// Copyright 2019 gRPC authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// 语法版本声明，必须放在非注释的第一行
// Syntax version declaration. Must be placed on the first line of non-commentary.

syntax = "proto3";
// The document of proto3: https://developers.google.com/protocol-buffers/docs/proto3

// 包名定义, Python中使用时可以省略不写
// Package name definition, which can be omitted in Python.
package demo;

/*
`message`是用来定义传输的数据的格式的, 等号后面的是字段编号
消息定义中的每个字段都有唯一的编号
总体格式类似于Python中定义一个类或者Golang中定义一个结构体
*/
/*
`message` is used to define the structure of the data to be transmitted, after the equal sign
is the field number. Each field in the message definition has a unique number.
The overall format is similar to defining a class in Python or a structure in Golang.
*/
message Request {
    int64 client_id = 1;
    string request_data = 2;
}

message Response {
    int64 server_id = 1;
    string response_data = 2;
}

// `service` 是用来给gRPC服务定义方法的, 格式固定, 类似于Golang中定义一个接口
// `service` is used to define methods for gRPC services in a fixed format, similar to defining
//an interface in Golang
service GRPCDemo {
    // 一元模式(在一次调用中, 客户端只能向服务器传输一次请求数据, 服务器也只能返回一次响应)
    // unary-unary(In a single call, the client can only send request once, and the server can
    // only respond once.)
    rpc SimpleMethod (Request) returns (Response);

    // 客户端流模式（在一次调用中, 客户端可以多次向服务器传输数据, 但是服务器只能返回一次响应）
    // stream-unary (In a single call, the client can transfer data to the server several times,
    // but the server can only return a response once.)
    rpc ClientStreamingMethod (stream Request) returns (Response);

    // 服务端流模式（在一次调用中, 客户端只能一次向服务器传输数据, 但是服务器可以多次返回响应）
    // unary-stream (In a single call, the client can only transmit data to the server at one time,
    // but the server can return the response many times.)
    rpc ServerStreamingMethod (Request) returns (stream Response);

    // 双向流模式 (在一次调用中, 客户端和服务器都可以向对方多次收发数据)
    // stream-stream (In a single call, both client and server can send and receive data
    // to each other multiple times.)
    rpc BidirectionalStreamingMethod (stream Request) returns (stream Response);
}