using System;

using System.Collections.Generic;

using System.Text;

using Edu.Psu.Cse.R_Tree_Framework.Framework;

using System.IO;



namespace Edu.Psu.Cse.R_Tree_Framework.CacheManagers

{

    public class LRUCacheManager : CacheManager

    {

        #region Events



        public event CacheEventHandler PageFault;

        public event CacheEventHandler PageWrite;



        #endregion

        #region Instance Variables



        protected Boolean disablePageFault;

        protected Int32 cacheSize, numberOfNodes;

        protected Int64 nextPageAddress, ticks;

        protected String storageFileLocation;

        protected FileStream storageReader;

        protected List<Page> dirtyPages;

        protected Queue<Int64> freePages;

        protected Dictionary<Int64, Page> pageTranslationTable;

        protected SortedList<Int64, Page> leastRecentlyUsed;

        protected SortedDictionary<Address, Int64> addressTranslationTable;



        #endregion

        #region Properties



        protected virtual Int32 CachePercentage

        {

            get { return cacheSize; }

        }

        protected virtual SortedDictionary<Address, Int64> AddressTranslationTable

        {

            get { return addressTranslationTable; }

            set { addressTranslationTable = value; }

        }

        protected virtual Int32 CacheSize

        {

            get

            {

                Int32 pages = cacheSize * NumberOfNodes / 100;

                if (pages > 0)

                    return pages;

                else if (cacheSize > 0)

                    return 1;

                else

                    return 0;

            }

            set { cacheSize = value; }

        }

        protected virtual Int32 NumberOfNodes

        {

            get { return numberOfNodes; }

            set { numberOfNodes = value; }

        }

        protected virtual List<Page> DirtyPages

        {

            get { return dirtyPages; }

            set { dirtyPages = value; }

        }

        protected virtual Boolean DisablePageFault

        {

            get { return disablePageFault; }

            set { disablePageFault = value; }

        }

        protected virtual Queue<Int64> FreePages

        {

            get { return freePages; }

            set { freePages = value; }

        }

        protected virtual SortedList<Int64, Page> LeastRecentlyUsed

        {

            get { return leastRecentlyUsed; }

            set { leastRecentlyUsed = value; }

        }

        protected virtual Int64 NextPageAddress

        {

            get

            {

                Int64 address = nextPageAddress;

                nextPageAddress += Constants.PAGE_SIZE;

                return address;

            }

            set { nextPageAddress = value; }

        }

        protected virtual Dictionary<Int64, Page> PageTranslationTable

        {

            get { return pageTranslationTable; }

            set { pageTranslationTable = value; }

        }

        protected virtual String StorageFileLocation

        {

            get { return storageFileLocation; }

            set { storageFileLocation = value; }

        }

        protected virtual FileStream StorageReader

        {

            get { return storageReader; }

            set { storageReader = value; }

        }

        protected virtual Int64 Ticks

        {

            get { return ticks; }

            set { ticks = value; }

        }



        #endregion

        #region Constructors



        public LRUCacheManager(String storageFileLocation, Int32 numberOfPagesToCache)

        {

            StorageFileLocation = storageFileLocation;

            StorageReader = new FileStream(

                StorageFileLocation,

                FileMode.Create,

                FileAccess.ReadWrite,

                FileShare.None,

                8,

                FileOptions.WriteThrough | FileOptions.RandomAccess);

            CacheSize = numberOfPagesToCache;

            NumberOfNodes = 0;

            AddressTranslationTable = new SortedDictionary<Address, Int64>();

            PageTranslationTable = new Dictionary<Int64, Page>();

            LeastRecentlyUsed = new SortedList<Int64, Page>();

            DirtyPages = new List<Page>();

            FreePages = new Queue<Int64>();

            Ticks = 0;

        }

        public LRUCacheManager(String savedLocation, String memoryRunLocation)

        {

            StreamReader reader = new StreamReader(savedLocation);

            StorageFileLocation = reader.ReadLine();

            File.Copy(StorageFileLocation, memoryRunLocation, true);

            StorageFileLocation = memoryRunLocation;

            NextPageAddress = Int64.Parse(reader.ReadLine());

            CacheSize = Int32.Parse(reader.ReadLine());

            NumberOfNodes = Int32.Parse(reader.ReadLine());

            StorageReader = new FileStream(

                memoryRunLocation,

                FileMode.OpenOrCreate,

                FileAccess.ReadWrite,

                FileShare.None,

                8,

                FileOptions.WriteThrough | FileOptions.RandomAccess);

            AddressTranslationTable = new SortedDictionary<Address, Int64>();

            PageTranslationTable = new Dictionary<Int64, Page>();

            LeastRecentlyUsed = new SortedList<Int64, Page>();

            DirtyPages = new List<Page>();

            FreePages = new Queue<Int64>();

            Ticks = 0;

            if (!reader.ReadLine().Equals("AddressTranslationTable"))

                throw new Exception();

            String buffer;

            while (!(buffer = reader.ReadLine()).Equals("FreePages"))

                AddressTranslationTable.Add(

                    new Address(buffer),

                    Int64.Parse(reader.ReadLine()));

            while (!reader.EndOfStream)

                FreePages.Enqueue(Int64.Parse(reader.ReadLine()));

            reader.Close();

        }



        #endregion

        #region Public Methods



        public virtual void DeletePageData(PageData data)

        {

            if (!(data is Record))

                NumberOfNodes--;

            Int64 address = AddressTranslationTable[data.Address];

            AddressTranslationTable.Remove(data.Address);

            if (PageTranslationTable.ContainsKey(address))

            {

                Page page = PageTranslationTable[address];

                PageTranslationTable.Remove(address);

                LeastRecentlyUsed.RemoveAt(LeastRecentlyUsed.IndexOfValue(page));

                while (DirtyPages.Contains(page))

                    DirtyPages.Remove(page);

            }

            FreePages.Enqueue(address);

        }

        public virtual void Dispose()

        {

            StorageReader.Close();

            File.Delete(StorageFileLocation);

        }

        public virtual void FlushCache()

        {

            while (PageTranslationTable.Count > 0)

                EvictPage();

        }

        public virtual Node LookupNode(Address address)

        {

            return LookupPageData(address) as Node;

        }

        public virtual Record LookupRecord(Address address)

        {

            DisablePageFault = true;

            Record record = LookupPageData(address) as Record;

            DisablePageFault = false;

            return record;

        }

        public virtual Sector LookupSector(Address address)

        {

            return LookupPageData(address) as Sector;

        }

        public virtual void SaveCache(String cacheSaveLocation, String memorySaveLocation)

        {

            FlushCache();

            Int64 position = StorageReader.Position;

            StorageReader.Close();

            File.Copy(StorageFileLocation, memorySaveLocation, true);

            StorageReader = new FileStream(

                StorageFileLocation,

                FileMode.Open,

                FileAccess.ReadWrite,

                FileShare.None,

                8,

                FileOptions.WriteThrough | FileOptions.RandomAccess);

            StorageReader.Seek(position, SeekOrigin.Begin);

            StreamWriter writer = new StreamWriter(cacheSaveLocation);

            writer.WriteLine(memorySaveLocation);

            writer.WriteLine(NextPageAddress);

            writer.WriteLine(CachePercentage);

            writer.WriteLine(NumberOfNodes);

            writer.WriteLine("AddressTranslationTable");

            foreach (KeyValuePair<Address, Int64> entry in AddressTranslationTable)

            {

                writer.WriteLine(entry.Key);

                writer.WriteLine(entry.Value);

            }

            writer.WriteLine("FreePages");

            foreach (Int64 page in FreePages)

                writer.WriteLine(page);

            writer.Close();

        }

        public virtual void WritePageData(PageData data)

        {

            Page page;

            if (!AddressTranslationTable.ContainsKey(data.Address))

            {

                page = AllocateNewPage(data.Address);

                if (!(data is Record))

                    NumberOfNodes++;

            }

            else

            {

                Int64 address = AddressTranslationTable[data.Address];

                if (PageTranslationTable.ContainsKey(address))

                    page = PageTranslationTable[address];

                else

                {

                    page = LoadPageFromMemory(address);

                    PageTranslationTable.Add(page.Address, page);

                }

            }

            page.Data = data.GeneratePageData();

            DirtyPages.Add(page);

            if (LeastRecentlyUsed.ContainsValue(page))

                LeastRecentlyUsed.RemoveAt(LeastRecentlyUsed.IndexOfValue(page));

            LeastRecentlyUsed.Add(Ticks++, page);

            CacheOverflowCheck();

        }



        #endregion

        #region Protected Methods



        protected virtual Page AllocateNewPage(Address address)

        {

            Int64 pageAddress;

            if (FreePages.Count > 0)

                pageAddress = FreePages.Dequeue();

            else

                pageAddress = NextPageAddress;

            AddressTranslationTable.Add(address, pageAddress);

            Page newPage = new Page(Address.NewAddress(), pageAddress, new Byte[Constants.PAGE_SIZE]);

            PageTranslationTable.Add(pageAddress, newPage);

            return newPage;

        }

        protected virtual void CacheOverflowCheck()

        {

            while (PageTranslationTable.Count > CacheSize)

                EvictPage();

        }

        protected virtual void EvictPage()

        {

            Page page = leastRecentlyUsed[leastRecentlyUsed.Keys[0]];

            if (DirtyPages.Contains(page))

                WritePageToMemory(page);

            LeastRecentlyUsed.RemoveAt(0);

            while (DirtyPages.Contains(page))

                DirtyPages.Remove(page);

            PageTranslationTable.Remove(page.Address);

        }

        protected virtual Page LoadPageFromMemory(Int64 offset)

        {

            Byte[] data = new Byte[Constants.PAGE_SIZE];

            StorageReader.Seek(offset - offset % Constants.PAGE_SIZE, SeekOrigin.Begin);

            StorageReader.Read(data, 0, Constants.PAGE_SIZE);

            Page page = new Page(Address.NewAddress(), offset, data);

            if (PageFault != null && !DisablePageFault)

                PageFault(this, new LRUCacheEventArgs(page));

            return page;

        }

        protected virtual Page LookupPage(Address address)

        {

            Page page;

            Int64 offset = AddressTranslationTable[address];

            if (PageTranslationTable.ContainsKey(offset))

            {

                page = PageTranslationTable[offset];

                LeastRecentlyUsed.RemoveAt(LeastRecentlyUsed.IndexOfValue(page));

            }

            else

            {

                page = LoadPageFromMemory(offset);

                PageTranslationTable.Add(page.Address, page);

            }

            LeastRecentlyUsed.Add(Ticks++, page);

            return page;

        }

        protected virtual PageData LookupPageData(Address address)

        {

            PageData data;

            Page page = LookupPage(address);

            Byte type = page.Data[0], childType = page.Data[1];

            if (type == (Byte)PageDataType.Node || type == (Byte)PageDataType.Leaf)

                if (childType == (Byte)NodeChildType.Leaf)

                    data = new Node(address, typeof(Leaf), page.Data);

                else if (childType == (Byte)NodeChildType.Node)

                    data = new Node(address, typeof(Node), page.Data);

                else if (childType == (Byte)NodeChildType.Record)

                    data = new Leaf(address, page.Data);

                else

                    throw new Exception("Not a node");

            else if (type == (Byte)PageDataType.Record)

                data = new Record(address, page.Data);

            else if (type == (Byte)PageDataType.IndexUnitSector)

                data = new Sector(address, page.Data);

            else

                throw new Exception("Not valid Page Data");

            CacheOverflowCheck();

            return data;

        }

        protected virtual void WritePageToMemory(Page page)

        {

            StorageReader.Seek(page.Address, SeekOrigin.Begin);

            StorageReader.Write(page.Data, 0, Constants.PAGE_SIZE);

            if (PageWrite != null)

                PageWrite(this, new LRUCacheEventArgs(page));

        }



        #endregion



    }

}