feat(fusion_clock): schedule parity — overnight, split shifts, open shifts [B1-B3]

is_open + crosses_midnight fields; employee_id optional (open shifts);
company_id computed w/ env.company fallback; drop hard one-per-day UNIQUE
(allow split + open). Overnight math in planned_hours/_check_schedule_times/
scheduled_times. _get_fclk_day_plan resolves multiple posted rows into ONE
work-window so penalties/overtime/absence stay correct. Migration drops the
old constraint defensively. Tests for overnight, window, open shifts.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

fusion_clock/models/clock_schedule.py

@@ -21,10 +21,16 @@ class FusionClockSchedule(models.Model):
     employee_id = fields.Many2one(
         'hr.employee',
         string='Employee',
-        required=True,
+        required=False,  # open (unassigned) shifts have no employee until claimed
         index=True,
         ondelete='cascade',
     )
+    is_open = fields.Boolean(
+        string='Open Shift',
+        default=False,
+        index=True,
+        help="An unassigned shift any eligible employee can claim from the portal.",
+    )
     schedule_date = fields.Date(
         string='Date',
         required=True,
@@ -57,6 +63,13 @@ class FusionClockSchedule(models.Model):
         compute='_compute_planned_hours',
         store=True,
     )
+    crosses_midnight = fields.Boolean(
+        string='Overnight',
+        compute='_compute_planned_hours',
+        store=True,
+        help="Set automatically when the shift ends on the next day "
+             "(end time on or before start time).",
+    )
     note = fields.Char(string='Note')
     role_id = fields.Many2one(
         'fusion.clock.role',
@@ -75,9 +88,10 @@ class FusionClockSchedule(models.Model):
     company_id = fields.Many2one(
         'res.company',
         string='Company',
-        related='employee_id.company_id',
+        compute='_compute_fclk_company',
         store=True,
-        readonly=True,
+        readonly=False,
+        index=True,
     )
     department_id = fields.Many2one(
         'hr.department',
@@ -100,18 +114,41 @@ class FusionClockSchedule(models.Model):
     )
     posted_date = fields.Datetime(string='Posted On', readonly=True)
 
-    _employee_date_unique = models.Constraint(
-        'UNIQUE(employee_id, schedule_date)',
-        'Only one shift schedule is allowed per employee per day.',
-    )
+    # No hard UNIQUE(employee, date): the per-day model now allows split shifts
+    # and open (unassigned) shifts. The shift planner still manages one cell per
+    # day in place; the attendance contract (_get_fclk_day_plan) resolves
+    # multiple posted rows into a single work-window.
+
+    @api.depends('employee_id')
+    def _compute_fclk_company(self):
+        for rec in self:
+            if rec.employee_id:
+                rec.company_id = rec.employee_id.company_id
+            elif not rec.company_id:
+                rec.company_id = self.env.company
+
+    @api.constrains('employee_id', 'is_open')
+    def _check_employee_or_open(self):
+        for rec in self:
+            if not rec.employee_id and not rec.is_open:
+                raise ValidationError(
+                    _("A shift must have an employee unless it is an open shift."))
 
     @api.depends('is_off', 'start_time', 'end_time', 'break_minutes')
     def _compute_planned_hours(self):
         for rec in self:
+            rec.crosses_midnight = False
             if rec.is_off:
                 rec.planned_hours = 0.0
                 continue
-            raw_hours = (rec.end_time or 0.0) - (rec.start_time or 0.0)
+            start = rec.start_time or 0.0
+            end = rec.end_time or 0.0
+            if end <= start:
+                # Overnight: the shift ends on the following day.
+                rec.crosses_midnight = True
+                raw_hours = (24.0 - start) + end
+            else:
+                raw_hours = end - start
             rec.planned_hours = round(max(raw_hours - ((rec.break_minutes or 0.0) / 60.0), 0.0), 2)
 
     @api.depends('employee_id', 'schedule_date', 'is_off', 'start_time', 'end_time')
@@ -130,11 +167,13 @@ class FusionClockSchedule(models.Model):
                 continue
             if rec.start_time < 0 or rec.start_time >= 24:
                 raise ValidationError(_("Start time must be between 00:00 and 23:59."))
-            if rec.end_time <= 0 or rec.end_time > 24:
-                raise ValidationError(_("End time must be between 00:01 and 24:00."))
+            if rec.end_time < 0 or rec.end_time > 24:
+                raise ValidationError(_("End time must be between 00:00 and 24:00."))
+            # Overnight shifts (end on/before start) are allowed and span midnight.
             if rec.end_time <= rec.start_time:
-                raise ValidationError(_("End time must be after start time. Overnight shifts are not supported yet."))
-            shift_minutes = (rec.end_time - rec.start_time) * 60.0
+                shift_minutes = ((24.0 - rec.start_time) + rec.end_time) * 60.0
+            else:
+                shift_minutes = (rec.end_time - rec.start_time) * 60.0
             if rec.break_minutes >= shift_minutes:
                 raise ValidationError(_("Break duration must be shorter than the scheduled shift."))