From a2a489d1f8b0c40ae7d72870feceefc19c7bb234 Mon Sep 17 00:00:00 2001
From: Simey Lameze <simey@moodle.com>
Date: Wed, 14 Aug 2019 09:02:08 +0800
Subject: [PATCH] MDL-56223 calendar: skip events updating if nothing has
 changed

---
 calendar/lib.php                      | 58 +++++++++++++++++++--------
 lang/en/calendar.php                  |  1 +
 lib/tests/calendar_cron_task_test.php |  2 +-
 3 files changed, 43 insertions(+), 18 deletions(-)

diff --git a/calendar/lib.php b/calendar/lib.php
index 0747773010c..f716b6c069d 100644
--- a/calendar/lib.php
+++ b/calendar/lib.php
@@ -104,6 +104,11 @@ define('CALENDAR_IMPORT_FROM_FILE', 0);
  */
 define('CALENDAR_IMPORT_FROM_URL',  1);
 
+/**
+ * CALENDAR_IMPORT_EVENT_UPDATED_SKIPPED - imported event was skipped
+ */
+define('CALENDAR_IMPORT_EVENT_SKIPPED',  -1);
+
 /**
  * CALENDAR_IMPORT_EVENT_UPDATED - imported event was updated
  */
@@ -2862,11 +2867,23 @@ function calendar_add_icalendar_event($event, $unused = null, $subscriptionid, $
 
     if ($updaterecord = $DB->get_record('event', array('uuid' => $eventrecord->uuid,
         'subscriptionid' => $eventrecord->subscriptionid))) {
-        $eventrecord->id = $updaterecord->id;
-        $return = CALENDAR_IMPORT_EVENT_UPDATED; // Update.
+
+        // Compare iCal event data against the moodle event to see if something has changed.
+        $result = array_diff((array) $eventrecord, (array) $updaterecord);
+
+        // Unset timemodified field because it's always going to be different.
+        unset($result['timemodified']);
+
+        if (count($result)) {
+            $eventrecord->id = $updaterecord->id;
+            $return = CALENDAR_IMPORT_EVENT_UPDATED; // Update.
+        } else {
+            return CALENDAR_IMPORT_EVENT_SKIPPED;
+        }
     } else {
         $return = CALENDAR_IMPORT_EVENT_INSERTED; // Insert.
     }
+
     if ($createdevent = \calendar_event::create($eventrecord, false)) {
         if (!empty($event->properties['RRULE'])) {
             // Repeating events.
@@ -3000,18 +3017,13 @@ function calendar_import_icalendar_events($ical, $unused = null, $subscriptionid
     $return = '';
     $eventcount = 0;
     $updatecount = 0;
+    $skippedcount = 0;
 
     // Large calendars take a while...
     if (!CLI_SCRIPT) {
         \core_php_time_limit::raise(300);
     }
 
-    // Mark all events in a subscription with a zero timestamp.
-    if (!empty($subscriptionid)) {
-        $sql = "UPDATE {event} SET timemodified = :time WHERE subscriptionid = :id";
-        $DB->execute($sql, array('time' => 0, 'id' => $subscriptionid));
-    }
-
     // Grab the timezone from the iCalendar file to be used later.
     if (isset($ical->properties['X-WR-TIMEZONE'][0]->value)) {
         $timezone = $ical->properties['X-WR-TIMEZONE'][0]->value;
@@ -3019,8 +3031,9 @@ function calendar_import_icalendar_events($ical, $unused = null, $subscriptionid
         $timezone = 'UTC';
     }
 
-    $return = '';
+    $icaluuids = [];
     foreach ($ical->components['VEVENT'] as $event) {
+        $icaluuids[] = $event->properties['UID'][0]->value;
         $res = calendar_add_icalendar_event($event, null, $subscriptionid, $timezone);
         switch ($res) {
             case CALENDAR_IMPORT_EVENT_UPDATED:
@@ -3029,6 +3042,9 @@ function calendar_import_icalendar_events($ical, $unused = null, $subscriptionid
             case CALENDAR_IMPORT_EVENT_INSERTED:
                 $eventcount++;
                 break;
+            case CALENDAR_IMPORT_EVENT_SKIPPED:
+                $skippedcount++;
+                break;
             case 0:
                 $return .= '<p>' . get_string('erroraddingevent', 'calendar') . ': ';
                 if (empty($event->properties['SUMMARY'])) {
@@ -3041,18 +3057,26 @@ function calendar_import_icalendar_events($ical, $unused = null, $subscriptionid
         }
     }
 
-    $return .= "<p>" . get_string('eventsimported', 'calendar', $eventcount) . "</p> ";
-    $return .= "<p>" . get_string('eventsupdated', 'calendar', $updatecount) . "</p>";
-
-    // Delete remaining zero-marked events since they're not in remote calendar.
     if (!empty($subscriptionid)) {
-        $deletecount = $DB->count_records('event', array('timemodified' => 0, 'subscriptionid' => $subscriptionid));
-        if (!empty($deletecount)) {
-            $DB->delete_records('event', array('timemodified' => 0, 'subscriptionid' => $subscriptionid));
-            $return .= "<p> " . get_string('eventsdeleted', 'calendar') . ": {$deletecount} </p>\n";
+        $eventsuuids = $DB->get_records_menu('event', ['subscriptionid' => $subscriptionid], '', 'id, uuid');
+
+        $icaleventscount = count($icaluuids);
+        $tobedeleted = [];
+        if (count($eventsuuids) > $icaleventscount) {
+            foreach ($eventsuuids as $eventid => $eventuuid) {
+                if (!in_array($eventuuid, $icaluuids)) {
+                    $tobedeleted[] = $eventid;
+                }
+            }
+            if (!empty($tobedeleted)) {
+                $DB->delete_records_list('event', 'id', $tobedeleted);
+            }
         }
     }
 
+    $return .= "<p>" . get_string('eventsimported', 'calendar', $eventcount) . "</p> ";
+    $return .= "<p>" . get_string('eventsskipped', 'calendar', $skippedcount) . "</p> ";
+    $return .= "<p>" . get_string('eventsupdated', 'calendar', $updatecount) . "</p>";
     return $return;
 }
 
diff --git a/lang/en/calendar.php b/lang/en/calendar.php
index 8a0f70350e5..a573276d398 100644
--- a/lang/en/calendar.php
+++ b/lang/en/calendar.php
@@ -110,6 +110,7 @@ $string['eventsall'] = 'All events';
 $string['eventsdeleted'] = 'Events deleted';
 $string['eventsimported'] = 'Events imported: {$a}';
 $string['eventsource'] = 'Event source';
+$string['eventsskipped'] = 'Events skipped: {$a}';
 $string['eventsupdated'] = 'Events updated: {$a}';
 $string['eventsfor'] = '{$a} events';
 $string['eventskey'] = 'Events key';
diff --git a/lib/tests/calendar_cron_task_test.php b/lib/tests/calendar_cron_task_test.php
index f17ab150ece..6b099876807 100644
--- a/lib/tests/calendar_cron_task_test.php
+++ b/lib/tests/calendar_cron_task_test.php
@@ -58,7 +58,7 @@ class core_calendar_cron_task_testcase extends advanced_testcase {
         $subscription->lastupdated = 0;
         calendar_add_subscription($subscription);
 
-        $this->expectOutputRegex('/Events imported: .* Events updated:/');
+        $this->expectOutputRegex('/Events imported: .* Events skipped: .* Events updated:/');
         $task = new \core\task\calendar_cron_task();
         $task->execute();
     }