api.ts

interface IChainLink {
  type: 'resource' | 'value';
  value: string;
}

type SingleApiIndex<T> = { [p in keyof T]: SingleApi<T[p]>; };
type ApiIndex<T> = { [p in keyof T]: Api<T[p]>; };

interface BaseApi<T> {
  (id: number): SingleApi<T>;
  _config: T;
  _chain: IChainLink[];
  post(): T;
  delete(): boolean
}

interface SingleApiFunction<T> extends BaseApi<T> {
  get(): T;
}

interface ApiFunction<T> extends BaseApi<T> {
  get(): T[];
}

type SingleApi<T> = SingleApiIndex<T> & SingleApiFunction<T>;
type Api<T> = ApiIndex<T> & ApiFunction<T>;


function parseChain(chain: IChainLink[]): string {
  return '/' + chain.map(link => link.value).join('/');
}

function get<T>(this: Api<T>): T[] {
  const chain = parseChain(this._chain);
  // TODO
}

function post<T>(this: Api<T>): T {
  const chain = parseChain(this._chain);
  // TODO
}

function _delete<T>(this: Api<T>): void {
  const chain = parseChain(this._chain);
  // TODO
}


function makeApi<T>(config: T, chain = [] as IChainLink[]): Api<T> {
  function target(id: number): Api<T> {
    const link: IChainLink = { type: 'value', value: String(id) };
    return makeApi(config, [ link, ...chain ])
  }

  Object.assign(target, {
    _config: config,
    _chain: chain,
    get,
    post,
    delete: _delete,
  });

  return new Proxy({} as Api<T>, {
      get(target, name: string) {
        if (target.hasOwnProperty(name))
          return target[name];

        const link: IChainLink = { type: 'resource', value: name };
        return makeApi(config[name], [ link, ...chain ])
      },
  });
}

class ImageModel {
  toFile() {}
}
class CosasModel {}
class PatataModel {}

const api = makeApi({
  _config: 'patata',
  collections: {
    images: new ImageModel(),
    cosas: new CosasModel(),
    patatas: new PatataModel(),
  },
  users: {
    images: {
      patata: new PatataModel(),
    }
  }
});

const a = api.collections(1)
  .images(3)
  .get()
  .toFile();

function doSomething<T>(api: Api<T>) { return api; }

doSomething(api)
  .collections
  .images
  .post()
  .toFile();

api.collections.images.get()[0].toFile();