"""Tests for B5.3: melee reach depends on weapon reach and creature size.

Covers the PF1e reach rules implemented in this phase (R1 conformance:
CRB "Big and Little Creatures in Combat" — natural reach is a disk, a
reach weapon is a ring):
- natural reach (plain weapons and natural attacks) threatens the DISK of
  effective reach: a Large creature's 10 ft bite still strikes and
  threatens ADJACENT squares;
- reach weapons (``reach_weapon=True``) threaten only the RING beyond the
  wielder's natural reach up to double it (the PF1e reach dead zone: a
  longspear cannot hit an adjacent target);
- ``weapon_for`` respects the reach dead zone;
- AoOs trigger from ring squares threatened by a reach weapon.
"""

from __future__ import annotations

from pf1e_simulator.combat import Action, 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


def make_combatant(
    cid: str,
    *,
    size: str = "Medium",
    reach_ft: int = 5,
    reach_weapon: bool = False,
    hp: int = 20,
    ac: int = 15,
    attack_bonus: int = 5,
    speed: int = 30,
) -> Combatant:
    """Build a single-melee-weapon combatant (used by most reach tests)."""
    attack = AttackSpec(
        id=f"{cid}-w",
        name="longspear" if reach_weapon else "short sword",
        kind="melee",
        attack_bonus=attack_bonus,
        damage=[DamageComponent(formula=parse_dice("1d6"), types=["piercing"])],
        reach_ft=reach_ft,
        reach_weapon=reach_weapon,
    )
    return Combatant(
        id=cid,
        name=cid,
        level=1,
        size=size,
        abilities=AbilityScores(
            str_score=10,
            dex_score=10,
            con_score=12,
            int_score=10,
            wis_score=10,
            cha_score=10,
        ),
        hp_max=hp,
        ac=ACProfile(total=ac, touch=ac, flat_footed=ac),
        bab=attack_bonus,
        initiative_mod=0,
        speed_land_ft=speed,
        saves=Saves(fort=0, ref=0, will=0),
        attacks=[attack],
    )


def make_state(combatant: Combatant, side: str, pos: tuple[int, int]) -> CombatantState:
    return CombatantState(combatant=combatant, side=side, pos=pos, hp=combatant.hp_max)


def make_grid() -> 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(states: list[CombatantState]) -> CombatEngine:
    return CombatEngine(ScriptedRng([]), make_grid(), states)


def _grid_distance(a: tuple[int, int], b: tuple[int, int]) -> int:
    """5-10-5 diagonal distance in squares (mirrors Grid.distance)."""
    d_row = abs(a[0] - b[0])
    d_col = abs(a[1] - b[1])
    return max(d_row, d_col) + min(d_row, d_col) // 2


def _ring(pos: tuple[int, int], radius: int) -> set[tuple[int, int]]:
    """Cells at exactly ``radius`` squares from ``pos`` (5-10-5 distance)."""
    r, c = pos
    return {
        (r + dr, c + dc)
        for dr in range(-radius, radius + 1)
        for dc in range(-radius, radius + 1)
        if (dr, dc) != (0, 0) and _grid_distance(pos, (r + dr, c + dc)) == radius
    }


def _disk(pos: tuple[int, int], radius: int) -> set[tuple[int, int]]:
    """Cells within ``radius`` squares of ``pos`` (5-10-5 distance), excluding pos."""
    r, c = pos
    return {
        (r + dr, c + dc)
        for dr in range(-radius, radius + 1)
        for dc in range(-radius, radius + 1)
        if (dr, dc) != (0, 0) and _grid_distance(pos, (r + dr, c + dc)) <= radius
    }


def _adjacent(pos: tuple[int, int]) -> set[tuple[int, int]]:
    """The 8 cells adjacent to ``pos``."""
    return _disk(pos, 1)


def test_medium_5ft_weapon_threatens_adjacent_only() -> None:
    """A Medium combatant with a 5 ft weapon threatens exactly the 8 adjacent squares."""
    fighter = make_combatant("fighter")
    state = make_state(fighter, "players", (3, 3))
    engine = make_engine([state])
    assert engine.threatened_squares(state) == frozenset(_adjacent((3, 3)))


def test_reach_weapon_threatens_ring_not_adjacent() -> None:
    """A longspear (reach weapon) threatens the ring at distance 2, not adjacent squares.

    R1: the ring is now driven by ``reach_weapon=True``, not by ``reach_ft > 5``.
    """
    spearman = make_combatant("spearman", reach_ft=10, reach_weapon=True)
    state = make_state(spearman, "players", (3, 3))
    engine = make_engine([state])
    threatened = engine.threatened_squares(state)
    assert threatened == frozenset(_ring((3, 3), 2))
    assert (3, 2) not in threatened  # adjacent orthogonal
    assert (3, 4) not in threatened
    assert (2, 2) not in threatened  # adjacent diagonal
    assert (4, 4) not in threatened


def test_sword_plus_reach_weapon_union() -> None:
    """A combatant with a 5 ft sword and a reach weapon threatens disk(1) plus ring(2)."""
    sword = AttackSpec(
        id="sword",
        name="short sword",
        kind="melee",
        attack_bonus=5,
        damage=[DamageComponent(formula=parse_dice("1d6"), types=["slashing"])],
        reach_ft=5,
    )
    spear = AttackSpec(
        id="spear",
        name="longspear",
        kind="melee",
        attack_bonus=5,
        damage=[DamageComponent(formula=parse_dice("1d6"), types=["piercing"])],
        reach_ft=10,
        reach_weapon=True,
    )
    combatant = Combatant(
        id="dual",
        name="dual",
        level=1,
        size="Medium",
        abilities=AbilityScores(
            str_score=10,
            dex_score=10,
            con_score=12,
            int_score=10,
            wis_score=10,
            cha_score=10,
        ),
        hp_max=20,
        ac=ACProfile(total=15, touch=15, flat_footed=15),
        bab=5,
        initiative_mod=0,
        speed_land_ft=30,
        saves=Saves(fort=0, ref=0, will=0),
        attacks=[sword, spear],
    )
    state = make_state(combatant, "players", (3, 3))
    engine = make_engine([state])
    assert engine.threatened_squares(state) == frozenset(
        _adjacent((3, 3)) | _ring((3, 3), 2)
    )


def test_large_creature_sword_threatens_disk_radius_2() -> None:
    """A Large creature (2x2 footprint, natural reach 10 ft) with a 5 ft sword
    threatens the union of radius-2 disks around each occupied cell."""
    giant = make_combatant("giant", size="Large")
    state = make_state(giant, "players", (3, 3))
    engine = make_engine([state])
    footprint = state.occupied_cells()
    expected = set()
    for cell in footprint:
        expected |= _disk(cell, 2)
    expected -= footprint
    assert engine.threatened_squares(state) == frozenset(expected)


def test_unknown_size_defaults_to_5ft() -> None:
    """An unlisted size falls back to the current 5 ft natural reach."""
    weird = make_combatant("weird", size="Weird")
    state = make_state(weird, "players", (3, 3))
    engine = make_engine([state])
    assert engine.threatened_squares(state) == frozenset(_adjacent((3, 3)))


# ── R1 conformance: natural reach is a disk, a reach weapon is a ring ────────


def _natural_attack_combatant(
    cid: str, *, size: str, reach_ft: int, reach_weapon: bool
) -> Combatant:
    """Combatant with one melee attack carrying the given reach flags."""
    attack = AttackSpec(
        id=f"{cid}-w",
        name="bite" if not reach_weapon else "longspear",
        kind="melee",
        attack_bonus=5,
        damage=[DamageComponent(formula=parse_dice("1d6"), types=["piercing"])],
        reach_ft=reach_ft,
        reach_weapon=reach_weapon,
    )
    return Combatant(
        id=cid,
        name=cid,
        level=1,
        size=size,
        abilities=AbilityScores(
            str_score=10, dex_score=10, con_score=12,
            int_score=10, wis_score=10, cha_score=10,
        ),
        hp_max=20,
        ac=ACProfile(total=15, touch=15, flat_footed=15),
        bab=5,
        initiative_mod=0,
        speed_land_ft=30,
        saves=Saves(fort=0, ref=0, will=0),
        attacks=[attack],
    )


def test_large_natural_attack_threatens_adjacent_disk() -> None:
    """R1 (CRB "Big and Little Creatures in Combat"): a Large creature's
    natural 10 ft bite is a DISK — it threatens adjacent squares too, unlike
    a reach weapon's ring. The old model keyed the ring off ``reach_ft > 5``
    and wrongly gave the bite a 5 ft dead zone (giant_belostomatid.json,
    esha_mount.json, jeanne.json all have reach-10 natural attacks)."""
    bug = _natural_attack_combatant("bug", size="Large", reach_ft=10, reach_weapon=False)
    state = make_state(bug, "players", (3, 3))
    engine = make_engine([state])
    threatened = engine.threatened_squares(state)
    footprint = state.occupied_cells()
    expected: set[tuple[int, int]] = set()
    for cell in footprint:
        expected |= _disk(cell, 2)
    expected -= footprint
    assert threatened == frozenset(expected)
    # Adjacent to the footprint (1 cell) is threatened: the disk, not a ring.
    assert (3, 2) in threatened
    assert (2, 2) in threatened


def _bug_attack_policy(engine: CombatEngine, state: CombatantState) -> tuple[Action, ...]:
    if state.combatant.id == "bug":
        return (Action(kind="attack", target_id="rider-target"),)
    return (Action(kind="wait"),)


def test_large_natural_attack_hits_adjacent_target() -> None:
    """R1: the reach-10 natural attack of a Large creature STRIKES an adjacent
    target (disk), which the old ring model refused."""
    bug = _natural_attack_combatant("bug", size="Large", reach_ft=10, reach_weapon=False)
    target = make_combatant("rider-target", hp=20, ac=12)
    bug_state = make_state(bug, "players", (3, 3))
    target_state = make_state(target, "monsters", (3, 5))  # adjacent to (3, 4)
    engine = CombatEngine(
        ScriptedRng([20, 1, 15, 3]),
        make_grid(), [bug_state, target_state],
        round_cap=1, policy=_bug_attack_policy,
    )
    result = engine.run()
    assert any("bite vs rider-target" in line and "-> HIT" in line
               for line in result.transcript), result.transcript
    assert target_state.hp == 17  # 20 - 1d6(3)


def test_large_reach_weapon_ring_beyond_natural_reach() -> None:
    """R1 (CRB): "Large or larger creatures using reach weapons can strike up
    to double their natural reach but can't strike at their natural reach or
    less" — for a Large longspear wielder the usable band is 15..20 ft: dead
    at 10 ft (natural reach), live at 15 ft, dead beyond 20 ft."""
    giant = _natural_attack_combatant(
        "giant", size="Large", reach_ft=10, reach_weapon=True
    )
    target = make_combatant("target")
    attacker = make_state(giant, "players", (3, 3))
    # Footprint spans cols 3-4; distance = foe_col - 4 cells (x5 ft).
    # (3, 6): 10 ft = natural reach -> dead zone. (3, 7): 15 ft -> in ring.
    for foe_col, in_ring in ((6, False), (7, True)):
        foe = make_state(target, "monsters", (3, foe_col))
        engine = make_engine([attacker, foe])
        weapon = engine.weapon_for(attacker, foe)
        assert (weapon is not None) is in_ring, f"distance {foe_col - 4} cells"


def test_weapon_for_reach_weapon_at_distance_2_not_1() -> None:
    """weapon_for selects a reach weapon at distance 2 but not at distance 1 (dead zone)."""
    spearman = make_combatant("spearman", reach_ft=10, reach_weapon=True)
    target = make_combatant("target")
    attacker = make_state(spearman, "players", (3, 3))

    foe_at_ring = make_state(target, "monsters", (3, 5))  # distance 2
    engine_ring = make_engine([attacker, foe_at_ring])
    weapon = engine_ring.weapon_for(attacker, foe_at_ring)
    assert weapon is not None
    assert weapon.reach_ft == 10

    foe_adjacent = make_state(target, "monsters", (3, 4))  # distance 1
    engine_adjacent = make_engine([attacker, foe_adjacent])
    assert engine_adjacent.weapon_for(attacker, foe_adjacent) is None


def test_weapon_for_large_creature_sword_at_distance_2() -> None:
    """A Large creature's 5 ft sword is selectable at distance 2 (natural reach 10 ft)."""
    giant = make_combatant("giant", size="Large")
    target = make_combatant("target")
    attacker = make_state(giant, "players", (3, 3))
    foe = make_state(target, "monsters", (3, 5))  # distance 2
    engine = make_engine([attacker, foe])
    weapon = engine.weapon_for(attacker, foe)
    assert weapon is not None
    assert weapon.reach_ft == 5


def _move_to_dest(engine: CombatEngine, state: CombatantState) -> tuple[Action, ...]:
    """Test policy: always move toward the 'dest' combatant."""
    return (Action(kind="move", target_id="dest"),)


def test_aoo_from_reach_ring() -> None:
    """Moving through a ring square threatened by a longspear provokes an AoO."""
    runner = make_combatant("runner", hp=20, ac=12, speed=30)
    spearman = make_combatant(
        "spearman", hp=20, ac=15, attack_bonus=5, speed=0, reach_ft=10, reach_weapon=True,
    )
    dest = make_combatant("dest", hp=20, ac=15, attack_bonus=0, speed=0)
    states = [
        make_state(runner, "players", (4, 3)),
        make_state(spearman, "monsters", (3, 1)),
        make_state(dest, "monsters", (4, 5)),
    ]
    engine = CombatEngine(
        ScriptedRng([10, 9, 8, 15, 3, 5]),
        make_grid(), states, round_cap=1, policy=_move_to_dest,
    )
    result = engine.run()
    assert result.transcript == (
        "initiative: runner d20=10+0=10",
        "initiative: spearman d20=9+0=9",
        "initiative: dest d20=8+0=8",
        "round 1 spearman: AoO vs runner d20=15+5=20 AC 12 -> HIT 3 damage (20->17)",
        "round 1 runner: move (4,3)->(3,4)",
        "round 1 spearman: wait",
        "round 1 dest: wait",
        "battle over: draw after 1 rounds",
    )


def test_no_aoo_from_adjacent_to_reach_weapon() -> None:
    """A longspear does not threaten adjacent squares: no AoO when leaving one."""
    runner = make_combatant("runner", hp=20, ac=12, speed=30)
    spearman = make_combatant(
        "spearman", hp=20, ac=15, attack_bonus=5, speed=0, reach_ft=10, reach_weapon=True,
    )
    dest = make_combatant("dest", hp=20, ac=15, attack_bonus=0, speed=0)
    states = [
        make_state(runner, "players", (4, 1)),
        make_state(spearman, "monsters", (3, 1)),
        make_state(dest, "monsters", (4, 3)),
    ]
    engine = CombatEngine(
        ScriptedRng([10, 9, 8, 15, 3, 5]),
        make_grid(), states, round_cap=1, policy=_move_to_dest,
    )
    result = engine.run()
    assert result.transcript == (
        "initiative: runner d20=10+0=10",
        "initiative: spearman d20=9+0=9",
        "initiative: dest d20=8+0=8",
        "round 1 runner: move (4,1)->(3,2)",
        "round 1 spearman: wait",
        "round 1 dest: wait",
        "battle over: draw after 1 rounds",
    )


# ── S4c: Tiny/Diminutive/Fine natural reach 0 and co-occupancy ───────────────


def test_tiny_reach_zero_threatens_nothing() -> None:
    """S4c: a Tiny creature's natural reach is 0 — it threatens no squares
    (no AoO) and cannot strike adjacent squares."""
    tiny = make_combatant("tiny", size="Tiny", reach_ft=0)
    state = make_state(tiny, "players", (3, 3))
    engine = make_engine([state])
    assert engine.threatened_squares(state) == frozenset()
    assert (3, 2) not in engine.threatened_squares(state)


def test_tiny_reach_zero_attacks_own_cell_only() -> None:
    """S4c: a 0-reach Tiny can attack a creature in its OWN cell (distance 0)
    but not an adjacent one (distance 1)."""
    tiny = make_combatant("tiny", size="Tiny", reach_ft=0)
    target = make_combatant("target", hp=20, ac=12)
    tiny_state = make_state(tiny, "players", (3, 3))
    # Same cell: distance 0 -> the 0-reach attack is usable.
    foe_same = make_state(target, "monsters", (3, 3))
    engine_same = make_engine([tiny_state, foe_same])
    assert engine_same.weapon_for(tiny_state, foe_same) is not None
    # Adjacent cell: distance 1 (5 ft) -> out of the 0-reach zone.
    foe_adj = make_state(target, "monsters", (3, 4))
    engine_adj = make_engine([tiny_state, foe_adj])
    assert engine_adj.weapon_for(tiny_state, foe_adj) is None


def _tiny_attack_policy(engine: CombatEngine, state: CombatantState) -> tuple[Action, ...]:
    if state.combatant.id == "tiny":
        return (Action(kind="attack", target_id="target"),)
    return (Action(kind="wait"),)


def test_tiny_reach_zero_hits_creature_in_own_cell() -> None:
    """S4c: a 0-reach Tiny strikes a creature sharing its cell (the 'entered
    the square' abstraction) — the attack resolves at distance 0."""
    tiny = make_combatant("tiny", size="Tiny", reach_ft=0)
    target = make_combatant("target", hp=20, ac=12)
    tiny_state = make_state(tiny, "players", (3, 3))
    target_state = make_state(target, "monsters", (3, 3))
    engine = CombatEngine(
        ScriptedRng([20, 1, 15, 3]),
        make_grid(), [tiny_state, target_state],
        round_cap=1, policy=_tiny_attack_policy,
    )
    result = engine.run()
    assert any(
        "short sword vs target" in line and "-> HIT" in line
        for line in result.transcript
    ), result.transcript
    assert target_state.hp == 17  # 20 - 1d6(3)


def _tiny_move_policy(engine: CombatEngine, state: CombatantState) -> tuple[Action, ...]:
    if state.combatant.id == "tiny":
        return (Action(kind="move", destination=(3, 3)),)
    return (Action(kind="wait"),)


def test_tiny_ends_move_in_medium_cell() -> None:
    """S4c: a Tiny creature may END its move in a cell occupied by a larger
    creature (co-occupancy)."""
    tiny = make_combatant("tiny", size="Tiny", reach_ft=0)
    medium = make_combatant("medium", hp=20, ac=15, speed=0)
    tiny_state = make_state(tiny, "players", (3, 2))
    medium_state = make_state(medium, "monsters", (3, 3))
    engine = CombatEngine(
        ScriptedRng([20, 1, 5]),
        make_grid(), [tiny_state, medium_state],
        round_cap=1, policy=_tiny_move_policy,
    )
    result = engine.run()
    assert any("move -> (3,3)" in line for line in result.transcript), result.transcript
    assert tiny_state.pos == (3, 3)


def _medium_move_policy(engine: CombatEngine, state: CombatantState) -> tuple[Action, ...]:
    if state.combatant.id == "a":
        return (Action(kind="move", destination=(3, 3)),)
    return (Action(kind="wait"),)


def test_two_medium_cannot_share_cell() -> None:
    """S4c: two Medium creatures still cannot share a cell — the move onto
    the occupied cell is rejected."""
    a = make_combatant("a", speed=30)
    b = make_combatant("b", hp=20, ac=15, speed=0)
    a_state = make_state(a, "players", (3, 2))
    b_state = make_state(b, "monsters", (3, 3))
    engine = CombatEngine(
        ScriptedRng([20, 1]),
        make_grid(), [a_state, b_state],
        round_cap=1, policy=_medium_move_policy,
    )
    result = engine.run()
    assert any(
        "move rejected (unreachable_destination)" in line for line in result.transcript
    ), result.transcript
    assert a_state.pos == (3, 2)


def test_observation_exposes_natural_reach_ft() -> None:
    """S4c: the combatant snapshot exposes the size's natural reach."""
    tiny = make_combatant("tiny", size="Tiny", reach_ft=0)
    medium = make_combatant("medium")
    tiny_state = make_state(tiny, "players", (3, 3))
    medium_state = make_state(medium, "monsters", (3, 5))
    engine = make_engine([tiny_state, medium_state])
    obs = engine._build_observation(tiny_state).to_dict()
    combatants = {c["id"]: c for c in obs["combatants"]}
    assert combatants["tiny"]["natural_reach_ft"] == 0
    assert combatants["medium"]["natural_reach_ft"] == 5