// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
// Implements the Decorator pattern from Design Patterns for Stream
 
using System;
using System.IO;
 
using SR = System.Windows.TrustUI.SR;
 
namespace MS.Internal.Documents.Application
{
 
    internal sealed class RightsManagementSuppressedStream : StreamProxy
{
    #region Constructors
    //--------------------------------------------------------------------------
    // Constructors
    //--------------------------------------------------------------------------
 
    /// <summary>
    /// Will construct a RightsManagementSuppressedStream backed by the
    /// specified stream.
    /// </summary>
    /// <param name="targetOfProxy">The stream that is backing the proxy.
    /// </param>
    /// <param name="isWriteAllowed">Whether or not callers are allowed to
    /// write to the stream</param>
    internal RightsManagementSuppressedStream(Stream targetOfProxy, bool isWriteAllowed)
        : base(targetOfProxy, true)
    {
        _allowWrite = isWriteAllowed;
    }
 
    #endregion Constructors
 
    #region Stream Overrides
    //--------------------------------------------------------------------------
    // Stream Overrides
    //--------------------------------------------------------------------------
 
    /// <summary>
    /// <see cref="System.IO.Stream"/>
    /// </summary>
    public override bool CanRead
    {
        get
        {
            return base.CanRead;
        }
    }
 
    /// <summary>
    /// <see cref="System.IO.Stream"/>
    /// </summary>
    public override bool CanWrite
    {
        get
        {
            if (!AllowWrite)
            {
                return false;
            }
 
            return base.CanWrite;
        }
    }
 
    /// <summary>
    /// <see cref="System.IO.Stream"/>
    /// </summary>
    public override void Close()
    {
        base.Close();
    }
 
    /// <summary>
    /// <see cref="System.IO.Stream"/>
    /// </summary>
    public override void Flush()
    {
        base.Flush();
    }
 
    /// <summary>
    /// <see cref="System.IO.Stream"/>
    /// </summary>
    public override long Length
    {
        get
        {
            return base.Length;
        }
    }
 
    /// <summary>
    /// <see cref="System.IO.Stream"/>
    /// </summary>
    public override long Position
    {
        get
        {
            return base.Position;
        }
 
        set
        {
            base.Position = value;
        }
    }
 
    /// <summary>
    /// <see cref="System.IO.Stream"/>
    /// </summary>
    public override int Read(byte[] buffer, int offset, int count)
    {
        return base.Read(buffer, offset, count);
    }
 
    /// <summary>
    /// <see cref="System.IO.Stream"/>
    /// </summary>
    public override long Seek(long offset, SeekOrigin origin)
    {
        return base.Seek(offset, origin);
    }
 
    /// <summary>
    /// <see cref="System.IO.Stream"/>
    /// </summary>
    public override void SetLength(long value)
    {
        ThrowIfReadOnly();
 
        base.SetLength(value);
    }
 
    /// <summary>
    /// <see cref="System.IO.Stream"/>
    /// </summary>
    public override void Write(byte[] buffer, int offset, int count)
    {
        ThrowIfReadOnly();
 
        base.Write(buffer, offset, count);
    }
 
    #endregion Stream Overrides
 
    #region Private Methods
    //--------------------------------------------------------------------------
    // Private Methods
    //--------------------------------------------------------------------------
 
    /// <summary>
    /// Throws an appropriate exception if writing to the stream is not allowed.
    /// </summary>
    private void ThrowIfReadOnly()
    {
        if (!AllowWrite)
        {
            throw new InvalidOperationException(
                SR.RightsManagementExceptionNoRightsForOperation);
        }
    }
 
    #endregion Private Methods
 
    #region Private Properties
    //--------------------------------------------------------------------------
    // Private Properties
    //--------------------------------------------------------------------------
    
    /// <summary>
    /// Returns whether or not the current RM permission set allows writing to
    /// the stream.
    /// </summary>
    private bool AllowWrite
    {
        get
        {
            return _allowWrite;
        }
    }
 
    #endregion Private Properties
 
    #region Private Fields
    //--------------------------------------------------------------------------
    // Private Fields
    //--------------------------------------------------------------------------
 
    /// <summary>
    /// Whether or not the proxy should enforce that the stream is read-only.
    /// </summary>
    private bool _allowWrite;
 
    #endregion Private Fields
}
}