DimerceDemoApplication/services/ApplicationConfigurationService.cs

namespace Configuration
{
    public sealed class ApplicationConfigurationService
    {        
        private FileInfo[] jsonFiles;
        public FileInfo[] JsonFilesInfo
        {
            get { return jsonFiles; }
            private set
            {
                jsonFiles = value.Reverse().ToArray();
            }
        }
        private FileInfo outputFile;
        public FileInfo OutputFile{
            get {return outputFile;}
            private set
            {
                if (!canCreateFile(value.FullName))
                    throw new DemoApplicationConfigurationException($"Given output name '{value.FullName}' cannot be used");
                outputFile = value;
            }
        }

        public static ApplicationConfigurationService InitializeFrom(string[] args)
        {
            if (args.Length < 3)
                throw new DemoApplicationConfigurationException("Must have atleast: 1 flag, 1 path, 1 output filename");

            var outputFileName = new FileInfo(args.Last());

            // Remove last file-name arg, to get a more consistent array
            var strippedArgs = args.SkipLast(1).ToArray();


            string[] givenFlags = strippedArgs.Where((value, index) => index % 2 == 0).ToArray();
            string[] givenFilePaths = strippedArgs.Where((value, index) => index % 2 != 0).ToArray();
            
            try
            {
                // Assert only a single 'd' was passed
                if ( givenFlags.Length == 1 && givenFlags[0].Equals("-d") ) {
                string[] filesInDirectory = Directory.GetFiles(givenFilePaths[0]);
                return new ApplicationConfigurationService {
                    OutputFile = outputFileName,
                    JsonFilesInfo = filesInDirectory.Select(name => new FileInfo(name)).ToArray(),
                };
            }
                // Assert only '-f' were passed
                else if (givenFlags.All((string flag) => flag.Equals("-f"))) {
                    return new ApplicationConfigurationService {
                        OutputFile = outputFileName,
                        JsonFilesInfo = givenFilePaths.Select(name => new FileInfo(name)).ToArray(),
                    };
                }
                else {
                    throw new DemoApplicationConfigurationException("Must have either 1 flag that is '-d', or all flags must be '-f");
                }
            } catch (Exception)
            {
                Console.WriteLine("Something went wrong");
                throw;
            }
        }


        private static bool canCreateFile(string filename) {
            try
            {
                using (File.Create(filename)) {
                    File.Delete(filename);
                    return true;
                }            
            }
            catch
            {
                return false;
            }
        }

        [Serializable]
        internal sealed class DemoApplicationConfigurationException : Exception
        {
            public DemoApplicationConfigurationException()
            {
            }

            public DemoApplicationConfigurationException(string? message) : base(message)
            {
            }
        }
    }
}