Avalonia/PortfolioManager/Cache/SymbolCache.cs

using System;
using System.Collections.Generic;
using System.Threading;
using MarketData;
using MarketData.Utils;
using MarketData.DataAccess;

namespace PortfolioManager.Cache
{
  public class SymbolCache : IDisposable
  {
    private List<String> symbolCache=new List<String>();
    private Object thisLock=new Object();
    private Thread cacheMonitorThread=null;
    private volatile bool threadRun=true;
    private int cacheRefreshAfter=60000;        // Invalidate cache after
    private static SymbolCache symbolCacheInstance=null;

    private SymbolCache()
    {
      cacheMonitorThread=new Thread(new ThreadStart(ThreadProc));
      cacheMonitorThread.Start();
    }
    public static SymbolCache GetInstance()
    {
      lock(typeof(SymbolCache))
      {
        if(null==symbolCacheInstance) symbolCacheInstance=new SymbolCache();
        return symbolCacheInstance;
      }
    }
    public void Clear()
    {
      lock(thisLock)
      {
        symbolCache=new List<string>();
      }
    }
    public void Dispose()
    {
      lock(thisLock)
      {
	    if(null==symbolCacheInstance || false==threadRun)return;
        threadRun=false;
        if(null!=cacheMonitorThread)
        {
          MDTrace.WriteLine(LogLevel.DEBUG,String.Format("[SymbolCache:Dispose]Thread state is {0}.  Joining main thread...",Utility.ThreadStateToString(cacheMonitorThread)));
          cacheMonitorThread.Join(5000);
          cacheMonitorThread=null;
          MDTrace.WriteLine(LogLevel.DEBUG,"[SymbolCache:Dispose] End.");
        }
        symbolCacheInstance=null;
      }
    }

    public List<String> GetSymbols()
    {
      lock(this)
      {
        if(0==symbolCache.Count)symbolCache=PricingDA.GetSymbols();
        return symbolCache;
      }
    }
    private void ThreadProc()
    {
      int quantums=0;
      int quantumInterval=1000;
      while(threadRun)
      {
        Thread.Sleep(quantumInterval);
        quantums+=quantumInterval;
        if(quantums>cacheRefreshAfter)
        {
          quantums=0;
          lock(thisLock)
          {
            symbolCache=PricingDA.GetSymbols();
          }
        }
      }
    }
  }
}