//
// Copyright (c) 2008-2011, Kenneth Bell
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//

namespace DiscUtils.Ntfs
{
    using System;
    using System.Collections.Generic;
    using System.IO;

    internal class NtfsAttributeBuffer : DiscUtils.Buffer, IMappedBuffer
    {
        private File _file;
        private NtfsAttribute _attribute;

        public NtfsAttributeBuffer(File file, NtfsAttribute attribute)
        {
            _file = file;
            _attribute = attribute;
        }

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

        public override bool CanWrite
        {
            get { return _file.Context.RawStream.CanWrite; }
        }

        public override long Capacity
        {
            get
            {
                return _attribute.PrimaryRecord.DataLength;
            }
        }

        public long MapPosition(long pos)
        {
            if (_attribute.IsNonResident)
            {
                return ((IMappedBuffer)_attribute.RawBuffer).MapPosition(pos);
            }
            else
            {
                AttributeReference attrRef = new AttributeReference(_file.MftReference, _attribute.PrimaryRecord.AttributeId);
                ResidentAttributeRecord attrRecord = (ResidentAttributeRecord)_file.GetAttribute(attrRef).PrimaryRecord;

                long attrStart = _file.GetAttributeOffset(attrRef);
                long mftPos = attrStart + attrRecord.DataOffset + pos;

                return _file.Context.GetFileByIndex(MasterFileTable.MftIndex).GetAttribute(AttributeType.Data, null).OffsetToAbsolutePos(mftPos);
            }
        }

        public override int Read(long pos, byte[] buffer, int offset, int count)
        {
            var record = _attribute.PrimaryRecord;

            if (!CanRead)
            {
                throw new IOException("Attempt to read from file not opened for read");
            }

            Utilities.AssertBufferParameters(buffer, offset, count);

            if (pos >= Capacity)
            {
                return 0;
            }

            // Limit read to length of attribute
            int totalToRead = (int)Math.Min(count, Capacity - pos);
            int toRead = totalToRead;

            // Handle uninitialized bytes at end of attribute
            if (pos + totalToRead > record.InitializedDataLength)
            {
                if (pos >= record.InitializedDataLength)
                {
                    // We're just reading zero bytes from the uninitialized area
                    Array.Clear(buffer, offset, totalToRead);
                    pos += totalToRead;
                    return totalToRead;
                }
                else
                {
                    // Partial read of uninitialized area
                    Array.Clear(buffer, offset + (int)(record.InitializedDataLength - pos), (int)((pos + toRead) - record.InitializedDataLength));
                    toRead = (int)(record.InitializedDataLength - pos);
                }
            }

            int numRead = 0;
            while (numRead < toRead)
            {
                IBuffer extentBuffer = _attribute.RawBuffer;

                int justRead = extentBuffer.Read(pos + numRead, buffer, offset + numRead, toRead - numRead);
                if (justRead == 0)
                {
                    break;
                }

                numRead += justRead;
            }

            return totalToRead;
        }

        public override void SetCapacity(long value)
        {
            if (!CanWrite)
            {
                throw new IOException("Attempt to change length of file not opened for write");
            }

            if (value == Capacity)
            {
                return;
            }

            _attribute.RawBuffer.SetCapacity(value);
            _file.MarkMftRecordDirty();
        }

        public override void Write(long pos, byte[] buffer, int offset, int count)
        {
            var record = _attribute.PrimaryRecord;

            if (!CanWrite)
            {
                throw new IOException("Attempt to write to file not opened for write");
            }

            Utilities.AssertBufferParameters(buffer, offset, count);

            if (count == 0)
            {
                return;
            }

            _attribute.RawBuffer.Write(pos, buffer, offset, count);

            if (!record.IsNonResident)
            {
                _file.MarkMftRecordDirty();
            }
        }

        public override void Clear(long pos, int count)
        {
            var record = _attribute.PrimaryRecord;

            if (!CanWrite)
            {
                throw new IOException("Attempt to write to file not opened for write");
            }

            if (count == 0)
            {
                return;
            }

            _attribute.RawBuffer.Clear(pos, count);

            if (!record.IsNonResident)
            {
                _file.MarkMftRecordDirty();
            }
        }

        public override IEnumerable<StreamExtent> GetExtentsInRange(long start, long count)
        {
            return StreamExtent.Intersect(_attribute.RawBuffer.GetExtentsInRange(start, count), new StreamExtent(0, Capacity));
        }
    }
}