private void PreviewTransform()

in src/Microsoft.VisualStudio.SlowCheetah.VS/Package/PreviewTransformCommand.cs [178:270]
73 lines of code
14 McCabe index (conditional complexity)

        private void PreviewTransform(IVsHierarchy hier, string sourceFile, string transformFile)
        {
            if (string.IsNullOrWhiteSpace(sourceFile))
            {
                throw new ArgumentNullException(nameof(sourceFile));
            }

            if (string.IsNullOrWhiteSpace(transformFile))
            {
                throw new ArgumentNullException(nameof(transformFile));
            }

            if (!File.Exists(sourceFile))
            {
                throw new FileNotFoundException(string.Format(CultureInfo.CurrentCulture, Resources.Resources.Error_SourceFileNotFound, sourceFile), sourceFile);
            }

            if (!File.Exists(transformFile))
            {
                throw new FileNotFoundException(string.Format(CultureInfo.CurrentCulture, Resources.Resources.Error_TransformFileNotFound, transformFile), transformFile);
            }

            // Get our options
            using (OptionsDialogPage optionsPage = new OptionsDialogPage())
            using (AdvancedOptionsDialogPage advancedOptionsPage = new AdvancedOptionsDialogPage())
            {
                optionsPage.LoadSettingsFromStorage();
                advancedOptionsPage.LoadSettingsFromStorage();

                this.Logger.LogMessage("SlowCheetah PreviewTransform");
                FileInfo sourceFileInfo = new FileInfo(sourceFile);

                // Destination file
                // This should be kept as a temp file in case a custom diff tool is being used
                string destFile = PackageUtilities.GetTempFilename(true, sourceFileInfo.Extension);
                this.TempFilesCreated.Add(destFile);

                // Perform the transform and then display the result into the diffmerge tool that comes with VS.
                this.ErrorListProvider.Tasks.Clear();
                ITransformationLogger logger = new TransformationPreviewLogger(this.ErrorListProvider, hier);
                ITransformer transformer = TransformerFactory.GetTransformer(sourceFile, logger);
                if (!transformer.Transform(sourceFile, transformFile, destFile))
                {
                    throw new TransformFailedException(Resources.Resources.TransformPreview_ErrorMessage);
                }

                // Does the customer want a preview? If not, just open an editor window
                if (optionsPage.EnablePreview == false)
                {
                    ProjectUtilities.GetDTE().ItemOperations.OpenFile(destFile);
                }
                else
                {
                    // If the diffmerge service is available and no diff tool is specified, or diffmerge.exe is specifed we use the service
                    if (((IServiceProvider)this.ScPackage).GetService(typeof(SVsDifferenceService)) is IVsDifferenceService diffService && (!File.Exists(advancedOptionsPage.PreviewToolExecutablePath) || advancedOptionsPage.PreviewToolExecutablePath.EndsWith("diffmerge.exe", StringComparison.OrdinalIgnoreCase)))
                    {
                        if (!string.IsNullOrEmpty(advancedOptionsPage.PreviewToolExecutablePath) && !File.Exists(advancedOptionsPage.PreviewToolExecutablePath))
                        {
                            // If the user specified a preview tool, but it doesn't exist, log a warning
                            logger.LogWarning(string.Format(CultureInfo.CurrentCulture, Resources.Resources.Error_CantFindPreviewTool, advancedOptionsPage.PreviewToolExecutablePath));
                        }

                        // Write all the labels for the diff tool
                        string sourceName = Path.GetFileName(sourceFile);
                        string leftLabel = string.Format(CultureInfo.CurrentCulture, Resources.Resources.TransformPreview_LeftLabel, sourceName);
                        string rightLabel = string.Format(CultureInfo.CurrentCulture, Resources.Resources.TransformPreview_RightLabel, sourceName, Path.GetFileName(transformFile));
                        string caption = string.Format(CultureInfo.CurrentCulture, Resources.Resources.TransformPreview_Caption, sourceName);
                        string tooltip = string.Format(CultureInfo.CurrentCulture, Resources.Resources.TransformPreview_ToolTip, sourceName);

                        diffService.OpenComparisonWindow2(sourceFile, destFile, caption, tooltip, leftLabel, rightLabel, null, null, (uint)__VSDIFFSERVICEOPTIONS.VSDIFFOPT_RightFileIsTemporary);
                    }
                    else if (string.IsNullOrEmpty(advancedOptionsPage.PreviewToolExecutablePath))
                    {
                        throw new ArgumentException(Resources.Resources.Error_NoPreviewToolSpecified);
                    }
                    else if (!File.Exists(advancedOptionsPage.PreviewToolExecutablePath))
                    {
                        throw new FileNotFoundException(string.Format(CultureInfo.CurrentCulture, Resources.Resources.Error_CantFindPreviewTool, advancedOptionsPage.PreviewToolExecutablePath), advancedOptionsPage.PreviewToolExecutablePath);
                    }
                    else
                    {
                        // Open a process with the specified diff tool
                        // Add quotes to the file names
                        ProcessStartInfo psi = new ProcessStartInfo(advancedOptionsPage.PreviewToolExecutablePath, string.Format(CultureInfo.CurrentCulture, advancedOptionsPage.PreviewToolCommandLine, $"\"{sourceFile}\"", $"\"{destFile}\""))
                        {
                            CreateNoWindow = true,
                            UseShellExecute = false
                        };
                        System.Diagnostics.Process.Start(psi);
                    }
                }
            }
        }