feat(combat): effect and condition durations

src/pf1e_simulator/effects.py

@@ -20,6 +20,8 @@ from typing import TYPE_CHECKING, Literal
 if TYPE_CHECKING:
     from collections.abc import Iterable
 
+    from pf1e_simulator.conditions import Condition
+
 BonusType = Literal[
     "",               # untyped — stacks with everything
     "dodge",          # stacks with itself
@@ -65,6 +67,40 @@ class StatModifier:
     weapon_filter: str | None = None
 
 
+@dataclass(frozen=True)
+class ActiveBuff:
+    """A temporary buff with a remaining duration in rounds.
+
+    - ``modifiers``: the stat modifiers this buff provides.
+    - ``rounds_left``: how many more rounds this buff lasts (decremented at
+      the start of the affected creature's turn). When it reaches 0, the buff
+      expires and is removed.
+    - ``source``: a human-readable description of what created this buff
+      (e.g. "spell: bull's strength", "charge", "class ability: inspire courage").
+    """
+
+    modifiers: tuple[StatModifier, ...]
+    rounds_left: int
+    source: str
+
+
+@dataclass(frozen=True)
+class ActiveCondition:
+    """A temporary condition with a remaining duration in rounds.
+
+    - ``condition``: the Condition definition (modifiers + behavioral flags).
+    - ``rounds_left``: how many more rounds this condition lasts (decremented at
+      the start of the affected creature's turn). When it reaches 0, the condition
+      expires and is removed.
+    - ``source``: a human-readable description of what created this condition
+      (e.g. "spell: hold person", "monster ability: fear aura").
+    """
+
+    condition: Condition
+    rounds_left: int
+    source: str
+
+
 def resolve_modifiers(modifiers: Iterable[StatModifier]) -> int:
     """Sum stat modifiers applying PF1e stacking rules.