index.js

const Config = require('./config');
const Express = require('express');
const app = Express();
const Comms = require('./comms');
const Decoder = require('./decoder');
const timersPromises = require('timers/promises');
const debug = Config.debug;

const { SerialPort } = require('serialport');
const Readline = require('@serialport/parser-readline');
const arduino = new SerialPort({path: '/dev/ttyACM0', baudRate: 115200 });

const { Mutex } = require('async-mutex');
const mutex = new Mutex(); // Lock to prevent multiple commands from being sent at once

// Current display readout - non-blocking
app.get('/display', async function (req, res) {
    let panelData = Decoder.decodeDisplay((await Comms.readData()).dataArray);
    res.send(panelData);
});

// Get Spa status - blocking
app.get('/json', async function (req, res) {
    await mutex.runExclusive(async () => {
        let panelData = await currentState();
        res.send(panelData);
    })
});

// Read display data 100 times for debugging
app.get('/readcontrols', async function (req, res) {
    let response = "";
    for (let i=0; i< 100; i++) {
        let controlsData = (await Comms.readData()).controlsArray;
        response += `${controlsData.join('')}<br>`
    }
    res.send(response);
});

// Toggle Standard and Eco modes
app.get('/mode', async function (req, res) {
    await mutex.runExclusive(async () => {
        let commands = [Config.MODE_BUTTON]
        if (debug) console.log(`writing ${commands}`);
        arduino.write(commands, (err) => {
            if (err) {
            return console.log('Error on write: ', err.message);
            }
        });
    })
    res.send("ok");
});

app.get('/change', async function (req, res) {
    await mutex.runExclusive(async () => {
        if (req.query.temp == null) throw Error ("no temp specified")
        await changeTempTo(req.query.temp);
        res.send("ok");
    })
});

// Send command to arduino
app.get('/command', async function (req, res) {
    await mutex.runExclusive(async () => {
        try {
            const command = req.query.command;
            if (command == null) throw Error ("no command specified")
            const isValidCommand = /^\d+$/.test(command) && Number(command) >= 1 && Number(command) <= 15;
            if (!isValidCommand) throw Error("command must be a digit between 1 and 15");
            arduino.write([Number(command)]);
            res.send("ok")
        } catch (err) {
            res.send(err.message)
        }
    })
});

async function currentState() {
    let setTemp
    let currentTemp

    let panelData = Decoder.decodeDisplay((await Comms.readData()).dataArray);
    while (panelData.tempUp || panelData.tempDown) { // If the temp is being set, wait for it to complete
        await timersPromises.setTimeout(500);
        panelData = Decoder.decodeDisplay((await Comms.readData()).dataArray);
    }
    while (panelData.setHeat) {  // If it is already on the setHeat screen, read setTemp and wait for it to return
        // TODO:  Consider scenario where it is in the process of raising setTemp
        setTemp = panelData.temperature
        await timersPromises.setTimeout(500);
        panelData = Decoder.decodeDisplay((await Comms.readData()).dataArray);
    }
    currentTemp = panelData.temperature  // Now that we are not on setHeat, record the current temp
    while (!setTemp) {
        arduino.write([Config.DOWN_BUTTON]); // Send a keypress to activate the setHeat screen
        await timersPromises.setTimeout(500);
        panelData = Decoder.decodeDisplay((await Comms.readData()).dataArray);
        if (panelData.setHeat) setTemp = panelData.temperature  // Confirm setHeat screen and record setTemp
    }
    panelData.temperature = currentTemp
    panelData.setTemp = setTemp
    return panelData
}

async function changeTempTo(targetTemp) {
    if (targetTemp > Config.MAX_TEMP || targetTemp < Config.MIN_TEMP) throw new Error (`Temperature must be between ${Config.MIN_TEMP} and ${Config.MAX_TEMP}`)
    let state = await currentState();
    let currentTemp = state.setTemp
    let delta = targetTemp - currentTemp;
    let command;

    if (debug) console.log(`changeTempTo: ${targetTemp} from ${currentTemp} is ${delta}`);
    if (delta > 0) command = Config.UP_BUTTON;
    if (delta < 0) command = Config.DOWN_BUTTON;

    // Fill an array with delta button presses to reach target temp
    let commands = new Array(Math.abs(delta)).fill(command);
    if (!state.setHeat) commands.push(command); // add one more click if it is not already in setHeat mode
    arduino.write(commands);
}

app.listen(process.env.PORT || 3000);