<?php

namespace SilverStripe\PostgreSQL;

use DatabaseConfigurationHelper;
use PDO;
use Exception;
use DatabaseAdapterRegistry;

/**
 * This is a helper class for the SS installer.
 *
 * It does all the specific checking for PostgreSQLDatabase
 * to ensure that the configuration is setup correctly.
 *
 * @package postgresql
 */
class PostgreSQLDatabaseConfigurationHelper implements DatabaseConfigurationHelper
{
    /**
     * 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;
        $username = empty($databaseConfig['username']) ? '' : $databaseConfig['username'];
        $password = empty($databaseConfig['password']) ? '' : $databaseConfig['password'];
        $server = $databaseConfig['server'];

        try {
            switch ($databaseConfig['type']) {
                case 'PostgreSQLDatabase':
                    $userPart = $username ? " user=$username" : '';
                    $passwordPart = $password ? " password=$password" : '';
                    $connstring = "host=$server port=5432 dbname=postgres{$userPart}{$passwordPart}";
                    $conn = pg_connect($connstring);
                    break;
                case 'PostgrePDODatabase':
                    // May throw a PDOException if fails
                    $conn = @new PDO('postgresql:host='.$server.';dbname=postgres;port=5432', $username, $password);
                    break;
                default:
                    $error = 'Invalid connection type';
                    return null;
            }
        } catch (Exception $ex) {
            $error = $ex->getMessage();
            return null;
        }
        if ($conn) {
            return $conn;
        } else {
            $error = 'PostgreSQL requires a valid username and password to determine if the server exists.';
            return null;
        }
    }

    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, $error);
        if (!$conn) {
            return false;
        } elseif ($conn instanceof PDO) {
            return $conn->getAttribute(PDO::ATTR_SERVER_VERSION);
        } elseif (is_resource($conn)) {
            $info = pg_version($conn);
            return $info['server'];
        } else {
            return false;
        }
    }

    /**
     * Ensure that the PostgreSQL version is at least 8.3.
     *
     * @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, '8.3', '>=');
            if (!$success) {
                $error = "Your PostgreSQL version is $version. It's recommended you use at least 8.3.";
            }
        } else {
            $error = "Your PostgreSQL version could not be determined.";
        }

        return array(
            'success' => $success,
            'error' => $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) {
            foreach ($conn->query($sql) as $row) {
                $items[] = $row[0];
            }
        } elseif (is_resource($conn)) {
            $result =  pg_query($conn, $sql);
            while ($row = pg_fetch_row($result)) {
                $items[] = $row[0];
            }
        }
        return $items;
    }

    public function requireDatabaseOrCreatePermissions($databaseConfig)
    {
        $success = false;
        $alreadyExists = false;
        $conn = $this->createConnection($databaseConfig, $error);
        if ($conn) {
            // Check if db already exists
            $existingDatabases = $this->query($conn, "SELECT datname FROM pg_database");
            $alreadyExists = in_array($databaseConfig['database'], $existingDatabases);
            if ($alreadyExists) {
                $success = true;
            } else {
                // Check if this user has create privileges
                $allowedUsers = $this->query($conn, "select rolname from pg_authid where rolcreatedb = true;");
                $success = in_array($databaseConfig['username'], $allowedUsers);
            }
        }

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

    public function requireDatabaseAlterPermissions($databaseConfig)
    {
        $conn = $this->createConnection($databaseConfig, $error);
        if ($conn) {
            // if the account can even log in, it can alter tables
            return array(
                'success' => true,
                'applies' => true
            );
        }
        return array(
            'success' => false,
            'applies' => true
        );
    }
}