using System;
using Cosmos.Hardware.Storage;
using System.Collections.Generic;
using System.IO;

namespace Cosmos.Kernel.FileSystem {
	public unsafe partial class Ext2 {
		private class FileStream: Stream {
			private uint mINodeNumber;
			private Ext2 mFilesystem;
			private uint mPosition = 0;
			public FileStream(uint aINodeNumber, Ext2 aFilesystem) {
				mINodeNumber = aINodeNumber;
				mFilesystem = aFilesystem;
			}

			public override bool CanRead {
				get {
					return true;
				}
			}

			public override bool CanSeek {
				get {
					return true;
				}
			}

			public override bool CanWrite {
				get {
					return false;
				}
			}

			public override void Flush() {
			}

			public override long Length {
				get {
					INode xINode;
					mFilesystem.ReadINode(mINodeNumber, out xINode);
					long xSize = xINode.Size;
					return xSize;
				}
			}

			public override long Position {
				get {
					return mPosition;
				}
				set {
					mPosition = (uint)value;
				}
			}

			// todo: add support for reading one chunk of data which spans multiple logical blocks
			public override int Read(byte[] buffer, int offset, int count) {
				uint xBlock = (mPosition / mFilesystem.mBlockSize);
				if (xBlock != 0) {
					return 0;
				}
				INode xINode;
				if (!mFilesystem.ReadINode(mINodeNumber, out xINode)) {
					return -1;
				}
				int xBytesToRead = count;
                //byte* xBuffer = (byte*)Heap.MemAlloc(mFilesystem.mBlockSize);
                byte* xBuffer = null;
                while (xBytesToRead > 0) {
					if (!mFilesystem.ReadINodeContents(&xINode, xBlock, xBuffer)) {
						return -2;
					}
					uint xBufferOffset = mPosition % mFilesystem.mBlockSize;
					for (int i = 0; i < count; i++) {
						buffer[offset + i] = xBuffer[xBufferOffset + i];
					}
					xBytesToRead -= (int)(mFilesystem.mBlockSize - (mPosition % mFilesystem.mBlockSize));
					xBlock++;
				}
				return count;
			}

			public override long Seek(long offset, SeekOrigin origin) {
				throw new NotImplementedException();
			}

			public override void SetLength(long value) {
				throw new NotImplementedException();
			}

			public override void Write(byte[] buffer, int offset, int count) {
				throw new NotImplementedException();
			}
		}
		private Hardware.BlockDevice mBackend;
		private SuperBlock mSuperBlock;
		private uint mBlockSize;
		private uint mGroupsCount;
		private uint mGroupDescriptorsPerBlock;
		private GroupDescriptor[] mGroupDescriptors;
		public const uint EXT2_ROOT_INO = 0x02;

		public Ext2(Hardware.BlockDevice aBackend) {
			if (aBackend == null) {
				throw new ArgumentNullException("aBackend");
			}
			mBackend = aBackend;
		}

		private bool ReadSuperBlock() {
			
			var xBytes = mBackend.ReadBlock(2);
			fixed (byte* xByteBuff = &xBytes[0]) {
				var xByteBuffAsSuperBlock = (SuperBlock*)xByteBuff;
				mSuperBlock = xByteBuffAsSuperBlock[0];
//				DebugUtil.SendExt2_SuperBlock("", mSuperBlock);
				mBlockSize = (uint)(1024 << (byte)(mSuperBlock.LogBlockSize));
//				DebugUtil.SendDoubleNumber("Numbers", "", mSuperBlock.INodesCount, 32, mSuperBlock.INodesPerGroup, 32);
				mGroupsCount = mSuperBlock.INodesCount / mSuperBlock.INodesPerGroup;
				mGroupDescriptorsPerBlock = (uint)(mBlockSize / sizeof(GroupDescriptor));
				if (!ReadGroupDescriptorsOfBlock()) {
					return false;
				}
			}
			return true;
		}

		private unsafe bool ReadGroupDescriptorsOfBlock() {
			byte[] xBytes;
			mGroupDescriptors = new GroupDescriptor[mGroupsCount];
			GroupDescriptor* xDescriptorPtr=(GroupDescriptor*)0;
			for (int i = 0; i < mGroupsCount; i++) {
//				DebugUtil.SendNumber("Ext2", "ReadGroupDescriptorsOfBlock, I", (uint)i, 16);
				uint xATABlock = (uint)(mBlockSize / mBackend.BlockSize);
				xATABlock += (uint)(i / mGroupDescriptorsPerBlock);
				if ((i % 16) == 0) {
					xBytes= mBackend.ReadBlock(xATABlock);
					fixed (byte* xDescriptorPtr2 = &xBytes[0]) {
						xDescriptorPtr = (GroupDescriptor*)xDescriptorPtr2;
					}
				}
				//GroupDescriptor* xItem = (GroupDescriptor*)Heap.MemAlloc((uint)sizeof(GroupDescriptor));
				//CopyPointers((byte*)&xDescriptorPtr[i % mGroupDescriptorsPerBlock], (byte*)xItem, (uint)sizeof(GroupDescriptor));
				//mGroupDescriptors[i] = *xItem;
//				DebugUtil.SendExt2_GroupDescriptor("ReadGroupDescriptorsOfBlock", xATABlock, i, 0, xDescriptorPtr[i % mGroupDescriptorsPerBlock]);
			}
			return true;
		}

		public bool Initialize() {
			return ReadSuperBlock();
		}

		private static unsafe bool ConvertBitmapToBoolArray(uint* aBitmap, bool[] aArray) {
			if (aArray == null || aArray.Length != 32) {
				Console.WriteLine("[ConvertBitmapToBoolArray] Incorrect Array");
				return false;
			}
			uint xValue = *aBitmap;
			for (byte b = 0; b < 32; b++) {
				uint xCheckBit = (uint)(1 << b);
				aArray[b] = (xValue & xCheckBit) != 0;
			}
			return true;
		}

		private static void CopyPointers(byte* aSource, byte* aDest, uint aLength) {
			for (int i = 0; i < aLength; i++) {
				aDest[i] = aSource[i];
			}
		}

		public Stream OpenFile(string[] xPath) {
			//ushort* xBuffer = (ushort*)Heap.MemAlloc(mBackend.BlockSize);
			//byte* xExt2BlockBuffer = (byte*)Heap.MemAlloc(mBlockSize);
			//INode xCurrentINode;
			//if (!ReadINode(EXT2_ROOT_INO, out xCurrentINode)) {
			//    Heap.MemFree((uint)xBuffer);
			//    Heap.MemFree((uint)xExt2BlockBuffer);
			//    return null;
			//}
			//bool xCurrentINodeChanged = true;
			//uint xInspectedINodeCount = 0;
			//uint xINodeNumber = EXT2_ROOT_INO;
			//for (int i = 0; i < xPath.Length; i++) {
			//    Console.Write("ReadFile, Iteration ");
			//    ATAOld.WriteNumber((uint)i, 8);
			//    Console.WriteLine("");
			//    if (!xCurrentINodeChanged) {
			//        Console.WriteLine("Terminating for loop, CurrentINode didn't change");
			//        Heap.MemFree((uint)xBuffer);
			//        Heap.MemFree((uint)xExt2BlockBuffer);
			//        return null;
			//    }
			//    xCurrentINodeChanged = false;
			//    if (!ReadINodeContents(&xCurrentINode, 0, xExt2BlockBuffer)) {
			//        Heap.MemFree((uint)xBuffer);
			//        Heap.MemFree((uint)xExt2BlockBuffer);
			//        return null;
			//    }
			//    DirectoryEntry* xEntryPtr = (DirectoryEntry*)xExt2BlockBuffer;
			//    uint xTotalSize = mBlockSize;
			//    while (xTotalSize != 0) {
			//        DebugUtil.SendExt2_DirectoryEntry(xEntryPtr);
			//        uint xPtrAddress = (uint)xEntryPtr;
			//        char[] xName = new char[xEntryPtr->NameLength];
			//        byte* xNamePtr = &xEntryPtr->FirstNameChar;
			//        for (int c = 0; c < xName.Length; c++) {
			//            xName[c] = (char)xNamePtr[c];
			//        }
			//        xInspectedINodeCount++;
			//        if (EqualsName(xPath[i], xName)) {
			//            if (!ReadINode(xEntryPtr->INodeNumber, out xCurrentINode)) {
			//                Heap.MemFree((uint)xBuffer);
			//                Heap.MemFree((uint)xExt2BlockBuffer);
			//                return null;
			//            }
			//            xCurrentINodeChanged = true;
			//            xINodeNumber = xEntryPtr->INodeNumber;
			//            xTotalSize = 0;
			//            continue;
			//        }
			//        xPtrAddress += xEntryPtr->RecordLength;
			//        xTotalSize -= xEntryPtr->RecordLength;
			//        xEntryPtr = (DirectoryEntry*)xPtrAddress;
			//    }
			//}
			//if (xCurrentINodeChanged) {
			//    DebugUtil.SendMessage("Ext2", "ReadFile, for loop exited with an inode change");
			//} else {
			//    DebugUtil.SendMessage("Ext2", "ReadFile, for loop exited without an inode change");
			//}
			//if ((xCurrentINode.Mode & INodeModeEnum.RegularFile) == 0) {
			//    Console.WriteLine("No file after for loop");
			//    return null;
			//}
			//Stream xResult = new FileStream(xINodeNumber, this);
			//Heap.MemFree((uint)xBuffer);
			//Heap.MemFree((uint)xExt2BlockBuffer);
			//return xResult;
			throw new Exception("Ext2 not supported");
		}

		private unsafe bool ReadINode(uint aINodeNumber, out INode aINode) {
            //DebugUtil.SendNumber("Ext2", "reading INode", aINodeNumber, 32);
            //aINodeNumber--;
            //uint xGroup = aINodeNumber / mSuperBlock.INodesPerGroup;
            //DebugUtil.SendNumber("Ext2", "xGroup", xGroup, 32);
            //uint xIndex = (aINodeNumber % mSuperBlock.INodesPerGroup) * mSuperBlock.INodeSize;
            //DebugUtil.SendNumber("Ext2", "xIndex", xIndex, 32);
            //uint xOffset = xIndex % mBlockSize;
            //DebugUtil.SendNumber("Ext2", "xOffset", xOffset, 32);
            //uint xLogBlockNumber = mGroupDescriptors[xGroup].INodeTable;
            //DebugUtil.SendNumber("Ext2", "InodeBitmap", mGroupDescriptors[xGroup].INodeBitmap, 32);
            //DebugUtil.SendNumber("Ext2", "xLogBlockNumber(1)", xLogBlockNumber, 32);
            //xLogBlockNumber += (xIndex / mBlockSize);
            //DebugUtil.SendNumber("Ext2", "xLogBlockNumber(2)", xLogBlockNumber, 32);
            //uint xPhBlockNumber = (xLogBlockNumber * mBlockSize) / mBackend.BlockSize;
            uint xPhBlockNumber = 0;
            //xPhBlockNumber += xIndex / mBackend.BlockSize;
            //xIndex %= mBackend.BlockSize;
            var xBytes = mBackend.ReadBlock(xPhBlockNumber);
            //DebugUtil.SendNumber("Ext2", "BlockOffset", xIndex, 32);
            //fixed (byte* xINodePtr = &xBytes[xIndex]) {
            fixed (byte* xINodePtr = &xBytes[0]) {
                aINode = *(INode*)xINodePtr;
            }
            return true;
		}

		/// <summary>
		/// Reads the logical block at index <paramref name="aBlock"/>. Make sure the buffer is of the correct size
		/// </summary>
		private bool ReadINodeContents(INode* aINode, uint aBlock, byte* aBuffer) {
			uint xBlock;

			switch (aBlock) {
				case 0:
					xBlock = aINode->Block1;
					break;
				case 1:
					xBlock = aINode->Block2;
					break;
				case 2:
					xBlock = aINode->Block3;
					break;
				case 3:
					xBlock = aINode->Block4;
					break;
				case 4:
					xBlock = aINode->Block5;
					break;
				case 5:
					xBlock = aINode->Block6;
					break;
				case 6:
					xBlock = aINode->Block7;
					break;
				case 7:
					xBlock = aINode->Block8;
					break;
				case 8:
					xBlock = aINode->Block9;
					break;
				case 9:
					xBlock = aINode->Block10;
					break;
				case 10:
					xBlock = aINode->Block11;
					break;
				case 11:
					xBlock = aINode->Block12;
					break;
				default:
					Console.WriteLine("Ext2|ReadINodeContents, Only reading of direct blocks supported (12 logical blocks)");
					return false;
			}
			uint xBase = xBlock * (mBlockSize / mBackend.BlockSize);
			for (int i = 0; i < (mBlockSize / mBackend.BlockSize); i++) {
				var xBytes = mBackend.ReadBlock((uint)(xBase + i));
				for (int b = 0; b < xBytes.Length; b++) {
					aBuffer[(i * mBackend.BlockSize) + b] = xBytes[b];
				}
			}
			return true;
		}

		public unsafe byte[] ReadFile(string[] xPath) {
			INode xINode;
			if (!GetINodeByName(xPath, out xINode)) {
				return null;
			}
			uint xSize = xINode.Size;
			if (xSize > mBackend.BlockSize) {
				xSize = mBackend.BlockSize;
			}
//			DebugUtil.SendNumber("Ext2", "ReadFile, Block1", xINode.Block1, 32);
			//byte* xBuff = (byte*)Heap.MemAlloc(mBlockSize);
			try {
				//if (!ReadINodeContents(&xINode, 0, xBuff)) {
					return null;
				//}
				byte[] xResult = new byte[xSize];
				for (int i = 0; i < xSize; i++) {
					//xResult[i] = xBuff[i];
				}
				return xResult;
			} finally {
				//Heap.MemFree((uint)xBuff);
			}
		}

		private bool GetINodeByName(string[] aPath, out INode aINode) {
			//ushort* xBuffer = (ushort*)Heap.MemAlloc(mBackend.BlockSize);
            //byte* xExt2BlockBuffer = (byte*)Heap.MemAlloc(mBlockSize);
            byte* xExt2BlockBuffer = null;
            INode xCurrentINode = new INode();
			aINode = xCurrentINode;
			if (!ReadINode(EXT2_ROOT_INO, out xCurrentINode)) {
//				Heap.MemFree((uint)xBuffer);
//				Heap.MemFree((uint)xExt2BlockBuffer);
				return false;
			}
			bool xCurrentINodeChanged = true;
			uint xInspectedINodeCount = 0;
			for (int i = 0; i < aPath.Length; i++) {
				Console.Write("ReadFile, Iteration ");
				ATAOld.WriteNumber((uint)i, 8);
				Console.WriteLine("");
				if (!xCurrentINodeChanged) {
					Console.WriteLine("Terminating for loop, CurrentINode didn't change");
//					Heap.MemFree((uint)xBuffer);
//					Heap.MemFree((uint)xExt2BlockBuffer);
					return false;
				}
				xCurrentINodeChanged = false;
				if (!ReadINodeContents(&xCurrentINode, 0, xExt2BlockBuffer)) {
//					Heap.MemFree((uint)xBuffer);
//					Heap.MemFree((uint)xExt2BlockBuffer);
					return false;
				}
				DirectoryEntry* xEntryPtr = (DirectoryEntry*)xExt2BlockBuffer;
				uint xTotalSize = mBlockSize;
				while (xTotalSize != 0) {
//					DebugUtil.SendExt2_DirectoryEntry(xEntryPtr);
					uint xPtrAddress = (uint)xEntryPtr;
					char[] xName = new char[xEntryPtr->NameLength];
					byte* xNamePtr = &xEntryPtr->FirstNameChar;
					for (int c = 0; c < xName.Length; c++) {
						xName[c] = (char)xNamePtr[c];
					}
					xInspectedINodeCount++;
					if (EqualsName(aPath[i], xName)) {
						if (!ReadINode(xEntryPtr->INodeNumber, out xCurrentINode)) {
//							Heap.MemFree((uint)xBuffer);
							//Heap.MemFree((uint)xExt2BlockBuffer);
							return false;
						}
						xCurrentINodeChanged = true;
						xTotalSize = 0;
						continue;
					}
					xPtrAddress += xEntryPtr->RecordLength;
					xTotalSize -= xEntryPtr->RecordLength;
					xEntryPtr = (DirectoryEntry*)xPtrAddress;
				}
			}
			aINode = xCurrentINode;
			return true;
		}

		public string[] GetDirectoryEntries(string[] aPath) {
			List<string> xResult = new List<string>(32);
			INode xINode;
            //byte* xExt2BlockBuffer = (byte*)Heap.MemAlloc(mBlockSize);
            byte* xExt2BlockBuffer = null;
            if (!GetINodeByName(aPath, out xINode)) {
				throw new Exception("Couldn't find path!");
			}
			if ((xINode.Mode & INodeModeEnum.Directory) == 0) {
				Console.WriteLine("Ext2|GetDirectoryEntries, No directory after for loop");
				return null;
			}
//			if (!ReadINodeContents(&xINode, 0, xExt2BlockBuffer)) {
//				Heap.MemFree((uint)xExt2BlockBuffer);
				return null;
//			}
			DirectoryEntry* xEntry = (DirectoryEntry*)xExt2BlockBuffer;
			uint xSize = mBlockSize;
//			DebugUtil.SendMessage("Ext2", "GetDirectoryEntries");
			while (xSize != 0) {
//				DebugUtil.SendExt2_DirectoryEntry(xEntry);
				uint xPtrAddress = (uint)xEntry;
				char[] xName = new char[xEntry->NameLength];
				byte* xNamePtr = &xEntry->FirstNameChar;
				for (int c = 0; c < xName.Length; c++) {
					byte b = xNamePtr[c];
					xName[c] = (char)b;
				}
				xResult.Add(new String(xName));
				xPtrAddress += xEntry->RecordLength;
				xSize -= xEntry->RecordLength;
				xEntry = (DirectoryEntry*)xPtrAddress;
			}
//			Heap.MemFree((uint)xExt2BlockBuffer);
			return xResult.ToArray();
		}

		private static bool EqualsName(string a1, char[] a2) {
			if (a1 == null || a2 == null) {
				return false;
			}
			if (a1.Length != a2.Length) {
				return false;
			}
			for (int i = 0; i < a1.Length; i++) {
				if (a1[i] != a2[i]) {
					return false;
				}
			}
			return true;
		}
	}
}