public async Task _CreateDiskFromSnapshotAsync()

in tools/gsnapshot/Disks.cs [100:220]
116 lines of code
17 McCabe index (conditional complexity)

    public async Task<ComputeData.Disk?> _CreateDiskFromSnapshotAsync(
        string projectId, string diskName, ComputeData.Disk originalDisk,
        ComputeData.Snapshot snapshot, string snapshotDiskType, bool eraseVss) {
      ComputeBetaData.Disk requestBody = new ComputeBetaData.Disk();

      string diskType = _utils.GetLastPartN(originalDisk.Type, 4);
      bool regional = (diskType == "regions" ? true : false);

      requestBody.Name = diskName;
      requestBody.SourceSnapshot = snapshot.SelfLink;
      requestBody.Description = originalDisk.Description;
      requestBody.SizeGb = snapshot.DiskSizeGb;
      // Attempting to restore a 0 length snapshot means it can't have VSS signature
      requestBody.EraseWindowsVssSignature = eraseVss;
      if (!regional) {
        requestBody.Type =
            $"projects/{projectId}/zones/{_utils.GetLastPart(originalDisk.Zone)}/diskTypes/{snapshotDiskType}";
      } else {
        requestBody.Type =
            $"projects/{projectId}/regions/{_utils.GetLastPart(originalDisk.Region)}/diskTypes/{snapshotDiskType}";
        requestBody.ReplicaZones = originalDisk.ReplicaZones;
      }
      if (originalDisk.GuestOsFeatures != null) {
        requestBody.GuestOsFeatures = new List<ComputeBetaData.GuestOsFeature>();
        foreach (ComputeData.GuestOsFeature feature in originalDisk.GuestOsFeatures) {
          ComputeBetaData.GuestOsFeature betaFeature = new ComputeBetaData.GuestOsFeature();
          betaFeature.Type = feature.Type;
          betaFeature.ETag = feature.ETag;
          requestBody.GuestOsFeatures.Add(betaFeature);
        }
      }
      requestBody.Labels = originalDisk.Labels;
      requestBody.ResourcePolicies = originalDisk.ResourcePolicies;
      if (originalDisk.Labels == null) {
        requestBody.Labels = new Dictionary<string, string>();
      } else {
        requestBody.Labels = originalDisk.Labels;
      }
      requestBody.Labels["gsnapshot"] = snapshot.Name;

      if (!regional) {
        string zone = _utils.GetLastPart(originalDisk.Zone);
        _logger.LogInformation(
            $"Creating new zonal disk {diskName} in {zone} from snapshot {snapshot.Name}...");
        ComputeBeta.DisksResource.InsertRequest request =
            betaComputeService.Disks.Insert(requestBody, projectId, zone);
        ComputeBetaData.Operation response = await request.ExecuteAsync();
        bool operationCompleted = false;
        if (!eraseVss) {
          bool done = await _operations.WaitForOperation(projectId, Operations.ZONE, zone,
                                                         _utils.GetLastPart(response.SelfLink));
          if (done) {
            operationCompleted = true;
          }
        } else {
          string done = await _operations.WaitOrFailForOperation(
              projectId, Operations.ZONE, zone, _utils.GetLastPart(response.SelfLink));
          if (done == "INTERNAL_ERROR")  // Disk probably didn't have a VSS signature
          {
            _logger.LogDebug(
                "Disk creation resulted in internal error, will retry with VSS signature erasing turned off...");
            requestBody.EraseWindowsVssSignature = false;
            request = betaComputeService.Disks.Insert(requestBody, projectId, zone);
            response = await request.ExecuteAsync();
            done = await _operations.WaitOrFailForOperation(projectId, Operations.ZONE, zone,
                                                            _utils.GetLastPart(response.SelfLink));
          }
          if (done == "") {
            operationCompleted = true;
          }
        }
        if (operationCompleted) {
          var disk = await GetDiskAsync(projectId, zone, diskName);
          return disk;
        } else {
          _logger.LogCritical(
              $"Failed to create a zonal new disk, operation {response.SelfLink} failed to complete.");
          return null;
        }
      } else {
        string region = _utils.GetLastPart(originalDisk.Region);
        _logger.LogInformation(
            $"Creating new regional disk {diskName} in {region} from snapshot {snapshot.Name}...");
        ComputeBeta.RegionDisksResource.InsertRequest request =
            betaComputeService.RegionDisks.Insert(requestBody, projectId, region);
        ComputeBetaData.Operation response = await request.ExecuteAsync();
        bool operationCompleted = false;

        if (!eraseVss) {
          bool done = await _operations.WaitForOperation(projectId, Operations.REGION, region,
                                                         _utils.GetLastPart(response.SelfLink));
          if (done) {
            operationCompleted = true;
          }
        } else {
          string done = await _operations.WaitOrFailForOperation(
              projectId, Operations.REGION, region, _utils.GetLastPart(response.SelfLink));
          if (done == "INTERNAL_ERROR")  // Disk probably didn't have a VSS signature
          {
            _logger.LogDebug(
                "Disk creation resulted in internal error, will retry with VSS signature erasing turned off...");
            requestBody.EraseWindowsVssSignature = false;
            request = betaComputeService.RegionDisks.Insert(requestBody, projectId, region);
            response = await request.ExecuteAsync();
            done = await _operations.WaitOrFailForOperation(projectId, Operations.REGION, region,
                                                            _utils.GetLastPart(response.SelfLink));
          }
          if (done == "") {
            operationCompleted = true;
          }
        }
        if (operationCompleted) {
          var disk = await GetRegionalDiskAsync(projectId, region, diskName);
          return disk;
        } else {
          _logger.LogCritical(
              $"Failed to create a new regional disk, operation {response.SelfLink} failed to complete.");
          return null;
        }
      }
    }