app.js

/*
* Copyright (c) 2019-2022 JlnWntr (jlnwntr@gmail.com)
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/


/***
 * This will start a node.js server, which provides a simple message-queue.
 * See messagequeue_test.html
 */
var host_addr     = "0.0.0.0"
var host_port     = 3000
var dest_addr     = "localhost"
var dest_port     = 5000

if (process.argv[2] != undefined) host_addr = process.argv[2] 
if (process.argv[3] != undefined) host_port = process.argv[3] 
if (process.argv[4] != undefined) dest_addr = process.argv[4] 
if (process.argv[5] != undefined) dest_port = process.argv[5] 
//console.log(process.argv)
console.log(`Server will send to ${dest_addr}:${dest_port}`)

const Request =  {
    method: "GET",
    mode: "cors", // no-cors, cors, *same-origin
    cache: "no-cache", // *default, no-cache, reload, force-cache,
    timeout: 60000,        
    hostname: dest_addr,
    port: dest_port,
    path: "",        
    headers: {"user-agent": "Mozilla"}
}
const max_buffer_size = 100

function Scheduler() {
    this.running = false    
    this.queue = []
}

Scheduler.prototype.add = function (request, body, callback) {     
    let clone_request = JSON.parse(JSON.stringify(Request))
    clone_request.method = request.method

    this.queue.push({
        "request":  clone_request,
        "callback": callback,
        "body":     body
    })
    if (this.running == false) this.work()
}

Scheduler.prototype.work = function () {
    if (this.running == true) return true
    this.running = true

    var new_job = this.queue.shift()
    if (new_job == undefined) {
        this.running = false
        return false
    }
    
    const request = https.request(new_job.request, function (job, that, response){            
        response.on("data", function(callback, json){
            if (callback !== undefined) callback(json.toString())
        }.bind(null, job.callback))        
        that.running = false       
        that.work()
      }.bind(null, new_job, this)
    )  
    request.on("error", error => {console.error(error)})          
    request.end(new_job.body)
    return true
}

function write(key, d){
    for (var i=0; i<data.length; i++){
        if (data[i].key.localeCompare(key) == 0){                       
            if (data[i].data.length >= max_buffer_size)
                data[i].data.shift()
            data[i].data.push(d);//console.log(data)     
            return
        }
    }    
    if (data.length >= max_buffer_size)
        data.shift()
    data.push({key:key, data:[d]}); //console.log(data)       
}

function read(key){
    for (var i=0; i<data.length; i++)
        if (data[i].key.localeCompare(key) == 0)
            return data[i].data.shift()  
}

const http          = require("http")
const https         = http//require("https")
const url           = require("url")

var sch               = new Scheduler()
var data              = []

const server = http.createServer((request, response) => {   
    response.setHeader("Access-Control-Allow-Origin", "*")   
    response.setHeader("Access-Control-Allow-Methods", "GET, POST")   
    //response.setHeader("Access-Control-Allow-Credentials", true)
    response.statusCode = 200   
    //console.log(request);    response.end();    return
    
    const url_parts = url.parse(request.url, true)
    if (url_parts.query.channel == undefined) {
        response.end()
        return    
    } 
    const channel = url_parts.query.channel.toString() 

    let body = ""
    request.on("data", chunk => {body += chunk})
    request.on("end", () => {//console.log(JSON.parse(data).todo);       
        if (request.method == "POST") {
            response.end()
            sch.add(request, body, write.bind(null, channel))        
        } 
        else{    
            response.end(read(channel))
        }      
    })
    
})
server.listen(host_port, host_addr, () => {console.log(`Server running on ${host_addr}:${host_port}`)})