pf1e-simulator/tests/test_phase2_strategy.py

"""Phase-2 Etage A strategy compiler tests (docs/phase-2-llm-architecture.md 10 P2.1).

Deterministic, offline: no network, no LLM. Pins the ``StrategySpec`` /
``compile_strategy`` contract: the all-default spec compiles to
``default_policy`` by identity, ``select_target`` honours each priority with
deterministic tie-breaks, non-default specs drive real battles through
``run_encounter`` bit-identically under a fixed seed, and invalid specs are
rejected at construction.
"""

from __future__ import annotations

from pathlib import Path
from typing import TYPE_CHECKING

import pytest

from pf1e_simulator.combat import (
    Action,
    CombatantState,
    CombatEngine,
    default_policy,
)
from pf1e_simulator.grid import Grid
from pf1e_simulator.loaders import load_combatant
from pf1e_simulator.map import load_map
from pf1e_simulator.rng import SeededRng
from pf1e_simulator.runner import EncounterSpec, Side, run_encounter
from pf1e_simulator.spells import SPELLS_DIR, load_spell_registry
from pf1e_simulator.strategy import StrategySpec, compile_strategy, select_target

if TYPE_CHECKING:
    from pf1e_simulator.models import Combatant

ROOT = Path(__file__).resolve().parents[1]
MAP = ROOT / "data" / "maps" / "sample_arena.yaml"
_MAP_SPEC = load_map(MAP)
_SPELLS = load_spell_registry(SPELLS_DIR)


def _c(path: str) -> Combatant:
    return load_combatant(ROOT / "data" / path)


def _spec() -> EncounterSpec:
    """A fast 2v2 (goblin archer + orc vs orc + goblin) on the sample arena."""
    return EncounterSpec(
        map=_MAP_SPEC,
        round_cap=20,
        sides=(
            Side(
                name="players",
                combatants=(_c("monsters/goblin.json"), _c("monsters/orc.json")),
                zone="A",
            ),
            Side(
                name="monsters",
                combatants=(_c("monsters/orc.json"), _c("monsters/goblin.json")),
                zone="B",
            ),
        ),
    )


def _state(
    cid: str, side: str, pos: tuple[int, int], hp: int = 10, path: str = "monsters/orc.json"
) -> CombatantState:
    """A bare runtime state over a loaded combatant (no battle run)."""
    combatant = _c(path).model_copy(update={"id": cid})
    return CombatantState(combatant=combatant, side=side, pos=pos, hp=hp, resources_left={})


def _mini_engine(states: list[CombatantState]) -> CombatEngine:
    """A live engine over the 2v2 map with the given states (no battle run)."""
    return CombatEngine(SeededRng(1), Grid.from_spec(_MAP_SPEC), states, spell_registry=_SPELLS)


def test_compile_strategy_default_is_default_policy() -> None:
    """The all-default spec compiles to ``default_policy`` by identity."""
    assert compile_strategy(StrategySpec()) is default_policy


def test_select_target_nearest() -> None:
    """nearest picks the closest active enemy (ties keep list order)."""
    orc = _state("orc1", "monsters", (1, 1))
    goblin = _state("goblin1", "players", (1, 2), hp=6, path="monsters/goblin.json")
    far_orc = _state("orc2", "players", (1, 16), hp=6)
    engine = _mini_engine([orc, goblin, far_orc])
    assert select_target(engine, orc, "nearest") is goblin


def test_select_target_weakest_ac() -> None:
    """weakest_ac picks the lowest total AC (goblin 16 > orc 13)."""
    orc = _state("orc1", "monsters", (1, 1))
    goblin = _state("goblin1", "players", (1, 2), hp=6, path="monsters/goblin.json")
    far_orc = _state("orc2", "players", (1, 16), hp=6)
    engine = _mini_engine([orc, goblin, far_orc])
    assert select_target(engine, orc, "weakest_ac") is far_orc


def test_select_target_lowest_hp() -> None:
    """lowest_hp picks the most wounded active enemy."""
    orc = _state("orc1", "monsters", (1, 1))
    healthy = _state("goblin1", "players", (1, 2), hp=6, path="monsters/goblin.json")
    wounded = _state("goblin2", "players", (1, 16), hp=1, path="monsters/goblin.json")
    engine = _mini_engine([orc, healthy, wounded])
    assert select_target(engine, orc, "lowest_hp") is wounded


def test_select_target_no_active_enemy() -> None:
    """No active enemy -> None for every priority."""
    orc = _state("orc1", "monsters", (1, 1))
    dying = _state("goblin1", "players", (1, 2), hp=-5, path="monsters/goblin.json")
    engine = _mini_engine([orc, dying])
    assert select_target(engine, orc, "nearest") is None
    assert select_target(engine, orc, "weakest_ac") is None
    assert select_target(engine, orc, "lowest_hp") is None


def test_compiled_policy_melee_ladder() -> None:
    """A non-default spec still resolves the melee ladder on a live engine."""
    spec = StrategySpec(name="no-charge", use_charges=False)
    policy = compile_strategy(spec)
    assert policy is not default_policy
    orc = _state("orc1", "monsters", (1, 1))
    goblin = _state("goblin1", "players", (1, 2), hp=6, path="monsters/goblin.json")
    engine = _mini_engine([orc, goblin])
    assert policy(engine, orc) == (Action(kind="full_attack", target_id="goblin1"),)


def test_compiled_policy_charge_disabled() -> None:
    """use_charges=False skips the charge and falls to step + full-attack."""
    spec = StrategySpec(name="no-charge", use_charges=False)
    policy = compile_strategy(spec)
    # The celestial wolf is melee-only (Bite, reach 5 ft): at 2 cells no
    # weapon_for short-circuit, so the ladder reaches the charge branch. The
    # orc sits DIAGONALLY at (2, 3): straight ahead at (1, 3) the only
    # attackable charge end is 1 cell away (below the 2-cell minimum charge
    # move), while from (1, 1) the diagonal end (1, 3) is a legal 2-cell
    # straight line AND a single 5-foot step to (1, 2) still enters reach.
    wolf = _state("wolf1", "players", (1, 1), hp=13, path="monsters/celestial_wolf.json")
    orc = _state("orc1", "monsters", (2, 3))
    engine = _mini_engine([wolf, orc])
    assert default_policy(engine, wolf) == (Action(kind="charge", target_id="orc1"),)
    assert policy(engine, wolf) == (
        Action(kind="5foot_step", target_id="orc1"),
        Action(kind="full_attack", target_id="orc1"),
    )


def test_compiled_policy_retreats_below_threshold() -> None:
    """retreat_hp_fraction withdraws below the threshold, not at/above it."""
    spec = StrategySpec(name="coward", retreat_hp_fraction=0.5)
    policy = compile_strategy(spec)
    orc = _state("orc1", "monsters", (1, 1), hp=2)  # 2 < 0.5 * 6 = 3
    goblin = _state("goblin1", "players", (1, 2), hp=6, path="monsters/goblin.json")
    engine = _mini_engine([orc, goblin])
    assert policy(engine, orc) == (Action(kind="withdraw", target_id="goblin1"),)
    orc_ok = _state("orc2", "monsters", (1, 1), hp=3)  # 3 is not below 3
    engine_ok = _mini_engine([orc_ok, goblin])
    assert all(a.kind != "withdraw" for a in policy(engine_ok, orc_ok))


def test_compiled_policy_spell_policy_none_skips_casting() -> None:
    """spell_policy="none" never proposes a cast even for a caster with slots."""
    spec = StrategySpec(name="no-spells", spell_policy="none")
    policy = compile_strategy(spec)
    oni = _c("pcs/oni.json")
    oni_state = CombatantState(
        combatant=oni,
        side="players",
        pos=(1, 1),
        hp=oni.hp_max,
        resources_left={},
        spell_slots_left={1: 4, 2: 3},
    )
    goblin = _state("goblin1", "monsters", (1, 2), hp=6, path="monsters/goblin.json")
    engine = _mini_engine([oni_state, goblin])
    # With the default spell policy the same setup casts (Shield of Faith,
    # slot 1): no ally is below 50% HP and Sound Burst is an area spell, so
    # _find_offensive_spell (top-level DamageEffect only) skips it.
    assert default_policy(engine, oni_state) == (
        Action(kind="cast_spell", target_id="oni", spell_name="Shield of Faith"),
    )
    # With spell_policy="none" the melee ladder runs instead.
    actions = policy(engine, oni_state)
    assert all(a.kind != "cast_spell" for a in actions)


def test_compiled_policy_class_abilities_disabled() -> None:
    """use_class_abilities=False skips channel/hex even when they would fire."""
    spec = StrategySpec(name="no-class", use_class_abilities=False)
    policy = compile_strategy(spec)
    oni = _c("pcs/oni.json")
    oni_state = CombatantState(
        combatant=oni,
        side="players",
        pos=(1, 1),
        hp=oni.hp_max,
        resources_left={"channel_energy": 6},
        spell_slots_left={1: 4, 2: 3},
    )
    hurt = _state("hurt", "players", (1, 3), hp=1, path="monsters/goblin.json")
    goblin = _state("goblin1", "monsters", (1, 2), hp=6, path="monsters/goblin.json")
    engine = _mini_engine([oni_state, hurt, goblin])
    # With class abilities enabled the channel fires (ally below 50% hp).
    assert default_policy(engine, oni_state) == (
        Action(kind="channel_energy", target_id="goblin1", channel_mode="heal"),
    )
    # Disabled: the channel is skipped entirely.
    actions = policy(engine, oni_state)
    assert all(a.kind != "channel_energy" for a in actions)


def test_compiled_policy_deterministic_runs() -> None:
    """A compiled policy drives bit-identical battles under a fixed seed."""
    spec = StrategySpec(name="focus", target_priority="weakest_ac")
    policy = compile_strategy(spec)
    _, runs_a = run_encounter(_spec(), runs=3, seed=7, policy=policy, collect_runs=True)
    _, runs_b = run_encounter(_spec(), runs=3, seed=7, policy=policy, collect_runs=True)
    assert runs_a == runs_b


def test_strategy_spec_validation() -> None:
    """Invalid specs are rejected at construction."""
    with pytest.raises(ValueError, match="non-empty"):
        StrategySpec(name="")
    with pytest.raises(ValueError, match="within"):
        StrategySpec(retreat_hp_fraction=1.5)
    with pytest.raises(ValueError, match="within"):
        StrategySpec(retreat_hp_fraction=-0.1)