service.js
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"use strict";
module.exports = Service;
var util = require("../util/minimal");
// Extends EventEmitter
(Service.prototype = Object.create(util.EventEmitter.prototype)).constructor = Service;
/**
* A service method callback as used by {@link rpc.ServiceMethod|ServiceMethod}.
*
* Differs from {@link RPCImplCallback} in that it is an actual callback of a service method which may not return `response = null`.
* @typedef rpc.ServiceMethodCallback
* @template TRes extends Message<TRes>
* @type {function}
* @param {Error|null} error Error, if any
* @param {TRes} [response] Response message
* @returns {undefined}
*/
/**
* A service method part of a {@link rpc.Service} as created by {@link Service.create}.
* @typedef rpc.ServiceMethod
* @template TReq extends Message<TReq>
* @template TRes extends Message<TRes>
* @type {function}
* @param {TReq|Properties<TReq>} request Request message or plain object
* @param {rpc.ServiceMethodCallback<TRes>} [callback] Node-style callback called with the error, if any, and the response message
* @returns {Promise<Message<TRes>>} Promise if `callback` has been omitted, otherwise `undefined`
*/
/**
* Constructs a new RPC service instance.
* @classdesc An RPC service as returned by {@link Service#create}.
* @exports rpc.Service
* @extends util.EventEmitter
* @constructor
* @param {RPCImpl} rpcImpl RPC implementation
* @param {boolean} [requestDelimited=false] Whether requests are length-delimited
* @param {boolean} [responseDelimited=false] Whether responses are length-delimited
*/
function Service(rpcImpl, requestDelimited, responseDelimited) {
if (typeof rpcImpl !== "function")
throw TypeError("rpcImpl must be a function");
util.EventEmitter.call(this);
/**
* RPC implementation. Becomes `null` once the service is ended.
* @type {RPCImpl|null}
*/
this.rpcImpl = rpcImpl;
/**
* Whether requests are length-delimited.
* @type {boolean}
*/
this.requestDelimited = Boolean(requestDelimited);
/**
* Whether responses are length-delimited.
* @type {boolean}
*/
this.responseDelimited = Boolean(responseDelimited);
}
/**
* Calls a service method through {@link rpc.Service#rpcImpl|rpcImpl}.
* @param {Method|rpc.ServiceMethod<TReq,TRes>} method Reflected or static method
* @param {Constructor<TReq>} requestCtor Request constructor
* @param {Constructor<TRes>} responseCtor Response constructor
* @param {TReq|Properties<TReq>} request Request message or plain object
* @param {rpc.ServiceMethodCallback<TRes>} callback Service callback
* @returns {undefined}
* @template TReq extends Message<TReq>
* @template TRes extends Message<TRes>
*/
Service.prototype.rpcCall = function rpcCall(method, requestCtor, responseCtor, request, callback) {
if (!request)
throw TypeError("request must be specified");
var self = this;
if (!callback)
return util.asPromise(rpcCall, self, method, requestCtor, responseCtor, request);
if (!self.rpcImpl) {
setTimeout(function() { callback(Error("already ended")); }, 0);
return undefined;
}
try {
return self.rpcImpl(
method,
requestCtor[self.requestDelimited ? "encodeDelimited" : "encode"](request).finish(),
function rpcCallback(err, response) {
if (err) {
self.emit("error", err, method);
return callback(err);
}
if (response === null) {
self.end(/* endedByRPC */ true);
return undefined;
}
if (!(response instanceof responseCtor)) {
try {
response = responseCtor[self.responseDelimited ? "decodeDelimited" : "decode"](response);
} catch (err) {
self.emit("error", err, method);
return callback(err);
}
}
self.emit("data", response, method);
return callback(null, response);
}
);
} catch (err) {
self.emit("error", err, method);
setTimeout(function() { callback(err); }, 0);
return undefined;
}
};
/**
* Ends this service and emits the `end` event.
* @param {boolean} [endedByRPC=false] Whether the service has been ended by the RPC implementation.
* @returns {rpc.Service} `this`
*/
Service.prototype.end = function end(endedByRPC) {
if (this.rpcImpl) {
if (!endedByRPC) // signal end to rpcImpl
this.rpcImpl(null, null, null);
this.rpcImpl = null;
this.emit("end").off();
}
return this;
};