#region License

/*
    Adapted work from:

    DirectShowLib - Provide access to DirectShow interfaces via .NET
    Copyright (C) 2007
    http://sourceforge.net/projects/directshownet/
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.
    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.
    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

#endregion

using System;
using System.Runtime.InteropServices;

namespace ScreenToGif.Webcam.DirectShow
{
    internal abstract class DsMarshaler : ICustomMarshaler
    {
        #region Data Members

        //The cookie isn't currently being used.
        protected string ManagedCookie;

        //The managed object passed in to MarshalManagedToNative, and modified in MarshalNativeToManaged
        protected object ManagedObj;

        #endregion

        //The constructor. This is called from GetInstance (below).
        protected DsMarshaler(string cookie)
        {
            //If we get a cookie, save it.
            ManagedCookie = cookie;
        }

        //Called just before invoking the COM method.  The returned IntPtr is what goes on the stack
        //for the COM call. The input arg is the parameter that was passed to the method.
        public virtual IntPtr MarshalManagedToNative(object managedObj)
        {
            //Save off the passed-in value. Safe since we just checked the type.
            ManagedObj = managedObj;

            //Create an appropriately sized buffer, blank it, and send it to the marshaler to make the COM call with.
            var iSize = GetNativeDataSize() + 3;
            var p = Marshal.AllocCoTaskMem(iSize);

            for (var x = 0; x < iSize / 4; x++)
                Marshal.WriteInt32(p, x * 4, 0);

            return p;
        }

        // Called just after invoking the COM method.  The IntPtr is the same one that just got returned
        // from MarshalManagedToNative.  The return value is unused.
        public virtual object MarshalNativeToManaged(IntPtr pNativeData)
        {
            return ManagedObj;
        }

        // Release the (now unused) buffer
        public virtual void CleanUpNativeData(IntPtr pNativeData)
        {
            if (pNativeData != IntPtr.Zero)
                Marshal.FreeCoTaskMem(pNativeData);
        }

        // Release the (now unused) managed object
        public virtual void CleanUpManagedData(object managedObj)
        {
            ManagedObj = null;
        }

        // This routine is (apparently) never called by the marshaler.  However it can be useful.
        public abstract int GetNativeDataSize();

        // GetInstance is called by the marshaler in preparation to doing custom marshaling.  The (optional)
        // cookie is the value specified in MarshalCookie="asdf", or "" is none is specified.

        // It is commented out in this abstract class, but MUST be implemented in derived classes
        //public static ICustomMarshaler GetInstance(string cookie)
    }

    internal class EMTMarshaler : DsMarshaler
    {
        public EMTMarshaler(string cookie) : base(cookie)
        { }

        // Called just after invoking the COM method.  The IntPtr is the same one that just got returned
        // from MarshalManagedToNative.  The return value is unused.
        public override object MarshalNativeToManaged(IntPtr pNativeData)
        {
            var emt = ManagedObj as CoreStreaming.AmMediaType[];

            for (var x = 0; x < emt.Length; x++)
            {
                //Copy in the value, and advance the pointer.
                var p = Marshal.ReadIntPtr(pNativeData, x * IntPtr.Size);

                if (p != IntPtr.Zero)
                    emt[x] = (CoreStreaming.AmMediaType)Marshal.PtrToStructure(p, typeof(CoreStreaming.AmMediaType));
                else
                    emt[x] = null;
            }

            return null;
        }

        //The number of bytes to marshal out.
        public override int GetNativeDataSize()
        {
            //Get the array size.
            var i = ((Array)ManagedObj).Length;

            //Multiply that times the size of a pointer.
            return i * IntPtr.Size;
        }

        //This method is called by interop to create the custom marshaler.  The (optional)
        //cookie is the value specified in MarshalCookie="asdf", or "" is none is specified.
        public static ICustomMarshaler GetInstance(string cookie)
        {
            return new EMTMarshaler(cookie);
        }
    }
}