Let's Get Notified with Messenger When Parcels are Delivered

const fs = require('fs'),
      request = require('request'),
      Obniz = require('obniz'),
      { createCanvas } = require('canvas');

const LINE_NOTIFY_URL = 'https://notify-api.line.me/api/notify';
const TOKEN = 'LINE_NOTIFY_TOKEN_HERE';

const POSTED_THOREHOLD = 2.0;
const MESSAGE = "Your package is delievered!";

const HEADERS = {
  'Content-Type': 'application/x-www-form-urlencoded',
  'Authorization': 'Bearer ' + TOKEN
};

const OPTIONS = {
  url: LINE_NOTIFY_URL,
  method: 'POST',
  headers: HEADERS,
  json: true,
  form: {
    message: MESSAGE
  }
}

let distanceVals = [];
let passCount = 8;
let passFlag = false;
let obniz = new Obniz('OBNIZ_ID_HERE');

obniz.onconnect = async () => {
  obniz.display.clear();
  const canvas = createCanvas(128, 64); 
  const ctx = canvas.getContext('2d');
  ctx.fillStyle = "white";
  ctx.font = "20px Avenir";
  
  let disSensor = obniz.wired("GP2Y0A21YK0F", {vcc:0, gnd:1, signal:2});
  let rawDistance = 0;
  let changeDiffAbs = 0;
  
  rawDistance = await disSensor.getWait();
  await obniz.wait(500);
  rawDistance = await disSensor.getWait();
  await arrangeArray(distanceVals, rawDistance);
  
  obniz.repeat(async () => { 
    rawDistance = await disSensor.getWait();		
    changeDiffAbs  = await calChangeDiffAbs(distanceVals, rawDistance);
    await console.log(changeDiffAbs);
    
    if(passFlag){
      await passCount--;
      if(passCount <= 0){
        passCount = 8;
        passFlag = false;
        obniz.display.clear();
      }
      return;
    }
    
    if(changeDiffAbs < POSTED_THOREHOLD || Number.isNaN(changeDiffAbs)){
      return;
    }
    await request(OPTIONS, async(error, response, body) => {
      console.log(body);
      ctx.fillText('郵便物が', 0, 26);
      ctx.fillText('届いています',0,56);
      obniz.display.draw(ctx);
      
      passFlag = true;
      if(error){
        console.log(error);
      }
    });
    
  }, 300);
}

async function arrangeArray(arr, val){
  const ARR_LIMIT_NUM = 20;
  
  await arr.push(val);
  if(arr.length > ARR_LIMIT_NUM){
    await arr.shift();
  }
}

async function calPrevChangeAve(arr){
  let prevChanges = [];
  
  for(let i=0; i<arr.length-1; i++){
    await prevChanges.push((arr[i+1]-arr[i])/300 * 10);
  }
  
  let denoNum = prevChanges.length;
  let total = await prevChanges.reduce((sum, data) => {return sum + data}, 0);
  
  return total / denoNum;
}

async function calChangeDiffAbs(arr, val){
  let prevVal = arr[arr.length-1];
  let currentChange = (prevVal - val)/300 * 10;
  let prevChangeAve = await calPrevChangeAve(arr);
  let diff = await Math.abs(prevChangeAve - currentChange);
  
  await arrangeArray(arr, val);
  
  return diff;
}