pf1e-simulator/tests/test_pair_failure_reasons.py

"""U6b: per-pair attack/charge failure reasons in the Observation snapshot.

The pair dict now exposes WHY an attack or a charge is unavailable, not just
that it is: ``weapon_reason`` is None when ``weapon_for`` selected a weapon,
otherwise the blocking cause (``no_weapon`` / ``no_line_of_effect`` /
``out_of_range``, drawn from the U1 ``ACTION_RESULT_REASONS`` vocabulary);
``charge_reason`` is None when ``can_charge`` is True, otherwise the
``ChargeResult.reason`` verbatim (``no_line_of_effect`` / ``no_charge_path``)
or ``no_weapon`` when the actor has no usable melee weapon at all.

Covers:
- (a) unarmed actor -> ``weapon_reason`` / ``charge_reason`` ``no_weapon``;
- (b) wall column blocking the line -> ``no_line_of_effect``;
- (c) melee-only actor facing a distant target -> ``out_of_range``;
- (d) valid adjacent target -> ``weapon_reason`` None;
- (e) creatures interposed on every straight charge line -> the engine's
  ``no_charge_path``;
- (f) valid charge line -> ``charge_reason`` None; ranged-only actor ->
  ``no_weapon``;
- (g) ``to_dict()`` stays JSON-serializable.
"""

from __future__ import annotations

import json

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,
    ACProfile,
    AttackSpec,
    Combatant,
    DamageComponent,
    Saves,
)
from pf1e_simulator.rng import ScriptedRng
from tests.test_observation_enriched import _pair_for, _snapshot, make_state

_LEGEND = {
    ".": TerrainType(type="floor", move_cost=1),
    "#": TerrainType(type="wall", move_cost=None, blocks_los=True),
}


def _grid(rows: list[str]) -> Grid:
    spec = MapSpec(name="reasons-test", terrain=tuple(rows), legend=_LEGEND)
    return Grid.from_spec(spec)


def _open_rows() -> list[str]:
    return ["........"] * 8


def _bow(cid: str) -> AttackSpec:
    return AttackSpec(
        id=f"{cid}-bow",
        name="short bow",
        kind="ranged",
        attack_bonus=5,
        damage=[DamageComponent(formula=parse_dice("1d6"), types=["piercing"])],
        range_increment_ft=60,
    )


def _sword(cid: str) -> AttackSpec:
    return AttackSpec(
        id=f"{cid}-sword",
        name="short sword",
        kind="melee",
        attack_bonus=5,
        damage=[DamageComponent(formula=parse_dice("1d6"), types=["slashing"])],
    )


def _combatant(cid: str, attacks: list[AttackSpec]) -> Combatant:
    return Combatant(
        id=cid,
        name=cid,
        level=1,
        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=attacks,
    )


def _engine(states: list[CombatantState], rows: list[str]) -> CombatEngine:
    return CombatEngine(ScriptedRng([]), _grid(rows), states)


# (a) no usable weapon at all.


def test_weapon_reason_no_weapon_when_actor_unarmed() -> None:
    """Given: an actor with no attacks at all facing an adjacent foe
    When: the Observation is built for the actor
    Then: weapon_for is None with weapon_reason no_weapon, and the charge
    helper's no-melee-weapon None maps to charge_reason no_weapon too."""
    actor = make_state(_combatant("unarmed", []), "players", (1, 0))
    foe = make_state(_combatant("foe", [_sword("foe")]), "monsters", (1, 1))
    engine = _engine([actor, foe], _open_rows())

    obs = _snapshot(engine, actor)
    pair = _pair_for(obs, 1)
    assert pair["weapon_for"] is None
    assert pair["weapon_reason"] == "no_weapon"
    assert pair["can_charge"] is False
    assert pair["charge_reason"] == "no_weapon"


# (b) line of effect blocked by a wall column.


def test_weapon_reason_no_line_of_effect_behind_wall_column() -> None:
    """Given: an archer at (4, 0) and a foe at (4, 4) behind a full wall column
    When: the Observation is built for the archer
    Then: weapon_reason and charge_reason are both no_line_of_effect."""
    archer = make_state(_combatant("archer", [_bow("archer")]), "players", (4, 0))
    foe = make_state(_combatant("foe", [_sword("foe")]), "monsters", (4, 4))
    rows = ["..#....."] * 8
    engine = _engine([archer, foe], rows)

    obs = _snapshot(engine, archer)
    pair = _pair_for(obs, 1)
    assert pair["has_line_of_effect"] is False
    assert pair["weapon_for"] is None
    assert pair["weapon_reason"] == "no_line_of_effect"
    assert pair["can_charge"] is False
    assert pair["charge_reason"] == "no_line_of_effect"


# (c) weapon usable but the target out of reach.


def test_weapon_reason_out_of_range_with_clear_line() -> None:
    """Given: a melee-only actor at (1, 0) and a foe at (1, 4) on open ground
    When: the Observation is built for the actor
    Then: weapon_reason is out_of_range (weapon exists, LoE is clear)."""
    striker = make_state(_combatant("swordsman", [_sword("swordsman")]), "players", (1, 0))
    foe = make_state(_combatant("foe", [_sword("foe")]), "monsters", (1, 4))
    engine = _engine([striker, foe], _open_rows())

    obs = _snapshot(engine, striker)
    pair = _pair_for(obs, 1)
    assert pair["has_line_of_effect"] is True
    assert pair["weapon_for"] is None
    assert pair["weapon_reason"] == "out_of_range"


# (d) a valid attack carries no reason.


def test_weapon_reason_none_for_valid_adjacent_attack() -> None:
    """Given: an armed actor adjacent to a foe on open ground
    When: the Observation is built
    Then: weapon_for names the weapon and weapon_reason is None."""
    actor = make_state(_combatant("hero", [_sword("hero")]), "players", (1, 0))
    foe = make_state(_combatant("foe", [_sword("foe")]), "monsters", (1, 1))
    engine = _engine([actor, foe], _open_rows())

    obs = _snapshot(engine, actor)
    pair = _pair_for(obs, 1)
    assert pair["weapon_for"] == "short sword"
    assert pair["weapon_reason"] is None


# (e) charge blocked by interposed creatures despite a clear line of effect.


def test_charge_reason_no_charge_path_when_creatures_block_the_line() -> None:
    """Given: an actor at (1, 0), a foe at (1, 3), creatures at (1, 1), (0, 2)
    and (2, 2) — every straight Bresenham line to any attackable anchor passes
    through one of them, while terrain LoE stays clear
    When: the Observation is built for the actor
    Then: can_charge is False and charge_reason is the engine's no_charge_path."""
    actor = make_state(_combatant("hero", [_sword("hero")]), "players", (1, 0))
    foe = make_state(_combatant("foe", [_sword("foe")]), "monsters", (1, 3))
    guard_a = make_state(_combatant("guard-a", [_sword("guard-a")]), "monsters", (1, 1))
    guard_b = make_state(_combatant("guard-b", [_sword("guard-b")]), "monsters", (0, 2))
    guard_c = make_state(_combatant("guard-c", [_sword("guard-c")]), "monsters", (2, 2))
    engine = _engine([actor, foe, guard_a, guard_b, guard_c], _open_rows())

    obs = _snapshot(engine, actor)
    pair = _pair_for(obs, 1)
    assert pair["has_line_of_effect"] is True
    assert pair["can_charge"] is False
    assert pair["charge_reason"] == "no_charge_path"


# (f) valid charge, and the ranged-only charge refusal.


def test_charge_reason_none_for_valid_charge() -> None:
    """Given: an armed actor at (1, 0) and a foe at (1, 4) on an open straight line
    When: the Observation is built
    Then: can_charge is True and charge_reason is None."""
    actor = make_state(_combatant("hero", [_sword("hero")]), "players", (1, 0))
    foe = make_state(_combatant("foe", [_sword("foe")]), "monsters", (1, 4))
    engine = _engine([actor, foe], _open_rows())

    obs = _snapshot(engine, actor)
    pair = _pair_for(obs, 1)
    assert pair["can_charge"] is True
    assert pair["charge_reason"] is None


def test_charge_reason_no_weapon_for_ranged_only_actor() -> None:
    """Given: a bow-only actor facing a foe 20 ft away on open ground
    When: the Observation is built
    Then: the attack is valid (weapon_reason None) but the charge helper
    returns None (no melee weapon) -> charge_reason no_weapon."""
    archer = make_state(_combatant("archer", [_bow("archer")]), "players", (1, 0))
    foe = make_state(_combatant("foe", [_sword("foe")]), "monsters", (1, 4))
    engine = _engine([archer, foe], _open_rows())

    obs = _snapshot(engine, archer)
    pair = _pair_for(obs, 1)
    assert pair["weapon_for"] == "short bow"
    assert pair["weapon_reason"] is None
    assert pair["can_charge"] is False
    assert pair["charge_reason"] == "no_weapon"


# (g) JSON serializability of the extended snapshot.


def test_pair_failure_reasons_snapshot_is_json_serializable() -> None:
    """Given: a snapshot whose pairs carry weapon_reason and charge_reason
    When: to_dict() is dumped to JSON
    Then: serialization round-trips and keeps both new keys."""
    actor = make_state(_combatant("swordsman", [_sword("swordsman")]), "players", (1, 0))
    foe = make_state(_combatant("foe", [_sword("foe")]), "monsters", (1, 4))
    engine = _engine([actor, foe], _open_rows())

    obs = _snapshot(engine, actor)
    data = json.loads(json.dumps(obs))
    pair = _pair_for(data, 1)
    assert pair["weapon_reason"] == "out_of_range"
    assert pair["charge_reason"] is None