using System;
using System.IO;
using System.Net;
using System.Runtime.InteropServices;

namespace FileSystemApi
{
    public class File
    {
        private IntPtr m_hFile;
        private FileAccess m_fileAccess;
        private long m_length;

        internal File()
        {
            
        }

        internal int Read(byte[] buffer, int offset, int count)
        {
            int bytesRead = 0;
            int ret = FileSystem.ReadFile(Handle, buffer, count, offset, out bytesRead);
            
            return bytesRead;
        }

        internal long Seek(long offset, SeekOrigin origin)
        {
            MoveMethod method;

            switch (origin)
            {
                case SeekOrigin.Begin:
                    method = MoveMethod.Begin;
                    break;
                case SeekOrigin.Current:
                    method = MoveMethod.Current;
                    break;
                case SeekOrigin.End:
                    method = MoveMethod.End;
                    break;
                default:
                    throw new ArgumentOutOfRangeException("origin");
            }

            return FileSystem.SeekFile(Handle, (int)offset, method);
        }

        internal void Close()
        {
            FileSystem.CloseFile(m_hFile);
        }

        internal FileAccess FileAccess
        {
            get { return m_fileAccess; }
            private set { m_fileAccess = value; }
        }

        internal long Length
        {
            get { return m_length; }
            private set { m_length = value; }
        }

        internal long Position
        {
            get
            {
                return FileSystem.SeekFile(Handle, 0, MoveMethod.Current);
            }
        }

        internal IntPtr Handle
        {
            get { return m_hFile; }
            private set { m_hFile = value; }
        }

        public static FileStream Open(string lpFilename, 
                                      FileAccess dwDesiredAccess, 
                                      FileShare dwShareMode, 
                                      CreationDisposition dwCreationDisposition)
        {
            var dwFlagsAndAttributes = FileAttributes.Normal;

            var file = new File();
            
            file.FileAccess = dwDesiredAccess;

            int ret = FileSystem.OpenFile(lpFilename, 
                                          dwDesiredAccess, 
                                          dwShareMode, 
                                          dwCreationDisposition,
                                          dwFlagsAndAttributes, 
                                          out file.m_hFile);

            if(file.Handle == IntPtr.Zero)
                throw new Exception("Could not open file");

            file.m_length = FileSystem.GetFileSize(file.Handle);

            return new FileStream(file);
        }
    }
}