private async loop()

in src/election.ts [109:175]
57 lines of code
9 McCabe index (conditional complexity)

  private async loop() {
    // @see https://github.com/etcd-io/etcd/blob/28d1af294e4394df1ed967a4ac4fbaf437be3463/client/v3/concurrency/election.go#L177
    while (this.running) {
      const allKeys = await this.namespace.getAll().sort('Create', 'Ascend').limit(1).exec();
      let leader: IKeyValue | undefined = allKeys.kvs[0];
      let revision = allKeys.header.revision;

      if (!this.running) {
        return; // if closed when doing async work
      }

      if (!leader) {
        this.setLeader(undefined);

        const watcher = this.namespace
          .watch()
          .startRevision(allKeys.header.revision)
          .prefix('')
          .only('put')
          .watcher();

        await new Promise<void>((resolve, reject) => {
          watcher.on('data', data => {
            let done = false;
            for (const event of data.events) {
              if (event.type === 'Put') {
                leader = event.kv;
                revision = event.kv.mod_revision;
                done = true;
              }
            }
            if (done) {
              resolve();
            }
          });
          watcher.on('error', reject);
          this.disposer = resolve;
        }).finally(() => watcher.cancel());

        if (!this.running) {
          return; // if closed when doing async work
        }
      }

      if (!leader) {
        throw new ClientRuntimeError('unreachable lack of election leader');
      }

      this.setLeader(leader);

      const watcher = this.namespace
        .watch()
        .startRevision(new BigNumber(revision).plus(1).toString())
        .key(leader.key)
        .watcher();

      await new Promise<void>((resolve, reject) => {
        watcher!.on('put', kv => this.setLeader(kv));
        watcher!.on('delete', () => resolve());
        watcher!.on('error', reject);
        this.disposer = () => {
          resolve();
          return watcher.cancel();
        };
      }).finally(() => watcher.cancel());
    }
  }