<?php

namespace SilverStripe\Dev\Install;

use mysqli;
use PDO;
use Exception;
use mysqli_result;

/**
 * This is a helper class for the SS installer.
 *
 * It does all the specific checking for MySQLDatabase
 * to ensure that the configuration is setup correctly.
 */
class MySQLDatabaseConfigurationHelper implements DatabaseConfigurationHelper
{

    /**
     * Create a connection of the appropriate type
     *
     * @skipUpgrade
     * @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 'MySQLDatabase':
                    $conn = @new MySQLi(
                        $databaseConfig['server'],
                        $databaseConfig['username'],
                        $databaseConfig['password']
                    );
                    if ($conn && empty($conn->connect_errno)) {
                        $conn->query("SET sql_mode = 'ANSI'");
                        return $conn;
                    } else {
                        $error = ($conn->connect_errno)
                            ? $conn->connect_error
                            : 'Unknown connection error';
                        return null;
                    }
                case 'MySQLPDODatabase':
                    // May throw a PDOException if fails
                    $conn = @new PDO(
                        'mysql:host='.$databaseConfig['server'],
                        $databaseConfig['username'],
                        $databaseConfig['password']
                    );
                    if ($conn) {
                        $conn->query("SET sql_mode = 'ANSI'");
                        return $conn;
                    } else {
                        $error = 'Unknown connection error';
                        return null;
                    }
                default:
                    $error = 'Invalid connection type: ' . $databaseConfig['type'];
                    return null;
            }
        } catch (Exception $ex) {
            $error = $ex->getMessage();
            return null;
        }
    }

    /**
     * Helper function to quickly extract a column from a mysqi_result
     *
     * @param mixed $results mysqli_result or enumerable list of rows
     * @return array Resulting data
     */
    protected function column($results)
    {
        $array = array();
        if ($results instanceof mysqli_result) {
            while ($row = $results->fetch_array()) {
                $array[] = $row[0];
            }
        } else {
            foreach ($results as $row) {
                $array[] = $row[0];
            }
        }
        return $array;
    }

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

    public function requireDatabaseServer($databaseConfig)
    {
        $connection = $this->createConnection($databaseConfig, $error);
        $success = !empty($connection);

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

    public function getDatabaseVersion($databaseConfig)
    {
        $conn = $this->createConnection($databaseConfig, $error);
        if (!$conn) {
            return false;
        } elseif ($conn instanceof mysqli) {
            return $conn->server_info;
        } elseif ($conn instanceof PDO) {
            return $conn->getAttribute(PDO::ATTR_SERVER_VERSION);
        }
        return false;
    }

    /**
     * Ensure that the MySQL server version is at least 5.0.
     *
     * @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)
    {
        $version = $this->getDatabaseVersion($databaseConfig);
        $success = false;
        $error = '';
        if ($version) {
            $success = version_compare($version, '5.0', '>=');
            if (!$success) {
                $error = "Your MySQL server version is $version. It's recommended you use at least MySQL 5.0.";
            }
        } else {
            $error = "Could not determine your MySQL version.";
        }
        return array(
            'success' => $success,
            'error' => $error
        );
    }

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

        // Check database name only uses valid characters
        if ($success && !$this->checkValidDatabaseName($databaseConfig['database'])) {
            $success = false;
            $error = 'Invalid characters in database name.';
        }

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

    /**
     * Determines if a given database name is a valid Silverstripe name.
     *
     * @param string $database Candidate database name
     * @return boolean
     */
    public function checkValidDatabaseName($database)
    {

        // Reject filename unsafe characters (cross platform)
        if (preg_match('/[\\\\\/\?%\*\:\|"\<\>\.]+/', $database)) {
            return false;
        }

        // Restricted to characters in the ASCII and Extended ASCII range
        // @see http://dev.mysql.com/doc/refman/5.0/en/identifiers.html
        return preg_match('/^[\x{0001}-\x{FFFF}]+$/u', $database);
    }

    /**
     * Checks if a specified grant proves that the current user has the specified
     * permission on the specified database
     *
     * @param string $database Database name
     * @param string $permission Permission to check for
     * @param string $grant MySQL syntax grant to check within
     * @return boolean
     */
    public function checkDatabasePermissionGrant($database, $permission, $grant)
    {
        // Filter out invalid database names
        if (!$this->checkValidDatabaseName($database)) {
            return false;
        }

        // Escape all valid database patterns (permission must exist on all tables)
        $sqlDatabase = addcslashes($database, '_%'); // See http://dev.mysql.com/doc/refman/5.7/en/string-literals.html
        $dbPattern = sprintf(
            '((%s)|(%s)|(%s)|(%s))',
            preg_quote("\"$sqlDatabase\".*"), // Regexp escape sql-escaped db identifier
            preg_quote("\"$database\".*"),
            preg_quote('"%".*'),
            preg_quote('*.*')
        );
        $expression = '/GRANT[ ,\w]+((ALL PRIVILEGES)|('.$permission.'(?! ((VIEW)|(ROUTINE)))))[ ,\w]+ON '.
            $dbPattern.'/i';
        return preg_match($expression, $grant);
    }

    /**
     * Checks if the current user has the specified permission on the specified database
     *
     * @param mixed $conn Connection object
     * @param string $database Database name
     * @param string $permission Permission to check
     * @return boolean
     */
    public function checkDatabasePermission($conn, $database, $permission)
    {
        $grants = $this->column($conn->query("SHOW GRANTS FOR CURRENT_USER"));
        foreach ($grants as $grant) {
            if ($this->checkDatabasePermissionGrant($database, $permission, $grant)) {
                return true;
            }
        }
        return false;
    }

    public function requireDatabaseOrCreatePermissions($databaseConfig)
    {
        $success = false;
        $alreadyExists = false;
        $conn = $this->createConnection($databaseConfig, $error);
        if ($conn) {
            $list = $this->column($conn->query("SHOW DATABASES"));
            if (in_array($databaseConfig['database'], $list)) {
                $success = true;
                $alreadyExists = true;
            } else {
                // If no database exists then check DDL permissions
                $alreadyExists = false;
                $success = $this->checkDatabasePermission($conn, $databaseConfig['database'], 'CREATE');
            }
        }

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

    public function requireDatabaseAlterPermissions($databaseConfig)
    {
        $conn = $this->createConnection($databaseConfig, $error);
        $success = $this->checkDatabasePermission($conn, $databaseConfig['database'], 'ALTER');
        return array(
            'success' => $success,
            'applies' => true
        );
    }
}