import * as THREE from 'three';
import type { TTSObject } from '@tts/shared';

/**
 * The per-object tint (`ColorDiffuse`, 0–1 per channel) as a three.js color,
 * defaulting to white when absent. TTS multiplies this by the object's base
 * color, so textured faces are tinted too.
 */
export function objectTint(object: TTSObject): THREE.Color {
  const c = object.ColorDiffuse;
  return c ? new THREE.Color(c.r, c.g, c.b) : new THREE.Color(1, 1, 1);
}

/** A stable cache key fragment for a tint, so tinted variants don't collide. */
export function tintKey(color: THREE.Color): string {
  return `${color.r},${color.g},${color.b}`;
}

/** Multiply a base color by the object's tint. */
export function tintedColor(base: THREE.Color, tint: THREE.Color): THREE.Color {
  return base.clone().multiply(tint);
}

/**
 * Module-level caches so the full-setup view can share geometry and materials
 * across many objects instead of rebuilding them per object. Keyed by a
 * canonical string describing the resource, so identical objects reuse one
 * instance. drei already caches textures globally by URL, so sharing the
 * material on top avoids per-object material allocation for tiles/tokens with
 * the same image.
 *
 * These caches live for the session (like drei's global texture cache) and are
 * not disposed on unmount; see `docs/status/full-setup-view.md`.
 */

const geometryCache = new Map<string, THREE.BufferGeometry>();
const materialCache = new Map<string, THREE.MeshStandardMaterial>();

/** Get or create a geometry for `key`. */
export function getSharedGeometry(
  key: string,
  build: () => THREE.BufferGeometry,
): THREE.BufferGeometry {
  let geo = geometryCache.get(key);
  if (!geo) {
    geo = build();
    geometryCache.set(key, geo);
  }
  return geo;
}

/** Get or create a standard material for `key`. */
export function getSharedMaterial(
  key: string,
  params: THREE.MeshStandardMaterialParameters,
): THREE.MeshStandardMaterial {
  let mat = materialCache.get(key);
  if (!mat) {
    mat = new THREE.MeshStandardMaterial(params);
    materialCache.set(key, mat);
  }
  return mat;
}