export class ExtensionRegistry {
  #values = new Map<string, unknown[]>();

  add<T>(name: string, value: T): void {
    const values = this.#values.get(name);

    if (values) {
      values.push(value);
    } else {
      this.#values.set(name, [value]);
    }
  }

  get<T>(name: string): T {
    const values = this.all<T>(name);

    if (values.length !== 1) {
      throw new Error(`"${name}" needs exactly one value, found ${values.length}.`);
    }

    return values[0] as T;
  }

  all<T>(name: string): T[] {
    return [...(this.#values.get(name) ?? [])] as T[];
  }

  clear(): void {
    this.#values.clear();
  }
}