lux/Lux.Data/Services/ImageCacheService.cs

using Microsoft.Extensions.Configuration;
using Newtonsoft.Json;
using NLog;
using StackExchange.Redis;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Lux.Data.Services
{
    public class ImageCacheService : BaseServ
    {
        #region Public Constructors

        public ImageCacheService(IConfiguration configuration) : base(configuration)
        {
            Log.Info("ImageCache Service Started");
        }

        #endregion Public Constructors

        #region Public Properties

        /// <summary>
        /// Message Dispatcher: oggetto comunicazione pub/sub via REDIS channels corrente
        /// </summary>
        public ISubscriber messageDisp
        {
            get
            {
                ISubscriber answ;
                // se già valorizzato uso oggetto private...
                if (_currSub != null)
                {
                    answ = _currSub;
                }
                else
                {
                    // init DB (sullo 0)
                    answ = redisConn.GetSubscriber();
                    _currSub = answ;
                    Log.Info($"Apertura di un Redis Message Subscriber");
                }
                // restituisco oggetto DB
                return answ;
            }
        }

        #endregion Public Properties

        #region Public Methods

        /// <summary>
        /// Recupera img redis SVG x id porta richiesta
        /// </summary>
        /// <param name="imgId"></param>
        public string LoadSvg(string imgId)
        {
            string rawVal = "";
            // recupero img da cache
            string currKey = $"{redisBaseKey}:{imgId.Replace("/", ":")}";
            rawVal = redisDb.StringGet(currKey);
            return rawVal;
        }

        /// <summary>
        /// Salva e invia su channel img redis SVG per il doc richiesto
        /// </summary>
        /// <param name="imgId"></param>
        /// <param name="notifyChannel"></param>
        /// <param name="svgContent"></param>
        public void SaveSvg(string imgId, string svgContent)
        {
            string notifyChannel = $"svg-gen:{imgId}";
            // invio notifica nuova imgsvg sul canale
            SendMessage(notifyChannel, svgContent);
            // salvo img in cache
            string currKey = $"{redisBaseKey}:{imgId.Replace("/", ":")}";
            redisDb.StringSet(currKey, svgContent);
        }

        #endregion Public Methods

        #region Private Fields

        private static Logger Log = LogManager.GetCurrentClassLogger();

        private string redisBaseKey = "Lux:Images";

        #endregion Private Fields

        #region Private Properties

        /// <summary>
        /// Oggetto subscriber x pubblicazione/sottoscrizione canali REDIS
        /// </summary>
        private ISubscriber _currSub { get; set; }

        #endregion Private Properties

        #region Private Methods

        /// <summary>
        /// invio su channel REDIS
        /// </summary>
        /// <param name="notifyChannel"></param>
        /// <param name="message"></param>
        private void SendMessage(string notifyChannel, string message)
        {
            // invio notifica tramite il canale richiesto
            RedisChannel pubNotifyChannel = new RedisChannel(notifyChannel, RedisChannel.PatternMode.Literal);
            messageDisp.Publish(pubNotifyChannel, message);
        }

        #endregion Private Methods
    }
}