/ number of records actually found.
      result[e.name] = { engine: e, maxRecords };
    }
    return result;
  },

  async _runValidators(engineInfos) {
    if (!Object.keys(engineInfos).length) {
      log.info("Skipping validation: no engines qualify");
      return;
    }

    if (Object.values(engineInfos).filter(i => i.maxRecords != -1).length) {
      // at least some of the engines have maxRecord restrictions which require
      // us to ask the server for the counts.
      let countInfo = await this._fetchCollectionCounts();
      for (let [engineName, recordCount] of Object.entries(countInfo)) {
        if (engineName in engineInfos) {
          engineInfos[engineName].recordCount = recordCount;
        }
      }
    }

    for (let [
      engineName,
      { engine, maxRecords, recordCount },
    ] of Object.entries(engineInfos)) {
      // maxRecords of -1 means "any number", so we can skip asking the server.
      // Used for tests.
      if (maxRecords >= 0 && recordCount > maxRecords) {
        log.debug(
          `Skipping validation for ${engineName} because ` +
            `the number of records (${recordCount}) is greater ` +
            `than the maximum allowed (${maxRecords}).`
        );
        continue;
      }
      let validator = engine.getValidator();
      if (!validator) {
        // This is probably only possible in profile downgrade cases.
        log.warn(
          `engine.getValidator returned null for ${engineName} but the pref that controls validation is enabled.`
        );
        continue;
      }

      if (!(await validator.canValidate())) {
        log.debug(
          `Skipping validation for ${engineName} because validator.canValidate() is false`
        );
        continue;
      }

      // Let's do it!
      Services.console.logStringMessage(
        `Sync is about to run a consistency check of ${engine.name}. This may be slow, and ` +
          `can be controlled using the pref "services.sync.${engine.name}.validation.enabled".\n` +
          `If you encounter any problems because of this, please file a bug.`
      );

      try {
        log.info(`Running validator for ${engine.name}`);
        let result = await validator.validate(engine);
        let { problems, version, duration, recordCount } = result;
        Observers.notify(
          "weave:engine:validate:finish",
          {
            version,
            checked: recordCount,
            took: duration,
            problems: problems ? problems.getSummary(true) : null,
          },
          engine.name
        );
      } catch (ex) {
        if (Async.isShutdownException(ex)) {
          throw ex;
        }
        log.error(`Failed to run validation on ${engine.name}!`, ex);
        Observers.notify("weave:engine:validate:error", ex, engine.name);
        // Keep validating -- there's no reason to think that a failure for one
        // validator would mean the others will fail.
      }
    }
  },

  // mainly for mocking.
  async _fetchCollectionCounts() {
    let collectionCountsURL = Service.userBaseURL + "info/collection_counts";
    try {
      let infoResp = await Service._fetchInfo(collectionCountsURL);
      if (!infoResp.success) {
        log.error(
          "Can't fetch collection counts: request to info/collection_counts responded with " +
            infoResp.status
        );
        return {};
      }
      return infoResp.obj; // might throw because obj is a getter which parses json.
    } catch (ex) {
      if (Async.isShutdownException(ex)) {
        throw ex;
      }
      // Not running validation is totally fine, so we just write an error log and return.
      log.error("Caught error when fetching counts", ex);
      return {};
    }
  },

  // functions used so tests can mock them
  _now() {
    // We use the server time, which is SECONDS
    return Resource.serverTime;
  },
};
PK