fix(rules): apply energy resistance per damage component

2026-09-11 11:24:11 +02:00
parent 1960b8f655
commit 9fb1c2d75a
3 changed files with 284 additions and 27 deletions
@@ -0,0 +1,208 @@
+"""Conformance B21: energy resistance/immunity apply per damage component.
+
+PF1e (CRB "Energy Resistance", "Immunity to Energy Damage"): resistance to
+an energy type reduces damage of THAT type only; immunity negates that type
+only. A weapon dealing 1d6 slashing + 1d6 fire against fire resistance 5
+keeps its slashing dice intact.
+"""
+
+from __future__ import annotations
+
+from typing import Literal
+
+from pf1e_simulator.abilities import AbilitySpec
+from pf1e_simulator.combat import CombatEngine
+from pf1e_simulator.dice import parse_dice
+from pf1e_simulator.models import (
+    AbilityScores,
+    ACProfile,
+    AttackSpec,
+    Combatant,
+    DamageComponent,
+    Saves,
+)
+from pf1e_simulator.rng import ScriptedRng
+from pf1e_simulator.spells import AreaEffect, DamageEffect, SpellSpec
+from tests.test_observation_enriched import make_grid, make_state
+
+
+def _combatant(
+    id_: str,
+    *,
+    level: int = 1,
+    attacks: tuple[AttackSpec, ...] = (),
+    resistances: dict[str, int] | None = None,
+    immunities: tuple[str, ...] = (),
+    features: tuple[str, ...] = (),
+    spell_slots: dict[int, int] | None = None,
+) -> Combatant:
+    return Combatant(
+        id=id_,
+        name=id_,
+        level=level,
+        abilities=AbilityScores(
+            str_score=10, dex_score=10, con_score=10,
+            int_score=10, wis_score=10, cha_score=10,
+        ),
+        ac=ACProfile(total=10, touch=10, flat_footed=10),
+        bab=1,
+        initiative_mod=0,
+        speed_land_ft=30,
+        hp_max=100,
+        saves=Saves(fort=0, ref=0, will=0),
+        attacks=list(attacks),
+        resistances=resistances or {},
+        immunities=immunities,
+        features=[AbilitySpec(name=f, category="feat") for f in features],
+        spell_slots=spell_slots or {},
+    )
+
+
+def _attack(
+    aid: str,
+    components: tuple[tuple[str, tuple[str, ...]], ...],
+    *,
+    kind: Literal["melee", "ranged", "touch"] = "melee",
+) -> AttackSpec:
+    return AttackSpec(
+        id=aid,
+        name=aid,
+        kind=kind,
+        attack_bonus=20,
+        damage=[
+            DamageComponent(formula=parse_dice(formula), types=list(types))
+            for formula, types in components
+        ],
+    )
+
+
+def _engine(
+    combatants: list[Combatant],
+    positions: list[tuple[int, int]],
+    sides: list[str],
+    rng: list[int],
+    spell_registry: dict[str, SpellSpec] | None = None,
+) -> CombatEngine:
+    states = [
+        make_state(c, side, pos)
+        for c, side, pos in zip(combatants, sides, positions, strict=True)
+    ]
+    return CombatEngine(
+        ScriptedRng(rng), make_grid(), states, spell_registry=spell_registry
+    )
+
+
+_MIXED = (
+    ("1d6", ("slashing",)),
+    ("1d6", ("fire",)),
+)
+
+
+def test_fire_resistance_spares_slashing_component() -> None:
+    """(a) 1d6 slashing + 1d6 fire vs fire resistance 5: only the fire
+    portion is reduced (2 - 5 floors to 0); the slashing dice are intact."""
+    weapon = _attack("fiery-blade", _MIXED)
+    hero = _combatant("hero", attacks=(weapon,))
+    foe = _combatant("foe", resistances={"fire": 5})
+    eng = _engine([hero, foe], [(0, 0), (0, 1)], ["players", "monsters"],
+                  [15, 6, 2])
+    result = eng.resolve_attack(eng._states[0], eng._states[1], weapon)
+    # d20=15 hits (no threat); slashing 1d6=6, fire 1d6=2 → fire floored at 0.
+    assert result.damage == 6
+    assert eng._states[1].hp == 94
+
+
+def test_fire_immunity_negates_only_fire_component() -> None:
+    """(b) fire immunity zeroes the fire portion; the slashing portion lands."""
+    weapon = _attack("fiery-blade", _MIXED)
+    hero = _combatant("hero", attacks=(weapon,))
+    foe = _combatant("foe", immunities=("fire",))
+    eng = _engine([hero, foe], [(0, 0), (0, 1)], ["players", "monsters"],
+                  [15, 6, 4])
+    result = eng.resolve_attack(eng._states[0], eng._states[1], weapon)
+    assert result.damage == 6
+    assert eng._states[1].hp == 94
+
+
+def test_physical_only_weapon_ignores_energy_resistance() -> None:
+    """(c) a physical-only weapon vs fire resistance is untouched."""
+    weapon = _attack("sword", (("1d6", ("slashing",)),))
+    hero = _combatant("hero", attacks=(weapon,))
+    foe = _combatant("foe", resistances={"fire": 5})
+    eng = _engine([hero, foe], [(0, 0), (0, 1)], ["players", "monsters"],
+                  [15, 5])
+    result = eng.resolve_attack(eng._states[0], eng._states[1], weapon)
+    assert result.damage == 5
+    assert eng._states[1].hp == 95
+
+
+def test_mixed_energy_component_uses_largest_matching_resistance() -> None:
+    """(d) one component with several energy types (fire+cold) vs resist
+    fire 5 / cold 10 → the largest matching resistance (10) applies."""
+    weapon = _attack("dual-energy", (("2d6", ("fire", "cold")),))
+    hero = _combatant("hero", attacks=(weapon,))
+    foe = _combatant("foe", resistances={"fire": 5, "cold": 10})
+    eng = _engine([hero, foe], [(0, 0), (0, 1)], ["players", "monsters"],
+                  [15, 6, 6])
+    result = eng.resolve_attack(eng._states[0], eng._states[1], weapon)
+    # 2d6 = 12, reduced by cold 10 (largest match), not by fire 5.
+    assert result.damage == 2
+    assert eng._states[1].hp == 98
+
+
+_FIREBALL = SpellSpec(
+    name="Fireball",
+    level=3,
+    school="evocation",
+    range="long",
+    save="ref",
+    base_dc=10,
+    effects=(
+        AreaEffect(
+            radius_ft=20,
+            effects=(
+                DamageEffect(
+                    formula=parse_dice("8d6"),
+                    types=("fire",),
+                    half_on_save=True,
+                ),
+            ),
+            save_for_half=True,
+        ),
+    ),
+)
+
+
+def test_spell_fire_damage_resistance_regression() -> None:
+    """(e) a fire spell vs fire resistance still reduces like before the
+    refactor: 8d6 = 24 (save failed on natural 1) - 5 = 19."""
+    caster = _combatant("caster", spell_slots={3: 9})
+    foe = _combatant("foe", resistances={"fire": 5})
+    eng = _engine(
+        [caster, foe], [(0, 0), (0, 5)], ["players", "monsters"],
+        [1, 3, 3, 3, 3, 3, 3, 3, 3],
+        spell_registry={"Fireball": _FIREBALL},
+    )
+    eng._cast_spell(eng._states[0], eng._states[1], "Fireball")
+    assert eng._states[1].hp == 81
+
+
+def test_sneak_precision_not_reduced_by_energy_resistance() -> None:
+    """(f) sneak attack d6s are untyped precision — energy resistance may
+    only eat the weapon's own energy dice, never the precision dice."""
+    weapon = _attack("flame-dagger", (("1d6", ("fire",)),))
+    rogue = _combatant(
+        "rogue", attacks=(weapon,), features=("Sneak Attack",)
+    )
+    ally = _combatant(
+        "ally", attacks=(_attack("club", (("1d6", ("bludgeoning",)),)),)
+    )
+    foe = _combatant("foe", resistances={"fire": 10})
+    # Rogue (0,0) and ally (0,2) flank the foe (0,1): the sneak attack lands.
+    eng = _engine([rogue, ally, foe], [(0, 0), (0, 2), (0, 1)],
+                  ["players", "players", "monsters"], [15, 6, 4])
+    result = eng.resolve_attack(eng._states[0], eng._states[2], weapon)
+    # d20=15 hits, sneak 1d6=6, fire 1d6=4 → fire floored at 0 by resist 10;
+    # the 6 precision dice survive intact (the old lumped path dealt 0).
+    assert result.damage == 6
+    assert eng._states[2].hp == 94