delete excess tracks on show time change

fixes #425

api/Playlists.php

@@ -575,7 +575,7 @@ public function patchResource(RequestInterface $request): ResponseInterface {
         }
 
         $success = $attrs->isEmpty() ? true :
-                        $api->updatePlaylist($key, $date, $time, $name, $aid);
+                        $api->updatePlaylist($key, $date, $time, $name, $aid, true);
 
         if($success) {
             PushServer::sendAsyncNotification();

js/playlists.pick.js

@@ -75,6 +75,24 @@ $().ready(function(){
         return roundedDate.toISOString().split('T');
     }
 
+    /**
+     * return duration in minutes between two specified times
+     *
+     * if end is less than start, it is assumed to be the next day
+     *
+     * @param start string formatted 'hhmm'
+     * @param end string formatted 'hhmm'
+     * @returns duration in minutes
+     */
+    function duration(start, end) {
+        var startTime = new Date('2020-01-01T' + localTimeIntl(start) + ':00Z');
+        var endTime = new Date('2020-01-01T' + localTimeIntl(end) + ':00Z');
+        if(endTime < startTime)
+            endTime.setDate(endTime.getDate() + 1);
+
+        return (endTime.getTime() - startTime.getTime()) / 60000;
+    }
+
     function isEditing(cancel = false) {
         if(editing && cancel)
             editing.find('#cancel').trigger('click');
@@ -575,6 +593,14 @@ $().ready(function(){
             return;
 
         var list = getEditRow(row);
+
+        var newTime = list.attributes.time.split('-');
+        var oldTime = row.data('orig').attributes.time.split('-');
+
+        if(duration(newTime[0], newTime[1]) < duration(oldTime[0], oldTime[1])
+               && !confirm("Show has been shortened.  Tracks past the end will be deleted.\n\nAre you sure you want to do this?"))
+            return;
+
         var postData = {
             data: {
                 type: 'show',