back: Serve all next passings instead of only the next one

back/data/realtime.js

@@ -1,7 +1,22 @@
 const tam = require('./sources/tam');
 const util = require('../util');
 
+/**
+ * Comparison function between two stop passings.
+ *
+ * @param passing1 First stop passing.
+ * @param passing2 Second stop passing.
+ * @return Negative value if passing1 is sooner than passing2, positive
+ * otherwise, zero if they occur at the same time.
+ */
+const passingCompare = ({arrivalTime: time1}, {arrivalTime: time2}) => (
+    time1 - time2
+);
+
+// Time at which the course data needs to be updated next
 let nextUpdate = null;
+
+// Current information about courses
 let currentCourses = null;
 
 /**
@@ -14,10 +29,10 @@ let currentCourses = null;
  *
  * - `id`: Unique identifier for the course.
  * - `line`: Line number.
- * - `nextStop`: Identifier of the next stop of the course.
- * - `arrivalTime`: Timestamp at which the vehicle is predicted to arrive
- *                  to the next stop.
  * - `finalStop`: The final stop to which the course is headed.
+ * - `nextPassings`: Next passings of the vehicle, sorted by increasing
+ *   arrival time, containing both the stop identifier (`stopId`) and the
+ *   expected arrival timestamp (`arrivalTime`).
  *
  * @return Mapping from active course IDs to information about each course.
  */
@@ -42,6 +57,13 @@ const getCourses = () => new Promise((res, rej) =>
 
         if (!util.isObject(entry))
         {
+            // End of courses information stream. Sort next stops by increasing
+            // arrival time in each course then save result in memory cache
+            for (let course of Object.values(courses))
+            {
+                course.nextPassings.sort(passingCompare);
+            }
+
             currentCourses = courses;
             res(currentCourses);
             return;
@@ -49,6 +71,7 @@ const getCourses = () => new Promise((res, rej) =>
 
         if ('lastUpdate' in entry)
         {
+            // Metadata header
             lastUpdate = entry.lastUpdate;
             nextUpdate = entry.nextUpdate;
             return;
@@ -57,7 +80,7 @@ const getCourses = () => new Promise((res, rej) =>
         const {
             course: id,
             routeShortName: line,
-            stopId: nextStop,
+            stopId,
             destArCode: finalStop,
         } = entry;
 
@@ -65,14 +88,14 @@ const getCourses = () => new Promise((res, rej) =>
 
         if (!(id in courses))
         {
-            courses[id] = {id, line, nextStop, arrivalTime, finalStop};
+            courses[id] = {
+                id, line, finalStop,
+                nextPassings: [{stopId, arrivalTime}],
+            };
         }
-        else if (arrivalTime < courses[id].arrivalTime)
+        else
         {
-            // The stop where the next passing is soonest is assumed
+            courses[id].nextPassings.push({stopId, arrivalTime});
-            // to be the next stop
-            courses[id].nextStop = nextStop;
-            courses[id].arrivalTime = arrivalTime;
         }
     });
 });