@rschedule/rschedule/src/lib/rule/pipes/rev-11-result.pipe.ts

A typescript library for working with recurring dates and events.

import { DateTime } from '../../date-time';
import { IPipeRule, IPipeRunFn, PipeError, PipeRule } from './interfaces';

export class RevResultPipe extends PipeRule<unknown> implements IPipeRule<unknown> {
  firstPipe!: IPipeRule<unknown>;

  private invalidIterationCount = 0;
  private previousIterationDate?: DateTime;

  // This pipe exists to facilitate the adding of dev callbacks to an iteration
  // of the pipe. It is meant to always be the last pipe in the chain.
  run(args: IPipeRunFn) {
    if (args.date.isBefore(this.start)) {
      return null;
    }

    if (args.invalidDate) {
      // To prevent getting into an infinite loop.
      // - I somewhat arbitrarily chose 50
      // - I noticed that, when limited to 10 iterations, some tests failed
      this.invalidIterationCount++;

      if (this.invalidIterationCount > 50) {
        throw new PipeError(
          'Failed to find a single matching occurrence in 50 iterations. ' +
            `Last iterated date: "${args.date.toISOString()}"`,
        );
      }
    } else {
      if (this.previousIterationDate && this.previousIterationDate.isBeforeOrEqual(args.date)) {
        console.error(
          `Previous run's date is after or equal current run's date of "${args.date.toISOString()}". ` +
            'This is probably caused by a bug.',
        );
        return null;
      }

      this.previousIterationDate = args.date;
      this.invalidIterationCount = 0;
    }

    return args.invalidDate ? this.firstPipe.run(args) : args.date;
  }
}