javascript/greeter/functions.js

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */
"use strict";

const http = require("http");

const {StateFun, Message, Context, messageBuilder, egressMessageBuilder} = require("apache-flink-statefun");

// ------------------------------------------------------------------------------------------------------
// Greeter
// ------------------------------------------------------------------------------------------------------

const GreetRequestType = StateFun.jsonType("example/GreetRequest");
const EgressRecordType = StateFun.jsonType("io.statefun.playground/EgressRecord")

/**
 * A Stateful function that represents a person.
 *
 * @param {Context} context a StateFun context.
 * @param {Message} message the input message.
 * @returns {Promise<void>}
 */
async function person(context, message) {
	// update the visit count
	let visits = context.storage.visits;
	visits += 1;
	context.storage.visits = visits

	// enrich the request with the number of vists.
  	let request = message.as(GreetRequestType)
	request.visits = visits

	// next, we will forward a message to a special greeter function,
	// that will compute a super-doper-personalized greeting based on the
	// number of visits that this person has.
	context.send(messageBuilder({
		typename: "example/greeter",
		id: request.name,
		value: request,
		valueType: GreetRequestType
	}));
}


async function greeter(context, message) {
	const request = message.as(GreetRequestType);
	const person_name = request.name;
	const visits = request.visits;

	const greeting = await compute_fancy_greeting(person_name, visits);
	const egressRecord = {
		topic: "greetings",
		payload: greeting,
	}

	context.send(egressMessageBuilder({
			typename: "io.statefun.playground/egress",
			value: egressRecord,
			valueType: EgressRecordType,
	}));
}


async function compute_fancy_greeting(name, seen) {
	if (seen === 0) {
		return "";
	} else if (seen === 1) {
		return `Welcome ${name}`;
	} else if (seen === 2) {
		return `Nice to see you again ${name}`;
	} else if (seen === 3) {
		return `Third time is a charm ${name}`;
	} else {
		return `Nice to see you at the ${seen}-nth time ${name}!`;
	}
}


// ------------------------------------------------------------------------------------------------------
// Bind all the functions
// ------------------------------------------------------------------------------------------------------

let statefun = new StateFun();

statefun.bind({
	typename: "example/person",
	fn: person,
	specs: [
		{
			name: "visits",
			type: StateFun.intType(),
		}
	]
});


statefun.bind({
	typename: "example/greeter",
	fn: greeter
});

// ------------------------------------------------------------------------------------------------------
// Serve all the functions
// ------------------------------------------------------------------------------------------------------

http.createServer(statefun.handler()).listen(8000);