///////////////////////////////////////////////////////////////////////////////
//
//  Microsoft Research Singularity
//
//  Copyright (c) Microsoft Corporation.  All rights reserved.
//
//  Note: WebFileCache holds copies of files served from disk
//        This is used for asymmetric computing environments where
//        going to the disk service might be expensive.
//

using System;
using System.Collections;
using System.Diagnostics;
using Microsoft.SingSharp;
using Microsoft.SingSharp.Runtime;
using Microsoft.Singularity.Channels;
using Microsoft.Singularity.WebApps;
using Microsoft.Singularity.WebApps.Contracts;
using Microsoft.Singularity;
using System.Io;
using System.Text;
using System.Threading;
using System.Web;
using Microsoft.Singularity.V1.Services;

namespace Microsoft.Singularity.WebApps
{
    public class CachedWebFile
    {
        public VContainer<byte> fileBytes;

        public CachedWebFile([Claims] byte[]! in ExHeap bytes)
        {
            this.fileBytes = new VContainer<byte> (bytes);
        }
    }

    public class WebFileCache
    {
        private Hashtable fileCacheHashTable;
        public static int CachedFileMaxSize = 1024 * 1024; //1 MB


        public WebFileCache ()
        {
            Hashtable fileCacheHashTableTemp = new Hashtable();
            fileCacheHashTable = Hashtable.Synchronized(fileCacheHashTableTemp);
        }

        public bool AddFileToWebCache(string! filename, [Claims] byte[]! in ExHeap fileBytes)
        {

            if (fileCacheHashTable.ContainsKey(filename) == true) {
                DebugStub.WriteLine("Got filename {0} we're aleady tracking.  ignoring\n",
                                    __arglist(filename));
            }

            DebugStub.Print("Adding file {0} to web cache\n", __arglist(filename));
            CachedWebFile cachedFile = new CachedWebFile(fileBytes);
            fileCacheHashTable.Add(filename, cachedFile);

            return true;
        }

        public bool GetFromFileCache(string! filename, out byte[] in ExHeap fileBytes)
        {
            CachedWebFile cachedFile = (CachedWebFile) fileCacheHashTable[filename];
            if(cachedFile == null) {
                fileBytes = null;
                DebugStub.Print("Failed to find file {0} in web cache\n", __arglist(filename));
                return false;
            }

            byte [] in ExHeap! cachedFileBytes = cachedFile.fileBytes.Acquire();
            fileBytes = new[ExHeap]  byte[cachedFileBytes.Length];
            Bitter.Copy(fileBytes, 0, cachedFileBytes.Length, cachedFileBytes, 0);
            cachedFile.fileBytes.Release(cachedFileBytes);
            DebugStub.Print("Returning file {0} from web cache\n", __arglist(filename));
            return true;
        }

        //XXX memory leak?
        public bool RemoveFileFromWebCache(string! filename)
        {
            DebugStub.Print("Removing file {0} from web cache\n", __arglist(filename));
            fileCacheHashTable.Remove(filename);

            return true;
        }

    }
}