// ==========================================================================
//  Squidex Headless CMS
// ==========================================================================
//  Copyright (c) Squidex UG (haftungsbeschränkt)
//  All rights reserved. Licensed under the MIT license.
// ==========================================================================

using System;
using System.Collections.Concurrent;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.IO;
using System.Text;
using System.Threading;
using NodaTime;

namespace Squidex.Infrastructure.Log.Internal
{
    [ExcludeFromCodeCoverage]
    public sealed class FileLogProcessor : DisposableObjectBase
    {
        private const int MaxQueuedMessages = 1024;
        private const int Retries = 10;
        private readonly BlockingCollection<LogMessageEntry> messageQueue = new BlockingCollection<LogMessageEntry>(MaxQueuedMessages);
        private readonly Thread outputThread;
        private readonly string path;
        private StreamWriter writer;

        public FileLogProcessor(string path)
        {
            this.path = path;

            outputThread = new Thread(ProcessLogQueue)
            {
                IsBackground = true,
                Name = "Logging"
            };
        }

        public void Initialize()
        {
            var fileInfo = new FileInfo(path);
            try
            {
                if (!fileInfo.Directory.Exists)
                {
                    fileInfo.Directory.Create();
                }

                var fs = new FileStream(fileInfo.FullName, FileMode.Append, FileAccess.Write, FileShare.ReadWrite);

                writer = new StreamWriter(fs, Encoding.UTF8)
                {
                    AutoFlush = true
                };

                writer.WriteLine($"--- Started Logging {SystemClock.Instance.GetCurrentInstant()} ---", 1);

                outputThread.Start();
            }
            catch (Exception ex)
            {
                throw new ConfigurationException($"Log directory '{fileInfo.Directory.FullName}' does not exist or cannot be created.", ex);
            }
        }

        public void EnqueueMessage(LogMessageEntry message)
        {
            messageQueue.Add(message);
        }

        private void ProcessLogQueue()
        {
            try
            {
                foreach (var entry in messageQueue.GetConsumingEnumerable())
                {
                    for (var i = 1; i <= Retries; i++)
                    {
                        try
                        {
                            writer.WriteLine(entry.Message);
                            break;
                        }
                        catch (Exception ex)
                        {
                            Thread.Sleep(i * 10);

                            if (i == Retries)
                            {
                                Console.WriteLine($"Failed to write to log file '{path}': {ex}");
                            }
                        }
                    }
                }
            }
            catch
            {
                try
                {
                    messageQueue.CompleteAdding();
                }
                catch
                {
                    return;
                }
            }
        }

        protected override void DisposeObject(bool disposing)
        {
            if (disposing)
            {
                messageQueue.CompleteAdding();

                try
                {
                    outputThread.Join(1500);
                }
                catch (Exception ex)
                {
                    Debug.WriteLine($"Failed to shutdown log queue grateful: {ex}.");
                }
                finally
                {
                    writer.Dispose();
                }
            }
        }
    }
}