private IEnumerable GetConfigurations()

in tool/TeamCity.Docker/ConfigurationExplorer.cs [69:116]
39 lines of code
6 McCabe index (conditional complexity)

        private IEnumerable<Template> GetConfigurations([NotNull] string sourcePath, [NotNull] IReadOnlyDictionary<string, string> additionalVars)
        {
            if (sourcePath == null)
            {
                throw new ArgumentNullException(nameof(sourcePath));
            }

            if (additionalVars == null)
            {
                throw new ArgumentNullException(nameof(additionalVars));
            }

            var templateCounter = 0;
            foreach (var dockerfileTemplate in _fileSystem.EnumerateFileSystemEntries(sourcePath, "*.Dockerfile"))
            {
                var dockerfileTemplateRelative = Path.GetRelativePath(sourcePath, dockerfileTemplate);
                using (_logger.CreateBlock($"{++templateCounter:000} {dockerfileTemplateRelative}"))
                {
                    var dockerfileTemplateDir = Path.GetDirectoryName(dockerfileTemplate) ?? ".";
                    var dockerfileTemplatePath = Path.GetFileName(dockerfileTemplate);
                    // ReSharper disable once IdentifierTypo
                    var dockerignoreTemplatePath = Path.Combine(dockerfileTemplateDir, Path.GetFileNameWithoutExtension(dockerfileTemplatePath) + ".Dockerignore");
                    var variants = new List<Variant>();
                    var configCounter = 0;
                    
                    // Get all configuration files for particular OS (e.g. Ubuntu/20.04/..., Ubuntu/18.04/, ...
                    foreach (var configFile in _fileSystem.EnumerateFileSystemEntries(dockerfileTemplateDir, dockerfileTemplatePath + ".config"))
                    {
                        var buildPath = Path.GetDirectoryName(Path.GetRelativePath(sourcePath, configFile)) ?? "";
                        using (_logger.CreateBlock($"{templateCounter:000}.{++configCounter:000} {Path.GetRelativePath(sourcePath, configFile)}"))
                        {
                            var vars = UpdateVariables(additionalVars, GetVariables(configFile));
                            variants.Add(new Variant(buildPath, configFile, vars.Select(i => new Variable(i.Key, i.Value)).ToList()));
                        }
                    }


                    var ignore = new List<string>();
                    if (_fileSystem.IsFileExist(dockerignoreTemplatePath))
                    {
                        // Add .Dockerignore files
                        ignore.AddRange(_fileSystem.ReadLines(dockerignoreTemplatePath));
                    }
                    
                    yield return new Template(_fileSystem.ReadLines(dockerfileTemplate).ToImmutableList(), variants.AsReadOnly(), ignore.AsReadOnly());
                }
            }
        }