remove after_utc parameter when no signals found (#481)

src/components/Cars/CANSignals/index.jsx

@@ -35,7 +35,7 @@ const Main = ({ vin }) => {
       <Box sx={{ display: "flex", alignItems: "baseline", gap: "8px" }}>
         <span>Searching every</span>
         <DelayController delays={delays} delayIndex={delayIndex} setDelayIndex={setDelayIndex} />
-        <span>seconds for signals sent after {queryDate}.</span>
+        {queryDate && <span>for signals sent after {queryDate}.</span>}
       </Box>
       <Table>
         <TableHead>
@@ -86,7 +86,7 @@ const DelayController = ({
       >
         {delays.map((delay, i) => {
           return (
-            <MenuItem value={i} selected={i === delayIndex} key={delay}>{delay / 1000}</MenuItem>
+            <MenuItem value={i} selected={i === delayIndex} key={delay}>{delay / 1000} seconds</MenuItem>
           );
         })}
       </Select>

src/components/Contexts/CANSignalsContext.jsx

@@ -32,6 +32,7 @@ export const CANSignalProvider = ({ token, children }) => {
   const [vin, setVIN] = useState(null);
   const [signals, setSignals] = useState([]);
   const [utc, setUtc] = useState(undefined);
+  const [hasFoundSignalsBefore, setHasFoundSignalsBefore] = useState(false);
 
   useInterval(
     () => {
@@ -55,14 +56,15 @@ export const CANSignalProvider = ({ token, children }) => {
       if (mostRecentTimestamp) {
         setUtc(new Date(mostRecentTimestamp).getTime() - 50); // apply slight offset to ensure last CAN Signals sent before sleep are returned.
       } else {
-        setUtc(new Date().getTime());
+        setUtc(undefined);
       }
 
       const items = transformSignals(result.data);
 
       if (items.length > 0) {
         setSignals(items);
-      } else {
+        setHasFoundSignalsBefore(true)
+      } else if (!hasFoundSignalsBefore) {
         setSignals([BlankSignal("No signals")]);
       }
     } catch (e) {
@@ -73,7 +75,7 @@ export const CANSignalProvider = ({ token, children }) => {
   return (
     <CANSignalContext.Provider
       value={{
-        queryDate: new Date(utc).toLocaleTimeString(),
+        queryDate: utc && new Date(utc).toLocaleTimeString(),
         signals,
         setVIN,
         delays,