src/world_simulator/simulation/mechanics.py

from __future__ import annotations

import math

from world_simulator.domain import Npc, Vec3

GRID_BLOCKS = 20
BLOCK_SIZE = 4.0

# Common melee reach for every attacker: NPC vs NPC, NPC vs beast, beast vs NPC.
ATTACK_RADIUS = 0.5 * BLOCK_SIZE
TALK_RADIUS = 3.0 * BLOCK_SIZE
VISIBLE_RADIUS = 5.0 * BLOCK_SIZE
MAX_WALK_DISTANCE = 1.0 * BLOCK_SIZE


def is_alive(npc: Npc) -> bool:
    return npc.health > 0


def distance_between(first: Npc, second: Npc) -> float:
    return math.hypot(first.position.x - second.position.x, first.position.z - second.position.z)


def vec_distance(first: Vec3, second: Vec3) -> float:
    """Planar distance between two world positions (x/z plane)."""
    return math.hypot(first.x - second.x, first.z - second.z)


def move_toward(
    origin: Vec3,
    destination: Vec3,
    step: float,
    *,
    half_width: float | None = None,
    half_depth: float | None = None,
) -> Vec3:
    """Move ``origin`` up to ``step`` world units toward ``destination``."""
    delta_x = destination.x - origin.x
    delta_z = destination.z - origin.z
    distance = math.hypot(delta_x, delta_z)
    if distance == 0 or distance <= step:
        target_x, target_z = destination.x, destination.z
    else:
        scale = step / distance
        target_x = origin.x + (delta_x * scale)
        target_z = origin.z + (delta_z * scale)
    return _bounded_vec(target_x, target_z, half_width=half_width, half_depth=half_depth)


def move_away(
    origin: Vec3,
    threat: Vec3,
    step: float,
    *,
    half_width: float | None = None,
    half_depth: float | None = None,
) -> Vec3:
    """Move ``origin`` up to ``step`` world units directly away from ``threat``."""
    delta_x = origin.x - threat.x
    delta_z = origin.z - threat.z
    distance = math.hypot(delta_x, delta_z)
    if distance == 0:
        delta_x = -1.0 if origin.x > 0 else 1.0
        delta_z = 0.0
        distance = 1.0
    scale = step / distance
    return _bounded_vec(
        origin.x + (delta_x * scale),
        origin.z + (delta_z * scale),
        half_width=half_width,
        half_depth=half_depth,
    )


def _bounded_vec(
    x: float,
    z: float,
    *,
    half_width: float | None,
    half_depth: float | None,
) -> Vec3:
    if half_width is not None:
        x = _clamp(x, -half_width, half_width)
    if half_depth is not None:
        z = _clamp(z, -half_depth, half_depth)
    return Vec3(x=round(x, 3), y=0.0, z=round(z, 3))


_HOSTILE_KEYWORDS = frozenset(
    {
        "attack",
        "destroy",
        "eliminate",
        "fight",
        "harm",
        "hostile",
        "hunt",
        "hurt",
        "kill",
        "murder",
        "slay",
        "violent",
        "violence",
    }
)
def has_hostile_intent(npc: Npc) -> bool:
    if not is_alive(npc):
        return False
    return _contains_any(npc.god_directive, _HOSTILE_KEYWORDS) or _contains_any(
        npc.intention,
        _HOSTILE_KEYWORDS,
    )


def walk_away_target(
    npc: Npc,
    threat: Npc,
    *,
    half_width: float,
    half_depth: float,
) -> Vec3:
    delta_x = npc.position.x - threat.position.x
    delta_z = npc.position.z - threat.position.z
    distance = math.hypot(delta_x, delta_z)

    if distance == 0:
        delta_x = -1.0 if npc.position.x > 0 else 1.0
        delta_z = 0.0
        distance = 1.0

    scale = MAX_WALK_DISTANCE / distance
    return Vec3(
        x=round(_clamp(npc.position.x + (delta_x * scale), -half_width, half_width), 3),
        y=0.0,
        z=round(_clamp(npc.position.z + (delta_z * scale), -half_depth, half_depth), 3),
    )


def _contains_any(text: str | None, keywords: frozenset[str]) -> bool:
    if not text:
        return False
    lowered = text.lower()
    return any(keyword in lowered for keyword in keywords)


def _clamp(value: float, minimum: float, maximum: float) -> float:
    return min(max(value, minimum), maximum)