// Copyright Epic Games, Inc. All Rights Reserved.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Runtime.CompilerServices;
using System.Diagnostics;
using UnrealBuildTool;

namespace AutomationTool
{
	public static class LogUtils
	{
		/// <summary>
		/// Stores the log filename.
		/// </summary>
		public static string LogFileName
		{
			get;
			set;
		}

        /// <summary>
		/// Stores the final log filename. The build system uses this to display the network path that the log will be copied to once builds complete.
        /// </summary>
		public static string FinalLogFileName
        {
			get;
			set;
        }

        /// <summary>
        /// Creates the TraceListener used for file logging.
        /// We cannot simply use a TextWriterTraceListener because we need more flexibility when the file cannot be created.
        /// TextWriterTraceListener lazily creates the file, silently failing when it cannot.
        /// </summary>
        /// <returns>The newly created TraceListener, or null if it could not be created.</returns>
        public static TraceListener AddLogFileListener(string LogFolder, string FinalLogFolder)
        {
			int NumAttempts = 0;
			for(;;)
            {
                try
                {
                    // We do not need to set AutoFlush on the StreamWriter because we set Trace.AutoFlush, which calls it for us.
                    // Not only would this be redundant, StreamWriter AutoFlush does not flush the encoder, while a direct call to 
                    // StreamWriter.Flush() will, which is what the Trace system with AutoFlush = true will do.
                    // Internally, FileStream constructor opens the file with good arguments for writing to log files.
					string Name = (NumAttempts == 0) ? "Log.txt" : string.Format("Log_{0}.txt", NumAttempts + 1);
	                string LogFileName = CommandUtils.CombinePaths(LogFolder, Name);

                    TextWriterTraceListener Listener = new TextWriterTraceListener(new StreamWriter(LogFileName), "AutomationFileLogListener");
					Trace.Listeners.Add(Listener);

					LogUtils.LogFileName = LogFileName;
					LogUtils.FinalLogFileName = CommandUtils.CombinePaths(FinalLogFolder, Name);;

					return Listener;
                }
                catch (Exception Ex)
                {
					if(NumAttempts++ >= 10)
                    {
						throw new AutomationException(Ex, "Unable to create log file after {0} attempts.", NumAttempts);
					}
                    }
                }
        }

        /// <summary>
		/// Dumps exception info to log.
		/// @todo: Remove this function as it doesn't do a good job printing the exception information.
		/// </summary>
		/// <param name="Ex">Exception</param>
		public static string FormatException(Exception Ex)
		{
			var Message = String.Format("Exception in {0}: {1}{2}Stacktrace: {3}", Ex.Source, Ex.Message, Environment.NewLine, Ex.StackTrace);
			if (Ex.InnerException != null)
			{
				Message += String.Format("InnerException in {0}: {1}{2}Stacktrace: {3}", Ex.InnerException.Source, Ex.InnerException.Message, Environment.NewLine, Ex.InnerException.StackTrace);
			}
			return Message;
		}

		/// <summary>
		/// Returns a unique logfile name.
		/// </summary>
		/// <param name="Base">Base name for the logfile</param>
		/// <returns>Unique logfile name.</returns>
		public static string GetUniqueLogName(string Base)
		{
			const int MaxAttempts = 1000;

			var Now     = DateTime.Now;
			int Attempt = 0;

			string LogFilename;
			for (;;)
			{
				var NowStr = Now.ToString("yyyy.MM.dd-HH.mm.ss");

				LogFilename = String.Format("{0}-{1}.txt", Base, NowStr);

				if (!File.Exists(LogFilename))
				{
					try
					{
						Directory.CreateDirectory(Path.GetDirectoryName(LogFilename));
						using (FileStream Stream = File.Open(LogFilename, FileMode.CreateNew, FileAccess.Write, FileShare.None))
						{
						}
						break;
					}
					catch (IOException)
					{
					}
				}

				++Attempt;
				if (Attempt == MaxAttempts)
				{
					throw new AutomationException(String.Format("Failed to create logfile {0}.", LogFilename));
				}

				Now = Now.AddSeconds(1);
			}

			return LogFilename;
		}

	}

}