<?php

/**
 * This is a helper class for the SS installer.
 * 
 * It does all the specific checking for MSSQLDatabase
 * to ensure that the configuration is setup correctly.
 * 
 * @package mssql
 */
class MSSQLDatabaseConfigurationHelper implements DatabaseConfigurationHelper {
	
	protected function isAzure($databaseConfig) {
		return $databaseConfig['type'] === 'MSSQLAzureDatabase';
	}
	
	/**
	 * Create a connection of the appropriate type
	 * 
	 * @param array $databaseConfig
	 * @param string $error Error message passed by value
	 * @return mixed|null Either the connection object, or null if error
	 */
	protected function createConnection($databaseConfig, &$error) {
		$error = null;
		try {
			switch($databaseConfig['type']) {
				case 'MSSQLDatabase':
				case 'MSSQLAzureDatabase':
					$parameters = array(
						'UID' => $databaseConfig['username'], 
						'PWD' => $databaseConfig['password']
					);
					
					// Azure has additional parameter requirements
					if($this->isAzure($databaseConfig)) {
						$parameters['database'] = $databaseConfig['database'];
						$parameters['multipleactiveresultsets'] = 0;
					}
					$conn = @sqlsrv_connect($databaseConfig['server'], $parameters);
					if($conn) return $conn;
					
					// Get error
					if($errors = sqlsrv_errors()) {
						$error = '';
						foreach($errors as $detail) {
							$error .= "{$detail['message']}\n";
						}
					} else {
						$error = 'Unknown connection error';
					}
					return null;
				case 'MSSQLPDODatabase':
					// May throw a PDOException if fails
					$conn = @new PDO('sqlsrv:Server='.$databaseConfig['server'], $databaseConfig['username'], $databaseConfig['password']);
					if($conn) {
						return $conn;
					} else {
						$error = 'Unknown connection error';
						return null;
					}
				default:
					$error = 'Invalid connection type';
					return null;
			}
		} catch(Exception $ex) {
			$error = $ex->getMessage();
			return null;
		}
	}
	
	/**
	 * Helper function to quote a string value
	 * 
	 * @param mixed $conn Connection object/resource
	 * @param string $value Value to quote
	 * @return string Quoted strieng
	 */
	protected function quote($conn, $value) {
		if($conn instanceof PDO) {
			return $conn->quote($value);
		} elseif(is_resource($conn)) {
			$value = str_replace("'", "''", $value);
			$value = str_replace("\0", "[NULL]", $value);
			return "N'$value'";
		} else {
			user_error('Invalid database connection', E_USER_ERROR);
		}
	}
	
	/**
	 * Helper function to execute a query
	 * 
	 * @param mixed $conn Connection object/resource
	 * @param string $sql SQL string to execute
	 * @return array List of first value from each resulting row
	 */
	protected function query($conn, $sql) {
		$items = array();
		if($conn instanceof PDO) {
			$result = $conn->query($sql);
			if($result) foreach($result as $row) {
				$items[] = $row[0];
			}
		} elseif(is_resource($conn)) {
			$result = sqlsrv_query($conn, $sql);
			if($result) while ($row = sqlsrv_fetch_array($result, SQLSRV_FETCH_NUMERIC)) {
				$items[] = $row[0];
			}
		}
		return $items;
	}

	public function requireDatabaseFunctions($databaseConfig) {
		$data = DatabaseAdapterRegistry::get_adapter($databaseConfig['type']);
		return !empty($data['supported']);
	}

	public function requireDatabaseServer($databaseConfig) {
		$conn = $this->createConnection($databaseConfig, $error);
		$success = !empty($conn);
		
		return array(
			'success' => $success,
			'error' => $error
		);
	}

	public function requireDatabaseConnection($databaseConfig) {
		$conn = $this->createConnection($databaseConfig, $error);
		$success = !empty($conn);
		
		return array(
			'success' => $success,
			'connection' => $conn,
			'error' => $error
		);
	}

	public function getDatabaseVersion($databaseConfig) {
		$conn = $this->createConnection($databaseConfig, $error);
		$result = $this->query($conn, "SELECT CONVERT(char(15), SERVERPROPERTY('ProductVersion'))");
		return empty($result) ? 0 : reset($result);
	}

	/**
	 * Ensure that the SQL Server version is at least 10.00.2531 (SQL Server 2008 SP1).
	 * 
	 * @see http://www.sqlteam.com/article/sql-server-versions
	 * @param array $databaseConfig Associative array of db configuration, e.g. "server", "username" etc
	 * @return array Result - e.g. array('success' => true, 'error' => 'details of error')
	 */
	public function requireDatabaseVersion($databaseConfig) {
		$success = false;
		$error = '';
		$version = $this->getDatabaseVersion($databaseConfig);

		if($version) {
			$success = version_compare($version, '10.00.2531', '>=');
			if(!$success) {
				$error = "Your SQL Server version is $version. It's recommended you use at least 10.00.2531 (SQL Server 2008 SP1).";
			}
		} else {
			$error = "Your SQL Server version could not be determined.";
		}

		return array(
			'success' => $success,
			'error' => $error
		);
	}

	public function requireDatabaseOrCreatePermissions($databaseConfig) {
		$conn = $this->createConnection($databaseConfig, $error);
		if(empty($conn)) {
			$success = false;
			$alreadyExists = false;
		} elseif($databaseConfig['type'] == 'MSSQLAzureDatabase') {
			// Don't bother with DB selection for azure, as it's not supported
			$success = true;
			$alreadyExists = true;
		} else {
			// does this database exist already?
			$list = $this->query($conn, 'SELECT NAME FROM sys.sysdatabases');
			if(in_array($databaseConfig['database'], $list)) {
				$success = true;
				$alreadyExists = true;
			} else {
				$permissions = $this->query($conn, "select COUNT(*) from sys.fn_my_permissions('','') where permission_name like 'CREATE ANY DATABASE' or permission_name like 'CREATE DATABASE';");
				$success = $permissions[0] > 0;
				$alreadyExists = false;
			}
		}

		return array(
			'success' => $success,
			'alreadyExists' => $alreadyExists
		);
	}

	public function requireDatabaseAlterPermissions($databaseConfig) {
		$success = false;
		$conn = $this->createConnection($databaseConfig, $error);
		if(!empty($conn)) {
			if(!$this->isAzure($databaseConfig)) {
				// Make sure to select the current database when checking permission against this database
				$this->query($conn, "USE \"{$databaseConfig['database']}\"");
			}
			$permissions = $this->query($conn, "select COUNT(*) from sys.fn_my_permissions(NULL,'DATABASE') WHERE permission_name like 'create table';");
			$success = $permissions[0] > 0;
		}
		
		return array(
			'success' => $success,
			'applies' => true
		);
	}
}