Feature: Support neighbor functions in res 0 & 1

a5/traversal/global_neighbors.py

@@ -90,6 +90,69 @@ def _add_delta_neighbors(
         _add_neighbor(ctx, neighbor_triple, orientation, neighbor_origin, neighbor_segment)
 
 
+def _serialize_res1(origin: Origin, quintant: int) -> int:
+    """Serialize a res 1 cell from origin and quintant."""
+    segment, _ = quintant_to_segment(quintant, origin)
+    return serialize({'origin': origin, 'segment': segment, 'S': 0, 'resolution': 1})
+
+
+def _get_res0_neighbors(origin: Origin) -> List[int]:
+    """
+    Get neighbors of a resolution 0 cell (dodecahedron face).
+    """
+    neighbor_set: Set[int] = set()
+    for q in range(5):
+        adjacent_face_id, _ = FACE_ADJACENCY[origin.id][q]
+        neighbor_set.add(serialize({
+            'origin': origins[adjacent_face_id], 'segment': 0,
+            'S': 0, 'resolution': 0
+        }))
+    return sorted(neighbor_set)
+
+
+def _get_res1_neighbors(origin: Origin, segment: int, edge_only: bool) -> List[int]:
+    """
+    Get neighbors of a resolution 1 cell (quintant).
+    """
+    quintant, _ = segment_to_quintant(segment, origin)
+    neighbor_set: Set[int] = set()
+
+    # Left and right quintant on the same face (A, B)
+    left_q = (quintant - 1 + 5) % 5
+    right_q = (quintant + 1) % 5
+    neighbor_set.add(_serialize_res1(origin, left_q))
+    neighbor_set.add(_serialize_res1(origin, right_q))
+
+    # Adjacent quintant on adjacent face (C)
+    adjacent_face_id, adjacent_quintant = FACE_ADJACENCY[origin.id][quintant]
+    adjacent_origin = origins[adjacent_face_id]
+    neighbor_set.add(_serialize_res1(adjacent_origin, adjacent_quintant))
+
+    if edge_only:
+        return sorted(neighbor_set)
+
+    # Remaining neighbors on face
+    neighbor_set.add(_serialize_res1(origin, (quintant - 2 + 5) % 5))
+    neighbor_set.add(_serialize_res1(origin, (quintant + 2) % 5))
+
+    # Left & right quintant neighbors of C
+    neighbor_set.add(_serialize_res1(adjacent_origin, (adjacent_quintant - 1 + 5) % 5))
+    neighbor_set.add(_serialize_res1(adjacent_origin, (adjacent_quintant + 1) % 5))
+
+    # Two neighbors each from adjacent faces of A & B
+    left_adjacent_face_id, left_adjacent_quintant = FACE_ADJACENCY[origin.id][left_q]
+    left_adjacent_origin = origins[left_adjacent_face_id]
+    neighbor_set.add(_serialize_res1(left_adjacent_origin, left_adjacent_quintant))
+    neighbor_set.add(_serialize_res1(left_adjacent_origin, (left_adjacent_quintant - 1 + 5) % 5))
+
+    right_adjacent_face_id, right_adjacent_quintant = FACE_ADJACENCY[origin.id][right_q]
+    right_adjacent_origin = origins[right_adjacent_face_id]
+    neighbor_set.add(_serialize_res1(right_adjacent_origin, right_adjacent_quintant))
+    neighbor_set.add(_serialize_res1(right_adjacent_origin, (right_adjacent_quintant + 1) % 5))
+
+    return sorted(neighbor_set)
+
+
 def get_global_cell_neighbors(cell_id: int, edge_only: bool = False) -> List[int]:
     """
     Get all neighbors of a cell across quintant and face boundaries.
@@ -101,8 +164,10 @@ def get_global_cell_neighbors(cell_id: int, edge_only: bool = False) -> List[int
     """
     cell = deserialize(cell_id)
     origin, segment, S, resolution = cell['origin'], cell['segment'], cell['S'], cell['resolution']
-    if resolution < FIRST_HILBERT_RESOLUTION:
-        return []  # No neighbors for res 0-1
+    if resolution == 0:
+        return _get_res0_neighbors(origin)
+    if resolution == 1:
+        return _get_res1_neighbors(origin, segment, edge_only)
 
     hilbert_res = resolution - FIRST_HILBERT_RESOLUTION + 1
     source_quintant, source_orientation = segment_to_quintant(segment, origin)

tests/traversal/fixtures/cap.json

@@ -427,7 +427,7 @@
     "estimateCellRadius": [
       {
         "resolution": 0,
-        "expectedMeters": 7356605.443858088
+        "expectedMeters": 7356605.443858089
       },
       {
         "resolution": 1,