using System;
using System.Collections.Generic;
using System.Linq;

namespace TINK.Model.Logging
{
	public class LoggingDirectoryManager : ILoggingDirectoryManager
	{
		/// <summary> Name of logging subdirectory.</summary>
		private const string LOGDIRECTORYTITLE = "Log";

		/// <summary> Prevents an invalid instance to be created. </summary>
		private LoggingDirectoryManager() { }

		public LoggingDirectoryManager(
			Func<string, IList<string>> fileListProvider,
			Func<string, bool> directoryExistsChecker,
			Action<string> directoryCreator,
			Action<string> fileEraser,
			string logFilePath,
			char directorySeparatorChar,
			int p_iRetainedFilesCountLimit)
		{
			m_oFileListProvider = fileListProvider ?? throw new ArgumentException($"Can not instantiate {nameof(LoggingDirectoryManager)}- object. File list provider delegate can not be null.");

			if (directoryExistsChecker == null)
			{
				throw new ArgumentException($"Can not instantiate {nameof(LoggingDirectoryManager)}- object. Directory existence checker delegate can not be null.");
			}

			if (directoryCreator == null)
			{
				throw new ArgumentException($"Can not instantiate {nameof(LoggingDirectoryManager)}- object. Directory creator delegate can not be null.");
			}

			m_oFileEraser = fileEraser ?? throw new ArgumentException($"Can not instantiate {nameof(LoggingDirectoryManager)}- object. File eraser delegate can not be null.");

			if (string.IsNullOrEmpty(logFilePath))
			{
				throw new ArgumentException($"Can not instantiate {nameof(LoggingDirectoryManager)}- object. Log file path can not be null or empty.");
			}

			if (string.IsNullOrEmpty(directorySeparatorChar.ToString()))
			{
				throw new ArgumentException($"Can not instantiate {nameof(LoggingDirectoryManager)}- object. Directory separator character can not be null or empty.");
			}

			if (p_iRetainedFilesCountLimit < 1)
			{
				throw new ArgumentException($"Can not instantiate {nameof(LoggingDirectoryManager)}- object. Count of retained log files is {p_iRetainedFilesCountLimit} but must be equal or larger one.");
			}

			DirectorySeparatorChar = directorySeparatorChar.ToString();

			LogFilePath = $"{logFilePath}{DirectorySeparatorChar}{LOGDIRECTORYTITLE}";


			m_iRetainedFilesCountLimit = p_iRetainedFilesCountLimit;

			if (string.IsNullOrEmpty(LogFileTitle))
			{
				LogFileTitle = $"{DateTime.Now:yyyy_MM_dd_HH_mm_ss}.jsnl";
			}

			// Create directory if direcotry does not exist.
			if (directoryExistsChecker(LogFilePath) == false)
			{
				try
				{
					directoryCreator(LogFilePath);
				}
				catch (Exception l_oException)
				{

					throw new FileOperationException($"Logging directory {LogFilePath} could not be created successfully.", l_oException);
				}
			}
		}

		/// <summary> Deletes files which are out of retainment scope. </summary>
		public void DeleteObsoleteLogs()
		{
			var l_oExceptions = new List<Exception>();
			var l_oSortedFileArray = m_oFileListProvider(LogFilePath).OrderByDescending(x => x).ToArray();

			for (int l_iIndex = l_oSortedFileArray.Length - 1;
				l_iIndex >= m_iRetainedFilesCountLimit - 1; /* files remaining count must be  m_iRetainedFilesCountLimit - 1 because new log file will be added afterwards */
				l_iIndex--)
			{
				try
				{
					m_oFileEraser(l_oSortedFileArray[l_iIndex]);
				}
				catch (Exception l_oExpetion)
				{
					// Getting list of log files found.
					l_oExceptions.Add(l_oExpetion);
				}
			}

			if (l_oExceptions.Count <= 0)
			{
				return;
			}

			throw new AggregateException("Deleting obsolete log files failed.", l_oExceptions.ToArray());
		}

		/// <summary> Gets all log files in logging directory. </summary>
		/// <param name="p_oLogger"></param>
		/// <returns>List of log files.</returns>
		public IList<string> GetLogFiles()
		{
			try
			{
				return m_oFileListProvider(LogFilePath).OrderBy(x => x).ToList();
			}
			catch (Exception l_oExpetion)
			{
				// Getting list of log files found.
				throw new FileOperationException("Getting list of log files failed.", l_oExpetion);
			}
		}

		/// <summary>Holds delegate to provide file names.</summary>
		private readonly Func<string, IList<string>> m_oFileListProvider;

		/// <summary>Holds delegate to delete files.</summary>
		private readonly Action<string> m_oFileEraser;

		/// <summary>Holds delegate to provide file names.</summary>
		private int m_iRetainedFilesCountLimit;

		/// <summary> Holds the log file name. </summary>
		private string LogFileTitle { get; }

		/// <summary> Holds the log file name. </summary>
		public string LogFilePath { get; }

		/// <summary> Holds the directory separator character. </summary>
		private string DirectorySeparatorChar { get; }

		/// <summary> Holds the log file name. </summary>
		public string LogFileName { get { return $"{LogFilePath}{DirectorySeparatorChar}{LogFileTitle}"; } }
	}
}