<?php


namespace ComboStrap;

/**
 * Class Event
 * @package ComboStrap
 * Asynchronous pub/sub system
 *
 * Dokuwiki allows event but they are synchronous
 * because php does not live in multiple thread
 *
 * With the help of Sqlite, we make them asynchronous
 */
class Event
{

    const EVENT_TABLE_NAME = "EVENTS_QUEUE";

    const CANONICAL = "support";
    const EVENT_NAME_ATTRIBUTE = "name";
    const EVENT_DATA_ATTRIBUTE = "data";

    /**
     * process all replication request, created with {@link Event::createEvent()}
     *
     * by default, there is 5 pages in a default dokuwiki installation in the wiki namespace)
     */
    public static function dispatchEvent($maxEvent = 10)
    {

        $sqlite = Sqlite::createOrGetBackendSqlite();
        if ($sqlite === null) {
            LogUtility::msg("Sqlite is mandatory for asynchronous event");
            return;
        }

        /**
         * In case of a start or if there is a recursive bug
         * We don't want to take all the resources
         */
        $maxBackgroundEventLow = 10;

        $version = $sqlite->getVersion();
        $rows = [];
        if ($version > "3.35.0") {

            // returning clause is available since 3.35 on delete
            // https://www.sqlite.org/lang_returning.html

            $eventTableName = self::EVENT_TABLE_NAME;
            $statement = "delete from {$eventTableName} returning *";
            // https://www.sqlite.org/lang_delete.html#optional_limit_and_order_by_clauses
            if ($sqlite->hasOption("SQLITE_ENABLE_UPDATE_DELETE_LIMIT")) {
                $statement .= "order by timestamp limit {$maxBackgroundEventLow}";
            }
            $request = $sqlite->createRequest()
                ->setStatement($statement);
            try {
                $rows = $request->execute()
                    ->getRows();
                if (sizeof($rows) === 0) {
                    return;
                }
            } catch (ExceptionCombo $e) {
                LogUtility::msg($e->getMessage(), LogUtility::LVL_MSG_ERROR, $e->getCanonical());
            } finally {
                $request->close();
            }

        }

        /**
         * Error in the block before or not the good version
         * We try to get the records with a select/delete
         */
        if (sizeof($rows) === 0) {


            // technically the lock system of dokuwiki does not allow two process to run on
            // the indexer, we trust it
            $attributes = [self::EVENT_NAME_ATTRIBUTE, self::EVENT_DATA_ATTRIBUTE, DatabasePageRow::ROWID];
            $select = Sqlite::createSelectFromTableAndColumns(self::EVENT_TABLE_NAME, $attributes);
            $request = $sqlite->createRequest()
                ->setQuery($select);

            $rowsSelected = [];
            try {
                $rowsSelected = $request->execute()
                    ->getRows();
                if (sizeof($rowsSelected) === 0) {
                    return;
                }
            } catch (ExceptionCombo $e) {
                LogUtility::msg("Error while retrieving the event {$e->getMessage()}", LogUtility::LVL_MSG_ERROR, $e->getCanonical());
                return;
            } finally {
                $request->close();
            }

            $eventTableName = self::EVENT_TABLE_NAME;
            $rows = [];
            foreach ($rowsSelected as $row) {
                $request = $sqlite->createRequest()
                    ->setQueryParametrized("delete from $eventTableName where rowid = ? ", [$row[DatabasePageRow::ROWID]]);
                try {
                    $changeCount = $request->execute()
                        ->getChangeCount();
                    if ($changeCount !== 1) {
                        LogUtility::msg("The delete of the event was not successful or it was deleted by another process", LogUtility::LVL_MSG_ERROR);
                    } else {
                        $rows[] = $row;
                    }
                } catch (ExceptionCombo $e) {
                    LogUtility::msg("Error while deleting the event. Message {$e->getMessage()}", LogUtility::LVL_MSG_ERROR, $e->getCanonical());
                    return;
                } finally {
                    $request->close();
                }
            }


        }


        $eventCounter = 0;
        foreach ($rows as $row) {
            $eventCounter++;
            $eventName = $row[self::EVENT_NAME_ATTRIBUTE];
            $eventData = [];
            $eventDataJson = $row[self::EVENT_DATA_ATTRIBUTE];
            if ($eventDataJson !== null) {
                try {
                    $eventData = Json::createFromString($eventDataJson)->toArray();
                } catch (ExceptionCombo $e) {
                    LogUtility::msg("The stored data for the event $eventName was not in the json format");
                    continue;
                }
            }
            \dokuwiki\Extension\Event::createAndTrigger($eventName, $eventData);

            if ($eventCounter >= $maxEvent) {
                break;
            }

        }

    }

    /**
     * Ask a replication in the background
     * @param string $name - a string with the reason
     * @param array $data
     */
    public static
    function createEvent(string $name, array $data)
    {

        $sqlite = Sqlite::createOrGetBackendSqlite();
        if ($sqlite === null) {
            LogUtility::msg("Unable to create the event $name. Sqlite is not available");
            return;
        }


        /**
         * If not present
         */
        $entry = array(
            "name" => $name,
            "timestamp" => Iso8601Date::createFromNow()->toString()
        );

        if ($data !== null) {
            $entry["data"] = Json::createFromArray($data)->toPrettyJsonString();
        }

        /**
         * Execute
         */
        $request = $sqlite->createRequest()
            ->setTableRow(self::EVENT_TABLE_NAME, $entry);
        try {
            $request->execute();
        } catch (ExceptionCombo $e) {
            LogUtility::msg("Unable to create the event $name. Error:" . $e->getMessage(), LogUtility::LVL_MSG_ERROR, $e->getCanonical());
        } finally {
            $request->close();
        }


    }

    /**
     * @param $pageId
     *
     * This is equivalent to {@link TaskRunner}
     *
     * lib/exe/taskrunner.php?id='.rawurlencode($ID)
     * $taskRunner = new \dokuwiki\TaskRunner();
     * $taskRunner->run();
     *
     */
    public static function startTaskRunnerForPage($pageId)
    {
        $tmp = []; // No event data
        $tmp['page'] = $pageId;
        $evt = new \dokuwiki\Extension\Event('INDEXER_TASKS_RUN', $tmp);
        $evt->advise_after();
    }

    public static function getQueueSize()
    {
        $sqlite = Sqlite::createOrGetBackendSqlite();
        if ($sqlite === null) {
            LogUtility::msg("Unable to count the number of event in the queue. Sqlite is not available");
            return;
        }


        /**
         * Execute
         */
        $request = $sqlite->createRequest()
            ->setQuery("select count(1) from " . self::EVENT_TABLE_NAME);
        $count = 0;
        try {
            $count = $request->execute()
                ->getFirstCellValueAsInt();
        } catch (ExceptionCombo $e) {
            LogUtility::msg("Unable to count the number of event in the queue. Error:" . $e->getMessage(), LogUtility::LVL_MSG_ERROR, $e->getCanonical());
        } finally {
            $request->close();
        }
        return $count;
    }


}