feat(combat): enforce spell resistance checks and energy resistances

src/pf1e_simulator/combat.py

@@ -842,6 +842,9 @@ class CombatEngine:
             "spells": tuple(
                 self._spell_snapshot(state, name) for name in state.combatant.spells
             ),
+            "spell_resistance": state.combatant.spell_resistance,
+            "resistances": dict(state.combatant.resistances),
+            "immunities": tuple(state.combatant.immunities),
         }
 
     def _pair_snapshot(
@@ -1373,6 +1376,12 @@ class CombatEngine:
             if crit:
                 damage *= weapon.crit_mult
             damage = self._apply_dr(damage, weapon, target)
+            weapon_types = frozenset(
+                t for comp in weapon.damage for t in comp.types
+            )
+            damage = self._apply_energy_resistance(
+                damage, weapon_types, target
+            )
         target.hp -= damage
         damage = self._consume_up_close_and_deadly(
             attacker, target, weapon, dist_ft, damage, hit=hit
@@ -1427,6 +1436,55 @@ class CombatEngine:
             return damage
         return max(0, damage - dr.amount)
 
+    def _check_spell_resistance(
+        self, caster: CombatantState, target: CombatantState
+    ) -> bool:
+        """SR check: d20 + caster level vs target spell_resistance.
+
+        Returns True if the spell affects the target (SR passed or no SR).
+        Returns False if the target resists the spell (all effects skipped).
+        """
+        sr = target.combatant.spell_resistance
+        if sr == 0:
+            return True
+        caster_level = caster.combatant.level
+        roll = self._rng.d20()
+        total = roll + caster_level
+        if total >= sr:
+            return True
+        self._log(
+            f"round {self._current_round} {caster.combatant.id}: "
+            f"spell resistance {target.combatant.id}: "
+            f"d20({roll}) + CL({caster_level}) = {total} vs SR {sr} "
+            f"— resisted"
+        )
+        return False
+
+    def _apply_energy_resistance(
+        self,
+        damage: int,
+        damage_types: frozenset[str],
+        target: CombatantState,
+    ) -> int:
+        """Energy resistance / immunity at the final-damage stage.
+
+        Immunity: if any damage type matches → 0. Resistance: subtract the
+        max resistance among matching energy types, floored at 0.
+        Physical types (slashing/piercing/bludgeoning/physical) are ignored —
+        they stay on the DR path.
+        """
+        immunities = target.combatant.immunities
+        if immunities and damage_types & frozenset(immunities):
+            return 0
+        resistances = target.combatant.resistances
+        if not resistances:
+            return damage
+        max_resist = max(
+            (resistances[t] for t in damage_types if t in resistances),
+            default=0,
+        )
+        return max(0, damage - max_resist)
+
     def resolve_save(
         self,
         state: CombatantState,
@@ -2890,6 +2948,9 @@ class CombatEngine:
         if self._check_casting_aoo(caster, spell.level):
             return
         caster.spend_spell_slot(spell.level)
+        _has_area = any(isinstance(e, AreaEffect) for e in spell.effects)
+        if not _has_area and not self._check_spell_resistance(caster, target):
+            return
         dc = self._spell_dc(caster, spell)
         save_result = (
             self.resolve_save(
@@ -3023,6 +3084,7 @@ class CombatEngine:
             dmg = raw
         if empower:
             dmg = int(dmg * 1.5)
+        dmg = self._apply_energy_resistance(dmg, frozenset(effect.types), target)
         target.hp -= dmg
         caster_live.damage_dealt += dmg
         target_live.damage_taken += dmg
@@ -3115,6 +3177,8 @@ class CombatEngine:
         total_buffs = 0
 
         for affected_state in affected:
+            if not self._check_spell_resistance(caster, affected_state):
+                continue
             creature_saved = self._area_save(
                 affected_state, target, effect, saved=saved, dc=dc
             )