using System;
using System.IO;
using System.Threading;
using System.Collections.Generic;

namespace FileSystemWatcherExample {
    class Program {a
        static void Main(string[] args) {
            // If a directory and filter are not specified, exit program
            if (args.Length !=2) {
                // Display the proper way to call the program
                Console.WriteLine("Usage: Watcher.exe \"directory\" \"filter\"");
                return;
            }

            FileProcessor fileProcessor = new FileProcessor();

            // Create a new FileSystemWatcher
            FileSystemWatcher fileSystemWatcher1 = new FileSystemWatcher();

            // Set FileSystemWatcher's properties
            fileSystemWatcher1.Path = args[0];
            fileSystemWatcher1.Filter = args[1];
            fileSystemWatcher1.IncludeSubdirectories = false;

            // Add event handlers
            fileSystemWatcher1.Created += new System.IO.FileSystemEventHandler(this.fileSystemWatcher1_Created);

            // Start to watch
            fileSystemWatcher1.EnableRaisingEvents = true;

            // Wait for the user to quit the program
            Console.WriteLine("Press \'q\' to quit the program.");
            while(Console.Read()!='q');

            // Turn off FileSystemWatcher
            if (fileSystemWatcher1 != null) {
                fileSystemWatcher1.EnableRaisingEvents = false;
                fileSystemWatcher1.Dispose();
                fileSystemWatcher1 = null;
            }

            // Dispose fileProcessor
            if (fileProcessor != null)
                fileProcessor.Dispose();
        }

        // Define the event handler
        private void fileSystemWatcher1_Created(object sender, FileSystemEventArgs e) {
            // If file is created...
            if (e.ChangeType == WatcherChangeTypes.Created) {
                // ...enqueue it's file name so it can be processed...
                fileProcessor.EnqueueFileName(e.FullPath);
            }
            // ...and immediately finish event handler
        }
    }


    // File processor class
    class FileProcessor : IDisposable {
        // Create an AutoResetEvent EventWaitHandle
        private EventWaitHandle eventWaitHandle = new AutoResetEvent(false);
        private Thread worker;
        private readonly object locker = new object();
        private Queue<string> fileNamesQueue = new Queue<string>();

        public FileProcessor() {
            // Create worker thread
            worker = new Thread(Work);
            // Start worker thread
            worker.Start();
        }

        public void EnqueueFileName(string FileName) {
            // Enqueue the file name
            // This statement is secured by lock to prevent other thread to mess with queue while enqueuing file name
            lock (locker) fileNamesQueue.Enqueue(FileName);
            // Signal worker that file name is enqueued and that it can be processed
            eventWaitHandle.Set();
        }

        private void Work() {
            while (true) {
                string fileName = null;

                // Dequeue the file name
                lock (locker)
                    if (fileNamesQueue.Count > 0) {
                        fileName = fileNamesQueue.Dequeue();
                        // If file name is null then stop worker thread
                        if (fileName == null) return;
                    }

                if (fileName != null) {
                    // Process file
                    ProcessFile(fileName);
                } else {
                    // No more file names - wait for a signal
                    eventWaitHandle.WaitOne();
                }
            }
        }

        private ProcessFile(string FileName) {
            // Maybe it has to wait for file to stop being used by process that created it before it can continue
            // Unzip file
            // Read its content
            // Log file data to database
            // Move file to archive folder
        }


        #region IDisposable Members

        public void Dispose() {
            // Signal the FileProcessor to exit
            EnqueueFileName(null);
            // Wait for the FileProcessor's thread to finish
            worker.Join();
            // Release any OS resources
            eventWaitHandle.Close();
        }

        #endregion
    }
}