<?php
/**
 * Piwik - free/libre analytics platform
 *
 * @link http://piwik.org
 * @license http://www.gnu.org/licenses/gpl-3.0.html GPL v3 or later
 *
 */
namespace Piwik\Plugins\PrivacyManager;

use Piwik\Common;
use Piwik\Date;
use Piwik\Db;
use Piwik\Log;
use Piwik\Piwik;

/**
 * Purges the log_visit, log_conversion and related tables of old visit data.
 */
class LogDataPurger
{
    const TEMP_TABLE_NAME = 'tmp_log_actions_to_keep';

    /**
     * The max set of rows each table scan select should query at one time.
     */
    public static $selectSegmentSize = 100000;

    /**
     * The number of days after which log entries are considered old.
     */
    private $deleteLogsOlderThan;

    /**
     * The number of rows to delete per DELETE query.
     */
    private $maxRowsToDeletePerQuery;

    /**
     * Constructor.
     *
     * @param int $deleteLogsOlderThan The number of days after which log entires are considered old.
     *                                 Visits and related data whose age is greater than this number
     *                                 will be purged.
     * @param int $maxRowsToDeletePerQuery The maximum number of rows to delete in one query. Used to
     *                                     make sure log tables aren't locked for too long.
     */
    public function __construct($deleteLogsOlderThan, $maxRowsToDeletePerQuery)
    {
        $this->deleteLogsOlderThan = $deleteLogsOlderThan;
        $this->maxRowsToDeletePerQuery = $maxRowsToDeletePerQuery;
    }

    /**
     * Purges old data from the following tables:
     * - log_visit
     * - log_link_visit_action
     * - log_conversion
     * - log_conversion_item
     * - log_action
     */
    public function purgeData()
    {
        $maxIdVisit = $this->getDeleteIdVisitOffset();

        // break if no ID was found (nothing to delete for given period)
        if (empty($maxIdVisit)) {
            return;
        }

        $logTables = self::getDeleteTableLogTables();

        // delete data from log tables
        $where = "WHERE idvisit <= ?";
        foreach ($logTables as $logTable) {
            // deleting from log_action must be handled differently, so we do it later
            if ($logTable != Common::prefixTable('log_action')) {
                Db::deleteAllRows($logTable, $where, "idvisit ASC", $this->maxRowsToDeletePerQuery, array($maxIdVisit));
            }
        }

        // delete unused actions from the log_action table (but only if we can lock tables)
        if (Db::isLockPrivilegeGranted()) {
            $this->purgeUnusedLogActions();
        } else {
            $logMessage = get_class($this) . ": LOCK TABLES privilege not granted; skipping unused actions purge";
            Log::warning($logMessage);
        }

        // optimize table overhead after deletion
        Db::optimizeTables($logTables);
    }

    /**
     * Returns an array describing what data would be purged if purging were invoked.
     *
     * This function returns an array that maps table names with the number of rows
     * that will be deleted.
     *
     * @return array
     */
    public function getPurgeEstimate()
    {
        $result = array();

        // deal w/ log tables that will be purged
        $maxIdVisit = $this->getDeleteIdVisitOffset();
        if (!empty($maxIdVisit)) {
            foreach ($this->getDeleteTableLogTables() as $table) {
                // getting an estimate for log_action is not supported since it can take too long
                if ($table != Common::prefixTable('log_action')) {
                    $rowCount = $this->getLogTableDeleteCount($table, $maxIdVisit);
                    if ($rowCount > 0) {
                        $result[$table] = $rowCount;
                    }
                }
            }
        }

        return $result;
    }

    /**
     * Safely delete all unused log_action rows.
     */
    private function purgeUnusedLogActions()
    {
        $this->createTempTable();

        // get current max ID in log tables w/ idaction references.
        $maxIds = $this->getMaxIdsInLogTables();

        // do large insert (inserting everything before maxIds) w/o locking tables...
        $this->insertActionsToKeep($maxIds, $deleteOlderThanMax = true);

        // ... then do small insert w/ locked tables to minimize the amount of time tables are locked.
        $this->lockLogTables();
        $this->insertActionsToKeep($maxIds, $deleteOlderThanMax = false);

        // delete before unlocking tables so there's no chance a new log row that references an
        // unused action will be inserted.
        $this->deleteUnusedActions();
        Db::unlockAllTables();
    }

    /**
     * get highest idVisit to delete rows from
     * @return string
     */
    private function getDeleteIdVisitOffset()
    {
        $logVisit = Common::prefixTable("log_visit");

        // get max idvisit
        $maxIdVisit = Db::fetchOne("SELECT MAX(idvisit) FROM $logVisit");
        if (empty($maxIdVisit)) {
            return false;
        }

        // select highest idvisit to delete from
        $dateStart = Date::factory("today")->subDay($this->deleteLogsOlderThan);
        $sql = "SELECT idvisit
		          FROM $logVisit
		         WHERE '" . $dateStart->toString('Y-m-d H:i:s') . "' > visit_last_action_time
		           AND idvisit <= ?
		           AND idvisit > ?
		      ORDER BY idvisit DESC
		         LIMIT 1";

        return Db::segmentedFetchFirst($sql, $maxIdVisit, 0, -self::$selectSegmentSize);
    }

    private function getLogTableDeleteCount($table, $maxIdVisit)
    {
        $sql = "SELECT COUNT(*) FROM $table WHERE idvisit <= ?";
        return (int)Db::fetchOne($sql, array($maxIdVisit));
    }

    private function createTempTable()
    {
        $sql = "CREATE TEMPORARY TABLE " . Common::prefixTable(self::TEMP_TABLE_NAME) . " (
					idaction INT(11),
					PRIMARY KEY (idaction)
				)";
        Db::query($sql);
    }

    private function getMaxIdsInLogTables()
    {
        $tables = array('log_conversion', 'log_link_visit_action', 'log_visit', 'log_conversion_item');
        $idColumns = $this->getTableIdColumns();

        $result = array();
        foreach ($tables as $table) {
            $idCol = $idColumns[$table];
            $result[$table] = Db::fetchOne("SELECT MAX($idCol) FROM " . Common::prefixTable($table));
        }

        return $result;
    }

    private function insertActionsToKeep($maxIds, $olderThan = true)
    {
        $tempTableName = Common::prefixTable(self::TEMP_TABLE_NAME);

        $idColumns = $this->getTableIdColumns();
        foreach ($this->getIdActionColumns() as $table => $columns) {
            $idCol = $idColumns[$table];

            foreach ($columns as $col) {
                $select = "SELECT $col FROM " . Common::prefixTable($table) . " WHERE $idCol >= ? AND $idCol < ?";
                $sql = "INSERT IGNORE INTO $tempTableName $select";

                if ($olderThan) {
                    $start = 0;
                    $finish = $maxIds[$table];
                } else {
                    $start = $maxIds[$table];
                    $finish = Db::fetchOne("SELECT MAX($idCol) FROM " . Common::prefixTable($table));
                }

                Db::segmentedQuery($sql, $start, $finish, self::$selectSegmentSize);
            }
        }

        // allow code to be executed after data is inserted. for concurrency testing purposes.
        if ($olderThan) {
            /**
             * @ignore
             */
            Piwik::postEvent("LogDataPurger.ActionsToKeepInserted.olderThan");
        } else {
            /**
             * @ignore
             */
            Piwik::postEvent("LogDataPurger.ActionsToKeepInserted.newerThan");
        }
    }

    private function lockLogTables()
    {
        Db::lockTables(
            $readLocks = Common::prefixTables('log_conversion',
                'log_link_visit_action',
                'log_visit',
                'log_conversion_item'),
            $writeLocks = Common::prefixTables('log_action')
        );
    }

    private function deleteUnusedActions()
    {
        list($logActionTable, $tempTableName) = Common::prefixTables("log_action", self::TEMP_TABLE_NAME);

        $deleteSql = "DELETE LOW_PRIORITY QUICK IGNORE $logActionTable
						FROM $logActionTable
				   LEFT JOIN $tempTableName tmp ON tmp.idaction = $logActionTable.idaction
					   WHERE tmp.idaction IS NULL";

        Db::query($deleteSql);
    }

    private function getIdActionColumns()
    {
        return array(
            'log_link_visit_action' => array('idaction_url',
                                             'idaction_url_ref',
                                             'idaction_name',
                                             'idaction_name_ref',
                                             'idaction_event_category',
                                             'idaction_event_action'
            ),

            'log_conversion'        => array('idaction_url'),

            'log_visit'             => array('visit_exit_idaction_url',
                                             'visit_exit_idaction_name',
                                             'visit_entry_idaction_url',
                                             'visit_entry_idaction_name'),

            'log_conversion_item'   => array('idaction_sku',
                                             'idaction_name',
                                             'idaction_category',
                                             'idaction_category2',
                                             'idaction_category3',
                                             'idaction_category4',
                                             'idaction_category5')
        );
    }

    private function getTableIdColumns()
    {
        return array(
            'log_link_visit_action' => 'idlink_va',
            'log_conversion'        => 'idvisit',
            'log_visit'             => 'idvisit',
            'log_conversion_item'   => 'idvisit'
        );
    }

    // let's hardcode, since these are not dynamically created tables
    public static function getDeleteTableLogTables()
    {
        $result = Common::prefixTables('log_conversion',
            'log_link_visit_action',
            'log_visit',
            'log_conversion_item');
        if (Db::isLockPrivilegeGranted()) {
            $result[] = Common::prefixTable('log_action');
        }
        return $result;
    }

    /**
     * Utility function. Creates a new instance of LogDataPurger with the supplied array
     * of settings.
     *
     * $settings must contain values for the following keys:
     * - 'delete_logs_older_than': The number of days after which log entries are considered
     *                             old.
     * - 'delete_logs_max_rows_per_query': Max number of rows to DELETE in one query.
     *
     * @param array $settings Array of settings
     * @param bool $useRealTable
     * @return \Piwik\Plugins\PrivacyManager\LogDataPurger
     */
    public static function make($settings, $useRealTable = false)
    {
        return new LogDataPurger(
            $settings['delete_logs_older_than'],
            $settings['delete_logs_max_rows_per_query']
        );
    }
}