app.py

# this is all background stuff and shouldn't have to be changed

from flask import Flask, jsonify, request, render_template
import time, os, threading, sys
import logging

#so it doesn't print every connection
log = logging.getLogger('werkzeug')
log.setLevel(logging.ERROR)

app = Flask(__name__)

def read_and_reset(filename):
    #wait until there's something in the text file, read it, and clear the file.
    while True:
        #time.sleep(0.01) # so that it isn't a constain strain on the computer
        f = open(filename, 'r+')
        message = f.read().strip()
        if message:
            break
        f.close()
    f.truncate(0)
    f.close()
    return message

#Flask stuff that I don't quite understand, taken from Andrew Healey
#https://healeycodes.com/javascript/python/beginners/webdev/2019/04/11/talking-between-languages.html
@app.route('/hello', methods=['GET', 'POST'])
def hello():

    # GET request
    if request.method == 'GET':
        instructions, time_lim = read_and_reset('py_to_js.txt').split('$$$$$$$')
        to_send = {'instructions': instructions, 'time_lim': time_lim}
        return jsonify(to_send)  # serialize and use JSON headers

    # POST request
    else:
        js_to_py = request.get_json(force=True)['response']  # parse as JSON
        f = open('js_to_py.txt', 'w+')
        f.write(js_to_py)
        f.close()
        return 'OK', 200

@app.route('/')
def test_page():
    # look inside `templates` and serve `index.html`
    # this is what actually creates the page
    return render_template('index.html')