<?php
/**
 * MyBB 1.8
 * Copyright 2014 MyBB Group, All Rights Reserved
 *
 * Website: http://www.mybb.com
 * License: http://www.mybb.com/about/license
 *
 */

class DB_SQLite implements DB_Base
{
	/**
	 * The title of this layer.
	 *
	 * @var string
	 */
	public $title = "SQLite 3";

	/**
	 * The short title of this layer.
	 *
	 * @var string
	 */
	public $short_title = "SQLite";

	/**
	 * The type of db software being used.
	 *
	 * @var string
	 */
	public $type;

	/**
	 * PDOStatement objects of performed queries.
	 *
	 * @var array 
	 */
	public $query_objects = array();

	/**
	 * A count of the number of queries.
	 *
	 * @var int
	 */
	public $query_count = 0;

	/**
	 * A list of the performed queries.
	 *
	 * @var array
	 */
	public $querylist = array();

	/**
	 * 1 if error reporting enabled, 0 if disabled.
	 *
	 * @var boolean
	 */
	public $error_reporting = 1;

	/**
	 * The database connection resource.
	 *
	 * @var resource
	 */
	public $link;

	/**
	 * @var array
	 */
	public $connections = array();

	/**
	 * Explanation of a query.
	 *
	 * @var string
	 */
	public $explain;

	/**
	 * The current version of SQLite.
	 *
	 * @var string
	 */
	public $version;

	/**
	 * The current table type in use (myisam/innodb)
	 *
	 * @var string
	 */
	public $table_type = "myisam";

	/**
	 * The table prefix used for simple select, update, insert and delete queries
	 *
	 * @var string
	 */
	public $table_prefix;

	/**
	 * The extension used to run the SQL database
	 *
	 * @var string
	 */
	public $engine = "pdo";

	/**
	 * Weather or not this engine can use the search functionality
	 *
	 * @var boolean
	 */
	public $can_search = true;

	/**
	 * The database encoding currently in use (if supported)
	 *
	 * @var string
	 */
	public $db_encoding = "";

	/**
	 * The time spent performing queries
	 *
	 * @var float
	 */
	public $query_time = 0;

	/**
	 * Our pdo implementation
	 *
	 * @var dbpdoEngine
	 */
	var $db;

	/**
	 * Connect to the database server.
	 *
	 * @param array $config Array of DBMS connection details.
	 * @return bool Returns false on failure, otherwise true
	 */
	function connect($config)
	{
		get_execution_time();

		require_once MYBB_ROOT."inc/db_pdo.php";

		try {
			$this->db = new dbpdoEngine("sqlite:{$config['database']}");
		} catch (Exception $ex) {
			$this->error("[READ] Unable to open the SQLite database");

			return false;
		}

		$query_time = get_execution_time();

		$this->query_time += $query_time;

		$this->connections[] = "[WRITE] {$config['database']} (Connected in ".format_time_duration($query_time).")";

		if($this->db)
		{
			$this->query('PRAGMA short_column_names = 1');
			return true;
		}
		else
		{
			return false;
		}
	}

	/**
	 * Query the database.
	 *
	 * @param string $string The query SQL.
	 * @param boolean|int $hide_errors 1 if hide errors, 0 if not.
	 * @param integer $write_query 1 if executes on master database, 0 if not.
	 * @return PDOStatement The query data.
	 */
	function query($string, $hide_errors=0, $write_query=0)
	{
		global $mybb;

		get_execution_time();

		if(strtolower(substr(ltrim($string), 0, 5)) == 'alter')
		{
			$string = preg_replace("#\sAFTER\s([a-z_]+?)(;*?)$#i", "", $string);

			$queryparts = preg_split("/[\s]+/", $string, 4, PREG_SPLIT_NO_EMPTY);
			$tablename = $queryparts[2];
			$alterdefs = $queryparts[3];
			if(strtolower($queryparts[1]) != 'table' || $queryparts[2] == '')
			{
				$this->error_msg = "near \"{$queryparts[0]}\": syntax error";
			}
			else
			{
				// SQLITE 3 supports ADD and RENAME TO alter statements
				if(strtolower(substr(ltrim($alterdefs), 0, 3)) == 'add' || strtolower(substr(ltrim($alterdefs), 0, 9)) == "rename to")
				{
					$query = $this->db->query($string);
					$query->closeCursor();
				}
				else
				{
					$query = $this->alter_table_parse($tablename, $alterdefs, $string);
				}
			}
		}
	  	else
	  	{
			try
			{
				$query = $this->db->query($string);
			}
			catch(PDOException $exception)
			{
				$error = array(
					"message" => $exception->getMessage(),
					"code" => $exception->getCode()
				);

				$this->error($error['message'], $error['code']);
			}
		}

		$this->query_objects[] = $query;

		if($this->error_number($query) > 0 && !$hide_errors)
		{
			$this->error($string, $query);
			exit;
		}

		$query_time = get_execution_time();
		$this->query_time += $query_time;
		$this->query_count++;

		if($mybb->debug_mode)
		{
			$this->explain_query($string, $query_time);
		}

		if(strtolower(substr(ltrim($string), 0, 6)) == "create")
		{
			$query->closeCursor();
			return null;
		}

		return $query;
	}

	/**
	 * Explain a query on the database.
	 *
	 * @param string $string The query SQL.
	 * @param string $qtime The time it took to perform the query.
	 */
	function explain_query($string, $qtime)
	{
		if(preg_match("#^\s*select#i", $string))
		{
			$this->explain .= "<table style=\"background-color: #666;\" width=\"95%\" cellpadding=\"4\" cellspacing=\"1\" align=\"center\">\n".
				"<tr>\n".
				"<td colspan=\"8\" style=\"background-color: #ccc;\"><strong>#".$this->query_count." - Select Query</strong></td>\n".
				"</tr>\n".
				"<tr>\n".
				"<td colspan=\"8\" style=\"background-color: #fefefe;\"><span style=\"font-family: Courier; font-size: 14px;\">".htmlspecialchars_uni($string)."</span></td>\n".
				"</tr>\n".
				"<tr>\n".
				"<td colspan=\"8\" style=\"background-color: #fff;\">Query Time: ".format_time_duration($qtime)."</td>\n".
				"</tr>\n".
				"</table>\n".
				"<br />\n";
		}
		else
		{
			$this->explain .= "<table style=\"background-color: #666;\" width=\"95%\" cellpadding=\"4\" cellspacing=\"1\" align=\"center\">\n".
				"<tr>\n".
				"<td style=\"background-color: #ccc;\"><strong>#".$this->query_count." - Write Query</strong></td>\n".
				"</tr>\n".
				"<tr style=\"background-color: #fefefe;\">\n".
				"<td><span style=\"font-family: Courier; font-size: 14px;\">".htmlspecialchars_uni($string)."</span></td>\n".
				"</tr>\n".
				"<tr>\n".
				"<td bgcolor=\"#ffffff\">Query Time: ".format_time_duration($qtime)."</td>\n".
				"</tr>\n".
				"</table>\n".
				"<br />\n";
		}

		$this->querylist[$this->query_count]['query'] = $string;
		$this->querylist[$this->query_count]['time'] = $qtime;
	}

	/**
	 * Execute a write query on the database
	 *
	 * @param string $query The query SQL.
	 * @param boolean|int $hide_errors 1 if hide errors, 0 if not.
	 * @return PDOStatement The query data.
	 */
	function write_query($query, $hide_errors=0)
	{
		return $this->query($query, $hide_errors);
	}

	/**
	 * Return a result array for a query.
	 *
	 * @param PDOStatement $query The result data.
	 * @param int $resulttype One of PDO's constants: FETCH_ASSOC, FETCH_BOUND, FETCH_CLASS, FETCH_INTO, FETCH_LAZY, FETCH_NAMED, FETCH_NUM, FETCH_OBJ or FETCH_BOTH
	 * @return array The array of results.
	 */
	function fetch_array($query, $resulttype=PDO::FETCH_BOTH)
	{
		$array = $this->db->fetch_array($query, $resulttype);
		return $array;
	}

	/**
	 * Return a specific field from a query.
	 *
	 * @param PDOStatement $query The query ID.
	 * @param string $field The name of the field to return.
	 * @param int|bool $row The number of the row to fetch it from.
	 * @return mixed
	 */
	function fetch_field($query, $field, $row=false)
	{
		if($row !== false)
		{
			$this->data_seek($query, $row);
		}
		$array = $this->fetch_array($query);
		if($array !== null && $array !== false)
		{
			return $array[$field];
		}
		return null;
	}

	/**
	 * Moves internal row pointer to the next row
	 *
	 * @param PDOStatement $query The query ID.
	 * @param int $row The pointer to move the row to.
	 */
	function data_seek($query, $row)
	{
		$this->db->seek($query, $row);
	}

	/**
	 * Closes cursors of registered queries.
	 *
	 */
	function close_cursors()
	{
		$result = true;

		foreach($this->query_objects as $query)
		{
			if(!$query->closeCursor())
			{
				$result = false;
			}
		}

		return $result;
	}

	/**
	 * Return the number of rows resulting from a query.
	 *
	 * @param PDOStatement $query The query data.
	 * @return int The number of rows in the result.
	 */
	function num_rows($query)
	{
		return $this->db->num_rows($query);
	}

	/**
	 * Return the last id number of inserted data.
	 *
	 * @param string $name
	 * @return int The id number.
	 */
	function insert_id($name="")
	{
		return $this->db->insert_id($name);
	}

	/**
	 * Close the connection with the DBMS.
	 *
	 */
	function close()
	{
		return;
	}

	/**
	 * Return an error number.
	 *
	 * @param PDOStatement $query
	 * @return int The error number of the current error.
	 */
	function error_number($query=null)
	{
		if($query == null)
		{
			$query = $this->db->last_query;
		}

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

		return $this->error_number;
	}

	/**
	 * Return an error string.
	 *
	 * @param PDOStatement $query
	 * @return string The explanation for the current error.
	 */
	function error_string($query=null)
	{
		if($this->error_number != "")
		{
			if($query == null)
			{
				$query = $this->db->last_query;
			}

			$error_string = $this->db->error_string($query);
			$this->error_number = "";

			return $error_string;
		}

		return '';
	}

	/**
	 * Output a database error.
	 *
	 * @param string $string The string to present as an error.
	 * @param PDOStatement $query
	 * @param string $error
	 * @param int $error_no
	 */
	function error($string="", $query=null, $error="", $error_no=0)
	{
		if($this->error_reporting)
		{
			if($query == null)
			{
				$query = $this->db->last_query;
			}

			if($error_no == 0)
			{
				$error_no = $this->error_number($query);
			}

			if($error == "")
			{
				$error = $this->error_string($query);
			}

			if(class_exists("errorHandler"))
			{
				global $error_handler;

				if(!is_object($error_handler))
				{
					require_once MYBB_ROOT."inc/class_error.php";
					$error_handler = new errorHandler();
				}

				$error = array(
					"error_no" => $error_no,
					"error" => $error,
					"query" => $string
				);
				$error_handler->error(MYBB_SQL, $error);
			}
			else
			{
				trigger_error("<strong>[SQL] [{$error_no}] {$error}</strong><br />{$string}", E_USER_ERROR);
			}
		}
	}

	/**
	 * Returns the number of affected rows in a query.
	 *
	 * @param PDOStatement $query
	 * @return int The number of affected rows.
	 */
	function affected_rows($query=null)
	{
		if($query == null)
		{
			$query = $this->db->last_query;
		}

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

	/**
	 * Return the number of fields.
	 *
	 * @param PDOStatement $query The query data.
	 * @return int The number of fields.
	 */
	function num_fields($query)
	{
		if(!$query)
		{
			$query = $this->db->last_query;
		}

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

	/**
	 * Lists all tables in the database.
	 *
	 * @param string $database The database name.
	 * @param string $prefix Prefix of the table (optional)
	 * @return array The table list.
	 */
	function list_tables($database, $prefix='')
	{
		if($prefix)
		{
			$query = $this->query("SELECT tbl_name FROM sqlite_master WHERE type = 'table' AND tbl_name LIKE '".$this->escape_string($prefix)."%'");
		}
		else
		{
			$query = $this->query("SELECT tbl_name FROM sqlite_master WHERE type = 'table'");
		}

		$tables = array();
		while($table = $this->fetch_array($query))
		{
			$tables[] = $table['tbl_name'];
		}
		$query->closeCursor();
		return $tables;
	}

	/**
	 * Check if a table exists in a database.
	 *
	 * @param string $table The table name.
	 * @return boolean True when exists, false if not.
	 */
	function table_exists($table)
	{
		$query = $this->query("SELECT COUNT(name) as count FROM sqlite_master WHERE type='table' AND name='{$this->table_prefix}{$table}'");
		$exists = $this->fetch_field($query, "count");
		$query->closeCursor();

		if($exists > 0)
		{
			return true;
		}
		else
		{
			return false;
		}
	}

	/**
	 * Check if a field exists in a database.
	 *
	 * @param string $field The field name.
	 * @param string $table The table name.
	 * @return boolean True when exists, false if not.
	 */
	function field_exists($field, $table)
	{
		$query = $this->query("PRAGMA table_info('{$this->table_prefix}{$table}')");

		$exists = 0;

		while($row = $this->fetch_array($query))
		{
			if($row['name'] == $field)
			{
				++$exists;
			}
		}

		$query->closeCursor();

		if($exists > 0)
		{
			return true;
		}
		else
		{
			return false;
		}
	}

	/**
	 * Add a shutdown query.
	 *
	 * @param PDOStatement $query The query data.
	 * @param string $name An optional name for the query.
	 */
	function shutdown_query($query, $name="")
	{
		global $shutdown_queries;
		if($name)
		{
			$shutdown_queries[$name] = $query;
		}
		else
		{
			$shutdown_queries[] = $query;
		}
	}

	/**
	 * Performs a simple select query.
	 *
	 * @param string $table The table name to be queried.
	 * @param string $fields Comma delimetered list of fields to be selected.
	 * @param string $conditions SQL formatted list of conditions to be matched.
	 * @param array $options List of options: group by, order by, order direction, limit, limit start.
	 * @return PDOStatement The query data.
	 */
	function simple_select($table, $fields="*", $conditions="", $options=array())
	{
		$query = "SELECT ".$fields." FROM ".$this->table_prefix.$table;

		if($conditions != "")
		{
			$query .= " WHERE ".$conditions;
		}

		if(isset($options['group_by']))
		{
			$query .= " GROUP BY ".$options['group_by'];
		}

		if(isset($options['order_by']))
		{
			$query .= " ORDER BY ".$options['order_by'];

			if(isset($options['order_dir']))
			{
				$query .= " ".strtoupper($options['order_dir']);
			}
		}

		if(isset($options['limit_start']) && isset($options['limit']))
		{
			$query .= " LIMIT ".$options['limit_start'].", ".$options['limit'];
		}
		else if(isset($options['limit']))
		{
			$query .= " LIMIT ".$options['limit'];
		}

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

	/**
	 * Build an insert query from an array.
	 *
	 * @param string $table The table name to perform the query on.
	 * @param array $array An array of fields and their values.
	 * @return int|bool The insert ID if available or false if an error is found
	 */
	function insert_query($table, $array)
	{
		global $mybb;

		if(!is_array($array))
		{
			return false;
		}

		foreach($array as $field => $value)
		{
			if(isset($mybb->binary_fields[$table][$field]) && $mybb->binary_fields[$table][$field])
			{
				if($value[0] != 'X') // Not escaped?
				{
					$value = $this->escape_binary($value);
				}
				
				$array[$field] = $value;
			}
			else
			{
				$array[$field] = $this->quote_val($value);
			}
		}

		$fields = implode(",", array_keys($array));
		$values = implode(",", $array);
		$query = $this->write_query("
			INSERT
			INTO {$this->table_prefix}{$table} (".$fields.")
			VALUES (".$values.")
		");
		$query->closeCursor();
		return $this->insert_id();
	}

	/**
	 * Build one query for multiple inserts from a multidimensional array.
	 *
	 * @param string $table The table name to perform the query on.
	 * @param array $array An array of inserts.
	 * @return void
	 */
	function insert_query_multiple($table, $array)
	{
		global $mybb;

		if(!is_array($array))
		{
			return;
		}
		// Field names
		$fields = array_keys($array[0]);
		$fields = implode(",", $fields);

		$insert_rows = array();
		foreach($array as $values)
		{
			foreach($values as $field => $value)
			{
				if(isset($mybb->binary_fields[$table][$field]) && $mybb->binary_fields[$table][$field])
				{
					if($value[0] != 'X') // Not escaped?
					{
						$value = $this->escape_binary($value);
					}
				
					$values[$field] = $value;
				}
				else
				{
					$values[$field] = $this->quote_val($value);
				}
			}
			$insert_rows[] = "(".implode(",", $values).")";
		}
		$insert_rows = implode(", ", $insert_rows);

		$query = $this->write_query("
			INSERT
			INTO {$this->table_prefix}{$table} ({$fields})
			VALUES {$insert_rows}
		");
		$query->closeCursor();
	}

	/**
	 * Build an update query from an array.
	 *
	 * @param string $table The table name to perform the query on.
	 * @param array $array An array of fields and their values.
	 * @param string $where An optional where clause for the query.
	 * @param string $limit An optional limit clause for the query.
	 * @param boolean $no_quote An option to quote incoming values of the array.
	 * @return PDOStatement|false The query data.
	 */
	function update_query($table, $array, $where="", $limit="", $no_quote=false)
	{
		global $mybb;

		if(!is_array($array))
		{
			return false;
		}

		$comma = "";
		$query = "";
		$quote = "'";

		if($no_quote == true)
		{
			$quote = "";
		}

		foreach($array as $field => $value)
		{
			if(isset($mybb->binary_fields[$table][$field]) && $mybb->binary_fields[$table][$field])
			{
				if($value[0] != 'X') // Not escaped?
				{
					$value = $this->escape_binary($value);
				}
				
				$query .= $comma.$field."=".$value;
			}
			else
			{
				$quoted_value = $this->quote_val($value, $quote);

				$query .= $comma.$field."={$quoted_value}";
			}
			$comma = ', ';
		}

		if(!empty($where))
		{
			$query .= " WHERE $where";
		}

		$query = $this->query("UPDATE {$this->table_prefix}$table SET $query");
		$query->closeCursor();
		return $query;
	}

	/**
	 * @param int|string $value
	 * @param string $quote
	 *
	 * @return int|string
	 */
	private function quote_val($value, $quote="'")
	{
		if(is_int($value))
		{
			$quoted = $value;
		}
		else
		{
			$quoted = $quote . $value . $quote;
		}

		return $quoted;
	}

	/**
	 * Build a delete query.
	 *
	 * @param string $table The table name to perform the query on.
	 * @param string $where An optional where clause for the query.
	 * @param string $limit An optional limit clause for the query.
	 * @return PDOStatement The query data.
	 */
	function delete_query($table, $where="", $limit="")
	{
		$query = "";
		if(!empty($where))
		{
			$query .= " WHERE $where";
		}

		$query = $this->query("DELETE FROM {$this->table_prefix}$table $query");
		$query->closeCursor();
		return $query;
	}

	/**
	 * Escape a string
	 *
	 * @param string $string The string to be escaped.
	 * @return string The escaped string.
	 */
	function escape_string($string)
	{
		$string = $this->db->escape_string($string);
		return $string;
	}

	/**
	 * Serves no purposes except compatibility
	 *
	 * @param PDOStatement $query
	 * @return boolean Returns true on success, false on failure
	 */
	function free_result($query)
	{
		return true;
	}

	/**
	 * Escape a string used within a like command.
	 *
	 * @param string $string The string to be escaped.
	 * @return string The escaped string.
	 */
	function escape_string_like($string)
	{
		return $this->escape_string(str_replace(array('\\', '%', '_') , array('\\\\', '\\%' , '\\_') , $string));
	}

	/**
	 * Gets the current version of SQLLite.
	 *
	 * @return string Version of MySQL.
	 */
	function get_version()
	{
		if($this->version)
		{
			return $this->version;
		}
		$this->version = $this->db->get_attribute("ATTR_SERVER_VERSION");

		return $this->version;
	}

	/**
	 * Optimizes a specific table.
	 *
	 * @param string $table The name of the table to be optimized.
	 */
	function optimize_table($table)
	{
		// SQLite doesn't support table level optimization.
		// Using `VACUUM [main | $db_name]` may also be blocked by any opened query cursor, hence generating an error.
	}

	/**
	 * Analyzes a specific table.
	 *
	 * @param string $table The name of the table to be analyzed.
	 */
	function analyze_table($table)
	{
		$query = $this->query("ANALYZE ".$this->table_prefix.$table."");
		$query->closeCursor();
	}

	/**
	 * Show the "create table" command for a specific table.
	 *
	 * @param string $table The name of the table.
	 * @return string The SQLite command to create the specified table.
	 */
	function show_create_table($table)
	{
		$old_tbl_prefix = $this->table_prefix;
		$this->set_table_prefix("");
		$query = $this->simple_select("sqlite_master", "sql", "type = 'table' AND name = '{$old_tbl_prefix}{$table}' ORDER BY type DESC, name");
		$this->set_table_prefix($old_tbl_prefix);

		$result = $this->fetch_field($query, 'sql');

		$query->closeCursor();

		return $result;
	}

	/**
	 * Show the "show fields from" command for a specific table.
	 *
	 * @param string $table The name of the table.
	 * @return array Field info for that table
	 */
	function show_fields_from($table)
	{
		$query = $this->write_query("PRAGMA TABLE_INFO('".$this->table_prefix.$table."')");
		$field_info = array();
		while($field = $this->fetch_array($query))
		{
			if(!empty($field['pk']))
			{
				$field['_key'] = 'PRI';
				$field['_extra'] = 'auto_increment';
			}
			else
			{
				$field['_key'] = '';
				$field['_extra'] = '';
			}

			// SQLite allows NULLs in most PRIMARY KEY columns due to a bug in early versions, even in an INTEGER PRIMARY KEY column, read https://sqlite.org/lang_createtable.html for details. We won't fix this for consistency among other database engines.
			$field['_nullable'] = $field['notnull'] ? 'NO' : 'YES';

			$field_info[] = array(
				'Field' => $field['name'],
				'Type' => $field['type'],
				'Null' => $field['_nullable'],
				'Key' => $field['_key'],
				'Default' => $field['dflt_value'],
				'Extra' => $field['_extra'],
			);
		}
		$query->closeCursor();
		return $field_info;
	}

	/**
	 * Returns whether or not the table contains a fulltext index.
	 *
	 * @param string $table The name of the table.
	 * @param string $index Optionally specify the name of the index.
	 * @return boolean True or false if the table has a fulltext index or not.
	 */
	function is_fulltext($table, $index="")
	{
		return false;
	}

	/**
	 * Returns whether or not this database engine supports fulltext indexing.
	 *
	 * @param string $table The table to be checked.
	 * @return boolean True or false if supported or not.
	 */

	function supports_fulltext($table)
	{
		return false;
	}

	/**
	 * Returns whether or not this database engine supports boolean fulltext matching.
	 *
	 * @param string $table The table to be checked.
	 * @return boolean True or false if supported or not.
	 */
	function supports_fulltext_boolean($table)
	{
		return false;
	}

	/**
	 * Creates a fulltext index on the specified column in the specified table with optional index name.
	 *
	 * @param string $table The name of the table.
	 * @param string $column Name of the column to be indexed.
	 * @param string $name The index name, optional.
	 * @return bool
	 */
	function create_fulltext_index($table, $column, $name="")
	{
		return false;
	}

	/**
	 * Drop an index with the specified name from the specified table
	 *
	 * @param string $table The name of the table.
	 * @param string $name The name of the index.
	 */
	function drop_index($table, $name)
	{
		$query = $this->query("ALTER TABLE {$this->table_prefix}$table DROP INDEX $name");
		$query->closeCursor();
	}

	/**
	 * Checks to see if an index exists on a specified table
	 *
	 * @param string $table The name of the table.
	 * @param string $index The name of the index.
	 * @return bool Returns whether index exists
	 */
	function index_exists($table, $index)
	{
		return false;
	}

	/**
	 * Drop an table with the specified table
	 *
	 * @param string $table The name of the table.
	 * @param boolean $hard hard drop - no checking
	 * @param boolean $table_prefix use table prefix
	 */
	function drop_table($table, $hard=false, $table_prefix=true)
	{
		if($table_prefix == false)
		{
			$table_prefix = "";
		}
		else
		{
			$table_prefix = $this->table_prefix;
		}

		$table_prefix_bak = $this->table_prefix;
		$this->table_prefix = '';
		if($hard == false)
		{
			if($this->table_exists($table_prefix.$table))
			{
				$query = $this->query('DROP TABLE '.$table_prefix.$table);
			}
		}
		else
		{
			$query = $this->query('DROP TABLE '.$table_prefix.$table);
		}
		$this->table_prefix = $table_prefix_bak;

		if(isset($query))
		{
			$query->closeCursor();
		}
	}

	/**
	 * Renames a table
	 *
	 * @param string $old_table The old table name
	 * @param string $new_table the new table name
	 * @param boolean $table_prefix use table prefix
	 * @return PDOStatement
	 */
	function rename_table($old_table, $new_table, $table_prefix=true)
	{
		if($table_prefix == false)
		{
			$table_prefix = "";
		}
		else
		{
			$table_prefix = $this->table_prefix;
		}

		$query = $this->write_query("ALTER TABLE {$table_prefix}{$old_table} RENAME TO {$table_prefix}{$new_table}");
		$query->closeCursor();
		return $query;
	}

	/**
	 * Replace contents of table with values
	 *
	 * @param string $table The table
	 * @param array $replacements The replacements
	 * @param string|array $default_field The default field(s)
	 * @param boolean $insert_id Whether or not to return an insert id. True by default
	 * @return int|PDOStatement|bool Returns either the insert id (if a new row is inserted), the query resource (if a row is updated) or false on failure
	 */
	function replace_query($table, $replacements=array(), $default_field="", $insert_id=true)
	{
		global $mybb;

		$columns = '';
		$values = '';
		$comma = '';
		foreach($replacements as $column => $value)
		{
			$columns .= $comma.$column;
			if(isset($mybb->binary_fields[$table][$column]) && $mybb->binary_fields[$table][$column])
			{
				if($value[0] != 'X') // Not escaped?
				{
					$value = $this->escape_binary($value);
				}
				
				$values .= $comma.$value;
			}
			else
			{
				$values .= $comma.$this->quote_val($value);
			}

			$comma = ',';
		}

		if(empty($columns) || empty($values))
		{
			 return false;
		}

		if($default_field == "")
		{
			$query = $this->query("REPLACE INTO {$this->table_prefix}{$table} ({$columns}) VALUES({$values})");
			$query->closeCursor();
			return $query;
		}
		else
		{
			$update = false;
			if(is_array($default_field) && !empty($default_field))
			{
				$search_bit = array();
				foreach($default_field as $field)
				{
					$search_bit[] = "{$field} = '".$replacements[$field]."'";
				}

				$search_bit = implode(" AND ", $search_bit);
				$query = $this->write_query("SELECT COUNT(".$default_field[0].") as count FROM {$this->table_prefix}{$table} WHERE {$search_bit} LIMIT 1");
				if($this->fetch_field($query, "count") == 1)
				{
					$update = true;
				}
			}
			else
			{
				$query = $this->write_query("SELECT {$default_field} FROM {$this->table_prefix}{$table}");
				$search_bit = "{$default_field}='".$replacements[$default_field]."'";

				while($column = $this->fetch_array($query))
				{
					if($column[$default_field] == $replacements[$default_field])
					{
						$update = true;
						break;
					}
				}
			}

			if($update === true)
			{
				return $this->update_query($table, $replacements, $search_bit);
			}
			else
			{
				return $this->insert_query($table, $replacements);
			}
		}
	}

	/**
	 * Sets the table prefix used by the simple select, insert, update and delete functions
	 *
	 * @param string $prefix The new table prefix
	 */
	function set_table_prefix($prefix)
	{
		$this->table_prefix = $prefix;
	}

	/**
	 * Fetched the total size of all mysql tables or a specific table
	 *
	 * @param string $table The table (optional) (ignored)
	 * @return integer the total size of all mysql tables or a specific table
	 */
	function fetch_size($table='')
	{
		global $config, $lang;

		$total = @filesize($config['database']['database']);
		if(!$total || $table != '')
		{
			$total = $lang->na;
		}
		return $total;
	}

	/**
	 * Perform an "Alter Table" query in SQLite < 3.2.0 - Code taken from http://code.jenseng.com/db/
	 *
	 * @param string $table The table (optional)
	 * @param string $alterdefs
	 * @param string $fullquery
	 * @return bool True on success, false on failure
	 */
	function alter_table_parse($table, $alterdefs, $fullquery="")
	{
		if(!$fullquery)
		{
			$fullquery = " ... {$alterdefs}";
		}

		if(!defined("TIME_NOW"))
		{
			define("TIME_NOW", time());
		}

		if($alterdefs != '')
		{
			$result = $this->query("SELECT sql,name,type FROM sqlite_master WHERE tbl_name = '{$table}' ORDER BY type DESC");
			if($this->num_rows($result) > 0)
			{
				$row = $this->fetch_array($result); // Table sql
				$result->closeCursor();
				$tmpname = 't'.TIME_NOW;
				$origsql = trim(preg_replace("/[\s]+/", " ", str_replace(",", ", ", preg_replace("/[\(]/","( ", $row['sql'], 1))));
				$createtemptableSQL = 'CREATE TEMPORARY '.substr(trim(preg_replace("'".$table."'", $tmpname, $origsql, 1)), 6);
				$defs = preg_split("/[,]+/", $alterdefs, -1, PREG_SPLIT_NO_EMPTY);
				$prevword = $table;
				$oldcols = preg_split("/[,]+/", substr(trim($createtemptableSQL), strpos(trim($createtemptableSQL), '(')+1), -1, PREG_SPLIT_NO_EMPTY);
				$newcols = array();

				for($i = 0; $i < sizeof($oldcols); $i++)
				{
					$colparts = preg_split("/[\s]+/", $oldcols[$i], -1, PREG_SPLIT_NO_EMPTY);
					$oldcols[$i] = $colparts[0];
					$newcols[$colparts[0]] = $colparts[0];
				}

				$newcolumns = '';
				$oldcolumns = '';
				reset($newcols);

				foreach($newcols as $key => $val)
				{
					$newcolumns .= ($newcolumns ? ', ' : '').$val;
					$oldcolumns .= ($oldcolumns ? ', ' : '').$key;
				}

				$copytotempsql = 'INSERT INTO '.$tmpname.'('.$newcolumns.') SELECT '.$oldcolumns.' FROM '.$table;
				$dropoldsql = 'DROP TABLE '.$table;
				$createtesttableSQL = $createtemptableSQL;

				foreach($defs as $def)
				{
					$defparts = preg_split("/[\s]+/", $def, -1, PREG_SPLIT_NO_EMPTY);
					$action = strtolower($defparts[0]);

					switch($action)
					{
						case 'change':
							if(sizeof($defparts) <= 3)
							{
								$this->error($alterdefs, 'near "'.$defparts[0].($defparts[1] ? ' '.$defparts[1] : '').($defparts[2] ? ' '.$defparts[2] : '').'": syntax error', E_USER_WARNING);
								return false;
							}

							if($severpos = strpos($createtesttableSQL, ' '.$defparts[1].' '))
							{
								if($newcols[$defparts[1]] != $defparts[1])
								{
									$this->error($alterdefs, 'unknown column "'.$defparts[1].'" in "'.$table.'"');
									return false;
								}

								$newcols[$defparts[1]] = $defparts[2];
								$nextcommapos = strpos($createtesttableSQL, ',', $severpos);
								$insertval = '';

								for($i = 2; $i < sizeof($defparts); $i++)
								{
									$insertval .= ' '.$defparts[$i];
								}

								if($nextcommapos)
								{
									$createtesttableSQL = substr($createtesttableSQL, 0, $severpos).$insertval.substr($createtesttableSQL, $nextcommapos);
								}
								else
								{
									$createtesttableSQL = substr($createtesttableSQL, 0, $severpos-(strpos($createtesttableSQL, ',') ? 0 : 1)).$insertval.')';
								}
							}
							else
							{
								$this->error($fullquery, 'unknown column "'.$defparts[1].'" in "'.$table.'"', E_USER_WARNING);
								return false;
							}
							break;
						case 'drop':
							if(sizeof($defparts) < 2)
							{
								$this->error($fullquery, 'near "'.$defparts[0].($defparts[1] ? ' '.$defparts[1] : '').'": syntax error');
								return false;
							}

							if($severpos = strpos($createtesttableSQL, ' '.$defparts[1].' '))
							{
								$nextcommapos = strpos($createtesttableSQL, ',', $severpos);

								if($nextcommapos)
								{
									$createtesttableSQL = substr($createtesttableSQL, 0, $severpos).substr($createtesttableSQL, $nextcommapos + 1);
								}
								else
								{
									$createtesttableSQL = substr($createtesttableSQL, 0, $severpos-(strpos($createtesttableSQL, ',') ? 0 : 1) - 1).')';
								}

								unset($newcols[$defparts[1]]);
							}
							else
							{
								$this->error($fullquery, 'unknown column "'.$defparts[1].'" in "'.$table.'"');
								return false;
							}
							break;
						default:
							$this->error($fullquery, 'near "'.$prevword.'": syntax error');
							return false;
					}

					$prevword = $defparts[sizeof($defparts)-1];
				}

				// This block of code generates a test table simply to verify that the columns specifed are valid in an sql statement
				// This ensures that no reserved words are used as columns, for example
				$this->query($createtesttableSQL);

				$droptempsql = 'DROP TABLE '.$tmpname;
				$query = $this->query($droptempsql, 0);	
				if($query === false)
				{
					return false;
				}
				$query->closeCursor();
				// End block


				$createnewtableSQL = 'CREATE '.substr(trim(preg_replace("'{$tmpname}'", $table, $createtesttableSQL, 1)), 17);
				$newcolumns = '';
				$oldcolumns = '';
				reset($newcols);

				foreach($newcols as $key => $val)
				{
					$newcolumns .= ($newcolumns ? ', ' : '').$val;
					$oldcolumns .= ($oldcolumns ? ', ' : '').$key;
				}

				$copytonewsql = 'INSERT INTO '.$table.'('.$newcolumns.') SELECT '.$oldcolumns.' FROM '.$tmpname;


				$this->query($createtemptableSQL); // Create temp table
				$query = $this->query($copytotempsql); // Copy to table
				$query->closeCursor();
				$query = $this->query($dropoldsql); // Drop old table
				$query->closeCursor();

				$this->query($createnewtableSQL); // Recreate original table
				$query = $this->query($copytonewsql); // Copy back to original table
				$query->closeCursor();
				$query = $this->query($droptempsql); // Drop temp table
				$query->closeCursor();
			}
			else
			{
				$this->error($fullquery, 'no such table: '.$table);
				return false;
			}
		}
		return true;
	}

	/**
	 * Drops a column
	 *
	 * @param string $table The table
	 * @param string $column The column name
	 * @return PDOStatement
	 */
	function drop_column($table, $column)
	{
		return $this->write_query("ALTER TABLE {$this->table_prefix}{$table} DROP {$column}");
	}

	/**
	 * Adds a column
	 *
	 * @param string $table The table
	 * @param string $column The column name
	 * @param string $definition the new column definition
	 * @return PDOStatement
	 */
	function add_column($table, $column, $definition)
	{
		$query = $this->write_query("ALTER TABLE {$this->table_prefix}{$table} ADD {$column} {$definition}");
		$query->closeCursor();
		return $query;
	}

	/**
	 * Modifies a column
	 *
	 * @param string $table The table
	 * @param string $column The column name
	 * @param string $new_definition the new column definition
	 * @param boolean|string $new_not_null Whether to "drop" or "set" the NOT NULL attribute (no change if false)
	 * @param boolean|string $new_default_value The new default value, or false to drop the attribute
	 * @return bool Returns true if all queries are executed successfully or false if one of them failed
	 */
	function modify_column($table, $column, $new_definition, $new_not_null=false, $new_default_value=false)
	{
		// We use a rename query as both need to duplicate the table etc...
		return $this->rename_column($table, $column, $column, $new_definition, $new_not_null, $new_default_value);
	}

	/**
	 * Renames a column
	 *
	 * @param string $table The table
	 * @param string $old_column The old column name
	 * @param string $new_column the new column name
	 * @param string $new_definition the new column definition
	 * @param boolean|string $new_not_null Whether to "drop" or "set" the NOT NULL attribute (no change if false)
	 * @param boolean|string $new_default_value The new default value, or false to drop the attribute
	 * @return bool Returns true if all queries are executed successfully
	 */
	function rename_column($table, $old_column, $new_column, $new_definition, $new_not_null=false, $new_default_value=false)
	{
		if($new_not_null !== false)
		{
			if(strtolower($new_not_null) == "set")
			{
				$not_null = "NOT NULL";
			}
			else
			{
				$not_null = "NULL";
			}
		}
		else
		{
			$not_null = '';
		}

		if($new_default_value !== false)
		{
			$default = "DEFAULT ".$new_default_value;
		}
		else
		{
			$default = '';
		}

		// This will trigger the "alter_table_parse" function which will copy the table and rename the column
		return (bool) $this->write_query("ALTER TABLE {$this->table_prefix}{$table} CHANGE {$old_column} {$new_column} {$new_definition} {$not_null} {$default}");
	}

	/**
	 * Fetch a list of database character sets this DBMS supports
	 *
	 * @return array|bool Array of supported character sets with array key being the name, array value being display name. False if unsupported
	 */
	function fetch_db_charsets()
	{
		return false;
	}

	/**
	 * Fetch a database collation for a particular database character set
	 *
	 * @param string $charset The database character set
	 * @return string|bool The matching database collation, false if unsupported
	 */
	function fetch_charset_collation($charset)
	{
		return false;
	}

	/**
	 * Fetch a character set/collation string for use with CREATE TABLE statements. Uses current DB encoding
	 *
	 * @return string The built string, empty if unsupported
	 */
	function build_create_table_collation()
	{
		return '';
	}

	/**
	 * Time how long it takes for a particular piece of code to run. Place calls above & below the block of code.
	 *
	 * @deprecated
	 */
	function get_execution_time()
	{
		return get_execution_time();
	}

	/**
	 * Binary database fields require special attention.
	 *
	 * @param string $string Binary value
	 * @return string Encoded binary value
	 */
	function escape_binary($string)
	{
		return "X'".$this->escape_string(bin2hex($string))."'";
	}

	/**
	 * Unescape binary data.
	 *
	 * @param string $string Binary value
	 * @return string Encoded binary value
	 */
	function unescape_binary($string)
	{
		// Nothing to do
		return $string;
	}
}

