using System;
using System.Text;

using SabreTools.Library.Data;
using SabreTools.Library.Tools;

#if MONO
using System.IO;
#else
using Alphaleonis.Win32.Filesystem;

using FileStream = System.IO.FileStream;
using StreamWriter = System.IO.StreamWriter;
#endif

namespace SabreTools.Library
{
	/// <summary>
	/// Log either to file or to the console
	/// </summary>
	/// <remarks>
	/// TODO: Allow for "triggerable" logging done on an interval (async)
	/// </remarks>
	public class Logger
	{
		// Private instance variables
		private bool _tofile;
		private bool _warnings;
		private bool _errors;
		private string _filename;
		private LogLevel _filter;
		private DateTime _start;
		private StreamWriter _log;

		// Private required variables
		private string _basepath = Path.Combine(Globals.ExeDir, "logs") + Path.DirectorySeparatorChar;

		/// <summary>
		/// Initialize a console-only logger object
		/// </summary>
		public Logger()
		{
			_tofile = false;
			_warnings = false;
			_errors = false;
			_filename = null;
			_filter = LogLevel.VERBOSE;

			Start();
		}

		/// <summary>
		/// Initialize a Logger object with the given information
		/// </summary>
		/// <param name="tofile">True if file should be written to instead of console</param>
		/// <param name="filename">Filename representing log location</param>
		/// <param name="filter">Highest filtering level to be kept, default VERBOSE</param>
		public Logger(bool tofile, string filename, LogLevel filter = LogLevel.VERBOSE)
		{
			_tofile = tofile;
			_warnings = false;
			_errors = false;
			_filename = Path.GetFileNameWithoutExtension(filename) + " (" + DateTime.Now.ToString("yyyy-MM-dd HH-mm-ss") + ")" + Path.GetExtension(filename);
			_filter = filter;

			if (!Directory.Exists(_basepath))
			{
				Directory.CreateDirectory(_basepath);
			}

			Start();
		}

		/// <summary>
		/// Start logging by opening output file (if necessary)
		/// </summary>
		/// <returns>True if the logging was started correctly, false otherwise</returns>
		public bool Start()
		{
			_start = DateTime.Now;
			if (!_tofile)
			{
				return true;
			}

			try
			{
				FileStream logfile = FileTools.TryCreate(Path.Combine(_basepath, _filename));
				_log = new StreamWriter(logfile, Encoding.UTF8, (int)(4 * Constants.KibiByte), true);
				_log.AutoFlush = true;

				_log.WriteLine("Logging started " + DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"));
				_log.WriteLine(string.Format("Command run: {0}", Globals.CommandLineArgs));
			}
			catch
			{
				return false;
			}

			return true;
		}

		/// <summary>
		/// End logging by closing output file (if necessary)
		/// </summary>
		/// <param name="suppress">True if all ending output is to be suppressed, false otherwise (default)</param>
		/// <returns>True if the logging was ended correctly, false otherwise</returns>
		public bool Close(bool suppress = false)
		{
			if (!suppress)
			{
				if (_warnings)
				{
					Console.WriteLine("There were warnings in the last run! Check the log for more details");
				}
				if (_errors)
				{
					Console.WriteLine("There were errors in the last run! Check the log for more details");
				}

				TimeSpan span = DateTime.Now.Subtract(_start);

				// Special case for multi-day runs
				string total = "";
				if (span >= TimeSpan.FromDays(1))
				{
					total = span.ToString(@"d\:hh\:mm\:ss");
				}
				else
				{
					total = span.ToString(@"hh\:mm\:ss");
				}

				if (!_tofile)
				{
					Console.WriteLine("Total runtime: " + total);
					return true;
				}

				try
				{
					_log.WriteLine("Logging ended " + DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"));
					_log.WriteLine("Total runtime: " + total);
					Console.WriteLine("Total runtime: " + total);
					_log.Close();
				}
				catch
				{
					return false;
				}
			}
			else
			{
				try
				{
					_log.Close();
				}
				catch
				{
					return false;
				}
			}

			return true;
		}

		/// <summary>
		/// Write the given string to the log output
		/// </summary>
		/// <param name="output">String to be written log</param>
		/// <param name="loglevel">Severity of the information being logged</param>
		/// <param name="appendPrefix">True if the level and datetime should be prepended to each statement, false otherwise</param>
		/// <returns>True if the output could be written, false otherwise</returns>
		private bool Log(string output, LogLevel loglevel, bool appendPrefix)
		{
			// If the log level is less than the filter level, we skip it but claim we didn't
			if (loglevel < _filter)
			{
				return true;
			}

			// USER and ERROR writes to console
			if (loglevel == LogLevel.USER || loglevel == LogLevel.ERROR)
			{
				Console.WriteLine((loglevel == LogLevel.ERROR && appendPrefix ? loglevel.ToString() + " " : "") + output);
			}

			// If we're writing to file, use the existing stream
			if (_tofile)
			{
				try
				{
					_log.WriteLine((appendPrefix ? loglevel.ToString() + " - " + DateTime.Now + " - " : "" ) + output);
				}
				catch (Exception ex)
				{
					Console.WriteLine(ex);
					Console.WriteLine("Could not write to log file!");
					return false;
				}
			}

			return true;
		}

		/// <summary>
		/// Write the given exact string to the log output
		/// </summary>
		/// <param name="output">String to be written log</param>
		/// <param name="line">Line number to write out to</param>
		/// <param name="column">Column number to write out to</param>
		/// <returns>True if the output could be written, false otherwise</returns>
		public bool WriteExact(string output, int line, int column)
		{
			// Set the cursor position (if not being redirected)
			if (!Console.IsOutputRedirected)
			{
				Console.CursorTop = line;
				Console.CursorLeft = column;
			}

			// Write out to the console
			Console.Write(output);

			// If we're writing to file, use the existing stream
			if (_tofile)
			{
				try
				{
					_log.Write(DateTime.Now + " - " + output);
				}
				catch
				{
					Console.WriteLine("Could not write to log file!");
					return false;
				}
			}

			return true;
		}

		/// <summary>
		/// Write the given string as a verbose message to the log output
		/// </summary>
		/// <param name="output">String to be written log</param>
		/// <param name="appendPrefix">True if the level and datetime should be prepended to each statement (default), false otherwise</param>
		/// <returns>True if the output could be written, false otherwise</returns>s
		public bool Verbose(string output, bool appendPrefix = true)
		{
			return Log(output, LogLevel.VERBOSE, appendPrefix);
		}

		/// <summary>
		/// Write the given string as a verbose message to the log output
		/// </summary>
		/// <param name="output">String to be written log</param>
		/// <param name="args">Optional arguments for string formatting</param>
		/// <returns>True if the output could be written, false otherwise</returns>s
		public bool Verbose(string output, params object[] args)
		{
			return Log(string.Format(output, args), LogLevel.VERBOSE, true);
		}

		/// <summary>
		/// Write the given string as a user message to the log output
		/// </summary>
		/// <param name="output">String to be written log</param>
		/// <param name="appendPrefix">True if the level and datetime should be prepended to each statement (default), false otherwise</param>
		/// <returns>True if the output could be written, false otherwise</returns>
		public bool User(string output, bool appendPrefix = true)
		{
			return Log(output, LogLevel.USER, appendPrefix);
		}

		/// <summary>
		/// Write the given string as a user message to the log output
		/// </summary>
		/// <param name="output">String to be written log</param>
		/// <param name="args">Optional arguments for string formatting</param>
		/// <returns>True if the output could be written, false otherwise</returns>
		public bool User(string output, params object[] args)
		{
			return Log(string.Format(output, args), LogLevel.USER, true);
		}

		/// <summary>
		/// Write the given string as a warning to the log output
		/// </summary>
		/// <param name="output">String to be written log</param>
		/// <param name="appendPrefix">True if the level and datetime should be prepended to each statement (default), false otherwise</param>
		/// <returns>True if the output could be written, false otherwise</returns>
		public bool Warning(string output, bool appendPrefix = true)
		{
			_warnings = true;
			return Log(output, LogLevel.WARNING, appendPrefix);
		}

		/// <summary>
		/// Write the given string as a warning to the log output
		/// </summary>
		/// <param name="output">String to be written log</param>
		/// <param name="args">Optional arguments for string formatting</param>
		/// <returns>True if the output could be written, false otherwise</returns>
		public bool Warning(string output, params object[] args)
		{
			_warnings = true;
			return Log(string.Format(output, args), LogLevel.WARNING, true);
		}

		/// <summary>
		/// Writes the given string as an error in the log
		/// </summary>
		/// <param name="output">String to be written log</param>
		/// <param name="appendPrefix">True if the level and datetime should be prepended to each statement (default), false otherwise</param>
		/// <returns>True if the output could be written, false otherwise</returns>
		public bool Error(string output, bool appendPrefix = true)
		{
			_errors = true;
			return Log(output, LogLevel.ERROR, appendPrefix);
		}

		/// <summary>
		/// Writes the given string as an error in the log
		/// </summary>
		/// <param name="output">String to be written log</param>
		/// <param name="args">Optional arguments for string formatting</param>
		/// <returns>True if the output could be written, false otherwise</returns>
		public bool Error(string output, params object[] args)
		{
			_errors = true;
			return Log(string.Format(output, args), LogLevel.ERROR, true);
		}

		/// <summary>
		/// Clear lines beneath the given line in the console
		/// </summary>
		/// <param name="line">Line number to clear beneath</param>
		/// <returns>True</returns>
		public bool ClearBeneath(int line)
		{
			if (!Console.IsOutputRedirected)
			{
				for (int i = line; i < Console.WindowHeight; i++)
				{
					// http://stackoverflow.com/questions/8946808/can-console-clear-be-used-to-only-clear-a-line-instead-of-whole-console
					Console.SetCursorPosition(0, Console.CursorTop);
					Console.Write(new string(' ', Console.WindowWidth));
					Console.SetCursorPosition(0, i);
				}
			}
			return true;
		}
	}
}