import { Iterable } from 'ix';

import { ObservableLike, ObservableOrValue } from '../../../WebRx';
import { PagerViewModel } from '../Pager/PagerViewModel';
import {
  DataGridViewModel,
  DataSourceRequest,
  DataSourceResponse,
} from './DataGridViewModel';

export type DataSourceResponseSelector<T, TContext> = (
  request?: DataSourceRequest<TContext>,
) => ObservableOrValue<DataSourceResponse<T> | undefined>;

export class AsyncDataGridViewModel<
  T,
  TRequestContext = any
> extends DataGridViewModel<T, TRequestContext> {
  public static displayName = 'AsyncDataGridViewModel';

  public static DefaultRateLimit = 250;

  /**
   * @param responseSelector delegate that produces a response from a request.
   * @param pager pager. if omitted a default pager will be created. use null for no pager.
   * @param context request context included in projection requests. if included requests are bound to context events.
   */
  constructor(
    protected readonly responseSelector: DataSourceResponseSelector<
      T,
      TRequestContext
    >,
    pager?: PagerViewModel,
    context?: ObservableLike<TRequestContext>,
    rateLimit = AsyncDataGridViewModel.DefaultRateLimit,
  ) {
    super(Iterable.empty<T>(), pager, context, undefined, rateLimit);
  }

  getResponse(request: DataSourceRequest | undefined) {
    return this.responseSelector(request);
  }
}