//filename: monitor.js
/**
 *
 * simple alive monitoring
 *
 */
const fs = require('fs');
const axios = require('axios');
const formdata = require('form-data');
const ping = require('ping');
const cred = require('./credentials');
const monitor = require('./servers');

/**
 * required variables for credentials
 *   file: credentials.js
 *   imagedir: the directory where required image files exist
 *   token: Token for LINE Notification API
 *   url: Access URI for LINE Notification API
 */

/**
 * for monitored nodes
 *   file: servers.js
 *
 *   servers = [
 *      {
 *         host:'192.168.1.1', //host address [editable]
 *         threshold: 1,       //counter triggered if 'count' exceeded the value [editable]
 *         count: 0,           //icmp req-timed-out counter
 *         status: false,      //current status (true:alive|false:dead)
 *         needtosend: false,  //boolean trigger for sending message
 *         hasdead: false      //whether the host has already dead (true:already dead|false:still alive)
 *      },
 *      {
 *      ...
 *      }, ...
 *   ]
 */
let servers=monitor.servers;
let timer1=monitor.interval; //interval of ping execution
let imageArray=['alive.jpg','dead.jpg'];  //0:alive, 1:dead

let sendMessage=async (msg, imagefile)=>{
    let message='テストメッセージ';
    let imageFile=imageArray[0];
    if(msg) message=msg;
    if(imagefile) imageFile=imagefile;
    let form=new formdata();
    form.append('imageFile', fs.createReadStream(cred.imagedir + '/' + imageFile));
    form.append('message', message);
    let headers = {
        'Authorization': 'Bearer ' + cred.token,
        ...form.getHeaders(),
    }

    try {
        const resp = await axios.post(cred.url, form, {headers});
        console.log(resp.data);
    } catch (error) {
        console.error(error);
    }
}

let serverStat=()=>{
    servers.forEach((server)=>{
        //validation
        ping.sys.probe(server.host, async (isAlive)=>{
            let msg='';
            let imageindex=0;
            //dead or alive
            if(!isAlive){
                //is dead
                server.count++;
                server.status=false;
                if(!server.hasdead&&server.count>=server.threshold){
                    msg='host:[' + server.host + '] is dead as a reason of request timeout'
                    server.needtosend=true;
                    server.hasdead=true;
                    imageindex++;
                }else{
                    msg='';
                }
            }else{
                //is alive
                server.status=true;
                if(server.hasdead&&server.count>=server.threshold){
                    msg='host:[' + server.host + '] is alive';
                    server.needtosend=true;
                    server.hasdead=false;
                    imageindex=imageindex*0;
                }
                server.count=server.count*0;
            }

            //sending message
            console.log(server);
            if(server.needtosend&&msg!==''){
                await sendMessage(msg, imageArray[imageindex]);
                server.needtosend=false;
            }
        });
    });
}

let main=()=>{
    let tid=setInterval(serverStat, timer1);
}

main();

//filename: credentials.js
exports.token='XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'; //LINE notification API
exports.url='https://notify-api.line.me/api/notify';  //LIVE Notification API URI
exports.imagedir='/tmp';

//filename: servers.js
//modify below
let monitored_servers = [
     {
        host:'192.168.1.1', //host address [editable]
        threshold: 1,       //counter triggered if 'count' exceeded the value [editable]
     },
     {
        host:'192.168.1.2',
        threshold: 1,
     },
     {
        host:'8.8.4.4',
        threshold: 1,
    }
];
let timer=5000; //interval for alive monitoring
//modify above

let props={ count: 0, status: false, needtosend: false, hasdead: false };
let servers=[];

monitored_servers.forEach(async (srv, i)=>{
    servers[i]={
            host: srv.host,
            threshold: srv.threshold,
            ...props };
});

exports.servers=servers;
exports.interval=timer;