"""Conformance B20: cover uses the ATTACKER's best corner/square.

PF1e CRB "Cover" (rule of corners): the attacker chooses the corner of its
square (and, for a multi-square creature, the occupied square) that gives it
the best shot, so a multi-cell attacker suffers the MINIMUM cover over its
own cells, not the maximum. The target side is unchanged: RAW checks ANY
line to ANY target corner, so each attacker cell is scored by the maximum
over its corner lines. 1x1 attackers are bit-identical to the old behavior.
"""

from __future__ import annotations

from pf1e_simulator.combat import CombatEngine
from pf1e_simulator.grid import Grid
from pf1e_simulator.los import cover_bonus_cells
from pf1e_simulator.map import MapSpec, TerrainType
from pf1e_simulator.rng import ScriptedRng
from tests.test_combat import make_combatant, make_state

_FLOOR = TerrainType(type="floor", move_cost=1)
_WALL = TerrainType(type="wall", move_cost=None, blocks_los=True)
_PARTIAL = TerrainType(type="ruin", move_cost=None, cover_bonus=2)


def _grid(rows: tuple[str, ...]) -> Grid:
    legend = {".": _FLOOR, "#": _WALL, "W": _PARTIAL}
    return Grid.from_spec(MapSpec(name="b20", terrain=rows, legend=legend))


# Two-cell attacker {(0,0),(1,0)} shooting right at target (1,4):
# the +2 ruins at (0,2)/(1,2) sit on the top cell's lines, the +4 wall at
# (2,1) additionally sits on the bottom cell's low lines.
_CORNER_GRID = ("..W..", "..W..", ".#...", ".....")


# ---------------------------------------------------------------------------
# (a) multi-cell attacker picks its best square: minimum, not maximum
# ---------------------------------------------------------------------------


def test_two_cell_attacker_uses_best_cell_cover() -> None:
    grid = _grid(_CORNER_GRID)
    top = frozenset({(0, 0)})
    bottom = frozenset({(1, 0)})
    target = frozenset({(1, 4)})
    # Per-cell scores pin the geometry: the top cell only sees +2 ruins,
    # the bottom cell's low lines also graze the +4 wall.
    assert cover_bonus_cells(grid, top, target, ranged=True) == 2
    assert cover_bonus_cells(grid, bottom, target, ranged=True) == 4
    # B20 fix: the attacker picks its best square -> min(2, 4) = 2.
    assert (
        cover_bonus_cells(grid, top | bottom, target, ranged=True) == 2
    )


def test_two_cell_attacker_best_cell_alone_is_unchanged() -> None:
    grid = _grid(_CORNER_GRID)
    target = frozenset({(1, 4)})
    # A single-square attacker is the golden path: exactly its own score.
    assert cover_bonus_cells(grid, frozenset({(0, 0)}), target, ranged=True) == 2
    assert cover_bonus_cells(grid, frozenset({(1, 0)}), target, ranged=True) == 4


# ---------------------------------------------------------------------------
# (b) 1x1 attacker vs 2x2 target: target side keeps the max over corners
# ---------------------------------------------------------------------------


def test_single_attacker_vs_large_target_pins_cover_level() -> None:
    grid = _grid(("......", "..W...", "......"))
    attacker = frozenset({(1, 0)})
    large_target = frozenset({(0, 4), (0, 5), (1, 4), (1, 5)})
    # Cover is evaluated over ALL target corners: the big target keeps the
    # +2 it gains from the ruin, exactly as before the B20 fix.
    assert cover_bonus_cells(grid, attacker, large_target, ranged=True) == 2
    assert cover_bonus_cells(grid, attacker, frozenset({(1, 4)}), ranged=True) == 2


# ---------------------------------------------------------------------------
# (c) regression: single-square attacker vs wall still gets exactly +4
# ---------------------------------------------------------------------------


def test_single_square_attacker_wall_cover_unchanged() -> None:
    grid = _grid((".....", "..#..", "....."))
    assert (
        cover_bonus_cells(
            grid, frozenset({(1, 0)}), frozenset({(1, 4)}), ranged=True
        )
        == 4
    )


# ---------------------------------------------------------------------------
# (d) engine: Large attacker resolves with its best cell; snapshot agrees
# ---------------------------------------------------------------------------


def _large_archer_engine() -> CombatEngine:
    grid = _grid(_CORNER_GRID)
    archer = make_combatant(
        "ogre-archer", attack_bonus=4, kind="ranged", range_increment_ft=60
    )
    large = archer.model_copy(update={"size": "Large"})
    target = make_combatant("target", ac=13)
    states = [
        make_state(large, "players", (0, 0)),
        make_state(target, "monsters", (1, 4)),
    ]
    return CombatEngine(ScriptedRng([12, 3, 2, 2]), grid, states)


def test_large_attacker_ac_uses_best_cell_cover() -> None:
    engine = _large_archer_engine()
    archer, target = engine._states[0], engine._states[1]
    assert len(archer.occupied_cells()) == 4
    result = engine.resolve_attack(archer, target, archer.combatant.attacks[0])
    # 13 base + 2 (best cell of the footprint), NOT 13 + 4 (worst cell).
    assert result.ac == 15
    assert result.hit is True  # 12 + 4 = 16 >= 15


def test_observation_pair_cover_bonus_matches_attack() -> None:
    engine = _large_archer_engine()
    archer, target = engine._states[0], engine._states[1]
    obs = engine._build_observation(archer).to_dict()
    pair = next(p for p in obs["pairs"] if p["target_index"] == 1)
    result = engine.resolve_attack(archer, target, archer.combatant.attacks[0])
    assert pair["cover_bonus"] == 2
    assert result.ac - target.combatant.ac.total == pair["cover_bonus"]


# ---------------------------------------------------------------------------
# (e) false-positive lock: cover still applies to touch attacks (Oracle)
# ---------------------------------------------------------------------------


def test_ranged_touch_attack_still_gets_cover() -> None:
    grid = _grid((".....", "..#..", "....."))
    caster = make_combatant(
        "sorcerer", attack_bonus=4, kind="touch", range_increment_ft=30
    )
    target = make_combatant("target", ac=13)
    states = [
        make_state(caster, "players", (1, 0)),
        make_state(target, "monsters", (1, 4)),
    ]
    engine = CombatEngine(ScriptedRng([12, 3]), grid, states)
    result = engine.resolve_attack(states[0], states[1], caster.attacks[0])
    # Touch AC 13 + 4 standard cover: cover is NOT removed for touch.
    assert result.ac == 17
    assert result.hit is False  # 12 + 4 = 16 < 17