Refactor motion search (#23378)

* refactor motion search

* cleanup dead code and tests

* tweaks

* fix multi-day seeking

* start playback a few seconds before the change so the motion is in view

frigate/test/test_motion_search_batch.py

@@ -0,0 +1,58 @@
+"""Tests for motion search batch helpers (runs + timestamp mapping)."""
+
+import unittest
+from dataclasses import dataclass
+
+from frigate.jobs.motion_search_batch import (
+    build_segment_time_map,
+    coalesce_runs,
+    stream_time_to_absolute,
+)
+
+
+@dataclass
+class _Seg:
+    path: str
+    start_time: float
+    end_time: float
+
+
+def _run_seconds(run):
+    return float(run[-1].end_time) - float(run[0].start_time)
+
+
+class TestCoalesceRuns(unittest.TestCase):
+    def test_contiguous_segments_form_one_run(self):
+        segs = [_Seg("a", 0.0, 10.0), _Seg("b", 10.0, 20.0), _Seg("c", 20.0, 30.0)]
+        runs = coalesce_runs(segs, max_seconds=600.0, epsilon=0.5)
+        self.assertEqual(len(runs), 1)
+        self.assertEqual(len(runs[0]), 3)
+
+    def test_time_gap_splits_runs(self):
+        # b ends 20, c starts 25 -> 5s gap > epsilon -> two runs.
+        segs = [_Seg("a", 0.0, 10.0), _Seg("b", 10.0, 20.0), _Seg("c", 25.0, 35.0)]
+        runs = coalesce_runs(segs, max_seconds=600.0, epsilon=0.5)
+        self.assertEqual([len(r) for r in runs], [2, 1])
+
+    def test_max_duration_caps_a_run(self):
+        # Five contiguous 10s segments, cap 25s.
+        segs = [_Seg(str(i), i * 10.0, i * 10.0 + 10.0) for i in range(5)]
+        runs = coalesce_runs(segs, max_seconds=25.0, epsilon=0.5)
+        self.assertTrue(all(_run_seconds(r) <= 30.0 for r in runs))
+        self.assertEqual(sum(len(r) for r in runs), 5)
+
+    def test_empty(self):
+        self.assertEqual(coalesce_runs([], max_seconds=600.0, epsilon=0.5), [])
+
+
+class TestTimestampMapping(unittest.TestCase):
+    def test_gapfree_run_maps_to_start_plus_pts(self):
+        run = [_Seg("a", 1000.0, 1010.0), _Seg("b", 1010.0, 1020.0)]
+        time_map = build_segment_time_map(run)
+        self.assertAlmostEqual(stream_time_to_absolute(time_map, 3.0), 1003.0)
+        self.assertAlmostEqual(stream_time_to_absolute(time_map, 12.0), 1012.0)
+
+    def test_past_end_clamps(self):
+        run = [_Seg("a", 1000.0, 1010.0)]
+        time_map = build_segment_time_map(run)
+        self.assertAlmostEqual(stream_time_to_absolute(time_map, 9.9), 1009.9)