Made of little things.

import { MOUTH_MODEL } from './layers.js';
import type { Point3 } from './case.js';

export interface MouthPart {
  id: string; label: string; part: string; kind: 'tooth' | 'tongue' | 'jaw'; jaw: 'upper' | 'lower'; fdi?: number;
  vertices: number; triangles: number; positions: number; indices: number;
}
export interface MouthData { parts: MouthPart[]; head: Point3; hinge: Point3; buffer: ArrayBuffer; start: number }
export function decodeMouth(buffer: ArrayBuffer): MouthData {
  const decoder = new TextDecoder(), view = new DataView(buffer);
  if (decoder.decode(new Uint8Array(buffer, 0, 8)) !== 'BJMOUTH1') throw new Error('Unsupported mouth asset.');
  const length = view.getUint32(8, true), start = 12 + length;
  const meta = JSON.parse(decoder.decode(new Uint8Array(buffer, 12, length)));
  if (meta.id !== MOUTH_MODEL || !Array.isArray(meta.parts) || meta.parts.length !== 32) throw new Error('Mouth version mismatch.');
  return { parts: meta.parts, head: meta.head, hinge: meta.hinge, buffer, start };
}