Got timer working

src/routes/+page.svelte

@@ -15,9 +15,9 @@ let score_red = 0;
 let score_blue = 0;
 let teams_red = ["6659A", "6659B"];
 let teams_blue = ["210Z", "210Y"];
-let timer_running = false;
 let timer_start = undefined;
-let timer_duration = undefined;
+let timer_end = undefined;
+let timer_next_tick = undefined;
 let timer = "Scheduled";
 
 const client = mqtt.connect("ws://127.0.0.1:8883");
@@ -49,6 +49,28 @@ client.on("connect", () => {
   });
 });
 
+function stop_timer() {
+  if(timer_next_tick === undefined) {
+  } else {
+    clearInterval(timer_next_tick);
+    timer_next_tick = undefined;
+  }
+}
+
+function tick_timer() {
+  const now = new Date()
+  const time_diff = timer_end - now;
+  if (time_diff <= 0) {
+    timer = "0:00";
+    stop_timer();
+  } else {
+    const seconds_total = Math.ceil(time_diff/ 1000);
+    const minutes = Math.floor(seconds_total / 60);
+    const seconds = seconds_total - (minutes * 60);
+    timer = `${minutes}:${seconds.toString().padStart(2, '0')}`;
+  }
+}
+
 client.on("message", (topic, message) => {
   let topic_str = topic.toString();
   let message_str = message.toString();
@@ -63,39 +85,39 @@ client.on("message", (topic, message) => {
     // TODO: fill match name based off metadata
     break;
   case arena_state_topic:
+    stop_timer();
+
     const state_obj = JSON.parse(message_str);
     // Convert seconds to ms *1000 convert ns to ms /1000000
-    const start_time = new Date((state_obj.start_s * 1000) + (state_obj.start_ns / 1000000));
+    const start_ms = (state_obj.start_s * 1000) + (state_obj.start_ns / 1000000);
+    const start_time = new Date(start_ms);
     switch(state_obj.state) {
     case "SCHEDULED":
       timer = "Scheduled";
-      timer_running = false;
       break;
     case "TIMEOUT":
       timer = "Timeout";
-      timer_running = false;
       break;
     case "DRIVER":
-      timer_running = true;
       timer_start = start_time;
-      timer_duration = 105000;
+      timer_end = new Date(start_ms + 105000);
+      tick_timer();
+      timer_next_tick = setInterval(tick_timer, 50);
       break;
     case "DRIVER_DONE":
       timer = "Driver Done";
-      timer_running = false;
       break;
     case "AUTONOMOUS":
-      timer_running = true;
       timer_start = start_time;
-      timer_duration = 15000;
+      timer_end = new Date(start_ms + 15000);
+      tick_timer();
+      timer_next_tick = setInterval(tick_timer, 50);
       break;
     case "AUTONOMOUS_DONE":
       timer = "Auton Done";
-      timer_running = false;
       break;
     case "ABANDONED":
       timer = "Abandoned";
-      timer_running = false;
       break;
     }
     break;