Add minimum duration argument for scans

This ensures that scans are at least `min_duration` long, otherwise it skips
the scan entirely.

src/sorunlib/seq.py

@@ -1,11 +1,16 @@
+import datetime as dt
+
 import sorunlib as run
+
+from sorunlib.commands import _timestamp_to_utc_datetime
 from sorunlib._internal import check_response, check_started, monitor_process
 
 
 OP_TIMEOUT = 60
 
 
-def scan(description, stop_time, width, az_drift=0, tag=None, subtype=None):
+def scan(description, stop_time, width, az_drift=0, tag=None, subtype=None,
+         min_duration=None):
     """Run a constant elevation scan, collecting detector data.
 
     Args:
@@ -19,8 +24,20 @@ def scan(description, stop_time, width, az_drift=0, tag=None, subtype=None):
         tag (str, optional): Tag or comma-separated listed of tags to attach to
             the operation. Passed through to the smurf stream command.
         subtype (str, optional): Operation subtype used to tag the stream.
+        min_duration (float, optional): Minimum duration required to scan,
+            specified in seconds. If not enough time exists between now and the
+            ``stop_time`` the scan is not executed. Defaults to None.
 
     """
+    now = dt.datetime.now(dt.timezone.utc)
+    scan_stop = _timestamp_to_utc_datetime(stop_time)
+
+    # Check there is enough time to perform scan
+    if min_duration is not None:
+        start_by_time = scan_stop - dt.timedelta(seconds=min_duration)
+        if now > start_by_time:
+            return
+
     acu = run.CLIENTS['acu']
 
     # Enable SMuRF streams

tests/test_seq.py

@@ -24,14 +24,22 @@ def test_scan(patch_clients):
     seq.scan(description='test', stop_time=target.isoformat(), width=20.)
 
 
+@patch('sorunlib._internal.time.sleep', MagicMock())
+def test_scan_passed_min_duration(patch_clients):
+    # This affects test runtime duration keep it short
+    target = dt.datetime.now(dt.timezone.utc) + dt.timedelta(seconds=10)
+    seq.scan(description='test', stop_time=target.isoformat(), width=20., min_duration=60)
+    seq.run.CLIENTS['acu'].generate_scan.start.assert_not_called()
+
+
 @patch('sorunlib.commands.time.sleep', MagicMock())
 def test_scan_no_session(patch_clients):
     # Setup mock OCSReply without session object
     mock_reply = MagicMock()
     mock_reply.session = None
     sorunlib.CLIENTS['acu'].generate_scan.start = MagicMock(return_value=mock_reply)
 
-    target = dt.datetime.now() + dt.timedelta(seconds=1)
+    target = dt.datetime.now(dt.timezone.utc) + dt.timedelta(seconds=1)
     with pytest.raises(Exception):
         seq.scan(description='test', stop_time=target.isoformat(), width=20.)
 
@@ -60,6 +68,6 @@ def test_scan_failed_to_start(patch_clients):
     #   other keys in .session: op_code, data
     print(mock_reply)
 
-    target = dt.datetime.now() + dt.timedelta(seconds=1)
+    target = dt.datetime.now(dt.timezone.utc) + dt.timedelta(seconds=10)
     with pytest.raises(RuntimeError):
         seq.scan(description='test', stop_time=target.isoformat(), width=20.)