Add software basic trigger structure and test

ctapipe/instrument/tests/test_trigger.py

@@ -0,0 +1,52 @@
+from ctapipe.containers import ArrayEventContainer
+
+
+def test_softare_trigger(subarray_prod5_paranal):
+    from ctapipe.instrument.trigger import SoftwareTrigger
+
+    subarray = subarray_prod5_paranal
+    trigger = SoftwareTrigger(
+        subarray=subarray,
+        min_telescopes=2,
+        min_telescopes_by_type=[
+            ("type", "*", 1),
+            ("type", "LST*", 2),
+        ],
+    )
+
+    # only one telescope, no SWAT
+    event = ArrayEventContainer()
+    event.trigger.tels_with_trigger = [5]
+    assert trigger(event) == False
+    assert event.trigger.tels_with_trigger == []
+
+    # 1 LST + 1 MST, 1 LST would not have triggered LST hardware trigger
+    # and after LST is removed, we only have 1 telescope, so no SWAT either
+    event = ArrayEventContainer()
+    event.trigger.tels_with_trigger = [1, 6]
+    assert trigger(event) == False
+    assert event.trigger.tels_with_trigger == []
+
+    # two MSTs and 1 LST, -> remove single LST
+    event = ArrayEventContainer()
+    event.trigger.tels_with_trigger = [1, 5, 6]
+    assert trigger(event) == True
+    assert event.trigger.tels_with_trigger == [5, 6]
+
+    # two MSTs, nothing to change
+    event = ArrayEventContainer()
+    event.trigger.tels_with_trigger = [5, 6]
+    assert trigger(event) == True
+    assert event.trigger.tels_with_trigger == [5, 6]
+
+    # three LSTs, nothing to change
+    event = ArrayEventContainer()
+    event.trigger.tels_with_trigger = [1, 2, 3]
+    assert trigger(event) == True
+    assert event.trigger.tels_with_trigger == [1, 2, 3]
+
+    # thee LSTs, plus MSTs, nothing to change
+    event = ArrayEventContainer()
+    event.trigger.tels_with_trigger = [1, 2, 3, 5, 6, 7]
+    assert trigger(event) == True
+    assert event.trigger.tels_with_trigger == [1, 2, 3, 5, 6, 7]

ctapipe/instrument/trigger.py

@@ -0,0 +1,28 @@
+from ctapipe.containers import ArrayEventContainer
+from ctapipe.core import TelescopeComponent
+from ctapipe.core.traits import Integer, IntTelescopeParameter
+
+
+class SoftwareTrigger(TelescopeComponent):
+
+    min_telescopes = Integer(
+        default_value=1,
+        help=(
+            "Minimum number of telescopes required globally."
+            " Events with fewer telescopes will be filtered out completely."
+        ),
+    ).tag(config=True)
+
+    min_telescopes_by_type = IntTelescopeParameter(
+        default_value=1,
+        help=(
+            "Minimum number of telescopes required for a specific type."
+            " In events with fewer telescopes of a given type"
+            " , those telescopes will be removed from the array event."
+            " This might result in the event not fullfilling ``min_telescopes`` anymore"
+            " and thus being filtered completely."
+        ),
+    ).tag(config=True)
+
+    def __call__(self, event: ArrayEventContainer) -> bool:
+        return True