import { useFrame } from "@react-three/fiber";
import { useRef, useState, type ReactNode } from "react";
import { Group, Vector3 } from "three";
import type { MobVector3 } from "../game/mobPopulation";
import { useGameStore } from "../game/store";
import { DungeonOccludedHtml } from "./DungeonOccludedHtml";

export const WORLD_NPC_PROMPT_MAX_DISTANCE = 22;

const VISIBILITY_CHECK_INTERVAL_SECONDS = 0.1;
const VISIBILITY_HYSTERESIS = 2;

export function worldNpcPromptIsInRange(
  viewerPosition: MobVector3,
  promptPosition: MobVector3,
  maxDistance = WORLD_NPC_PROMPT_MAX_DISTANCE,
): boolean {
  if (!Number.isFinite(maxDistance) || maxDistance < 0) return false;
  const dx = viewerPosition[0] - promptPosition[0];
  const dy = viewerPosition[1] - promptPosition[1];
  const dz = viewerPosition[2] - promptPosition[2];
  return dx * dx + dy * dy + dz * dz <= maxDistance * maxDistance;
}

export function WorldNpcPrompt({
  children,
  position = [0, 0, 0],
  maxDistance = WORLD_NPC_PROMPT_MAX_DISTANCE,
  zIndexRange = [8, 0],
}: {
  readonly children: ReactNode;
  readonly position?: MobVector3;
  readonly maxDistance?: number;
  readonly zIndexRange?: readonly [number, number];
}) {
  const anchorRef = useRef<Group>(null);
  const worldPositionRef = useRef(new Vector3());
  const elapsedRef = useRef(VISIBILITY_CHECK_INTERVAL_SECONDS);
  const visibleRef = useRef(false);
  const [visible, setVisible] = useState(false);

  useFrame((_, delta) => {
    elapsedRef.current += delta;
    if (elapsedRef.current < VISIBILITY_CHECK_INTERVAL_SECONDS) return;
    elapsedRef.current = 0;
    if (!anchorRef.current) return;

    anchorRef.current.getWorldPosition(worldPositionRef.current);
    const worldPosition = worldPositionRef.current;
    const distanceLimit = maxDistance + (visibleRef.current ? VISIBILITY_HYSTERESIS : 0);
    const nextVisible = worldNpcPromptIsInRange(
      useGameStore.getState().playerPosition,
      [worldPosition.x, worldPosition.y, worldPosition.z],
      distanceLimit,
    );
    if (nextVisible === visibleRef.current) return;
    visibleRef.current = nextVisible;
    setVisible(nextVisible);
  });

  return (
    <group ref={anchorRef} position={[position[0], position[1], position[2]]}>
      {visible ? (
        <DungeonOccludedHtml center zIndexRange={[zIndexRange[0], zIndexRange[1]]}>
          {children}
        </DungeonOccludedHtml>
      ) : null}
    </group>
  );
}