
         * @param       array   $values
         * @return      string
         */
        protected function _update($table, $values)
        {
                $this->qb_limit = FALSE;
                $this->qb_orderby = array();
                return parent::_update($table, $values);
        }

        // --------------------------------------------------------------------

        /**
         * Truncate statement
         *
         * Generates a platform-specific truncate string from the supplied data
         *
         * If the database does not support the TRUNCATE statement,
         * then this method maps to 'DELETE FROM table'
         *
         * @param       string  $table
         * @return      string
         */
        protected function _truncate($table)
        {
                return 'TRUNCATE TABLE '.$table;
        }

        // --------------------------------------------------------------------

        /**
         * Delete statement
         *
         * Generates a platform-specific delete string from the supplied data
         *
         * @param       string  $table
         * @return      string
         */
        protected function _delete($table)
        {
                if ($this->qb_limit)
                {
                        return 'WITH ci_delete AS (SELECT TOP '.$this->qb_limit.' * FROM '.$table.$this->_compile_wh('qb_where').') DELETE FROM ci_delete';
                }

                return parent::_delete($table);
        }

        // --------------------------------------------------------------------

        /**
         * LIMIT
         *
         * Generates a platform-specific LIMIT clause
         *
         * @param       string  $sql    SQL Query
         * @return      string
         */
        protected function _limit($sql)
        {
                // As of SQL Server 2012 (11.0.*) OFFSET is supported
                if (version_compare($this->version(), '11', '>='))
                {
                        // SQL Server OFFSET-FETCH can be used only with the ORDER BY clause
                        empty($this->qb_orderby) && $sql .= ' ORDER BY 1';

                        return $sql.' OFFSET '.(int) $this->qb_offset.' ROWS FETCH NEXT '.$this->qb_limit.' ROWS ONLY';
                }

                $limit = $this->qb_offset + $this->qb_limit;

                // An ORDER BY clause is required for ROW_NUMBER() to work
                if ($this->qb_offset && ! empty($this->qb_orderby))
                {
                        $orderby = $this->_compile_order_by();

                        // We have to strip the ORDER BY clause
                        $sql = trim(substr($sql, 0, strrpos($sql, $orderby)));

                        // Get the fields to select from our subquery, so that we can avoid CI_rownum appearing in the actual results
                        if (count($this->qb_select) === 0 OR strpos(implode(',', $this->qb_select), '*') !== FALSE)
                        {
                                $select = '*'; // Inevitable
                        }
                        else
                        {
                                // Use only field names and their aliases, everything else is out of our scope.
                                $select = array();
                                $field_regexp = ($this->_quoted_identifier)
                                        ? '("[^\"]+")' : '(\[[^\]]+\])';
                                for ($i = 0, $c = count($this->qb_select); $i < $c; $i++)
                                {
                                        $select[] = preg_match('/(?:\s|\.)'.$field_regexp.'$/i', $this->qb_select[$i], $m)
                                                ? $m[1] : $this->qb_select[$i];
                                }
                                $select = implode(', ', $select);
                        }

                        return 'SELECT '.$select." FROM (\n\n"
                                .preg_replace('/^(SELECT( DISTINCT)?)/i', '\\1 ROW_NUMBER() OVER('.trim($orderby).') AS '.$this->escape_identifiers('CI_rownum').', ', $sql)
                                ."\n\n) ".$this->escape_identifiers('CI_subquery')
                                ."\nWHERE ".$this->escape_identifiers('CI_rownum').' BETWEEN '.($this->qb_offset + 1).' AND '.$limit;
                }

                return preg_replace('/(^\SELECT (DISTINCT)?)/i','\\1 TOP '.$limit.' ', $sql);
        }

        // --------------------------------------------------------------------

        /**
         * Insert batch statement
         *
         * Generates a platform-specific insert string from the supplied data.
         *
         * @param       string  $table  Table name
         * @param       array   $keys   INSERT keys
         * @param       array   $values INSERT values
         * @return      string|bool
         */
        protected function _insert_batch($table, $keys, $values)
        {
                // Multiple-value inserts are only supported as of SQL Server 2008
                if (version_compare($this->version(), '10', '>='))
                {
                        return parent::_insert_batch($table, $keys, $values);
                }

                return ($this->db_debug) ? $this->display_error('db_unsupported_feature') : FALSE;
        }

        // --------------------------------------------------------------------

        /**
         * Close DB Connection
         *
         * @return      void
         */
        protected function _close()
        {
                sqlsrv_close($this->conn_id);
        }

}