pf1e-simulator/tests/test_natural_attacks.py

"""Natural weapon attack rules (CRB "Natural Attacks").

Given an attacker with natural weapons and high BAB
When a full attack is resolved
Then natural weapons make exactly one swing each (no BAB iteratives)

Given a secondary natural attack
When a swing is resolved
Then the attack bonus is reduced by 5

Given a secondary natural attack and the attacker has the Multiattack feat
When a swing is resolved
Then the attack bonus is reduced by 2 (instead of 5)
"""

from __future__ import annotations

from pf1e_simulator.combat import CombatantState, CombatEngine
from pf1e_simulator.dice import parse_dice
from pf1e_simulator.grid import Grid
from pf1e_simulator.map import MapSpec, TerrainType
from pf1e_simulator.models import (
    AbilityScores,
    AbilitySpec,
    ACProfile,
    AttackSpec,
    Combatant,
    DamageComponent,
    Saves,
)
from pf1e_simulator.rng import ScriptedRng


def _make_combatant(
    cid: str,
    *,
    side: str,
    bab: int = 1,
    attack_bonus: int = 0,
    natural: bool = False,
    secondary: bool = False,
    features: tuple[str, ...] = (),
) -> Combatant:
    """Build a minimal Combatant with one attack."""
    attack = AttackSpec(
        id=f"{cid}-w",
        name="weapon",
        kind="melee",
        attack_bonus=attack_bonus,
        damage=[DamageComponent(formula=parse_dice("1d6"), types=["slashing"])],
        natural=natural,
        secondary=secondary,
    )
    return Combatant(
        id=cid,
        name=cid,
        level=1,
        size="Medium",
        bab=bab,
        abilities=AbilityScores(
            str_score=10, dex_score=10, con_score=10,
            int_score=10, wis_score=10, cha_score=10,
        ),
        hp_max=20,
        ac=ACProfile(total=15, touch=10, flat_footed=10),
        initiative_mod=0,
        speed_land_ft=30,
        saves=Saves(fort=0, ref=0, will=0),
        attacks=[attack],
        features=[AbilitySpec(name=f, category="feat") for f in features],
    )


def _make_grid() -> Grid:
    """8x8 floor grid."""
    legend = {".": TerrainType(type="floor", move_cost=1)}
    spec = MapSpec(name="test", terrain=tuple(["." * 8] * 8), legend=legend)
    return Grid.from_spec(spec)


def _make_engine(
    queue: list[int],
    attacker: Combatant,
    target: Combatant,
    attacker_pos: tuple[int, int] = (1, 1),
    target_pos: tuple[int, int] = (1, 2),
) -> tuple[CombatEngine, CombatantState, CombatantState]:
    """Create engine with two adjacent combatants and return (engine, atk_state, tgt_state)."""
    a = CombatantState(combatant=attacker, side="players", pos=attacker_pos,
                       hp=attacker.hp_max)
    t = CombatantState(combatant=target, side="monsters", pos=target_pos,
                       hp=target.hp_max)
    engine = CombatEngine(ScriptedRng(queue), _make_grid(), [a, t])
    return engine, a, t


def _swing_lines(engine: CombatEngine, target_id: str) -> list[str]:
    """Transcript lines that resolved a swing against the target."""
    return [line for line in engine._transcript if f"vs {target_id}" in line]


# BAB iteratives


def test_natural_weapon_no_bab_iteratives() -> None:
    """Natural weapon with BAB 16 produces exactly 1 swing, not 4.

    PF1e (CRB "Natural Attacks"): you do not receive additional natural
    attacks for a high base attack bonus.
    """
    atk = _make_combatant("a1", side="players", bab=16, attack_bonus=18, natural=True)
    tgt = _make_combatant("t1", side="monsters", bab=1)
    # RNG: [d20=15] attack roll; on hit -> damage dice (1d6=4)
    engine, a, t = _make_engine([15, 4], atk, tgt)
    engine._full_attack(a, t)
    swings = _swing_lines(engine, "t1")
    assert len(swings) == 1, f"natural weapon should swing once, got {len(swings)}: {swings}"


def test_manufactured_weapon_gets_iteratives() -> None:
    """Non-natural weapon with BAB 16 produces 4 iterative swings (16/11/6/1)."""
    atk = _make_combatant("a2", side="players", bab=16, attack_bonus=18)
    tgt = _make_combatant("t2", side="monsters", bab=1)
    # RNG: 4 swings, each = 1 attack d20 (15) + 1 damage roll (3); target
    # survives 4 x 3 = 12 damage (hp_max 20) so all iteratives resolve.
    queue = [15, 3] * 4
    engine, a, t = _make_engine(queue, atk, tgt)
    engine._full_attack(a, t)
    swings = _swing_lines(engine, "t2")
    assert len(swings) == 4, f"manufactured weapon should swing 4x, got {len(swings)}: {swings}"


def test_secondary_natural_attack_penalty() -> None:
    """Secondary natural attack has -5 penalty on attack bonus.

    PF1e (CRB "Natural Attacks"): secondary natural attacks are at
    base attack bonus -5.
    """
    atk = _make_combatant("a3", side="players", bab=1, attack_bonus=10,
                          natural=True, secondary=True)
    tgt = _make_combatant("t3", side="monsters", bab=1)
    # RNG: [d20=15] attack -> 10 - 5 = 5; total = 15 + 5 = 20 >= AC 15 -> hit; damage 1d6=4
    engine, a, t = _make_engine([15, 4], atk, tgt)
    engine._full_attack(a, t)
    swings = _swing_lines(engine, "t3")
    assert len(swings) == 1
    # base_bonus is 5 (10 - 5 secondary penalty)
    assert "d20=15+5=20" in swings[0]


def test_multiattack_feat_reduces_secondary_penalty() -> None:
    """Multiattack feat reduces secondary natural penalty from -5 to -2.

    PF1e (CRB "Multiattack"): secondary natural attacks are at
    base attack bonus -2 (instead of -5).
    """
    atk = _make_combatant("a4", side="players", bab=1, attack_bonus=10,
                          natural=True, secondary=True,
                          features=("Multiattack",))
    tgt = _make_combatant("t4", side="monsters", bab=1)
    # RNG: [d20=15] attack -> 10 - 2 = 8; total = 15 + 8 = 23 >= AC 15 -> hit; damage 1d6=4
    engine, a, t = _make_engine([15, 4], atk, tgt)
    engine._full_attack(a, t)
    swings = _swing_lines(engine, "t4")
    assert len(swings) == 1
    # base_bonus is 8 (10 - 2 Multiattack)
    assert "d20=15+8=23" in swings[0]