fix(fusion): bound moment components to shared overlapping interval (#87)

src/vidxp/search_fusion.py

@@ -33,7 +33,7 @@ def _query_id(
     return "fused:" + hashlib.sha256(identity.encode("utf-8")).hexdigest()
 
 
-def _connected_components(
+def _shared_overlap_components(
     hits: tuple[SearchHit, ...],
 ) -> list[list[SearchHit]]:
     ordered = sorted(
@@ -50,17 +50,21 @@ def _connected_components(
     components: list[list[SearchHit]] = []
     current: list[SearchHit] = []
     current_media: str | None = None
-    current_end = 0.0
+    current_overlap_end = 0.0
     for hit in ordered:
-        if not current or hit.media_id != current_media or hit.start > current_end:
+        if (
+            not current
+            or hit.media_id != current_media
+            or hit.start > current_overlap_end
+        ):
             if current:
                 components.append(current)
             current = [hit]
             current_media = hit.media_id
-            current_end = hit.end
+            current_overlap_end = hit.end
         else:
             current.append(hit)
-            current_end = max(current_end, hit.end)
+            current_overlap_end = min(current_overlap_end, hit.end)
     if current:
         components.append(current)
     return components
@@ -137,7 +141,7 @@ def fuse_search_results(
     ordered_results = tuple(by_modality[modality] for modality in searched_modalities)
     flattened = tuple(hit for result in ordered_results for hit in result.hits)
     candidates = []
-    for hits in _connected_components(flattened):
+    for hits in _shared_overlap_components(flattened):
         ordered_hits = tuple(
             sorted(
                 hits,
@@ -152,8 +156,8 @@ def fuse_search_results(
             {
                 "score": _score(hits),
                 "media_id": hits[0].media_id,
-                "start": min(hit.start for hit in hits),
-                "end": max(hit.end for hit in hits),
+                "start": max(hit.start for hit in hits),
+                "end": min(hit.end for hit in hits),
                 "modalities": tuple(sorted({hit.modality for hit in hits})),
                 "hits": ordered_hits,
             }

tests/test_search_fusion.py

@@ -57,8 +57,8 @@ def test_rrf_counts_only_the_best_rank_per_modality_in_a_moment(self):
         moment = result.moments[0]
         self.assertAlmostEqual(moment.score, 2 / (RRF_RANK_CONSTANT + 1))
         self.assertEqual(len(moment.hits), 3)
-        self.assertEqual(moment.start, 1)
-        self.assertEqual(moment.end, 4)
+        self.assertEqual(moment.start, 2.5)
+        self.assertEqual(moment.end, 3.0)
 
     def test_result_order_does_not_change_fusion_identity_or_output(self):
         scene = SearchResult(
@@ -96,9 +96,7 @@ def test_rewritten_atomic_query_identity_changes_fused_identity(self):
             modality="scene",
             hits=(hit("scene", 1, 1, 2, "scene:1"),),
         )
-        rewritten = original.model_copy(
-            update={"query_id": "scene:rewritten"}
-        )
+        rewritten = original.model_copy(update={"query_id": "scene:rewritten"})
         arguments = {
             "query": "Where is the taxi?",
             "requested_modalities": ("scene",),
@@ -109,6 +107,69 @@ def test_rewritten_atomic_query_identity_changes_fused_identity(self):
 
         self.assertNotEqual(first.query_id, second.query_id)
 
+    def test_bridging_hit_does_not_merge_separate_moments(self):
+        hit_a = hit("scene", 1, 10.0, 12.0, "scene:a")
+        hit_b = hit("speech", 1, 11.0, 25.0, "speech:b")
+        hit_c = hit("scene", 2, 24.0, 26.0, "scene:c")
+
+        scene = SearchResult(
+            query_id="scene:q",
+            query="car",
+            modality="scene",
+            hits=(hit_a, hit_c),
+        )
+        speech = SearchResult(
+            query_id="speech:q",
+            query="car",
+            modality="speech",
+            hits=(hit_b,),
+        )
+
+        result = fuse_search_results(
+            query="car",
+            requested_modalities=("scene", "speech"),
+            results=(scene, speech),
+        )
+
+        self.assertEqual(len(result.moments), 2)
+        moment_1, moment_2 = result.moments
+        self.assertEqual(moment_1.start, 11.0)
+        self.assertEqual(moment_1.end, 12.0)
+        self.assertIn("scene:a", [h.source_id for h in moment_1.hits])
+        self.assertEqual(moment_2.start, 24.0)
+        self.assertEqual(moment_2.end, 26.0)
+        self.assertIn("scene:c", [h.source_id for h in moment_2.hits])
+        self.assertNotIn("scene:c", [h.source_id for h in moment_1.hits])
+
+    def test_nearby_duplicate_hits_combine_into_one_moment(self):
+        hit_1 = hit("scene", 1, 1.0, 3.0, "scene:1")
+        hit_2 = hit("scene", 2, 2.0, 3.5, "scene:2")
+        hit_3 = hit("speech", 1, 2.2, 2.8, "speech:1")
+
+        scene = SearchResult(
+            query_id="scene:q",
+            query="dog",
+            modality="scene",
+            hits=(hit_1, hit_2),
+        )
+        speech = SearchResult(
+            query_id="speech:q",
+            query="dog",
+            modality="speech",
+            hits=(hit_3,),
+        )
+
+        result = fuse_search_results(
+            query="dog",
+            requested_modalities=("scene", "speech"),
+            results=(scene, speech),
+        )
+
+        self.assertEqual(len(result.moments), 1)
+        self.assertEqual(len(result.moments[0].hits), 3)
+        self.assertEqual(result.moments[0].start, 2.2)
+        self.assertEqual(result.moments[0].end, 2.8)
+
 
 if __name__ == "__main__":
     unittest.main()