using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
using System.Diagnostics;
using System.IO;

namespace time_tracker
{
    class Program
    {
        [DllImport("user32.dll")]
        static extern IntPtr GetForegroundWindow();

        [DllImport("user32.dll")]
        static extern int GetWindowText(IntPtr hWnd, StringBuilder text, int count);

        [DllImport("user32.dll", SetLastError = true)]
        static extern uint GetWindowThreadProcessId(IntPtr hWnd, out int lpdwProcessId);

        static void Main(string[] args)
        {
            TextWriter outputFile = null;
            if (args.Length > 0)
                outputFile = new StreamWriter(args[0], true);

            string currentProcess = null;
            DateTime currentBecameForeground = DateTime.Now;
            while (true)
            {
                IntPtr handle = GetForegroundWindow();
                StringBuilder desc = new StringBuilder();

                int pid = getWindowPID(handle);
                desc.AppendFormat("{0}, {1}, \"{2}\"", handle, pid, Process.GetProcessById(pid).ProcessName);

                string text = getWindowText(handle);
                desc.AppendFormat(", \"{0}\"", text ?? "");

                DateTime now = DateTime.Now;
                now = now.AddMilliseconds(-now.Millisecond);
                TimeSpan timeSpanAsCurrent = now - currentBecameForeground;
                string timeAsCurrent = timeSpanAsCurrent.ToString();
                if (timeAsCurrent.Contains('.'))
                    timeAsCurrent = timeAsCurrent.Substring(0, timeAsCurrent.LastIndexOf('.')); 
                /*String.Format("{0:2}:{1:2}:{2:2}",
                        (int)timeSpanAsCurrent.TotalHours,
                        timeSpanAsCurrent.Minutes,
                        timeSpanAsCurrent.Seconds);*/
                if (desc.ToString() != currentProcess)
                {
                    if (currentProcess != null)
                    {
                        Console.WriteLine("\r{0}, {1}", timeAsCurrent, currentProcess);
                        if (outputFile != null)
                        {
                            outputFile.WriteLine("{0}, {1}, {2}", now, timeAsCurrent, currentProcess);
                            outputFile.Flush();
                        }
                    }
                    currentProcess = desc.ToString();
                    currentBecameForeground = now;
                }
                Console.Write("\r{0}, {1}", timeAsCurrent, currentProcess);

                System.Threading.Thread.Sleep(1000);
            }
        }

        private static int getWindowPID(IntPtr handle)
        {
            int pid;
            GetWindowThreadProcessId(handle, out pid);
            return pid;
        }

        private static string getWindowText(IntPtr handle)
        {
            const int nChars = 256;
            StringBuilder Buff = new StringBuilder(nChars);

            if (GetWindowText(handle, Buff, nChars) > 0)
            {
                return Buff.ToString();
            }
            else
            {
                return null;
            }
        }
    }
}