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index.js
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index.js
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const grpc = require('grpc')
const _ = require('lodash')
const gi = require('grpc-inspect')
const pc = require('promisify-call')
const create = require('grpc-create-metadata')
module.exports = caller
/**
* Create client isntance.
* @param {String} host - The host to connect to
* @param {String|Object} proto Path to the protocol buffer definition file or
* Object specifying <code>root</code> directory and <code>file</code> to load or
* the static client constructor object itself
* @param {String} name - In case of proto path the name of the service as defined in the proto definition.
* @param {Object} options - Options to be passed to the gRPC client constructor
* @returns {Object}
*
* @example <caption>Create client dynamically</caption>
* const PROTO_PATH = path.resolve(__dirname, './protos/helloworld.proto')
* const client = caller('localhost:50051', PROTO_PATH, 'Greeter')
*
* const root = path.join(__dirname, 'protos');
* const file = 'helloworld.proto'
* const client = caller('localhost:50051', { root, file }, 'Greeter')
*
* @example <caption>Create a static client</caption>
* const services = require('./static/helloworld_grpc_pb')
* const client = caller('localhost:50051', services.GreeterClient)
*/
function caller (host, proto, name, options) {
let Ctor
if (_.isString(proto) || (_.isObject(proto) && proto.root && proto.file)) {
const loaded = grpc.load(proto)
const descriptor = gi(loaded)
if (!descriptor) {
throw new Error(String.raw `Error parsing protocol buffer`)
}
Ctor = descriptor.client(name)
if (!Ctor) {
throw new Error(String.raw `Service name ${name} not found in protocol buffer definition`)
}
} else if (_.isObject(proto)) {
Ctor = proto
options = name
}
// promisify the client
const clientProto = Ctor.prototype
_.forOwn(clientProto, (v, k) => {
if (typeof clientProto[k] === 'function') {
if (!v.responseStream && !v.requestStream) {
clientProto[k] = function (arg, metadata, options, fn) {
if (_.isFunction(options)) {
fn = options
options = undefined
}
if (_.isFunction(metadata)) {
fn = metadata
metadata = undefined
}
if (_.isPlainObject(metadata) && metadata instanceof grpc.Metadata === false) {
metadata = create(metadata)
}
const args = _.compact([arg, metadata, options, fn])
// only promisify-call functions in simple response / request scenario
return pc(this, v, ...args)
}
} else if (v.responseStream && !v.requestStream) {
clientProto[k] = function (arg, metadata, options) {
if (_.isPlainObject(metadata) && metadata instanceof grpc.Metadata === false) {
metadata = create(metadata)
}
const args = _.compact([arg, metadata, options])
return v.call(this, ...args)
}
} else if (!v.responseStream && v.requestStream) {
clientProto[k] = function (metadata, options, fn) {
if (_.isFunction(options)) {
fn = options
options = undefined
}
if (_.isFunction(metadata)) {
fn = metadata
metadata = undefined
}
if (_.isPlainObject(metadata) && metadata instanceof grpc.Metadata === false) {
metadata = create(metadata)
}
if (fn) { // normal call
const args = _.compact([metadata, options, fn])
return v.call(this, ...args)
} else { // dual return promsified call with return { call, res }
const r = {}
const p = new Promise((resolve, reject) => {
const args = _.compact([metadata, options, fn])
args.push((err, result) => {
if (err) reject(err)
else resolve(result)
})
r.call = v.call(this, ...args)
})
r.res = p
return r
}
}
} else if (v.responseStream && v.requestStream) {
clientProto[k] = function (metadata, options) {
if (_.isPlainObject(metadata) && metadata instanceof grpc.Metadata === false) {
metadata = create(metadata)
}
const args = _.compact([metadata, options])
return v.call(this, ...args)
}
}
}
})
return new Ctor(host, options || grpc.credentials.createInsecure())
}
/**
* Utility helper function to create <code>Metadata</code> object from plain Javascript object.
* See <code>grpc-create-metadata</code> module.
*/
caller.metadata = create