BE-AGT-003: implement multi-slot competition handling

- resolve_slot_competition: selects highest-priority slot as winner,
  marks remaining as Deferred with priority += 1 (capped at 99)
- defer_all_slots: defers all pending slots when agent is not idle
- CompetitionResult dataclass for structured return
- Full test coverage: winner selection, priority bumping, cap, ties,
  empty input, single slot, already-deferred slots

tests/test_slot_competition.py

@@ -0,0 +1,164 @@
+"""Tests for BE-AGT-003 — multi-slot competition handling.
+
+Covers:
+  - Winner selection (highest priority)
+  - Remaining slots marked Deferred with priority += 1
+  - Priority capping at MAX_PRIORITY (99)
+  - Empty input edge case
+  - Single slot (no competition)
+  - defer_all_slots when agent is not idle
+"""
+
+import pytest
+from datetime import date, time
+
+from app.models.calendar import SlotStatus, SlotType, TimeSlot
+from app.services.slot_competition import (
+    CompetitionResult,
+    MAX_PRIORITY,
+    defer_all_slots,
+    resolve_slot_competition,
+)
+
+
+def _make_slot(db, user_id: int, *, priority: int, status=SlotStatus.NOT_STARTED) -> TimeSlot:
+    """Helper — create a minimal TimeSlot in the test DB."""
+    slot = TimeSlot(
+        user_id=user_id,
+        date=date(2026, 4, 1),
+        slot_type=SlotType.WORK,
+        estimated_duration=30,
+        scheduled_at=time(9, 0),
+        priority=priority,
+        status=status,
+    )
+    db.add(slot)
+    db.flush()
+    return slot
+
+
+# ---------------------------------------------------------------------------
+# resolve_slot_competition
+# ---------------------------------------------------------------------------
+
+class TestResolveSlotCompetition:
+    """Tests for resolve_slot_competition."""
+
+    def test_empty_input(self, db, seed):
+        result = resolve_slot_competition(db, [])
+        assert result.winner is None
+        assert result.deferred == []
+
+    def test_single_slot_no_competition(self, db, seed):
+        slot = _make_slot(db, 1, priority=50)
+        result = resolve_slot_competition(db, [slot])
+
+        assert result.winner is slot
+        assert result.deferred == []
+        # Winner should NOT be modified
+        assert slot.status == SlotStatus.NOT_STARTED
+        assert slot.priority == 50
+
+    def test_winner_is_first_slot(self, db, seed):
+        """Input is pre-sorted by priority desc; first slot wins."""
+        high = _make_slot(db, 1, priority=80)
+        mid = _make_slot(db, 1, priority=50)
+        low = _make_slot(db, 1, priority=10)
+        slots = [high, mid, low]
+
+        result = resolve_slot_competition(db, slots)
+
+        assert result.winner is high
+        assert len(result.deferred) == 2
+        assert mid in result.deferred
+        assert low in result.deferred
+
+    def test_deferred_slots_status_and_priority(self, db, seed):
+        """Deferred slots get status=DEFERRED and priority += 1."""
+        winner = _make_slot(db, 1, priority=80)
+        loser1 = _make_slot(db, 1, priority=50)
+        loser2 = _make_slot(db, 1, priority=10)
+
+        resolve_slot_competition(db, [winner, loser1, loser2])
+
+        # Winner untouched
+        assert winner.status == SlotStatus.NOT_STARTED
+        assert winner.priority == 80
+
+        # Losers deferred + bumped
+        assert loser1.status == SlotStatus.DEFERRED
+        assert loser1.priority == 51
+
+        assert loser2.status == SlotStatus.DEFERRED
+        assert loser2.priority == 11
+
+    def test_priority_capped_at_max(self, db, seed):
+        """Priority bump should not exceed MAX_PRIORITY."""
+        winner = _make_slot(db, 1, priority=99)
+        at_cap = _make_slot(db, 1, priority=99)
+
+        resolve_slot_competition(db, [winner, at_cap])
+
+        assert at_cap.status == SlotStatus.DEFERRED
+        assert at_cap.priority == MAX_PRIORITY  # stays at 99, not 100
+
+    def test_already_deferred_slots_get_bumped(self, db, seed):
+        """Slots that were already DEFERRED still get priority bumped."""
+        winner = _make_slot(db, 1, priority=90)
+        already_deferred = _make_slot(db, 1, priority=40, status=SlotStatus.DEFERRED)
+
+        result = resolve_slot_competition(db, [winner, already_deferred])
+
+        assert already_deferred.status == SlotStatus.DEFERRED
+        assert already_deferred.priority == 41
+
+    def test_tie_breaking_first_wins(self, db, seed):
+        """When priorities are equal, the first in the list wins."""
+        a = _make_slot(db, 1, priority=50)
+        b = _make_slot(db, 1, priority=50)
+
+        result = resolve_slot_competition(db, [a, b])
+
+        assert result.winner is a
+        assert b in result.deferred
+        assert b.status == SlotStatus.DEFERRED
+
+
+# ---------------------------------------------------------------------------
+# defer_all_slots
+# ---------------------------------------------------------------------------
+
+class TestDeferAllSlots:
+    """Tests for defer_all_slots (agent not idle)."""
+
+    def test_empty_input(self, db, seed):
+        result = defer_all_slots(db, [])
+        assert result == []
+
+    def test_all_slots_deferred(self, db, seed):
+        s1 = _make_slot(db, 1, priority=70)
+        s2 = _make_slot(db, 1, priority=30)
+
+        result = defer_all_slots(db, [s1, s2])
+
+        assert len(result) == 2
+        assert s1.status == SlotStatus.DEFERRED
+        assert s1.priority == 71
+        assert s2.status == SlotStatus.DEFERRED
+        assert s2.priority == 31
+
+    def test_priority_cap_in_defer_all(self, db, seed):
+        s = _make_slot(db, 1, priority=99)
+
+        defer_all_slots(db, [s])
+
+        assert s.priority == MAX_PRIORITY
+
+    def test_already_deferred_still_bumped(self, db, seed):
+        """Even if already DEFERRED, priority still increases."""
+        s = _make_slot(db, 1, priority=45, status=SlotStatus.DEFERRED)
+
+        defer_all_slots(db, [s])
+
+        assert s.status == SlotStatus.DEFERRED
+        assert s.priority == 46