// ==++==
// 
//   Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// ==--==
// This class represents the Ole Automation binder.

// #define DISPLAY_DEBUG_INFO

namespace System {

    using System;
    using System.Runtime.InteropServices;
    using System.Reflection;
    using Microsoft.Win32;
    using CultureInfo = System.Globalization.CultureInfo;    

    // Made serializable in anticipation of this class eventually having state.
    [Serializable]
    internal class OleAutBinder : DefaultBinder
    {
        // ChangeType
        // This binder uses OLEAUT to change the type of the variant.
        [System.Security.SecuritySafeCritical] // overrides transparent member
        public override Object ChangeType(Object value, Type type, CultureInfo cultureInfo)
        {
            Variant myValue = new Variant(value);
            if (cultureInfo == null)
                cultureInfo = CultureInfo.CurrentCulture;
                
    #if DISPLAY_DEBUG_INFO      
            Console.WriteLine("In OleAutBinder::ChangeType converting variant of type: {0} to type: {1}", myValue.VariantType, type.Name);
    #endif

            if (type.IsByRef)
            {
    #if DISPLAY_DEBUG_INFO      
                Console.WriteLine("Stripping byref from the type to convert to.");
    #endif      
                type = type.GetElementType();
            }

            // If we are trying to convert from an object to another type then we don't
            // need the OLEAUT change type, we can just use the normal COM+ mechanisms.
            if (!type.IsPrimitive && type.IsInstanceOfType(value))
            {
    #if DISPLAY_DEBUG_INFO      
                Console.WriteLine("Source variant can be assigned to destination type");
    #endif      
                return value;
            }

            Type srcType = value.GetType();

            // Handle converting primitives to enums.
            if (type.IsEnum && srcType.IsPrimitive)
            {
    #if DISPLAY_DEBUG_INFO      
                Console.WriteLine("Converting primitive to enum");
    #endif      
                return Enum.Parse(type, value.ToString());
            }

#if !FEATURE_CORECLR
            // Special case the convertion from DBNull.
            if (srcType == typeof(DBNull))
            {
                // The requested type is a DBNull so no convertion is required.            
                if (type == typeof(DBNull))
                    return value;

                // Visual J++ supported converting from DBNull to null so customers
                // have requested (via a CDCR) that DBNull be convertible to null.
                // We don't however allow this when converting to a value class, since null
                // doesn't make sense for these, or to object since this would change existing
                // semantics.               
                if ((type.IsClass && type != typeof(Object)) || type.IsInterface)
                    return null;
            }
#endif //!FEATURE_CORECLR

#if FEATURE_COMINTEROP
            // Use the OA variant lib to convert primitive types.
            try
            {
#if DISPLAY_DEBUG_INFO      
                Console.WriteLine("Using OAVariantLib.ChangeType() to do the conversion");
#endif      
                // Specify the LocalBool flag to have BOOL values converted to local language rather
                // than 0 or -1.
                Object RetObj = OAVariantLib.ChangeType(myValue, type, OAVariantLib.LocalBool, cultureInfo).ToObject();

#if DISPLAY_DEBUG_INFO      
                Console.WriteLine("Object returned from ChangeType is of type: " + RetObj.GetType().Name);
#endif

                return RetObj;
            }
#if DISPLAY_DEBUG_INFO      
            catch(NotSupportedException e)
#else
            catch(NotSupportedException)
#endif      
            {
#if DISPLAY_DEBUG_INFO      
                Console.Write("Exception thrown: ");
                Console.WriteLine(e);
#endif      
                throw new COMException(Environment.GetResourceString("Interop.COM_TypeMismatch"), unchecked((int)0x80020005));
            }
            
#else // !FEATURE_COMINTEROP

            return base.ChangeType(value, type, cultureInfo);

#endif // !FEATURE_COMINTEROP
        }
        
        
#if !FEATURE_COMINTEROP         
        // CanChangeType
        public override bool CanChangeType(Object value, Type type, CultureInfo cultureInfo)
        {
            Variant myValue = new Variant(value);
            if (cultureInfo == null)
                cultureInfo = CultureInfo.CurrentCulture;
                
    #if DISPLAY_DEBUG_INFO      
            Console.WriteLine("In OleAutBinder::CanChangeType converting variant of type: {0} to type: {1}", myValue.VariantType, type.Name);
    #endif

            // If we are trying to convert to variant then there is nothing to do.
            if (type == typeof(Variant))
            {
    #if DISPLAY_DEBUG_INFO      
                Console.WriteLine("Variant being changed to type variant is always legal");
    #endif      
                return true;
            }
    
            if (type.IsByRef)
            {
    #if DISPLAY_DEBUG_INFO      
                Console.WriteLine("Stripping byref from the type to convert to.");
    #endif      
                type = type.GetElementType();
            }

            // If we are trying to convert from an object to another type then we don't
            // need the OLEAUT change type, we can just use the normal COM+ mechanisms.
            if (!type.IsPrimitive && type.IsInstanceOfType(value))
            {
    #if DISPLAY_DEBUG_INFO      
                Console.WriteLine("Source variant can be assigned to destination type");
    #endif      
                return true;
            }

            // Handle converting primitives to enums.
            if (type.IsEnum && value.GetType().IsPrimitive)
            {
    #if DISPLAY_DEBUG_INFO      
                Console.WriteLine("Converting primitive to enum");
    #endif      
                return true;
            }

            return base.CanChangeType(value, type, cultureInfo);
        }
#endif // FEATURE_COMINTEROP        
    }
}
