using System;
using System.Collections.Generic;
using System.ServiceModel.Channels;
using System.Text;
using Grpc.Core;

namespace Grpc.Extension.Client.Internal
{
    /// <summary>
    /// 自动负载Channel的CallInvoker
    /// </summary>
    internal class AutoChannelCallInvoker : CallInvoker
    {
        private ChannelPool _channelManager;

        /// <summary>
        /// 自动负载Channel的CallInvoker
        /// </summary>
        public AutoChannelCallInvoker(ChannelPool channelManager)
        {
            this._channelManager = channelManager;
        }

        /// <summary>
        /// Invokes a simple remote call in a blocking fashion.
        /// </summary>
        public override TResponse BlockingUnaryCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
        {
            var call = CreateCall(method, host, options);
            return Calls.BlockingUnaryCall(call, request);
        }

        /// <summary>
        /// Invokes a simple remote call asynchronously.
        /// </summary>
        public override AsyncUnaryCall<TResponse> AsyncUnaryCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
        {
            var call = CreateCall(method, host, options);
            return Calls.AsyncUnaryCall(call, request);
        }

        /// <summary>
        /// Invokes a server streaming call asynchronously.
        /// In server streaming scenario, client sends on request and server responds with a stream of responses.
        /// </summary>
        public override AsyncServerStreamingCall<TResponse> AsyncServerStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options, TRequest request)
        {
            var call = CreateCall(method, host, options);
            return Calls.AsyncServerStreamingCall(call, request);
        }

        /// <summary>
        /// Invokes a client streaming call asynchronously.
        /// In client streaming scenario, client sends a stream of requests and server responds with a single response.
        /// </summary>
        public override AsyncClientStreamingCall<TRequest, TResponse> AsyncClientStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options)
        {
            var call = CreateCall(method, host, options);
            return Calls.AsyncClientStreamingCall(call);
        }

        /// <summary>
        /// Invokes a duplex streaming call asynchronously.
        /// In duplex streaming scenario, client sends a stream of requests and server responds with a stream of responses.
        /// The response stream is completely independent and both side can be sending messages at the same time.
        /// </summary>
        public override AsyncDuplexStreamingCall<TRequest, TResponse> AsyncDuplexStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options)
        {
            var call = CreateCall(method, host, options);
            return Calls.AsyncDuplexStreamingCall(call);
        }

        /// <summary>Creates call invocation details for given method.</summary>
        protected virtual CallInvocationDetails<TRequest, TResponse> CreateCall<TRequest, TResponse>(Method<TRequest, TResponse> method, string host, CallOptions options)
                where TRequest : class
                where TResponse : class
        {
            var channel = _channelManager.GetChannel(method.ServiceName);
            return new CallInvocationDetails<TRequest, TResponse>(channel, method, host, options);
        }
    }
}