<?php

/**
 * Database connector driver for sqlsrv_ library
 * 
 * @package mssql
 */
class SQLServerConnector extends DBConnector {
	
	/**
	 * Connection to the DBMS.
	 * 
	 * @var resource
	 */
	protected $dbConn = null;

	/**
	 * Stores the affected rows of the last query.
	 * Used by sqlsrv functions only, as sqlsrv_rows_affected
	 * accepts a result instead of a database handle.
	 * 
	 * @var integer
	 */
	protected $lastAffectedRows;
	
	/**
	 * Name of the currently selected database
	 *
	 * @var string
	 */
	protected $selectedDatabase = null;

	public function connect($parameters, $selectDB = false) {
		// Disable default warnings as errors behaviour for sqlsrv to keep it in line with mssql functions
		if(ini_get('sqlsrv.WarningsReturnAsErrors')) {
			ini_set('sqlsrv.WarningsReturnAsErrors', 'Off');
		}

		$charset = isset($parameters['charset']) ? $parameters : 'UTF-8';
		$multiResultSets = isset($parameters['multipleactiveresultsets'])
				? $parameters['multipleactiveresultsets']
				: true;
		$options = array(
			'CharacterSet' => $charset,
			'MultipleActiveResultSets' => $multiResultSets
		);
		
		if( !(defined('MSSQL_USE_WINDOWS_AUTHENTICATION') && MSSQL_USE_WINDOWS_AUTHENTICATION == true)
			&& empty($parameters['windowsauthentication'])
		) {
			$options['UID'] = $parameters['username'];
			$options['PWD'] = $parameters['password'];
		}
		
		// Required by MS Azure database
		if($selectDB && !empty($parameters['database'])) {
			$options['Database'] = $parameters['database'];
		}

		$this->dbConn = sqlsrv_connect($parameters['server'], $options);
		
		if(empty($this->dbConn)) {
			$this->databaseError("Couldn't connect to SQL Server database");
		} elseif($selectDB && !empty($parameters['database'])) {
			// Check selected database (Azure)
			$this->selectedDatabase = $parameters['database'];
		}
	}
	
	/**
	 * Start transaction. READ ONLY not supported.
	 */
	public function transactionStart(){
		$result = sqlsrv_begin_transaction($this->dbConn);
		if (!$result) {
			$this->databaseError("Couldn't start the transaction.");
		}
	}
	
	/**
	 * Commit everything inside this transaction so far
	 */
	public function transactionEnd() {
		$result = sqlsrv_commit($this->dbConn);
		if (!$result) {
			$this->databaseError("Couldn't commit the transaction.");
		}
	}
	
	/**
	 * Rollback or revert to a savepoint if your queries encounter problems
	 * If you encounter a problem at any point during a transaction, you may
	 * need to rollback that particular query, or return to a savepoint
	 */
	public function transactionRollback(){
		$result = sqlsrv_rollback($this->dbConn);
		if (!$result) {
			$this->databaseError("Couldn't rollback the transaction.");
		}
	}

	public function affectedRows() {
		return $this->lastAffectedRows;
	}
	
	public function getLastError() {
		$errorMessages = array();
		$errors = sqlsrv_errors();
		if($errors) foreach($errors as $info) {
			$errorMessages[] = implode(', ', array($info['SQLSTATE'], $info['code'], $info['message']));
		}
		return implode('; ', $errorMessages);
	}

	public function isActive() {
		return $this->dbConn && $this->selectedDatabase;
	}

	public function preparedQuery($sql, $parameters, $errorLevel = E_USER_ERROR) {
		// Check if we should only preview this query
		if ($this->previewWrite($sql)) return;
		
		$parsedParameters = $this->parameterValues($parameters);
		
		// Benchmark query
		$dbConn = $this->dbConn;
		$handle = $this->benchmarkQuery($sql, function($sql) use($dbConn, $parsedParameters) {
			if(empty($parsedParameters)) {
				return sqlsrv_query($dbConn, $sql);
			} else {
				return sqlsrv_query($dbConn, $sql, $parsedParameters);
			}
		});
		
		if($handle) {
			$this->lastAffectedRows = sqlsrv_rows_affected($handle);
		} else {
			$this->databaseError($this->getLastError(), $errorLevel, $sql, $parsedParameters);
			return null;
		}
		
		return new SQLServerQuery($this, $handle);
	}

	public function query($sql, $errorLevel = E_USER_ERROR) {
		return $this->preparedQuery($sql, array(), $errorLevel);
	}

	public function selectDatabase($name) {
		$this->query("USE \"$name\"");
		$this->selectedDatabase = $name;
		return true;
	}

	public function __destruct() {
		if(is_resource($this->dbConn)) {
			sqlsrv_close($this->dbConn);
		}
	}

	public function getVersion() {
		// @todo - use sqlsrv_server_info?
		return trim($this->query("SELECT CONVERT(char(15), SERVERPROPERTY('ProductVersion'))")->value());
	}

	public function getGeneratedID($table) {
		return $this->query("SELECT IDENT_CURRENT('$table')")->value();
	}

	public function getSelectedDatabase() {
		return $this->selectedDatabase;
	}

	public function unloadDatabase() {
		$this->selectDatabase('Master');
		$this->selectedDatabase = null;
	}
	
	/**
	 * Quotes a string, including the "N" prefix so unicode
	 * strings are saved to the database correctly.
	 *
	 * @param string $string String to be encoded
	 * @return string Processed string ready for DB
	 */
	public function quoteString($value) {
		return "N'" . $this->escapeString($value) . "'";
	}	
	
	public function escapeString($value) {
		$value = str_replace("'", "''", $value);
		$value = str_replace("\0", "[NULL]", $value);
		return $value;
	}
}