barcode scanner beginnings

webui/src/scanner/ScannerApp/useScannerSpeech.js

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+// Scanner Speech Hook
+// Purpose: Speaks server-provided scan labels on the scanner computer.
+// Scope: Keeps browser TTS as a local output device while leaving scan meaning and phrase selection on the server.
+import { useEffect, useRef } from 'react';
+
+const SPEECH_START_TIMEOUT_MS = 1500;
+const SPEECH_RETRY_DELAY_MS = 700;
+
+export default function useScannerSpeech(scan) {
+  const retryTimerRef = useRef(null);
+  const startTimerRef = useRef(null);
+  const spokenScanKeyRef = useRef(null);
+
+  useEffect(() => {
+    return () => {
+      window.clearTimeout(retryTimerRef.current);
+      window.clearTimeout(startTimerRef.current);
+    };
+  }, []);
+
+  useEffect(() => {
+    const speechText = String(scan?.speechText || '').trim();
+    const scanKey = scan?.scannedAt ? `${scan.scannedAt}:${speechText}` : '';
+    if (!speechText || !scanKey || spokenScanKeyRef.current === scanKey) return undefined;
+
+    let cancelled = false;
+    spokenScanKeyRef.current = scanKey;
+
+    function clearSpeechTimers() {
+      window.clearTimeout(retryTimerRef.current);
+      window.clearTimeout(startTimerRef.current);
+      retryTimerRef.current = null;
+      startTimerRef.current = null;
+    }
+
+    function retryLater() {
+      if (cancelled) return;
+      clearSpeechTimers();
+      retryTimerRef.current = window.setTimeout(() => speakOnce(), SPEECH_RETRY_DELAY_MS);
+    }
+
+    function speakOnce() {
+      if (cancelled) return;
+      const synth = window.speechSynthesis;
+      if (!synth || typeof window.SpeechSynthesisUtterance !== 'function') {
+        retryLater();
+        return;
+      }
+
+      clearSpeechTimers();
+      // Cancelling before retrying prevents stale utterances from piling up if a
+      // browser reports an error or never fires the expected start callback.
+      synth.cancel();
+      const utterance = new window.SpeechSynthesisUtterance(speechText);
+      utterance.rate = 0.92;
+      utterance.pitch = 1;
+      utterance.volume = 1;
+      utterance.onstart = () => {
+        window.clearTimeout(startTimerRef.current);
+        startTimerRef.current = null;
+      };
+      utterance.onend = () => {
+        clearSpeechTimers();
+      };
+      utterance.onerror = () => {
+        retryLater();
+      };
+      synth.speak(utterance);
+
+      // Some browser/audio states fail without surfacing onerror. A small start
+      // watchdog keeps the required scanner audio from silently dying, while the
+      // UI remains clean and rover-readable.
+      startTimerRef.current = window.setTimeout(() => {
+        synth.cancel();
+        retryLater();
+      }, SPEECH_START_TIMEOUT_MS);
+    }
+
+    speakOnce();
+
+    return () => {
+      cancelled = true;
+      clearSpeechTimers();
+    };
+  }, [scan]);
+}