// Copyright (c) 2017 schick Informatik


using System;
using System.Collections.Generic;
using log4net;
using bsmd.database;
using System.ServiceModel.Activation;
using System.Timers;

namespace bsmd.LockingService
{
    
    [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
    public class LockingService : IService
    {
        private static ILog _log = LogManager.GetLogger(typeof(LockingService));
        private static Dictionary<Guid, LockEntry> lockDict = new Dictionary<Guid, LockEntry>();
        private static Timer staleTimer = new Timer(5000); // alle 5 Sekunden prüfen
        private const int staleTimeoutSeconds = 120; // wenn sie eine Anwendung 2 Minuten nicht meldet, werden die Locks freigegeben

        static LockingService()
        {
            staleTimer.Elapsed += StaleTimer_Elapsed;
        }

        private static void StaleTimer_Elapsed(object sender, ElapsedEventArgs e)
        {
            lock (lockDict)
            {
                List<Guid> deleteList = new List<Guid>();
                foreach (Guid key in lockDict.Keys)
                    if ((DateTime.Now - lockDict[key].lockAquired).TotalSeconds > staleTimeoutSeconds)
                        deleteList.Add(key);
                foreach (Guid key in deleteList)
                {
                    _log.WarnFormat("Stale remove message core id {0}, User {1}", key, lockDict[key].userId);
                    lockDict.Remove(key);
                }
            }
        }

        private ILog log = LogManager.GetLogger(typeof(LockingService));

        #region Implementation IService

        public Guid Lock(Guid messageCoreId, Guid userId)
        {
            Guid result = Guid.Empty;

            lock (lockDict)
            {
                if (!lockDict.ContainsKey(messageCoreId))
                {
                    LockEntry le = new LockEntry();
                    le.lockAquired = DateTime.Now;
                    le.userId = userId;
                    lockDict.Add(messageCoreId, le);                   
                }
                else
                {
                    if (lockDict[messageCoreId].userId == userId)
                    {
                        // this means "refresh"
                        lockDict[messageCoreId].lockAquired = DateTime.Now;                        
                    }
                    else
                    {
                        // lock taken by somebody else..
                        result = lockDict[messageCoreId].userId;
                    }
                }
            }
                        
            return result;
        }

        
        public void Unlock(Guid messageCoreId, Guid userId)
        {            
            lock(lockDict)
            {
                if(lockDict.ContainsKey(messageCoreId))
                {
                    if (lockDict[messageCoreId].userId == userId)
                        lockDict.Remove(messageCoreId);
                }
            }
        }
        
        public void LockRefresh(List<Guid> currentLocks, Guid userId)
        {
            foreach (Guid messageCoreId in currentLocks)
                this.Lock(messageCoreId, userId);
        }

        
        public void Log(string msg, string host, Guid userId)
        {
            log.Info(string.Format("{0} {1}:{2}", host, userId, msg));
        }
                
        public List<CoreLock> GetLocks()
        {
            List<CoreLock> result = new List<CoreLock>();
            lock (lockDict)
            {
                foreach (Guid messageCoreId in lockDict.Keys)
                {
                    CoreLock coreLock = new CoreLock();
                    coreLock.CoreId = messageCoreId;
                    coreLock.UserId = lockDict[messageCoreId].userId;
                    result.Add(coreLock);
                }
            }
            return result;
        }

        #endregion

        #region class LockEntry

        internal class LockEntry
        {
            public DateTime lockAquired = DateTime.Now;
            public Guid userId;
        }

        #endregion

    }
}