#region Copyright notice and license
// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd
#endregion

using Google.Protobuf.Collections;
using System;

namespace Google.Protobuf.Reflection
{
    /// <summary>
    /// Describes a single method in a service.
    /// </summary>
    public sealed class MethodDescriptor : DescriptorBase
    {
        /// <value>
        /// The service this method belongs to.
        /// </value>
        public ServiceDescriptor Service { get; }

        /// <value>
        /// The method's input type.
        /// </value>
        public MessageDescriptor InputType { get; private set; }

        /// <value>
        /// The method's input type.
        /// </value>
        public MessageDescriptor OutputType { get; private set; }

        /// <value>
        /// Indicates if client streams multiple requests.
        /// </value>
        public bool IsClientStreaming => Proto.ClientStreaming;

        /// <value>
        /// Indicates if server streams multiple responses.
        /// </value>
        public bool IsServerStreaming => Proto.ServerStreaming;

        /// <summary>
        /// The (possibly empty) set of custom options for this method.
        /// </summary>
        [Obsolete("CustomOptions are obsolete. Use the GetOptions() method.")]
        public CustomOptions CustomOptions => new CustomOptions(Proto.Options?._extensions?.ValuesByNumber);

        /// <summary>
        /// The <c>MethodOptions</c>, defined in <c>descriptor.proto</c>.
        /// If the options message is not present (i.e. there are no options), <c>null</c> is returned.
        /// Custom options can be retrieved as extensions of the returned message.
        /// NOTE: A defensive copy is created each time this property is retrieved.
        /// </summary>
        public MethodOptions GetOptions()
        {
            var clone = Proto.Options?.Clone();
            if (clone is null)
            {
                return null;
            }
            // Clients should be using feature accessor methods, not accessing features on the
            // options proto.
            clone.Features = null;
            return clone;
        }

        /// <summary>
        /// Gets a single value method option for this descriptor
        /// </summary>
        [Obsolete("GetOption is obsolete. Use the GetOptions() method.")]
        public T GetOption<T>(Extension<MethodOptions, T> extension)
        {
            var value = Proto.Options.GetExtension(extension);
            return value is IDeepCloneable<T> c ? c.Clone() : value;
        }

        /// <summary>
        /// Gets a repeated value method option for this descriptor
        /// </summary>
        [Obsolete("GetOption is obsolete. Use the GetOptions() method.")]
        public RepeatedField<T> GetOption<T>(RepeatedExtension<MethodOptions, T> extension)
        {
            return Proto.Options.GetExtension(extension).Clone();
        }

        internal MethodDescriptor(MethodDescriptorProto proto, FileDescriptor file,
                                  ServiceDescriptor parent, int index)
            : base(file, parent.FullName + "." + proto.Name, index, parent.Features.MergedWith(proto.Options?.Features))
        {
            Proto = proto;
            Service = parent;
            file.DescriptorPool.AddSymbol(this);
        }

        internal MethodDescriptorProto Proto { get; private set; }

        /// <summary>
        /// Returns a clone of the underlying <see cref="MethodDescriptorProto"/> describing this method.
        /// Note that a copy is taken every time this method is called, so clients using it frequently
        /// (and not modifying it) may want to cache the returned value.
        /// </summary>
        /// <returns>A protobuf representation of this method descriptor.</returns>
        public MethodDescriptorProto ToProto() => Proto.Clone();

        /// <summary>
        /// The brief name of the descriptor's target.
        /// </summary>
        public override string Name => Proto.Name;

        internal void CrossLink()
        {
            IDescriptor lookup = File.DescriptorPool.LookupSymbol(Proto.InputType, this);
            if (lookup is not MessageDescriptor inputType)
            {
                throw new DescriptorValidationException(this, "\"" + Proto.InputType + "\" is not a message type.");
            }
            InputType = inputType;

            lookup = File.DescriptorPool.LookupSymbol(Proto.OutputType, this);
            if (lookup is not MessageDescriptor outputType)
            {
                throw new DescriptorValidationException(this, "\"" + Proto.OutputType + "\" is not a message type.");
            }
            OutputType = outputType;
        }
    }
}