feature/basis for filtering cards by distance without external maps by akshaygajjala1 · Pull Request #8 · Longhorn-Developers/Longhorn-Studies

akshaygajjala1 · 2026-03-23T22:14:04Z

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Copilot

Pull request overview

Adds an initial end-to-end path for distance-based study-spot ordering by introducing user location capture in the Expo app and a backend API endpoint that sorts spots by haversine distance.

Changes:

Add latitude/longitude fields to the StudySpot model and expose them via to_dict().
Add a /api/study_spots/sort_by_distance endpoint that returns spots sorted by computed distance.
Update the frontend to request location permissions and call the new endpoint; add expo-location and adjust TS JSX settings.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 11 comments.

Show a summary per file

File	Description
instance/longhorn_studies.db	Adds a SQLite DB artifact containing a `study_spots` schema snapshot.
frontend/tsconfig.json	Sets `jsx` to `react-jsx`.
frontend/package.json	Adds `expo-location` dependency.
frontend/app/(tabs)/index.tsx	Requests user location and posts coordinates to the backend to fetch distance-sorted spots.
backend/routes.py	Introduces `/study_spots/sort_by_distance` and haversine distance helper.
backend/models.py	Adds `latitude`/`longitude` columns and includes them in API serialization.

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Copilot · 2026-03-23T22:50:31Z

+        # Get all study spots
+        spots = StudySpot.query.all()
+
+        # Calculate distances and sort
+        spots_with_distance = []
+        for spot in spots:
+            # Skip spots without coordinates
+            if not hasattr(spot, 'latitude') or not hasattr(spot, 'longitude'):
+                continue
+            if spot.latitude is None or spot.longitude is None:
+                continue
+
+            distance = _haversine_distance(user_lat, user_lng, spot.latitude, spot.longitude)
+            spot_dict = spot.to_dict()
+            spot_dict['distance_from_user'] = distance
+            spots_with_distance.append(spot_dict)
+
+        # Sort by distance (closest first)
+        spots_with_distance.sort(key=lambda x: x['distance_from_user'])


StudySpot.query.all() loads every row into memory and then sorts in Python. This won’t scale and can become a latency/memory issue as the table grows. Consider filtering out null coordinates at the DB level, selecting only needed columns, and optionally supporting paging/limits.

Copilot · 2026-03-23T22:50:32Z

+  useEffect(() => {
+    if (userLat && userLng) {
+      fetchSortedByDistance();
+    }


Same falsy-check issue here: if (userLat && userLng) will skip when either coordinate is 0. Prefer explicit null/undefined checks before calling fetchSortedByDistance().

Copilot · 2026-03-23T22:50:32Z

+
+  const [userLat, setUserLat] = useState<number | null>(null);
+  const [userLng, setUserLng] = useState<number | null>(null);
+  const [spots, setSpots] = useState<any[]>([]);


spots state is set but never read/rendered in this component, which is likely to trigger no-unused-vars lint noise and makes it harder to see intended behavior. Either render/use spots (even temporarily) or remove the state until it’s needed.

Copilot · 2026-03-23T22:50:32Z

+            # Skip spots without coordinates
+            if not hasattr(spot, 'latitude') or not hasattr(spot, 'longitude'):
+                continue
+            if spot.latitude is None or spot.longitude is None:
+                continue
+
+            distance = _haversine_distance(user_lat, user_lng, spot.latitude, spot.longitude)
+            spot_dict = spot.to_dict()
+            spot_dict['distance_from_user'] = distance
+            spots_with_distance.append(spot_dict)
+
+        # Sort by distance (closest first)
+        spots_with_distance.sort(key=lambda x: x['distance_from_user'])


This endpoint relies on StudySpot.latitude/longitude, but the create/update JSON handler (_study_spot_from_json) doesn’t accept/populate those fields. As a result, newly created/updated spots will have null coordinates and will be filtered out here, often returning an empty list. Add latitude/longitude handling (with validation) to the create/update flow, or adjust the endpoint’s behavior.

Suggested change

# Skip spots without coordinates

if not hasattr(spot, 'latitude') or not hasattr(spot, 'longitude'):

continue

if spot.latitude is None or spot.longitude is None:

continue

distance = _haversine_distance(user_lat, user_lng, spot.latitude, spot.longitude)

spot_dict = spot.to_dict()

spot_dict['distance_from_user'] = distance

spots_with_distance.append(spot_dict)

# Sort by distance (closest first)

spots_with_distance.sort(key=lambda x: x['distance_from_user'])

spot_dict = spot.to_dict()

# If the spot doesn't have usable coordinates, include it with no distance

if (not hasattr(spot, 'latitude') or not hasattr(spot, 'longitude') or

spot.latitude is None or spot.longitude is None):

spot_dict['distance_from_user'] = None

spots_with_distance.append(spot_dict)

continue

# Compute distance for spots with valid coordinates

distance = _haversine_distance(user_lat, user_lng, spot.latitude, spot.longitude)

spot_dict['distance_from_user'] = distance

spots_with_distance.append(spot_dict)

# Sort by distance (closest first); spots without distance go last

spots_with_distance.sort(

key=lambda x: (

x['distance_from_user'] is None,

x['distance_from_user'] if x['distance_from_user'] is not None else float('inf'),

)

)

Copilot · 2026-03-23T22:50:32Z

+            user_lat = float(user_lat)
+            user_lng = float(user_lng)
+        except (ValueError, TypeError):
+            return jsonify({'error': 'Invalid coordinates'}), 400


Coordinate validation here only checks “is present” and “can be cast to float”. It should also validate bounds (lat ∈ [-90, 90], lng ∈ [-180, 180]) to avoid nonsensical values and surprising distance calculations.

Suggested change

return jsonify({'error': 'Invalid coordinates'}), 400

return jsonify({'error': 'Invalid coordinates'}), 400

# Validate coordinate bounds

if not (-90 <= user_lat <= 90) or not (-180 <= user_lng <= 180):

return jsonify({'error': 'Coordinates out of range'}), 400

Copilot · 2026-03-23T22:50:33Z

+  }
+
+  async function fetchSortedByDistance() {
+    if (!userLat || !userLng) return;


if (!userLat || !userLng) return; treats 0 as “missing”, which is incorrect for valid coordinates. Use explicit null/undefined checks (e.g., userLat == null || userLng == null) to decide whether coordinates are available.

Suggested change

if (!userLat || !userLng) return;

if (userLat == null || userLng == null) return;

Copilot · 2026-03-23T22:50:33Z

+      const response = await fetch('http://localhost:8000/api/study_spots/sort_by_distance', {
+        method: 'POST',


Hard-coding http://localhost:8000 will fail on physical devices and many emulator/simulator setups because localhost resolves to the device itself. Consider centralizing the API base URL (env/config) and using platform-appropriate host resolution (e.g., dev machine LAN IP / Android emulator 10.0.2.2).

Copilot · 2026-03-23T22:50:33Z

+          user_lat: userLat,
+          user_lng: userLng
+        })
+      });


fetchSortedByDistance doesn’t check response.ok before calling response.json(), so non-2xx responses (or non-JSON error bodies) can throw or silently produce confusing UI state. Handle non-OK responses explicitly (and consider surfacing the API error message).

Suggested change

});

});

if (!response.ok) {

const errorText = await response.text().catch(() => '');

throw new Error(

`Request failed with status ${response.status} ${response.statusText}${

errorText ? `: ${errorText}` : ''

}`,

);

}

Copilot · 2026-03-23T22:50:34Z

+    const { status } = await Location.requestForegroundPermissionsAsync();
+    if (status !== 'granted') {
+      return;
+    }
+
+    const location = await Location.getCurrentPositionAsync({});
+    setUserLat(location.coords.latitude);
+    setUserLng(location.coords.longitude);


Location.getCurrentPositionAsync can throw (e.g., location services disabled, timeout). Wrap this call in try/catch and handle failures (at least log and avoid leaving state in an indeterminate null/partial state).

Suggested change

const { status } = await Location.requestForegroundPermissionsAsync();

if (status !== 'granted') {

return;

}

const location = await Location.getCurrentPositionAsync({});

setUserLat(location.coords.latitude);

setUserLng(location.coords.longitude);

try {

const { status } = await Location.requestForegroundPermissionsAsync();

if (status !== 'granted') {

console.warn('Location permission not granted');

setUserLat(null);

setUserLng(null);

return;

}

const location = await Location.getCurrentPositionAsync({});

if (!location || !location.coords) {

console.error('Failed to obtain location coordinates');

setUserLat(null);

setUserLng(null);

return;

}

setUserLat(location.coords.latitude);

setUserLng(location.coords.longitude);

} catch (error) {

console.error('Error getting user location:', error);

setUserLat(null);

setUserLng(null);

}

Copilot · 2026-03-23T22:50:34Z

+    latitude = db.Column(db.Float, nullable=True)
+    longitude = db.Column(db.Float, nullable=True)


Adding latitude/longitude columns requires a DB schema change. Since the app currently uses db.create_all() (which won’t alter existing tables), any existing SQLite DB will be incompatible and queries can fail. Consider adding a migration step / schema update script (or ensure the dev DB is recreated) as part of this change.

basis for filtering cards by distance without external maps

4fe9a6e

pi2chen changed the title ~~basis for filtering cards by distance without external maps~~ feature/basis for filtering cards by distance without external maps Mar 23, 2026

Merge branch 'main' into distance-filter-and-location-setup

45763bd

pi2chen requested a review from Copilot March 23, 2026 22:46

Copilot started reviewing on behalf of pi2chen March 23, 2026 22:46 View session

Copilot AI reviewed Mar 23, 2026

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feature/basis for filtering cards by distance without external maps#8

feature/basis for filtering cards by distance without external maps#8
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-            return jsonify({'error': 'Invalid coordinates'}), 400
+            return jsonify({'error': 'Invalid coordinates'}), 400
+        # Validate coordinate bounds
+        if not (-90 <= user_lat <= 90) or not (-180 <= user_lng <= 180):
+            return jsonify({'error': 'Coordinates out of range'}), 400

	if (!userLat \|\| !userLng) return;
	if (userLat == null \|\| userLng == null) return;

		const response = await fetch('http://localhost:8000/api/study_spots/sort_by_distance', {
		method: 'POST',

-      });
+      });
+      if (!response.ok) {
+        const errorText = await response.text().catch(() => '');
+        throw new Error(
+          `Request failed with status ${response.status} ${response.statusText}${
+            errorText ? `: ${errorText}` : ''
+          }`,
+        );
+      }

-    const { status } = await Location.requestForegroundPermissionsAsync();
-    if (status !== 'granted') {
-      return;
-    }
-    const location = await Location.getCurrentPositionAsync({});
-    setUserLat(location.coords.latitude);
-    setUserLng(location.coords.longitude);
+    try {
+      const { status } = await Location.requestForegroundPermissionsAsync();
+      if (status !== 'granted') {
+        console.warn('Location permission not granted');
+        setUserLat(null);
+        setUserLng(null);
+        return;
+      }
+      const location = await Location.getCurrentPositionAsync({});
+      if (!location || !location.coords) {
+        console.error('Failed to obtain location coordinates');
+        setUserLat(null);
+        setUserLng(null);
+        return;
+      }
+      setUserLat(location.coords.latitude);
+      setUserLng(location.coords.longitude);
+    } catch (error) {
+      console.error('Error getting user location:', error);
+      setUserLat(null);
+      setUserLng(null);
+    }

		latitude = db.Column(db.Float, nullable=True)
		longitude = db.Column(db.Float, nullable=True)

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