Test for shortest distance between members in a list and coordinate

Issue:
https://github.com/genenetwork/gn-gemtext-threads/blob/main/topics/gn1-migration-to-gn2/clustering.gmi

* gn3/computations/slink.py: add code to pass new test
* tests/unit/computations/test_slink.py: new test

  Given a list of members in a group, and a coordinate for a member in the
  same group, find the distance of the closest member from the given
  coordinate in the group.

2 files changed, 16 insertions, 1 deletions

diff --git a/gn3/computations/slink.py b/gn3/computations/slink.py
index 7b4016a..3156b31 100644
--- a/gn3/computations/slink.py
+++ b/gn3/computations/slink.py
@@ -70,6 +70,9 @@ This description should be updated once the form/type of 'distance' identified."
     raise_mirrorerror_of_distances_one_way_are_not_same_other_way(lists)
     raise_valueerror_on_negative_distances(lists)
     #### END: Guard Functions ####
-    return None
     if type(i) == int and type(j) == int: # From member i to member j
         return lists[i][j]
+    elif type(i) == int and (type(j) in [list, tuple]):
+        return min(map(lambda j_new: nearest(lists, i, j_new), j))
+    elif type(j) == int and (type(i) in [list, tuple]):
+        return min(map(lambda i_new: nearest(lists, i_new, j), i))
diff --git a/tests/unit/computations/test_slink.py b/tests/unit/computations/test_slink.py
index 166eff9..64d123c 100644
--- a/tests/unit/computations/test_slink.py
+++ b/tests/unit/computations/test_slink.py
@@ -172,3 +172,15 @@ class TestSlink(TestCase):
                                      4,4,0]]:
             with self.subTest(lst=lst):
                 self.assertEqual(nearest(lst, i, j), expected)
+
+    def test_given_a_list_or_tuple_of_members_distances_and_a_coordinate_find_closest_member_to_member_at_coordinate(self):
+        for md, ml, mc, ed in [
+                [[[0,9,3,6,11],[9,0,7,5,10],[3,7,0,9,2],[6,5,9,0,8],[11,10,2,8,0]],[0,1,2,3,4],3,0],
+                [[[0,9,3,6,11],[9,0,7,5,10],[3,7,0,9,2],[6,5,9,0,8],[11,10,2,8,0]],[0,1,2,4],3,5],
+                [[[0,9,3,6,11],[9,0,7,5,10],[3,7,0,9,2],[6,5,9,0,8],[11,10,2,8,0]],[0,2,4],3,6],
+                [[[0,9,3,6,11],[9,0,7,5,10],[3,7,0,9,2],[6,5,9,0,8],[11,10,2,8,0]],[2,4],3,8]]:
+            with self.subTest(
+                    members_distances=md, members_list=ml, member_coordinate=mc,
+                    expected_distance=ed):
+                self.assertEqual(nearest(md, ml, mc), ed)
+                self.assertEqual(nearest(md, mc, ml), ed)