From 0d7b3848211fbd0f450bf3677911749c5a4fd6c1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Matt=C3=A9o=20Delabre?= <spam@delab.re>
Date: Sun, 19 Jul 2020 01:45:36 +0200
Subject: [PATCH] front: Initial implementation of simulation

---
 front/data.js  | 195 +++++++++++++++++++++++++++++++++++++++++++++----
 front/index.js |   3 +
 2 files changed, 182 insertions(+), 16 deletions(-)

diff --git a/front/data.js b/front/data.js
index fe61b39..eaabce6 100644
--- a/front/data.js
+++ b/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);
diff --git a/front/index.js b/front/index.js
index 4691e3e..fdff2fd 100644
--- a/front/index.js
+++ b/front/index.js
@@ -1,4 +1,7 @@
 require('regenerator-runtime/runtime');
 
 const {createMap} = require('./map');
+
+require('./data');
+
 createMap(/* map = */ 'map');