using System;
using System.Collections.Generic;
using System.Drawing;
using System.IO;
using System.Threading;
using System.Windows.Forms;

// The 'windowHandle' parameter will contain the window handle for the:
//   - Active window when run by hotkey
//   - Trigger target when run by a Trigger rule
//   - TitleBar Button owner when run by a TitleBar Button
//   - Jump List owner when run from a Taskbar Jump List
//   - Currently focused window if none of these match
public static class DisplayFusionFunction
{
    /////////////////////////////////////////////////////////////////////////////////////
    //Note: Replace the "Path" variable with the file you want to watch,               //
    //      and replace the "SearchText" varaible with the text you want to watch for  //
    /////////////////////////////////////////////////////////////////////////////////////
    private static readonly string Path = @"C:\Users\UserName\AppData\Roaming\Slack\logs\browser.log";
    private static readonly string SearchText = "NEW_NOTIFICATION";

	public static void Run(IntPtr windowHandle)
	{
        // Create a new FileTailWatcher with the parameters of our choosing
		using(FileTailWatcher watcher = new FileTailWatcher(Path, SearchText))
		{
            // Assign the event that will get fired when the text is found in the file
            watcher.OnSearchTextFound += SlackWatcher_OnSearchTextFound;
            
            // Run the FileTailWatcher App
            Application.Run(watcher);
        }
	}
	
	// This event gets fired when the search text gets found
	private static void SlackWatcher_OnSearchTextFound()
	{
        // Put any code you want here
        BFS.Dialog.ShowTrayMessage("Hey You! You have a new slack message!!!");
	}
	
	// This custom class uses a FileSystemWatcher to watch for changes in
	private class FileTailWatcher : ApplicationContext
	{
        // Variables
        private long LastFileSize = 0;
        private FileSystemWatcher Watcher;
        private readonly string Path;
        private readonly string SearchText;
        
        // Delegates and Events
        public delegate void DelegateVoid();
        public event DelegateVoid OnSearchTextFound;
	
        // This function sets up the class, and starts watching the end of the file
        public FileTailWatcher(string path, string searchText)
        {
            this.Path = path;
			this.SearchText = searchText;
        
            FileInfo info = new FileInfo(this.Path);
            this.LastFileSize = info.Length;
			this.Watcher = new FileSystemWatcher(info.DirectoryName, info.Name);
			this.Watcher.Changed += this.Watcher_Changed;
			this.Watcher.EnableRaisingEvents = true;
        }
        
        // Do some cleanup
        protected override void Dispose(bool disposing)
        {
            if(this.Watcher != null)
                this.Watcher.Dispose();
            
            base.Dispose(disposing);
        }
        
        // This method gets run when the file we're watching changes
        private void Watcher_Changed(object sender, FileSystemEventArgs e)
		{
            // Get the new file size
            long length = new FileInfo(this.Path).Length;
            
            // No point of looking through an empty file
            // When other apps write to the file, they might also clear it, so don't set LastFileSize
            if(length == 0)
                return;
            
            // If the file is the same size, ignore the change
            if (length == this.LastFileSize)
                return;
		
            // Open the file for reading, but allow other programs to read and write from the file
			using (FileStream file = File.Open(this.Path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
			using (StreamReader reader = new StreamReader(file))
			{
				//set the position of the stream to the last file size
				reader.BaseStream.Position = this.LastFileSize;

				//read each line until we find the EOF, or what we're looking for
				while (true)
				{
					string line = reader.ReadLine();
					if (line == null)
						break;
                    
                    // The text we're looking for isn't going to be on an empty line
                    if(string.IsNullOrEmpty(line))
                        continue;

                    //if we havn't found our text on this line, continue to the next one
					if (line.IndexOf(this.SearchText, StringComparison.OrdinalIgnoreCase) == -1)
						continue;
                    
					// If we got this far, we found what we wanted. no need to keep looking through the file.
					// Fire the event
                    if(this.OnSearchTextFound != null)
                        this.OnSearchTextFound();
                    
					break;
				}
			}
			
			// Set our last position searched
            this.LastFileSize = length;
		}
	}
}