import { Injectable } from '@nestjs/common';
import type { DailyEvaluationStep } from '../jobs/daily-evaluation-steps';
import type { JobResult } from '../jobs/job';
import { DigestService, WINDOW_END_KEY } from './digest.service';

/**
 * Step "digest", the last of the daily evaluation: the in-app morning
 * digest of every user. Running it twice for one day writes nothing the
 * second time (the key holds the day and the user): `digestsWritten` is 0
 * on a same-day rerun.
 */
@Injectable()
export class DigestStep implements DailyEvaluationStep {
  readonly name = 'digest';

  constructor(private readonly digests: DigestService) {}

  async run(today: string): Promise<JobResult> {
    // The window of season changes ends here; the next run starts where
    // this one stopped, so every change is reported once.
    const until = new Date();
    const digestsWritten = await this.digests.runFor(today, undefined, {
      until,
    });
    // A run that wrote nothing (a same-day rerun, or no content) reported
    // no change: the next run must still read the earlier window.
    return digestsWritten === 0
      ? { digestsWritten }
      : { digestsWritten, [WINDOW_END_KEY]: until.toISOString() };
  }
}