import { interactionGroups } from "@react-three/rapier";
import type {
  QueryFilterFlags,
  Ray,
  Vector,
  World,
} from "@dimforge/rapier3d-compat";

interface RapierApi {
  readonly Ray: new (origin: Vector, direction: Vector) => Ray;
  readonly QueryFilterFlags: {
    readonly EXCLUDE_DYNAMIC: QueryFilterFlags;
    readonly EXCLUDE_KINEMATIC: QueryFilterFlags;
  };
}

type WorldPosition = readonly [number, number, number];

export const DUNGEON_LINE_OF_SIGHT_GROUP = 15;
export const DUNGEON_PHYSICAL_COLLISION_GROUPS = interactionGroups(0);
export const DUNGEON_SIGHT_BLOCKER_COLLISION_GROUPS = interactionGroups(DUNGEON_LINE_OF_SIGHT_GROUP);
export const DUNGEON_WALL_COLLISION_GROUPS = interactionGroups([0, DUNGEON_LINE_OF_SIGHT_GROUP]);
export const DUNGEON_SIGHT_QUERY_GROUPS = interactionGroups(
  DUNGEON_LINE_OF_SIGHT_GROUP,
  DUNGEON_LINE_OF_SIGHT_GROUP,
);

const ACTOR_SIGHT_HEIGHT = 1.05;
const TARGET_MARGIN = 0.08;

/**
 * Checks only the dedicated wall/pillar collision layer. Walkable terrain and
 * ceilings remain physical, but never participate in combat visibility.
 */
export function hasDungeonLineOfSight(
  rapier: RapierApi,
  world: World,
  start: WorldPosition,
  end: WorldPosition,
): boolean {
  const dx = end[0] - start[0];
  const dy = end[1] - start[1];
  const dz = end[2] - start[2];
  const distance = Math.hypot(dx, dy, dz);
  if (!Number.isFinite(distance)) return false;
  if (distance <= TARGET_MARGIN) return true;

  const ray = new rapier.Ray(
    { x: start[0], y: start[1] + ACTOR_SIGHT_HEIGHT, z: start[2] },
    { x: dx / distance, y: dy / distance, z: dz / distance },
  );
  const hit = world.castRay(
    ray,
    distance,
    true,
    rapier.QueryFilterFlags.EXCLUDE_DYNAMIC | rapier.QueryFilterFlags.EXCLUDE_KINEMATIC,
    DUNGEON_SIGHT_QUERY_GROUPS,
  );
  return !hit || hit.timeOfImpact >= distance - TARGET_MARGIN;
}