//! \file       ArcCommon.cs
//! \date       Tue Aug 19 09:45:38 2014
//! \brief      Classes and functions common for various resource files.
//
// Copyright (C) 2014-2015 by morkt
//
// 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.
//

using System;
using System.IO;

namespace GameRes.Formats
{
    public class PrefixStream : Stream
    {
        byte[]  m_header;
        Stream  m_stream;
        long    m_position = 0;

        public PrefixStream (byte[] header, Stream main)
        {
            m_header = header;
            m_stream = main;
        }

        public override bool CanRead  { get { return m_stream.CanRead; } }
        public override bool CanSeek  { get { return m_stream.CanSeek; } }
        public override bool CanWrite { get { return false; } }
        public override long Length   { get { return m_stream.Length + m_header.Length; } }
        public override long Position
        {
            get { return m_position; }
            set
            {
                m_position = Math.Max (value, 0);
                if (m_position > m_header.Length)
                {
                    long stream_pos = m_stream.Seek (m_position - m_header.Length, SeekOrigin.Begin);
                    m_position = m_header.Length + stream_pos;
                }
            }
        }

        public override void Flush()
        {
            m_stream.Flush();
        }

        public override long Seek (long offset, SeekOrigin origin)
        {
            if (SeekOrigin.Begin == origin)
                Position = offset;
            else if (SeekOrigin.Current == origin)
                Position = m_position + offset;
            else
                Position = Length + offset;

            return m_position;
        }

        public override int Read (byte[] buffer, int offset, int count)
        {
            int read = 0;
            if (m_position < m_header.Length)
            {
                int header_count = Math.Min (count, m_header.Length - (int)m_position);
                Buffer.BlockCopy (m_header, (int)m_position, buffer, offset, header_count);
                m_position += header_count;
                read += header_count;
                offset += header_count;
                count -= header_count;
                if (count > 0)
                    m_stream.Position = 0;
            }
            if (count > 0)
            {
                int stream_read = m_stream.Read (buffer, offset, count);
                m_position += stream_read;
                read += stream_read;
            }
            return read;
        }

        public override int ReadByte ()
        {
            if (m_position < m_header.Length)
                return m_header[m_position++];
            if (m_position == m_header.Length)
                m_stream.Position = 0;
            int b = m_stream.ReadByte();
            if (-1 != b)
                m_position++;
            return b;
        }

        public override void SetLength (long length)
        {
            throw new NotSupportedException ("PrefixStream.SetLength method is not supported");
        }

        public override void Write (byte[] buffer, int offset, int count)
        {
            throw new NotSupportedException ("PrefixStream.Write method is not supported");
        }

        public override void WriteByte (byte value)
        {
            throw new NotSupportedException ("PrefixStream.WriteByte method is not supported");
        }

        bool disposed = false;
        protected override void Dispose (bool disposing)
        {
            if (!disposed)
            {
                m_stream.Dispose();
                disposed = true;
                base.Dispose (disposing);
            }
        }
    }
}