Extend lookup table model (#142)

* Extend lookup table model

* Add tests

* PR comments

Author: jacob720

src/daq_config_server/models/converters/lookup_tables/_models.py

@@ -17,3 +17,45 @@ def check_row_length_matches_n_columns(self):
                     f"of columns: {self.column_names}"
                 )
         return self
+
+    def get_value(
+        self,
+        column_name: str,
+        value: int | float,
+        target_column_name: str,
+        value_must_exist: bool = True,
+    ) -> int | float:
+        """Look up a value in one columna nd return the corresponding entry from another
+        column.
+
+        Args:
+            column_name (str): The name of the column to search in.
+            value (int | float): The numeric value to look for within `column_name`.
+            target_column_name (str): The name of the column from which to return the
+            corresponding entry (same row as the matched value).
+            value_must_exist (bool, optional): If true, value must exist in the LUT or
+            an error will be thrown. Otherwise, the closest value will be used.
+            Defaults to True.
+
+        Returns:
+            int | float: The entry from `target_column_name` in the row where the
+        matching (or closest) value was found in `column_name`.
+        """
+        column_index = self.column_names.index(column_name)
+        column = [row[column_index] for row in self.rows]
+        target_column_index = self.column_names.index(target_column_name)
+
+        closest_value = (
+            min(column, key=lambda x: abs(x - value)) if not value_must_exist else value
+        )
+        try:
+            target_row = self.rows[column.index(closest_value)]
+        except ValueError as e:
+            raise ValueError(
+                f"'{closest_value}' doesn't exist in column '{column_name}': {column}"
+            ) from e
+
+        return target_row[target_column_index]
+
+    def columns(self) -> list[list[int | float]]:
+        return [[row[i] for row in self.rows] for i in range(len(self.column_names))]

tests/unit_tests/converters/test_lookup_tables_converters.py

@@ -1,3 +1,5 @@
+import re
+
 import pytest
 from tests.constants import TestDataPaths
 
@@ -113,3 +115,48 @@ def test_undulator_gap_lut_gives_expected_result():
     )
     result = undulator_energy_gap_lut(input)
     assert result == expected
+
+
+@pytest.mark.parametrize(
+    "args, expected_value",
+    [
+        (("detector_distances_mm", 150, "beam_centre_x_mm", True), 152.2),
+        (("beam_centre_y_mm", 160.96, "detector_distances_mm", True), 800),
+        (
+            ("beam_centre_x_mm", 153, "beam_centre_y_mm", False),
+            166.26,  # get closest value when value_must_exist == False
+        ),
+    ],
+)
+def test_generic_lut_model_get_value_function(
+    args: tuple[str, int | float, str, bool], expected_value: int | float
+):
+    my_lut = GenericLookupTable(
+        column_names=["detector_distances_mm", "beam_centre_x_mm", "beam_centre_y_mm"],
+        rows=[[150, 152.2, 166.26], [800, 152.08, 160.96]],
+    )
+    assert my_lut.get_value(*args) == expected_value
+
+
+def test_generic_lut_model_get_value_errors_if_value_doesnt_exist():
+    my_lut = GenericLookupTable(
+        column_names=["detector_distances_mm", "beam_centre_x_mm", "beam_centre_y_mm"],
+        rows=[[150, 152.2, 166.26], [800, 152.08, 160.96]],
+    )
+    with pytest.raises(
+        ValueError,
+        match=re.escape(
+            "'160.97' doesn't exist in column 'beam_centre_y_mm': [166.26, 160.96]"
+        ),
+    ):
+        # value doesn't exist
+        my_lut.get_value("beam_centre_y_mm", 160.97, "detector_distances_mm")
+
+
+def test_generic_lut_model_columns_function():
+    my_lut = GenericLookupTable(
+        column_names=["detector_distances_mm", "beam_centre_x_mm", "beam_centre_y_mm"],
+        rows=[[150, 152.2, 166.26], [800, 152.08, 160.96]],
+    )
+    expected_columns = [[150, 800], [152.2, 152.08], [166.26, 160.96]]
+    assert my_lut.columns() == expected_columns