using System;
using System.IO;            // file readers and writers
using System.Windows.Forms; // Application object
using System.Reflection;

namespace Standard
{

    public sealed class LogFile : IDisposable
    {

        private static int maxsize = 30000; // new file if old one exceeds maxsize
        private static string fileSuffix = "_log.txt"; // log file suffix
        private static string fileSpecification;       // log file full path and spec
        private static StreamWriter filewriter;        // log file stream writer
        private static LogFile instance = null;        // reference to this class


        private LogFile()
        {
        } // end constructor


        #region methods of IDisposable

        ~LogFile()
        {
            Dispose(false);
        }


        // clean up any resources being used.
        private void Dispose(bool disposing)
        {
            if (disposing)
            {
                GC.SuppressFinalize(this);
            }
            if (instance != null)
            {
                if (filewriter != null)
                {
                    filewriter.Flush();
                    filewriter.Close();
                    filewriter = null;  // dereference object
                }
            }
        }


        public void Dispose()
        {
            Dispose(true);
        }

        #endregion


        // user is encouraged to call this
        public static void Close()
        {
            instance.Dispose();
        }


        // main() calls this static method to start the log file;
        // after that, just call LogFile.WriteLine from anywhere
        public static void InitLogFile()
        {
            if (instance == null) instance = new LogFile();
            string stringMe = "LogFile: ";
            try
            {
                if (Application.ProductName.Length==0)
                {
                    fileSpecification = Application.StartupPath + "\\" +
                        "Test" + fileSuffix;
                }
                else
                {
                    fileSpecification = Application.StartupPath + "\\" +
                        Application.ProductName + fileSuffix;
                }

                if (File.Exists(fileSpecification)) // restart file if too big
                {
                    FileInfo myFileInfo = new FileInfo(fileSpecification);
                    if (myFileInfo.Length > maxsize) File.Delete(fileSpecification);
                    myFileInfo = null;
                }

                filewriter = File.AppendText(fileSpecification); // open, or create new

                // start log with standard info
                WriteLine("\r\n---------------------------------------------");
                string tempString = stringMe + Application.ProductName + " " + 
                    Application.ProductVersion + " log opened at " +
                    " " + DateTime.Now + ", username=" + SystemInformation.UserName;
                WriteLine(tempString);
                WriteLine(stringMe + ": using");
                WriteLine("   " + Application.LocalUserAppDataPath);
            }
            catch (Exception ex) { ex.ToString(); }
        }



        public static void WriteLine(String myInputLine)
        {
            try
            {   
                if (instance != null)
                {
                    if (myInputLine.Length!=0)
                    {
                        filewriter.WriteLine(myInputLine);
                        filewriter.Flush(); // update file
                    }
                }
            }
            catch (Exception ex) { ex.ToString(); }
        }


    } // end class LogFile()
} // end namespace