/*

This is a FileProcessor class which has the capaibility of reading a CSV file and add a new column by combining the firstname and lastname columns and write in the same csv file. It has only one publicly exposed methods and three private methods which are getting called inside that public method sequentially. Also please assume that this class is used in a very big application everywhere.

​

Now a change request has come. This class need to handle excel files as well. Please note that the logic to only the Read() and Write() has changed, the business logic is still the same. if the input file is excel, then this class has to read the first three columns in excel and append the second and third column and update the value in the forth column and write it back to the same excel.

​

Can you please implement this change in this class and let me know. Below are the important things to note.

1. This change should have as little impact on the overall project

2. There will be further change requests to follow.

3. Dont mind writting the actual code to read/write excel files, just add some dummy code in that area to simulate reading/writting excel files. The intention is to see how we refactor the code rather than implementing excel read/write.  

​

*/

​

using System;

using System.Data;

using System.IO;

using System.Text;

​

namespace ConsoleApp1

{

    class Program

    {

        static void Main(string[] args)

        {

            var fileProcessor = new FileProcessor(@"D:\data.csv");

            fileProcessor.Process();

            Console.WriteLine("File processed successfully.. !!");

            Console.ReadLine();

        }

    }

​

    public class FileProcessor

    {

        private readonly string _filePath;

        private readonly DataTable _data;

​

        public FileProcessor(string filePath)

        {

            _filePath = filePath;

            _data = new DataTable();

            _data.Columns.Add("PatientId");

            _data.Columns.Add("FirstName");

            _data.Columns.Add("LastName");

            _data.Columns.Add("FullName");

        }

​

        public void Process()

        {

            Read();

            ApplyBusinessLogic();

            Write();

        }

​

        private void Read()

        {

            // Logic to read CSV file.

            var fileContent = File.ReadAllLines(_filePath);

            foreach (var line in fileContent)

            {

                var arr = line.Split(',');

​

                var dataRow = _data.NewRow();

                dataRow["PatientId"] = int.Parse(arr[0]);

                dataRow["FirstName"] = arr[1];

                dataRow["LastName"] = arr[2];

            }

        }

​

        private void ApplyBusinessLogic()

        {

            // Business logic: append first name an last name in the full name field. 

            foreach (DataRow dataRow in _data.Rows)

            {

                dataRow["FullName"] = dataRow["FirstName"] + ", " + dataRow["LastName"];

            }

        }

​

        private void Write()

        {

            // Logic to write in the same CSV file.

            var output = new StringBuilder();

​

            foreach (DataRow dataRow in _data.Rows)

            {

                output.AppendLine($"{dataRow["PatientId"]}, {dataRow["FirstName"]}, {dataRow["LastName"]}, {dataRow["FullName"]}");

            }

​

            File.WriteAllText(_filePath, output.ToString());

        }

    }

}