using System;
using System.IO;
using System.Text;
using DCIT.Core.Models;

namespace DCIT.Core.Services
{
    public class LogService
    {
        private readonly object _syncRoot = new object();
        private readonly string _logFilePath;
        private bool _runtimeFailureActive;

        public LogService(string startupDirectory)
        {
            _logFilePath = Path.Combine(startupDirectory, string.Format("session-{0:yyyyMMdd}.log", DateTime.Today));
            EnsureWritable();
        }

        public event EventHandler<LogEntry> EntryWritten;

        public event EventHandler<LogWriteFailureEventArgs> WriteFailed;

        public string LogFilePath
        {
            get { return _logFilePath; }
        }

        public bool HasRuntimeFailure { get; private set; }

        public Exception LastRuntimeFailure { get; private set; }

        public void Info(string eventCode, string message, string detail = null)
        {
            Write(LogLevel.Info, eventCode, message, detail);
        }

        public void Warning(string eventCode, string message, string detail = null)
        {
            Write(LogLevel.Warning, eventCode, message, detail);
        }

        public void Error(string eventCode, string message, string detail = null)
        {
            Write(LogLevel.Error, eventCode, message, detail);
        }

        public void Write(LogLevel level, string eventCode, string message, string detail = null)
        {
            var entry = new LogEntry
            {
                Level = level,
                EventCode = eventCode,
                Message = message,
                Detail = detail,
            };

            var line = string.Format(
                "{0:yyyy-MM-dd HH:mm:ss.fff}\t{1}\t{2}\t{3}",
                entry.Timestamp,
                level.ToString().ToUpperInvariant(),
                entry.EventCode ?? string.Empty,
                entry.Message ?? string.Empty);

            if (!string.IsNullOrWhiteSpace(entry.Detail))
            {
                line += "\t" + entry.Detail.Replace("\r", " ").Replace("\n", " ");
            }

            try
            {
                lock (_syncRoot)
                {
                    File.AppendAllText(_logFilePath, line + Environment.NewLine, new UTF8Encoding(false));
                    _runtimeFailureActive = false;
                    HasRuntimeFailure = false;
                    LastRuntimeFailure = null;
                }

                EntryWritten?.Invoke(this, entry);
            }
            catch (Exception ex)
            {
                var shouldRaiseEvent = false;
                lock (_syncRoot)
                {
                    HasRuntimeFailure = true;
                    LastRuntimeFailure = ex;
                    if (!_runtimeFailureActive)
                    {
                        _runtimeFailureActive = true;
                        shouldRaiseEvent = true;
                    }
                }

                if (shouldRaiseEvent)
                {
                    WriteFailed?.Invoke(this, new LogWriteFailureEventArgs(entry, _logFilePath, ex));
                }
            }
        }

        private void EnsureWritable()
        {
            var directory = Path.GetDirectoryName(_logFilePath);
            Directory.CreateDirectory(directory);
            File.AppendAllText(_logFilePath, string.Empty, new UTF8Encoding(false));
        }
    }
}