public void DoAction()

in tools/gsnapshot/Runner.cs [400:510]
107 lines of code
21 McCabe index (conditional complexity)

    public void DoAction(Options options) {
      _logger.LogInformation($"gsnapshot {Version} - a snapshot/rollback utility");
      switch (options.Command) {
        case "snapshot":
          _logger.LogInformation("Operation specified: begin changes (create snapshots)");
          break;
        case "schedule-snapshot":
          _logger.LogInformation(
              "Operation specified: schedule snapshots (attach snapshot schedule to all of instance's disks)");
          break;
        case "rollback":
          _logger.LogInformation(
              "Operation specified: rollback changes (create new disks from snapshots and attach)");
          break;
        case "rollback-scheduled":
          _logger.LogInformation(
              "Operation specified: rollback to previous state (create new disks from scheduled snapshots and attach)");
          break;
        case "commit":
          _logger.LogInformation("Operation specified: commit changes (remove snapshots)");
          break;
        default:
          _logger.LogCritical(
              "Command not selected, select one of: snapshot, schedule-snapshot, rollback, rollback-scheduled, commit");
          string fileName = "gsnapshot";
          var currentProcess = System.Diagnostics.Process.GetCurrentProcess();
          if (currentProcess?.MainModule?.FileName != null) {
            fileName = currentProcess.MainModule.FileName;
          }
          _logger.LogCritical($"  Usage: {fileName} command [parameters...]");
          _logger.LogCritical("");
          _logger.LogCritical(
              "  snapshot             Takes a snapshot of a specified Compute Engine instance.");
          _logger.LogCritical(
              "  schedule-snapshot    Attaches a snapshot schedule to all disks of a Compute Engine instance.");
          _logger.LogCritical("  rollback             Rolls back to a previously made snapshot.");
          _logger.LogCritical(
              "  rollback-scheduled   Rolls back to a previous snapshot from a snapshot schedule.");
          _logger.LogCritical("  commit               Deletes previously made snapshots.");
          _logger.LogCritical("");
          System.Environment.Exit(2);
          break;
      }

      ReadDefaultSettings(options);
      if (String.IsNullOrEmpty(options.Project)) {
        options.Project = PickProject();
        if (String.IsNullOrEmpty(options.Project)) {
          _logger.LogCritical(
              "Project ID was not set, either enter it manually or specify via command line.");
          System.Environment.Exit(2);
        } else {
          _logger.LogInformation($"Selected project: {options.Project}");
        }
      }

      _resources.LoadAllZones(options.Project);
      if (String.IsNullOrEmpty(options.Region)) {
        _resources.LoadAllRegions(options.Project);
        options.Region = PickRegion();
        if (String.IsNullOrEmpty(options.Region)) {
          foreach (string region in _resources.AllRegions.Keys) {
            RegionsToQuery.Add(region);
          }
          _logger.LogWarning(
              $"Region was not set, querying all regions ({RegionsToQuery.Count} regions).");
        } else {
          if (_resources.AllRegions.ContainsKey(options.Region)) {
            _logger.LogInformation($"Selected region: {options.Region}");
            RegionsToQuery.Add(options.Region);
          } else {
            _logger.LogCritical($"Invalid region selected (\"{options.Region}\").");
            System.Environment.Exit(3);
          }
        }
      } else {
        _logger.LogInformation($"Selected region: {options.Region}");
        RegionsToQuery.Add(options.Region);
      }

      _instances.LoadInstances(options.Project, RegionsToQuery, _resources.AllZones);
      if (String.IsNullOrEmpty(options.Instance)) {
        options.Instance = PickInstance();
      }
      if (String.IsNullOrEmpty(options.Instance) ||
          !_instances.AllInstances.ContainsKey(options.Instance)) {
        _logger.LogCritical("Instance ID was not set, or set to non-existing instance.");
        System.Environment.Exit(4);
      }
      string description =
          _instances.GetMachineDescription(_instances.AllInstances[options.Instance]);
      _logger.LogInformation($"Selected instance: {options.Instance} ({description})");

      switch (options.Command) {
        case "snapshot":
          Snapshot(options);
          break;
        case "schedule-snapshot":
          ScheduleSnapshot(options);
          break;
        case "rollback":
          Rollback(options);
          break;
        case "rollback-scheduled":
          RollbackScheduled(options);
          break;
        case "commit":
          Commit(options);
          break;
      }
    }