//	Spludlow Software
//	Copyright © Samuel P. Ludlow 2020 All Rights Reserved
//	Distributed under the terms of the GNU General Public License version 3
//	Distributed WITHOUT ANY WARRANTY; without implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE
//	https://www.spludlow.co.uk/LICENCE.TXT
//	The Spludlow logo is a registered trademark of Samuel P. Ludlow and may not be used without permission
//	v1.14

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using System.IO;
using System.Data;

namespace Spludlow.Data
{
	/// <summary>
	///	Keep TextTable file locked while "using" this class
	///	Make sure you only use it for a short time so other users don't find the file locked for too long
	///	AppendMode will perform much better when simpily adding rows to the end of existing table, will only read schema, then you add the rows to append
	///	In Append mode if empty table is passed it will be cloned and used as the table rather than reading the file
	///	When using append mode you can prepare a table containing the rows to add in adavance then just set the LockedTextTable's table inside the using and that's it
	///	When append mode is false the whole table is read and then overwrites existing when finished
	///	An empty table can be passed that will be used if the file does not exist
	/// </summary>
	public class LockedTextTable : IDisposable
	{

		private FileStream FileStream = null;
		public DataTable Table = null;
		private Encoding Encoding;
		private bool AppendMode;

		private DataTable EmptyTable = null;

		public LockedTextTable(string filename, bool appendMode)
		{
			this.Start(filename, false, Encoding.Default, appendMode, null);
		}
		public LockedTextTable(string filename, Encoding encoding, bool appendMode)
		{
			this.Start(filename, false, encoding, appendMode, null);
		}
		public LockedTextTable(string filename, bool appendMode, DataTable emptyTable)
		{
			this.Start(filename, false, Encoding.Default, appendMode, emptyTable);
		}
		public LockedTextTable(string filename, bool removeEmptyEntries, Encoding encoding, bool appendMode, DataTable emptyTable)
		{
			this.Start(filename, removeEmptyEntries, encoding, appendMode, emptyTable);
		}

		private void Start(string filename, bool removeEmptyEntries, Encoding encoding, bool appendMode, DataTable emptyTable)
		{
			this.Encoding = encoding;
			this.AppendMode = appendMode;
			this.EmptyTable = emptyTable;

			this.FileStream = Spludlow.Io.Files.FileStreamOpenOrCreateReadWrite(filename);

			if (this.FileStream.Length == 0)
			{
				if (this.EmptyTable == null)
					throw new ApplicationException("LockedTextTable; No existing table and empty table not supplied: " + filename);

				Spludlow.Data.TextTable.Write(this.FileStream, this.EmptyTable, this.Encoding, false);

				this.FileStream.Position = 0;		
			}

			if (this.AppendMode == true && emptyTable != null)
				this.Table = emptyTable.Clone();
			else
				this.Table = Spludlow.Data.TextTable.ReadStream(this.FileStream, removeEmptyEntries, this.Encoding, this.AppendMode);
		}

		public void Dispose()
		{
			if (this.FileStream != null)
			{
				if (this.Table != null)
				{
					if (this.AppendMode == false)
					{
						this.FileStream.SetLength(0);
						this.FileStream.Position = 0;
					}
					else
					{
						this.FileStream.Seek(0, SeekOrigin.End);
					}

					Spludlow.Data.TextTable.Write(this.FileStream, this.Table, this.Encoding, this.AppendMode);
				}

				this.FileStream.Close();
				this.FileStream.Dispose();
			}
		}

		public static void TestLockedTextTable(string filename, int threads, int iterations)
		{
			Spludlow.Log.Report("TestLockedTextTable Starting");

			if (File.Exists(filename) == true)
				File.Delete(filename);

			DataTable table = Spludlow.Data.TextTable.ReadText(new string[]
			{
				"Thread	Pass	Time",
				"Int32	Int32	DateTime",
			});

			Spludlow.Data.TextTable.Write(filename, table);

			Task[] tasks = new Task[threads];
			for (int index = 0; index < threads; ++index)
			{
				int threadId = index;
				tasks[index] = new Task(() => TestLockedTextTableWorker(filename, iterations, threadId));
			}

			foreach (Task task in tasks)
				task.Start();

			Task.WaitAll(tasks);
		}
		public static void TestLockedTextTableWorker(string filename, int iterations, int threadId)
		{
			Random rand = new Random();

			for (int pass = 0; pass < iterations; ++pass)
			{
				using (LockedTextTable lockedTable = new LockedTextTable(filename, false))
				{
					System.Threading.Thread.Sleep(rand.Next(100));
					lockedTable.Table.Rows.Add(threadId, pass, DateTime.Now);
				}

				System.Threading.Thread.Sleep(rand.Next(500));

				Spludlow.Log.Info("TestLockedTextTable: Thread:" + threadId + ", Pass:" + pass);
			}
		}

	}
}