Provide geo-gated users optional GPS fallback for precise location data (#8973)

1 files changed, 58 insertions, 0 deletions

diff --git a/src/state/geolocation/useSyncedDeviceGeolocation.ts b/src/state/geolocation/useSyncedDeviceGeolocation.ts
new file mode 100644
index 000000000..602f29a30
--- /dev/null
+++ b/src/state/geolocation/useSyncedDeviceGeolocation.ts
@@ -0,0 +1,58 @@
+import {useEffect, useRef} from 'react'
+import * as Location from 'expo-location'
+
+import {logger} from '#/state/geolocation/logger'
+import {getDeviceGeolocation} from '#/state/geolocation/util'
+import {device, useStorage} from '#/storage'
+
+/**
+ * Hook to get and sync the device geolocation from the device GPS and store it
+ * using device storage. If permissions are not granted, it will clear any cached
+ * storage value.
+ */
+export function useSyncedDeviceGeolocation() {
+  const synced = useRef(false)
+  const [status] = Location.useForegroundPermissions()
+  const [deviceGeolocation, setDeviceGeolocation] = useStorage(device, [
+    'deviceGeolocation',
+  ])
+
+  useEffect(() => {
+    async function get() {
+      // no need to set this more than once per session
+      if (synced.current) return
+
+      logger.debug('useSyncedDeviceGeolocation: checking perms')
+
+      if (status?.granted) {
+        const location = await getDeviceGeolocation()
+        if (location) {
+          logger.debug('useSyncedDeviceGeolocation: syncing location')
+          setDeviceGeolocation(location)
+          synced.current = true
+        }
+      } else {
+        const hasCachedValue = device.get(['deviceGeolocation']) !== undefined
+
+        /**
+         * If we have a cached value, but user has revoked permissions,
+         * quietly (will take effect lazily) clear this out.
+         */
+        if (hasCachedValue) {
+          logger.debug(
+            'useSyncedDeviceGeolocation: clearing cached location, perms revoked',
+          )
+          device.set(['deviceGeolocation'], undefined)
+        }
+      }
+    }
+
+    get().catch(e => {
+      logger.error('useSyncedDeviceGeolocation: failed to sync', {
+        safeMessage: e,
+      })
+    })
+  }, [status, setDeviceGeolocation])
+
+  return [deviceGeolocation, setDeviceGeolocation] as const
+}