// ── Component ─────────────────────────────────────────
/**
 * A component definition carries both the type shape (via TypeScript inference)
 * and a unique key used for storage lookup.
 *
 * @example
 * ```ts
 * const Position = defineComponent('position', { x: 0, y: 0 });
 * type Position = typeof Position.type;
 * ```
 */
export interface ComponentDef<T extends Record<string, any>> {
  /** Unique symbol used as the storage key. */
  readonly _key: symbol;
  /** Human-readable name, used for serialization. */
  readonly name: string;
  /** Default values applied when a component is first added. */
  readonly defaults: T;
  /** Phantom type for inference. */
  readonly type: T;
}

/**
 * Define a component type. The name is used for serialization.
 * The defaults object provides both the TypeScript shape and initial values.
 */
export function defineComponent<T extends Record<string, any>>(
  name: string,
  defaults: T,
): ComponentDef<T> {
  return {
    _key: Symbol(),
    name,
    defaults: { ...defaults },
    type: undefined as unknown as T,
  };
}