Fix camera access checking in firefox (#84)

src/utils/checkCameraAccess.ts

@@ -3,7 +3,32 @@ export async function checkCameraAccess() {
     const permission = await navigator.permissions.query({
       name: 'camera' as PermissionName,
     })
-    return permission.state == 'granted'
+    return permission.state === 'granted'
+  } catch (error) {
+    // Firefox can't query 'camera' permission
+    if (isCameraPermissionDescriptorError(error as Error)) {
+      return await checkIfVideoDeviceHasLabel()
+    }
+
+    console.error(error)
+    return false
+  }
+}
+
+function isCameraPermissionDescriptorError(error: Error) {
+  return (
+    (error as Error).name === 'TypeError' &&
+    (error as Error).message.startsWith("'camera'")
+  )
+}
+
+// For security reasons, the `label` field is always blank
+// unless the user has granted persistent permission for media device access
+// @see: https://developer.mozilla.org/en-US/docs/Web/API/MediaDeviceInfo
+async function checkIfVideoDeviceHasLabel() {
+  try {
+    const devices = await navigator.mediaDevices.enumerateDevices()
+    return devices.some((d) => d.kind === 'videoinput' && d.label)
   } catch (error) {
     console.error(error)
     return false