Revert "Add EverySecondWeekendFreeConstraint and remove objective implementation"

src/cp/__init__.py

@@ -1,9 +1,6 @@
 from .constraints import (
     Constraint as Constraint,
 )
-from .constraints import (
-    EverySecondWeekendFreeConstraint as EverySecondWeekendFreeConstraint,
-)
 from .constraints import (
     FreeDayAfterNightShiftPhaseConstraint as FreeDayAfterNightShiftPhaseConstraint,
 )
@@ -32,6 +29,9 @@
     VacationDaysAndShiftsConstraint as VacationDaysAndShiftsConstraint,
 )
 from .model import Model as Model
+from .objectives import (
+    EverySecondWeekendFreeObjective as EverySecondWeekendFreeObjective,
+)
 from .objectives import (
     FreeDaysAfterNightShiftPhaseObjective as FreeDaysAfterNightShiftPhaseObjective,
 )

src/cp/constraints/__init__.py

@@ -1,7 +1,4 @@
 from .constraint import Constraint as Constraint
-from .every_second_weekend_free import (
-    EverySecondWeekendFreeConstraint as EverySecondWeekendFreeConstraint,
-)
 from .free_day_after_night_shift_phase import (
     FreeDayAfterNightShiftPhaseConstraint as FreeDayAfterNightShiftPhaseConstraint,
 )

src/cp/objectives/__init__.py

@@ -1,3 +1,6 @@
+from .every_second_weekend_free import (
+    EverySecondWeekendFreeObjective as EverySecondWeekendFreeObjective,
+)
 from .free_days_after_night_shift_phase import (
     FreeDaysAfterNightShiftPhaseObjective as FreeDaysAfterNightShiftPhaseObjective,
 )

src/cp/constraints/every_second_weekend_free.py → src/cp/objectives/every_second_weekend_free.py

@@ -1,39 +1,41 @@
 import logging
 from datetime import timedelta
+from typing import cast
 
-from ortools.sat.python.cp_model import CpModel
+from ortools.sat.python.cp_model import CpModel, IntVar, LinearExpr
 
 from src.day import Day
 from src.employee import Employee
-from src.shift import Shift
 
 from ..variables import EmployeeWorksOnDayVariables, ShiftAssignmentVariables
-from .constraint import Constraint
+from .objective import Objective
 
 
-class EverySecondWeekendFreeConstraint(Constraint):
+class EverySecondWeekendFreeObjective(Objective):
     @property
     def KEY(self) -> str:
         return "every-second-weekend-free"
 
     def __init__(
         self,
+        weight: float,
         employees: list[Employee],
         days: list[Day],
-        shifts: list[Shift],
     ):
         """
-        Initializes the constraint that enforces alternating free weekends.
+        Initializes the objective that encourages alternating free weekends.
         A weekend is defined as Saturday and Sunday, both days must be free.
         """
-        super().__init__(employees, days, shifts)
+        super().__init__(weight, employees, days, [])
 
     def create(
         self,
         model: CpModel,
         shift_assignment_variables: ShiftAssignmentVariables,
         employee_works_on_day_variables: EmployeeWorksOnDayVariables,
-    ) -> None:
+    ) -> LinearExpr:
+        penalties: list[IntVar] = []
+
         # Collect all complete weekends (Saturday-Sunday pairs) in the planning period
         weekends: list[tuple[Day, Day]] = []
 
@@ -57,21 +59,17 @@ def create(
         logging.info(f"Found {len(weekends)} complete weekends in the planning period")
 
         for employee in self._employees:
-            if employee.hidden:
-                continue
-
-            # For each pair of consecutive weekends, enforce alternating pattern
+            # For each pair of consecutive weekends, penalize if both are free or both have work
             for i in range(len(weekends) - 1):
                 # Get two consecutive weekends
                 weekend1_sat, weekend1_sun = weekends[i]
                 weekend2_sat, weekend2_sun = weekends[i + 1]
-
                 w1_sat_var = employee_works_on_day_variables[employee][weekend1_sat]
                 w1_sun_var = employee_works_on_day_variables[employee][weekend1_sun]
                 w2_sat_var = employee_works_on_day_variables[employee][weekend2_sat]
                 w2_sun_var = employee_works_on_day_variables[employee][weekend2_sun]
 
-                # Create boolean variables for weekend status
+                # Check if weekends are free (both days must be free)
                 w1_free = model.new_bool_var(f"w1_free_e:{employee.get_key()}_i:{i}")
                 w2_free = model.new_bool_var(f"w2_free_e:{employee.get_key()}_i:{i}")
 
@@ -81,7 +79,16 @@ def create(
 
                 model.add(w2_sat_var + w2_sun_var == 0).only_enforce_if(w2_free)
                 model.add(w2_sat_var + w2_sun_var >= 1).only_enforce_if(w2_free.Not())
+                same_status_penalty = model.new_bool_var(f"same_status_penalty_e:{employee.get_key()}_i:{i}")
+
+                # Penalty = 1 if (w1_free AND w2_free) OR (NOT w1_free AND NOT w2_free)
+                model.add(same_status_penalty == 1).only_enforce_if([w1_free, w2_free])
+                model.add(same_status_penalty == 1).only_enforce_if([w1_free.Not(), w2_free.Not()])
+
+                # these two penalties seem useless
+                model.add(same_status_penalty == 0).only_enforce_if([w1_free, w2_free.Not()])
+                model.add(same_status_penalty == 0).only_enforce_if([w1_free.Not(), w2_free])
+
+                penalties.append(same_status_penalty)
 
-                # Hard constraint: two consecutive weekends may not both be worked
-                # At least one of the two consecutive weekends must be free
-                model.add_bool_or([w1_free, w2_free])
+        return cast(LinearExpr, sum(penalties) * self.weight)

src/solve.py

@@ -3,7 +3,7 @@
 from datetime import date
 
 from src.cp import (
-    EverySecondWeekendFreeConstraint,
+    EverySecondWeekendFreeObjective,
     FreeDayAfterNightShiftPhaseConstraint,
     FreeDaysAfterNightShiftPhaseObjective,
     FreeDaysNearWeekendObjective,
@@ -53,6 +53,7 @@ def main(
             "rotate": 1,
             "wishes": 3,
             "after_night": 3,
+            "second_weekend": 1,
         }
 
     logging.info("General information:")
@@ -75,7 +76,6 @@ def main(
         VacationDaysAndShiftsConstraint(employees, days, shifts),
         HierarchyOfIntermediateShiftsConstraint(employees, days, shifts),
         PlannedShiftsConstraint(employees, days, shifts),
-        EverySecondWeekendFreeConstraint(employees, days, shifts),
     ]
     objectives = [
         FreeDaysNearWeekendObjective(weights["free_weekend"], employees, days),
@@ -86,6 +86,7 @@ def main(
         RotateShiftsForwardObjective(weights["rotate"], employees, days, shifts),
         MaximizeEmployeeWishesObjective(weights["wishes"], employees, days, shifts),
         FreeDaysAfterNightShiftPhaseObjective(weights["after_night"], employees, days, shifts),
+        EverySecondWeekendFreeObjective(weights["second_weekend"], employees, days),
     ]
 
     model = Model(employees, days, shifts)

tests/cp/constraints/test_all_constraints.py

@@ -26,6 +26,7 @@
 )
 from src.cp.model import Model
 from src.cp.objectives import (
+    EverySecondWeekendFreeObjective,
     FreeDaysAfterNightShiftPhaseObjective,
     FreeDaysNearWeekendObjective,
     MaximizeEmployeeWishesObjective,
@@ -114,6 +115,7 @@ def test_all_constraints_mass_case(
     model.add_objective(RotateShiftsForwardObjective(1.0, employees, days, shifts))
     model.add_objective(MaximizeEmployeeWishesObjective(3.0, employees, days, shifts))
     model.add_objective(FreeDaysAfterNightShiftPhaseObjective(3.0, employees, days, shifts))
+    model.add_objective(EverySecondWeekendFreeObjective(1.0, employees, days))
 
     model.add_constraint(FreeDayAfterNightShiftPhaseConstraint(employees, days, shifts))
     model.add_constraint(HierarchyOfIntermediateShiftsConstraint(employees, days, shifts))