front: Initial implementation of simulation

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
-            // to be the next stop
-            courses[id].nextStop = nextStop;
-            courses[id].arrivalTime = arrivalTime;
+            courses[id].nextPassings.push({stopId, arrivalTime});
         }
     });
 });

front/data.js

@@ -1,32 +1,195 @@
+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 getCurrentCourses();
+    const currentCourses = (await axios.get(`${server}/courses`)).data;
 
     for (let [id, course] of Object.entries(currentCourses))
     {
-        if (!(id in courses))
+        // Only track selected lines
+        if (!['1', '2', '3', '4'].includes(course.line))
         {
-            course.arrivalTime = now() + course.eta;
-            console.log(`${displayNow(now())} - New course ${id} @ ${course.line} departing from stop ${course.stop} at ${displayNow(course.arrivalTime)}`);
-            courses[id] = course;
+            continue;
         }
+
+        // Find out the next stop, ignoring the ones that are in the past
+        let nextStop = null;
+        let arrivalTime = null;
+
+        for (let {stopId, arrivalTime: time} of course.nextPassings)
+        {
+            if (time > Date.now())
+            {
+                nextStop = stopId;
+                arrivalTime = time;
+                break;
+            }
+        }
+
+        if (nextStop === null)
+        {
+            continue;
+        }
+
+        // Update an existing course
+        if (id in courses)
+        {
+            const prev = courses[id];
+
+            if (prev.state === 'stopped')
+            {
+                if (prev.currentStop !== nextStop)
+                {
+                    // Start traveling from the current stop to the next
+                    moveToStop(prev, nextStop, arrivalTime);
+                }
+            }
+            else
+            {
+                // Update the ETA if we’re still headed to the same stop
+                if (prev.arrivalStop === nextStop)
+                {
+                    prev.arrivalTime = arrivalTime;
+                    updateSpeed(prev);
+                }
+                // Otherwise, we missed a stop, try to go directly to the
+                // next segment
+                else
+                {
+                    arriveAtStop(prev, prev.arrivalStop);
+                    moveToStop(prev, nextStop, arrivalTime);
+                }
+            }
+        }
+        // Create a new course
         else
         {
-            course.arrivalTime = now() + course.eta;
-            console.log(`${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;
+            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 sleep = time => new Promise(res => setTimeout(res, time));
-const courses = {};
-
-const loop = async (courses = {}) =>
+const updatePositions = (courses, time) =>
 {
-    await updateFromTam(courses);
-    await sleep(30000);
-    return loop(courses);
+    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;
+            }
+        }
+    }
 };
 
-loop();
+const courses = {};
+let lastFrame = null;
+let lastUpdate = null;
+
+const loop = now =>
+{
+    const time = lastFrame === null ? 0 : now - lastFrame;
+
+    lastFrame = now;
+    updatePositions(courses, time);
+
+    if (lastUpdate === null || lastUpdate + 5000 <= now)
+    {
+        lastUpdate = now;
+        updateFromTam(courses);
+    }
+
+    requestAnimationFrame(loop);
+};
+
+requestAnimationFrame(loop);

front/index.js

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