Merge pull request #76 from NHSDigital/feature/ELI-237-offset-date-operators

ELI-237 Offset date operators

Author: acerathereinspirative-nhs-nvir

src/eligibility_signposting_api/services/rules/operators.py

@@ -177,8 +177,12 @@ def _matches(self, item: str | None) -> bool:
 
 
 class RangeOperator(Operator, ABC):
-    def __init__(self, rule_value: str) -> None:
-        super().__init__(rule_value=rule_value)
+    low_comparator: int
+    high_comparator: int
+
+    def __post_init__(self) -> None:
+        super().__post_init__()
+
         low_comparator_str, high_comparator_str = str(self.rule_value).split(",")
         self.low_comparator = min(int(low_comparator_str), int(high_comparator_str))
         self.high_comparator = max(int(low_comparator_str), int(high_comparator_str))
@@ -227,8 +231,17 @@ def _matches(self, item: str | None) -> bool:
 
 
 class DateOperator(Operator, ABC):
+    OFFSET_PATTERN: ClassVar[str] = r"(?P<rule_value>[^\[]+)\[\[OFFSET:(?P<offset>\d{8})\]\]"
     delta_type: ClassVar[str]
     comparator: ClassVar[Callable[[date, date], bool]]
+    offset: date | None = None
+
+    def __post_init__(self) -> None:
+        super().__post_init__()
+
+        if self.rule_value and (match := re.match(self.OFFSET_PATTERN, self.rule_value)):
+            self.rule_value = match.group("rule_value")
+            self.offset = datetime.strptime(match.group("offset"), "%Y%m%d").replace(tzinfo=UTC).date()
 
     @property
     def today(self) -> date:
@@ -242,7 +255,7 @@ def get_attribute_date(item: str | None) -> date | None:
     def cutoff(self) -> date:
         delta = relativedelta()
         setattr(delta, self.delta_type, int(self.rule_value))
-        return self.today + delta
+        return (self.offset if self.offset else self.today) + delta
 
     def _matches(self, item: str | None) -> bool:
         item = item if item is not None else self.item_default

tests/unit/services/operators/test_operators.py

@@ -519,6 +519,9 @@
     ("20260425", RuleOperator.year_gte, "2", False, "Past year"),
     ("20270425", RuleOperator.year_gte, "2", True, "Present year"),
     ("20280425", RuleOperator.year_gte, "2", True, "Future year"),
+    ("19680720", RuleOperator.year_gte, "-57[[OFFSET:20250721]]", False, "Include anyone older than Simon"),
+    ("19680721", RuleOperator.year_gte, "-57[[OFFSET:20250721]]", True, "Exclude anyone the same age as Simon"),
+    ("19680722", RuleOperator.year_gte, "-57[[OFFSET:20250721]]", True, "Exclude anyone younger than Simon"),
 ]
 
 # Year greater than
@@ -529,6 +532,9 @@
     ("20200424", RuleOperator.year_gt, "-5", False, "Exclude anyone under 5 on the day - 5 yesterday"),
     ("20200425", RuleOperator.year_gt, "-5", False, "Exclude anyone under 5 on the day-  5 today"),
     ("20200426", RuleOperator.year_gt, "-5", True, "Exclude anyone under 5 on the day - 5 tomorrow"),
+    ("19680720", RuleOperator.year_gt, "-57[[OFFSET:20250721]]", False, "Include anyone older than Simon"),
+    ("19680721", RuleOperator.year_gt, "-57[[OFFSET:20250721]]", False, "Include anyone the same age as Simon"),
+    ("19680722", RuleOperator.year_gt, "-57[[OFFSET:20250721]]", True, "Exclude anyone younger than Simon"),
 ]