cleaned filtration time

* filtration time is now fixed inside each range, instead
  of trying to follow linear curve
* don't bother being super accurate, that's too much
  over-engineering after all ;)

pool.js

@@ -28,12 +28,22 @@ let status = {
 
 // temperature->duration chart
 let filt_time = [
-  [  5,  1.0 ],  // at 5°C, 1 hour of filtering
-  [ 10,  2.0 ],
-  [ 12,  4.0 ],
-  [ 16,  6.0 ],
-  [ 24,  8.0 ],
-  [ 27, 12.0 ],
+  [  5,  2.0 ],  // at 5°C, 2 hours of filtering
+  [  8,  3.0 ],
+  [ 10,  4.0 ],
+  [ 11,  5.0 ],
+  [ 12,  6.0 ],
+  [ 14,  7.0 ],
+  [ 16,  8.0 ],
+  [ 18,  9.0 ],
+  [ 20, 10.0 ],
+  [ 22, 11.0 ],
+  [ 24, 12.0 ],
+  [ 25, 14.0 ],
+  [ 26, 17.0 ],
+  [ 27, 20.0 ],
+  [ 28, 22.0 ],
+  [ 29, 23.0 ],
   [ 30, 24.0 ]
 ];
 
@@ -62,25 +72,19 @@ function compute_filtration_time(t) {
 // [ start1, stop1, start2, stop2, ... ]
 
 function compute_schedule_filt(d) {
-  let s = null;
-  if (d < 2) {
-    s = [ 9, 9+d ];
-  } else if (d < 8) {
-    s = [ 9, 10, 14, 14+d-1 ];
-  } else if (d < 11) {
-    s = [ 9, 11, 14, 14+d-2 ];
-  } else if (d < 14) {
-    s = [ 9, 9+d-9, 14, 23];
-  } else if (d < 15) {
-    s = [ 9, 9+d ];
-  } else if (d < 18) {
-    s = [ 24-d, 0 ];
-  } else if (d < 24) {
-    s = [ 6, d-18 ];
-  } else {
-    s = [ 6 ];
+  let start = 17 - d/2;
+  let stop = 17 + d/2;
+
+  while (stop >= 24)
+    stop = stop - 24;
+
+  if (d < 24) {
+    let s = [ start, stop ];
   }
-  
+  else {
+    let s = [ start ];
+  }
+
   return s;
 }
 
@@ -295,7 +299,10 @@ MQTT.subscribe(
   "zigbee2mqtt/Piscine",
   function (topic, msg) {
     status.tick_mqtt++;
-    print("[POOL] mqtt", topic);
+    print("[POOL] mqtt", topic, msg);
+    if (msg == "") {
+      return;
+    }
     let obj = JSON.parse(msg);
     if (obj.temperature === undefined) {
       return;