#region Copyright notice and license



// Protocol Buffers - Google's data interchange format

// Copyright 2008 Google Inc.  All rights reserved.

// http://github.com/jskeet/dotnet-protobufs/

// Original C++/Java/Python code:

// http://code.google.com/p/protobuf/

//

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are

// met:

//

//     * Redistributions of source code must retain the above copyright

// notice, this list of conditions and the following disclaimer.

//     * Redistributions in binary form must reproduce the above

// copyright notice, this list of conditions and the following disclaimer

// in the documentation and/or other materials provided with the

// distribution.

//     * Neither the name of Google Inc. nor the names of its

// contributors may be used to endorse or promote products derived from

// this software without specific prior written permission.

//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.



#endregion



using System;

using System.Reflection;



namespace Google.ProtocolBuffers

{

    /// <summary>

    /// Utilities for arbitrary messages of an unknown type. This class does not use

    /// generics precisely because it is designed for dynamically discovered types.

    /// </summary>

    public static class MessageUtil

    {

        /// <summary>

        /// Returns the default message for the given type. If an exception is thrown

        /// (directly from this code), the message will be suitable to be displayed to a user.

        /// </summary>

        /// <param name="type"></param>

        /// <exception cref="ArgumentNullException">The type parameter is null.</exception>

        /// <exception cref="ArgumentException">The type doesn't implement IMessage, or doesn't

        /// have a static DefaultMessage property of the same type, or is generic or abstract.</exception>

        /// <returns></returns>

        public static IMessage GetDefaultMessage(Type type)

        {

            if (type == null)

            {

                throw new ArgumentNullException("type", "No type specified.");

            }

            if (type.IsAbstract || type.IsGenericTypeDefinition)

            {

                throw new ArgumentException("Unable to get a default message for an abstract or generic type (" +

                                            type.FullName + ")");

            }

            if (!typeof (IMessage).IsAssignableFrom(type))

            {

                throw new ArgumentException("Unable to get a default message for non-message type (" + type.FullName +

                                            ")");

            }

            PropertyInfo property = type.GetProperty("DefaultInstance",

                                                     BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic);

            if (property == null)

            {

                throw new ArgumentException(type.FullName + " doesn't have a static DefaultInstance property");

            }

            if (property.PropertyType != type)

            {

                throw new ArgumentException(type.FullName + ".DefaultInstance property is of the wrong type");

            }

            return (IMessage) property.GetValue(null, null);

        }



        /// <summary>

        /// Returns the default message for the type with the given name. This is just

        /// a convenience wrapper around calling Type.GetType and then GetDefaultMessage.

        /// If an exception is thrown, the message will be suitable to be displayed to a user.

        /// </summary>

        /// <param name="typeName"></param>

        /// <exception cref="ArgumentNullException">The typeName parameter is null.</exception>

        /// <exception cref="ArgumentException">The type doesn't implement IMessage, or doesn't

        /// have a static DefaultMessage property of the same type, or can't be found.</exception>

        public static IMessage GetDefaultMessage(string typeName)

        {

            if (typeName == null)

            {

                throw new ArgumentNullException("typeName", "No type name specified.");

            }

            Type type = Type.GetType(typeName);

            if (type == null)

            {

                throw new ArgumentException("Unable to load type " + typeName);

            }

            return GetDefaultMessage(type);

        }

    }

}