<?php

/**
 * CodeIgniter
 *
 * An open source application development framework for PHP
 *
 * This content is released under the MIT License (MIT)
 *
 * Copyright (c) 2014 - 2017, 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 - 2017, British Columbia Institute of Technology (http://bcit.ca/)
 * @license	http://opensource.org/licenses/MIT	MIT License
 * @link	https://codeigniter.com
 * @since	Version 1.0.0
 * @filesource
 */
defined('BASEPATH') OR exit('No direct script access allowed');

/**
 * Database Forge Class
 *
 * @category	Database
 * @author		EllisLab Dev Team
 * @link		https://codeigniter.com/user_guide/database/
 */
abstract class CI_DB_forge {

    /**
     * Database object
     *
     * @var	object
     */
    protected $db;

    /**
     * Fields data
     *
     * @var	array
     */
    public $fields = array();

    /**
     * Keys data
     *
     * @var	array
     */
    public $keys = array();

    /**
     * Primary Keys data
     *
     * @var	array
     */
    public $primary_keys = array();

    /**
     * Database character set
     *
     * @var	string
     */
    public $db_char_set = '';

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

    /**
     * CREATE DATABASE statement
     *
     * @var	string
     */
    protected $_create_database = 'CREATE DATABASE %s';

    /**
     * DROP DATABASE statement
     *
     * @var	string
     */
    protected $_drop_database = 'DROP DATABASE %s';

    /**
     * CREATE TABLE statement
     *
     * @var	string
     */
    protected $_create_table = "%s %s (%s\n)";

    /**
     * CREATE TABLE IF statement
     *
     * @var	string
     */
    protected $_create_table_if = 'CREATE TABLE IF NOT EXISTS';

    /**
     * CREATE TABLE keys flag
     *
     * Whether table keys are created from within the
     * CREATE TABLE statement.
     *
     * @var	bool
     */
    protected $_create_table_keys = FALSE;

    /**
     * DROP TABLE IF EXISTS statement
     *
     * @var	string
     */
    protected $_drop_table_if = 'DROP TABLE IF EXISTS';

    /**
     * RENAME TABLE statement
     *
     * @var	string
     */
    protected $_rename_table = 'ALTER TABLE %s RENAME TO %s;';

    /**
     * UNSIGNED support
     *
     * @var	bool|array
     */
    protected $_unsigned = TRUE;

    /**
     * NULL value representation in CREATE/ALTER TABLE statements
     *
     * @var	string
     */
    protected $_null = '';

    /**
     * DEFAULT value representation in CREATE/ALTER TABLE statements
     *
     * @var	string
     */
    protected $_default = ' DEFAULT ';

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

    /**
     * Class constructor
     *
     * @param	object	&$db	Database object
     * @return	void
     */
    public function __construct(&$db) {
        $this->db = & $db;
        log_message('info', 'Database Forge Class Initialized');
    }

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

    /**
     * Create database
     *
     * @param	string	$db_name
     * @return	bool
     */
    public function create_database($db_name) {
        if ($this->_create_database === FALSE) {
            return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
        } elseif (!$this->db->query(sprintf($this->_create_database, $this->db->escape_identifiers($db_name), $this->db->char_set, $this->db->dbcollat))) {
            return ($this->db->db_debug) ? $this->db->display_error('db_unable_to_drop') : FALSE;
        }

        if (!empty($this->db->data_cache['db_names'])) {
            $this->db->data_cache['db_names'][] = $db_name;
        }

        return TRUE;
    }

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

    /**
     * Drop database
     *
     * @param	string	$db_name
     * @return	bool
     */
    public function drop_database($db_name) {
        if ($this->_drop_database === FALSE) {
            return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
        } elseif (!$this->db->query(sprintf($this->_drop_database, $this->db->escape_identifiers($db_name)))) {
            return ($this->db->db_debug) ? $this->db->display_error('db_unable_to_drop') : FALSE;
        }

        if (!empty($this->db->data_cache['db_names'])) {
            $key = array_search(strtolower($db_name), array_map('strtolower', $this->db->data_cache['db_names']), TRUE);
            if ($key !== FALSE) {
                unset($this->db->data_cache['db_names'][$key]);
            }
        }

        return TRUE;
    }

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

    /**
     * Add Key
     *
     * @param	string	$key
     * @param	bool	$primary
     * @return	CI_DB_forge
     */
    public function add_key($key, $primary = FALSE) {
        // DO NOT change this! This condition is only applicable
        // for PRIMARY keys because you can only have one such,
        // and therefore all fields you add to it will be included
        // in the same, composite PRIMARY KEY.
        //
		// It's not the same for regular indexes.
        if ($primary === TRUE && is_array($key)) {
            foreach ($key as $one) {
                $this->add_key($one, $primary);
            }

            return $this;
        }

        if ($primary === TRUE) {
            $this->primary_keys[] = $key;
        } else {
            $this->keys[] = $key;
        }

        return $this;
    }

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

    /**
     * Add Field
     *
     * @param	array	$field
     * @return	CI_DB_forge
     */
    public function add_field($field) {
        if (is_string($field)) {
            if ($field === 'id') {
                $this->add_field(array(
                    'id' => array(
                        'type' => 'INT',
                        'constraint' => 9,
                        'auto_increment' => TRUE
                    )
                ));
                $this->add_key('id', TRUE);
            } else {
                if (strpos($field, ' ') === FALSE) {
                    show_error('Field information is required for that operation.');
                }

                $this->fields[] = $field;
            }
        }

        if (is_array($field)) {
            $this->fields = array_merge($this->fields, $field);
        }

        return $this;
    }

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

    /**
     * Create Table
     *
     * @param	string	$table		Table name
     * @param	bool	$if_not_exists	Whether to add IF NOT EXISTS condition
     * @param	array	$attributes	Associative array of table attributes
     * @return	bool
     */
    public function create_table($table, $if_not_exists = FALSE, array $attributes = array()) {
        if ($table === '') {
            show_error('A table name is required for that operation.');
        } else {
            $table = $this->db->dbprefix . $table;
        }

        if (count($this->fields) === 0) {
            show_error('Field information is required.');
        }

        $sql = $this->_create_table($table, $if_not_exists, $attributes);

        if (is_bool($sql)) {
            $this->_reset();
            if ($sql === FALSE) {
                return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
            }
        }

        if (($result = $this->db->query($sql)) !== FALSE) {
            isset($this->db->data_cache['table_names']) && $this->db->data_cache['table_names'][] = $table;

            // Most databases don't support creating indexes from within the CREATE TABLE statement
            if (!empty($this->keys)) {
                for ($i = 0, $sqls = $this->_process_indexes($table), $c = count($sqls); $i < $c; $i++) {
                    $this->db->query($sqls[$i]);
                }
            }
        }

        $this->_reset();
        return $result;
    }

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

    /**
     * Create Table
     *
     * @param	string	$table		Table name
     * @param	bool	$if_not_exists	Whether to add 'IF NOT EXISTS' condition
     * @param	array	$attributes	Associative array of table attributes
     * @return	mixed
     */
    protected function _create_table($table, $if_not_exists, $attributes) {
        if ($if_not_exists === TRUE && $this->_create_table_if === FALSE) {
            if ($this->db->table_exists($table)) {
                return TRUE;
            } else {
                $if_not_exists = FALSE;
            }
        }

        $sql = ($if_not_exists) ? sprintf($this->_create_table_if, $this->db->escape_identifiers($table)) : 'CREATE TABLE';

        $columns = $this->_process_fields(TRUE);
        for ($i = 0, $c = count($columns); $i < $c; $i++) {
            $columns[$i] = ($columns[$i]['_literal'] !== FALSE) ? "\n\t" . $columns[$i]['_literal'] : "\n\t" . $this->_process_column($columns[$i]);
        }

        $columns = implode(',', $columns)
                . $this->_process_primary_keys($table);

        // Are indexes created from within the CREATE TABLE statement? (e.g. in MySQL)
        if ($this->_create_table_keys === TRUE) {
            $columns .= $this->_process_indexes($table);
        }

        // _create_table will usually have the following format: "%s %s (%s\n)"
        $sql = sprintf($this->_create_table . '%s', $sql, $this->db->escape_identifiers($table), $columns, $this->_create_table_attr($attributes)
        );

        return $sql;
    }

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

    /**
     * CREATE TABLE attributes
     *
     * @param	array	$attributes	Associative array of table attributes
     * @return	string
     */
    protected function _create_table_attr($attributes) {
        $sql = '';

        foreach (array_keys($attributes) as $key) {
            if (is_string($key)) {
                $sql .= ' ' . strtoupper($key) . ' ' . $attributes[$key];
            }
        }

        return $sql;
    }

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

    /**
     * Drop Table
     *
     * @param	string	$table_name	Table name
     * @param	bool	$if_exists	Whether to add an IF EXISTS condition
     * @return	bool
     */
    public function drop_table($table_name, $if_exists = FALSE) {
        if ($table_name === '') {
            return ($this->db->db_debug) ? $this->db->display_error('db_table_name_required') : FALSE;
        }

        if (($query = $this->_drop_table($this->db->dbprefix . $table_name, $if_exists)) === TRUE) {
            return TRUE;
        }

        $query = $this->db->query($query);

        // Update table list cache
        if ($query && !empty($this->db->data_cache['table_names'])) {
            $key = array_search(strtolower($this->db->dbprefix . $table_name), array_map('strtolower', $this->db->data_cache['table_names']), TRUE);
            if ($key !== FALSE) {
                unset($this->db->data_cache['table_names'][$key]);
            }
        }

        return $query;
    }

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

    /**
     * Drop Table
     *
     * Generates a platform-specific DROP TABLE string
     *
     * @param	string	$table		Table name
     * @param	bool	$if_exists	Whether to add an IF EXISTS condition
     * @return	string
     */
    protected function _drop_table($table, $if_exists) {
        $sql = 'DROP TABLE';

        if ($if_exists) {
            if ($this->_drop_table_if === FALSE) {
                if (!$this->db->table_exists($table)) {
                    return TRUE;
                }
            } else {
                $sql = sprintf($this->_drop_table_if, $this->db->escape_identifiers($table));
            }
        }

        return $sql . ' ' . $this->db->escape_identifiers($table);
    }

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

    /**
     * Rename Table
     *
     * @param	string	$table_name	Old table name
     * @param	string	$new_table_name	New table name
     * @return	bool
     */
    public function rename_table($table_name, $new_table_name) {
        if ($table_name === '' OR $new_table_name === '') {
            show_error('A table name is required for that operation.');
            return FALSE;
        } elseif ($this->_rename_table === FALSE) {
            return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
        }

        $result = $this->db->query(sprintf($this->_rename_table, $this->db->escape_identifiers($this->db->dbprefix . $table_name), $this->db->escape_identifiers($this->db->dbprefix . $new_table_name))
        );

        if ($result && !empty($this->db->data_cache['table_names'])) {
            $key = array_search(strtolower($this->db->dbprefix . $table_name), array_map('strtolower', $this->db->data_cache['table_names']), TRUE);
            if ($key !== FALSE) {
                $this->db->data_cache['table_names'][$key] = $this->db->dbprefix . $new_table_name;
            }
        }

        return $result;
    }

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

    /**
     * Column Add
     *
     * @todo	Remove deprecated $_after option in 3.1+
     * @param	string	$table	Table name
     * @param	array	$field	Column definition
     * @param	string	$_after	Column for AFTER clause (deprecated)
     * @return	bool
     */
    public function add_column($table, $field, $_after = NULL) {
        // Work-around for literal column definitions
        is_array($field) OR $field = array($field);

        foreach (array_keys($field) as $k) {
            // Backwards-compatibility work-around for MySQL/CUBRID AFTER clause (remove in 3.1+)
            if ($_after !== NULL && is_array($field[$k]) && !isset($field[$k]['after'])) {
                $field[$k]['after'] = $_after;
            }

            $this->add_field(array($k => $field[$k]));
        }

        $sqls = $this->_alter_table('ADD', $this->db->dbprefix . $table, $this->_process_fields());
        $this->_reset();
        if ($sqls === FALSE) {
            return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
        }

        for ($i = 0, $c = count($sqls); $i < $c; $i++) {
            if ($this->db->query($sqls[$i]) === FALSE) {
                return FALSE;
            }
        }

        return TRUE;
    }

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

    /**
     * Column Drop
     *
     * @param	string	$table		Table name
     * @param	string	$column_name	Column name
     * @return	bool
     */
    public function drop_column($table, $column_name) {
        $sql = $this->_alter_table('DROP', $this->db->dbprefix . $table, $column_name);
        if ($sql === FALSE) {
            return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
        }

        return $this->db->query($sql);
    }

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

    /**
     * Column Modify
     *
     * @param	string	$table	Table name
     * @param	string	$field	Column definition
     * @return	bool
     */
    public function modify_column($table, $field) {
        // Work-around for literal column definitions
        is_array($field) OR $field = array($field);

        foreach (array_keys($field) as $k) {
            $this->add_field(array($k => $field[$k]));
        }

        if (count($this->fields) === 0) {
            show_error('Field information is required.');
        }

        $sqls = $this->_alter_table('CHANGE', $this->db->dbprefix . $table, $this->_process_fields());
        $this->_reset();
        if ($sqls === FALSE) {
            return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
        }

        for ($i = 0, $c = count($sqls); $i < $c; $i++) {
            if ($this->db->query($sqls[$i]) === FALSE) {
                return FALSE;
            }
        }

        return TRUE;
    }

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

    /**
     * ALTER TABLE
     *
     * @param	string	$alter_type	ALTER type
     * @param	string	$table		Table name
     * @param	mixed	$field		Column definition
     * @return	string|string[]
     */
    protected function _alter_table($alter_type, $table, $field) {
        $sql = 'ALTER TABLE ' . $this->db->escape_identifiers($table) . ' ';

        // DROP has everything it needs now.
        if ($alter_type === 'DROP') {
            return $sql . 'DROP COLUMN ' . $this->db->escape_identifiers($field);
        }

        $sql .= ($alter_type === 'ADD') ? 'ADD ' : $alter_type . ' COLUMN ';

        $sqls = array();
        for ($i = 0, $c = count($field); $i < $c; $i++) {
            $sqls[] = $sql
                    . ($field[$i]['_literal'] !== FALSE ? $field[$i]['_literal'] : $this->_process_column($field[$i]));
        }

        return $sqls;
    }

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

    /**
     * Process fields
     *
     * @param	bool	$create_table
     * @return	array
     */
    protected function _process_fields($create_table = FALSE) {
        $fields = array();

        foreach ($this->fields as $key => $attributes) {
            if (is_int($key) && !is_array($attributes)) {
                $fields[] = array('_literal' => $attributes);
                continue;
            }

            $attributes = array_change_key_case($attributes, CASE_UPPER);

            if ($create_table === TRUE && empty($attributes['TYPE'])) {
                continue;
            }

            isset($attributes['TYPE']) && $this->_attr_type($attributes);

            $field = array(
                'name' => $key,
                'new_name' => isset($attributes['NAME']) ? $attributes['NAME'] : NULL,
                'type' => isset($attributes['TYPE']) ? $attributes['TYPE'] : NULL,
                'length' => '',
                'unsigned' => '',
                'null' => '',
                'unique' => '',
                'default' => '',
                'auto_increment' => '',
                '_literal' => FALSE
            );

            isset($attributes['TYPE']) && $this->_attr_unsigned($attributes, $field);

            if ($create_table === FALSE) {
                if (isset($attributes['AFTER'])) {
                    $field['after'] = $attributes['AFTER'];
                } elseif (isset($attributes['FIRST'])) {
                    $field['first'] = (bool) $attributes['FIRST'];
                }
            }

            $this->_attr_default($attributes, $field);

            if (isset($attributes['NULL'])) {
                if ($attributes['NULL'] === TRUE) {
                    $field['null'] = empty($this->_null) ? '' : ' ' . $this->_null;
                } else {
                    $field['null'] = ' NOT NULL';
                }
            } elseif ($create_table === TRUE) {
                $field['null'] = ' NOT NULL';
            }

            $this->_attr_auto_increment($attributes, $field);
            $this->_attr_unique($attributes, $field);

            if (isset($attributes['COMMENT'])) {
                $field['comment'] = $this->db->escape($attributes['COMMENT']);
            }

            if (isset($attributes['TYPE']) && !empty($attributes['CONSTRAINT'])) {
                switch (strtoupper($attributes['TYPE'])) {
                    case 'ENUM':
                    case 'SET':
                        $attributes['CONSTRAINT'] = $this->db->escape($attributes['CONSTRAINT']);
                    default:
                        $field['length'] = is_array($attributes['CONSTRAINT']) ? '(' . implode(',', $attributes['CONSTRAINT']) . ')' : '(' . $attributes['CONSTRAINT'] . ')';
                        break;
                }
            }

            $fields[] = $field;
        }

        return $fields;
    }

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

    /**
     * Process column
     *
     * @param	array	$field
     * @return	string
     */
    protected function _process_column($field) {
        return $this->db->escape_identifiers($field['name'])
                . ' ' . $field['type'] . $field['length']
                . $field['unsigned']
                . $field['default']
                . $field['null']
                . $field['auto_increment']
                . $field['unique'];
    }

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

    /**
     * Field attribute TYPE
     *
     * Performs a data type mapping between different databases.
     *
     * @param	array	&$attributes
     * @return	void
     */
    protected function _attr_type(&$attributes) {
        // Usually overridden by drivers
    }

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

    /**
     * Field attribute UNSIGNED
     *
     * Depending on the _unsigned property value:
     *
     * 	- TRUE will always set $field['unsigned'] to 'UNSIGNED'
     * 	- FALSE will always set $field['unsigned'] to ''
     * 	- array(TYPE) will set $field['unsigned'] to 'UNSIGNED',
     * 		if $attributes['TYPE'] is found in the array
     * 	- array(TYPE => UTYPE) will change $field['type'],
     * 		from TYPE to UTYPE in case of a match
     *
     * @param	array	&$attributes
     * @param	array	&$field
     * @return	void
     */
    protected function _attr_unsigned(&$attributes, &$field) {
        if (empty($attributes['UNSIGNED']) OR $attributes['UNSIGNED'] !== TRUE) {
            return;
        }

        // Reset the attribute in order to avoid issues if we do type conversion
        $attributes['UNSIGNED'] = FALSE;

        if (is_array($this->_unsigned)) {
            foreach (array_keys($this->_unsigned) as $key) {
                if (is_int($key) && strcasecmp($attributes['TYPE'], $this->_unsigned[$key]) === 0) {
                    $field['unsigned'] = ' UNSIGNED';
                    return;
                } elseif (is_string($key) && strcasecmp($attributes['TYPE'], $key) === 0) {
                    $field['type'] = $key;
                    return;
                }
            }

            return;
        }

        $field['unsigned'] = ($this->_unsigned === TRUE) ? ' UNSIGNED' : '';
    }

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

    /**
     * Field attribute DEFAULT
     *
     * @param	array	&$attributes
     * @param	array	&$field
     * @return	void
     */
    protected function _attr_default(&$attributes, &$field) {
        if ($this->_default === FALSE) {
            return;
        }

        if (array_key_exists('DEFAULT', $attributes)) {
            if ($attributes['DEFAULT'] === NULL) {
                $field['default'] = empty($this->_null) ? '' : $this->_default . $this->_null;

                // Override the NULL attribute if that's our default
                $attributes['NULL'] = TRUE;
                $field['null'] = empty($this->_null) ? '' : ' ' . $this->_null;
            } else {
                $field['default'] = $this->_default . $this->db->escape($attributes['DEFAULT']);
            }
        }
    }

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

    /**
     * Field attribute UNIQUE
     *
     * @param	array	&$attributes
     * @param	array	&$field
     * @return	void
     */
    protected function _attr_unique(&$attributes, &$field) {
        if (!empty($attributes['UNIQUE']) && $attributes['UNIQUE'] === TRUE) {
            $field['unique'] = ' UNIQUE';
        }
    }

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

    /**
     * Field attribute AUTO_INCREMENT
     *
     * @param	array	&$attributes
     * @param	array	&$field
     * @return	void
     */
    protected function _attr_auto_increment(&$attributes, &$field) {
        if (!empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE && stripos($field['type'], 'int') !== FALSE) {
            $field['auto_increment'] = ' AUTO_INCREMENT';
        }
    }

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

    /**
     * Process primary keys
     *
     * @param	string	$table	Table name
     * @return	string
     */
    protected function _process_primary_keys($table) {
        $sql = '';

        for ($i = 0, $c = count($this->primary_keys); $i < $c; $i++) {
            if (!isset($this->fields[$this->primary_keys[$i]])) {
                unset($this->primary_keys[$i]);
            }
        }

        if (count($this->primary_keys) > 0) {
            $sql .= ",\n\tCONSTRAINT " . $this->db->escape_identifiers('pk_' . $table)
                    . ' PRIMARY KEY(' . implode(', ', $this->db->escape_identifiers($this->primary_keys)) . ')';
        }

        return $sql;
    }

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

    /**
     * Process indexes
     *
     * @param	string	$table
     * @return	string
     */
    protected function _process_indexes($table) {
        $sqls = array();

        for ($i = 0, $c = count($this->keys); $i < $c; $i++) {
            if (is_array($this->keys[$i])) {
                for ($i2 = 0, $c2 = count($this->keys[$i]); $i2 < $c2; $i2++) {
                    if (!isset($this->fields[$this->keys[$i][$i2]])) {
                        unset($this->keys[$i][$i2]);
                        continue;
                    }
                }
            } elseif (!isset($this->fields[$this->keys[$i]])) {
                unset($this->keys[$i]);
                continue;
            }

            is_array($this->keys[$i]) OR $this->keys[$i] = array($this->keys[$i]);

            $sqls[] = 'CREATE INDEX ' . $this->db->escape_identifiers($table . '_' . implode('_', $this->keys[$i]))
                    . ' ON ' . $this->db->escape_identifiers($table)
                    . ' (' . implode(', ', $this->db->escape_identifiers($this->keys[$i])) . ');';
        }

        return $sqls;
    }

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

    /**
     * Reset
     *
     * Resets table creation vars
     *
     * @return	void
     */
    protected function _reset() {
        $this->fields = $this->keys = $this->primary_keys = array();
    }

}
