back/data/realtime.js

@@ -1,22 +1,7 @@
 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;
 
 /**
@@ -29,10 +14,10 @@ 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.
  */
@@ -57,13 +42,6 @@ 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;
@@ -71,7 +49,6 @@ const getCourses = () => new Promise((res, rej) =>
 
         if ('lastUpdate' in entry)
         {
-            // Metadata header
             lastUpdate = entry.lastUpdate;
             nextUpdate = entry.nextUpdate;
             return;
@@ -80,7 +57,7 @@ const getCourses = () => new Promise((res, rej) =>
         const {
             course: id,
             routeShortName: line,
-            stopId,
+            stopId: nextStop,
             destArCode: finalStop,
         } = entry;
 
@@ -88,14 +65,14 @@ const getCourses = () => new Promise((res, rej) =>
 
         if (!(id in courses))
         {
-            courses[id] = {
-                id, line, finalStop,
-                nextPassings: [{stopId, arrivalTime}],
-            };
+            courses[id] = {id, line, nextStop, arrivalTime, finalStop};
         }
-        else
+        else if (arrivalTime < courses[id].arrivalTime)
         {
-            courses[id].nextPassings.push({stopId, arrivalTime});
+            // The stop where the next passing is soonest is assumed
+            // to be the next stop
+            courses[id].nextStop = nextStop;
+            courses[id].arrivalTime = arrivalTime;
         }
     });
 });

front/data.js

@@ -1,195 +1,32 @@
-const axios = require('axios');
-const network = require('../back/data/network.json');
-
-const server = 'http://localhost:4321';
-
-const arriveAtStop = (course, stop) =>
-{
-    course.state = 'stopped';
-    course.currentStop = stop;
-    delete course.departureStop;
-    delete course.arrivalStop;
-    delete course.arrivalTime;
-    delete course.traveledDistance;
-    delete course.speed;
-};
-
-const moveToStop = (course, stop, arrivalTime) =>
-{
-    course.state = 'moving';
-    course.departureStop = course.currentStop;
-    course.arrivalStop = stop;
-    course.arrivalTime = arrivalTime;
-    course.traveledDistance = 0;
-    course.speed = 0;
-    delete course.currentStop;
-
-    const segment = `${course.departureStop}-${course.arrivalStop}`;
-
-    if (!(segment in network.segments))
-    {
-        // There is no segment between the two requested stops, jump
-        // directly to the arrival stop
-        arriveAtStop(course, course.arrivalStop);
-    }
-    else
-    {
-        updateSpeed(course);
-    }
-};
-
-const getCurrentSegment = course =>
-{
-    if (course.state === 'stopped')
-    {
-        return null;
-    }
-
-    return network.segments[`${course.departureStop}-${course.arrivalStop}`];
-};
-
-const updateSpeed = course =>
-{
-    const segment = getCurrentSegment(course);
-    const length = segment.points[segment.points.length - 1].distance;
-
-    const remainingTime = course.arrivalTime - Date.now();
-    const remainingDistance = length - course.traveledDistance;
-
-    if (remainingTime <= 0 || remainingDistance <= 0)
-    {
-        arriveAtStop(course, course.arrivalStop);
-        return;
-    }
-
-    course.speed = remainingDistance / remainingTime;
-};
-
 const updateFromTam = async (courses) =>
 {
-    const currentCourses = (await axios.get(`${server}/courses`)).data;
+    const currentCourses = await getCurrentCourses();
 
     for (let [id, course] of Object.entries(currentCourses))
     {
-        // Only track selected lines
-        if (!['1', '2', '3', '4'].includes(course.line))
+        if (!(id in courses))
         {
-            continue;
-        }
-
-        // Find out the next stop, ignoring the ones that are in the past
-        let nextStop = null;
-        let arrivalTime = null;
-
-        for (let {stopId, arrivalTime: time} of course.nextPassings)
-        {
-            if (time > Date.now())
-            {
-                nextStop = stopId;
-                arrivalTime = time;
-                break;
-            }
-        }
-
-        if (nextStop === null)
-        {
-            continue;
-        }
-
-        // Update an existing course
-        if (id in courses)
-        {
-            const prev = courses[id];
-
-            if (prev.state === 'stopped')
-            {
-                if (prev.currentStop !== nextStop)
-                {
-                    // Start traveling from the current stop to the next
-                    moveToStop(prev, nextStop, arrivalTime);
-                }
+            course.arrivalTime = now() + course.eta;
+            console.log(`${displayNow(now())} - New course ${id} @ ${course.line} departing from stop ${course.stop} at ${displayNow(course.arrivalTime)}`);
+            courses[id] = course;
         }
         else
         {
-                // Update the ETA if we’re still headed to the same stop
-                if (prev.arrivalStop === nextStop)
-                {
-                    prev.arrivalTime = arrivalTime;
-                    updateSpeed(prev);
-                }
-                // Otherwise, we missed a stop, try to go directly to the
-                // next segment
-                else
-                {
-                    arriveAtStop(prev, prev.arrivalStop);
-                    moveToStop(prev, nextStop, arrivalTime);
-                }
-            }
-        }
-        // Create a new course
-        else
-        {
-            courses[id] = {
-                id,
-                line: course.line,
-                finalStop: course.finalStop,
-            };
-
-            arriveAtStop(courses[id], nextStop);
-        }
-    }
-
-    // Remove stale courses
-    for (let id of Object.keys(courses))
-    {
-        if (!(id in currentCourses))
-        {
-            delete courses[id];
-        }
-    }
-};
-
-const updatePositions = (courses, time) =>
-{
-    for (let [id, course] of Object.entries(courses))
-    {
-        if (course.state === 'moving')
-        {
-            const delta = course.speed * time;
-
-            const segment = getCurrentSegment(course);
-            const length = segment.points[segment.points.length - 1].distance;
-
-            if (course.traveledDistance + delta >= length)
-            {
-                course.traveledDistance = length;
-            }
-            else
-            {
-                course.traveledDistance += delta;
-            }
+            course.arrivalTime = now() + course.eta;
+            console.log(`${displayNow(now())} - Course ${id} @ ${course.line} will arrive to stop ${course.stop} at ${displayNow(course.arrivalTime)} (previously to stop ${courses[id].stop} at ${displayNow(courses[id].arrivalTime)})`);
+            courses[id] = course;
         }
     }
 };
 
+const sleep = time => new Promise(res => setTimeout(res, time));
 const courses = {};
-let lastFrame = null;
-let lastUpdate = null;
 
-const loop = now =>
+const loop = async (courses = {}) =>
 {
-    const time = lastFrame === null ? 0 : now - lastFrame;
-
-    lastFrame = now;
-    updatePositions(courses, time);
-
-    if (lastUpdate === null || lastUpdate + 5000 <= now)
-    {
-        lastUpdate = now;
-        updateFromTam(courses);
-    }
-
-    requestAnimationFrame(loop);
+    await updateFromTam(courses);
+    await sleep(30000);
+    return loop(courses);
 };
 
-requestAnimationFrame(loop);
+loop();

front/index.js

@@ -1,7 +1,4 @@
 require('regenerator-runtime/runtime');
 
 const {createMap} = require('./map');
-
-require('./data');
-
 createMap(/* map = */ 'map');