using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Logging;
using Newtonsoft.Json;
using NucuCar.Core.Utilities;

namespace NucuCar.Telemetry.Publishers
{
    /// <summary>
    /// The TelemetryPublisherDisk is used to publish telemetry data to a file on the disk.
    /// </summary>
    public class Disk : BasePublisher
    {
        private readonly FileStream _fileStream;
        private readonly string _separator;

        /// <summary>
        /// Constructs an instance of <see cref="Disk"/>.
        /// <remarks>
        ///    The connection string must contain the following options:
        ///     Filename (optional) - The path of the filename in which to log telemetry data.
        ///     FileExtension (optional) - The extension of the filename. Default csv
        ///     Separator (optional) - The separator of the messages. Default ,
        ///     BufferSize (optional) - The buffer size for the async writer. Default: 4096
        /// </remarks>
        /// </summary>
        /// <param name="opts"></param>
        public Disk(PublisherOptions opts) : base(opts)
        {
            var connectionStringParams = ConnectionStringParser.Parse(opts.ConnectionString);
            var fileName = connectionStringParams.GetValueOrDefault("FileName", "telemetry");
            var fileExtension = connectionStringParams.GetValueOrDefault("FileExtension", "csv");
            var bufferSize = connectionStringParams.GetValueOrDefault("BufferSize", "4096");
            _separator = connectionStringParams.GetValueOrDefault("Separator", ",");
            
            _fileStream = new FileStream(
                NormalizeFilename(fileName, fileExtension), FileMode.Append, FileAccess.Write, FileShare.Read, 
                // ReSharper disable once AssignNullToNotNullAttribute
                int.Parse(bufferSize), true);
            Logger?.LogDebug("Initialized the TelemetryPublisherDisk!");
        }

        public override async Task PublishAsync(CancellationToken cancellationToken)
        {
            var data = GetTelemetry();
            var messageString = JsonConvert.SerializeObject(data);
            Logger?.LogDebug("Telemetry message: {Message}", messageString);
            var encodedText = Encoding.UTF8.GetBytes($"{messageString}{_separator}");

            try
            {
                await _fileStream.WriteAsync(encodedText, 0,
                    encodedText.Length, cancellationToken);
                await _fileStream.FlushAsync(cancellationToken);
            }
            catch (ObjectDisposedException e)
            {
                Logger.LogCritical("{Message}", e.Message);
            }

        }

        public override void Dispose()
        {
            _fileStream.Close();
        }

        private static string NormalizeFilename(string filename, string extension)
        {
            var date = DateTime.UtcNow;
            return $"{filename}-{date.Year}-{date.Month}-{date.Day}_{date.ToFileTimeUtc()}.{extension}";
        }
    }
}