Resolve L2SS-572 "Refactor delays"

Closes L2SS-572

tangostationcontrol/tangostationcontrol/beam/delays.py

@@ -2,11 +2,11 @@ import casacore.measures
 import numpy
 import datetime
 
-def subtract(a, b):
+def subtract(a, b) -> numpy.ndarray:
     return numpy.array([x - y for x, y in zip(a, b)])
 
 
-class delay_calculator:
+class Delays:
     def __init__(self, itrf: list([float])):
 
         """ Create a measure object, configured for the specified terrestrial location. """
@@ -14,8 +14,8 @@ class delay_calculator:
         measure = casacore.measures.measures()
         frame_location = measure.position("ITRF", *[f"{x}m" for x in itrf])
 
-        result = measure.do_frame(frame_location)
-        assert result == True
+        if not measure.do_frame(frame_location):
+            raise ValueError(f"measure.do_frame failed for ITRF location {itrf}")
 
         self.reference_itrf = itrf
         self.measure = measure
@@ -23,10 +23,11 @@ class delay_calculator:
 
     def set_measure_time(self, utc_time: datetime.datetime):
         """ Configure the measure object for the specified time. """
-        frame_time = self.measure.epoch("UTC", utc_time.isoformat(' '))
+        utc_time_str = utc_time.isoformat(' ')
+        frame_time = self.measure.epoch("UTC", utc_time_str)
 
-        result = self.measure.do_frame(frame_time)
-        assert result == True
+        if not self.measure.do_frame(frame_time):
+            raise ValueError(f"measure.do_frame failed for UTC time {utc_time_str}")
 
     def get_direction_vector(self, pointing: numpy.ndarray) -> numpy.ndarray:
         """ Compute direction vector for a given pointing, relative to the measure. """
@@ -53,7 +54,8 @@ class delay_calculator:
         # Return array [directions][angles]
         return direction_vectors.T
 
-    def is_valid_direction(self, direction):
+    def is_valid_direction(self, direction) -> bool:
+        """ Check validity of the direction measure """
         try:
             _ = self.measure.direction(*direction)
         except (RuntimeError, TypeError) as e:
@@ -61,14 +63,14 @@ class delay_calculator:
 
         return True
 
-    def convert(self, direction, antenna_absolute_itrf: list([float])):
+    def delays(self, direction, antenna_absolute_itrf: list([float])) -> numpy.ndarray:
         """ Get the delays for a direction and *absolute* antenna positions.
         
             Returns delays[antenna]. """
 
-        return self.convert_bulk([direction], numpy.array(antenna_absolute_itrf) - self.reference_itrf).flatten()
+        return self.delays_bulk([direction], numpy.array(antenna_absolute_itrf) - self.reference_itrf).flatten()
 
-    def convert_bulk(self, directions: numpy.ndarray, antenna_relative_itrfs: numpy.ndarray) -> numpy.ndarray:
+    def delays_bulk(self, directions: numpy.ndarray, antenna_relative_itrfs: numpy.ndarray) -> numpy.ndarray:
         """ Get the delays for each direction and each *relative* antenna position.
         
             Returns delays[antenna][direction]. """