Purple AQI Widget

purpleaqijsnell.js

const API_URL = "https://www.purpleair.com/json?show=";
// const CACHE_FILE = "aqi_data.json"
// Find a nearby PurpleAir sensor ID via https://fire.airnow.gov/
// Click a sensor near your location: the ID is the trailing integers
// https://www.purpleair.com/json has all sensors by location & ID.
let SENSOR_ID = args.widgetParameter || "4896"

async function getSensorData(url, id) {
  let req = new Request(`${url}${id}`)
  let json = await req.loadJSON()
  
  return {
  	"val": json.results[0].PM2_5Value,
  	"ts": json.results[0].LastSeen,
    "loc": json.results[0].Label
  }
}


// Calculates the AQI level based on 
// https://cfpub.epa.gov/airnow/index.cfm?action=aqibasics.aqi#unh
function calculateLevel(aqi) {
	let res = {
		level: "OK",
		color: Color.white()
	}
  
	let level = parseInt(aqi, 10) || 0
  	if (level > 300) {
    	res.level = "Hazardous"
    	res.color = new Color('7e0023')
   	return res
    } else if (level > 200) {
    	res.level = "Very Unhealthy"
    	res.color = new Color('8f3f97')
   	return res
    } else if (level > 151) {
    	res.level = "Unhealthy"
    	res.color = Color.red()
   	return res
  	} else if (level > 101) {
    	res.level = "Unhealthy (S.G.)"
    	res.color = new Color('ff7e00')
		return res
	} else if (level > 51) {
  		res.level = "Moderate"
  		res.color = new Color('ffff00')
  		return res
	} else if (level > 0) {
  		res.level = "Good"
  		res.color = new Color('00e400')
  		return res
	}

	return res
}


//Function to get AQI number from PPM reading
function aqiFromPM (pm) {
	if (pm > 350.5) {
		return calcAQI(pm, 500.0, 401.0, 500.0, 350.5)
	} else if (pm > 250.5) {
    return calcAQI(pm, 400.0, 301.0, 350.4, 250.5)
  } else if (pm > 150.5) {
    return calcAQI(pm, 300.0, 201.0, 250.4, 150.5)
  } else if (pm > 55.5) {
    return calcAQI(pm, 200.0, 151.0, 150.4, 55.5)
  } else if (pm > 35.5) {
    return calcAQI(pm, 150.0, 101.0, 55.4, 35.5)
  } else if (pm > 12.1) {
    return calcAQI(pm, 100.0, 51.0, 35.4, 12.1)
  } else if (pm >= 0.0) {
    return calcAQI(pm, 50.0, 0.0, 12.0, 0.0)
  } else {
    return "-"
  }
}

//Function that actually calculates the AQI number
function calcAQI(Cp, Ih, Il, BPh, BPl) {
  let a = (Ih - Il);
  let b = (BPh - BPl);
  let c = (Cp - BPl);
  return Math.round((a/b) * c + Il);     
}

async function run() {
	let wg = new ListWidget()

	try {
  

  		console.log(`Using sensor ID: ${SENSOR_ID}`)
  		let data = await getSensorData(API_URL, SENSOR_ID)
  		console.log(data)
  
  
  	let header = wg.addText("Air Quality")
		header.textSize = 15
		header.textColor =  Color.black()

	let aqi = aqiFromPM(data.val)
	let level = calculateLevel(aqi)
	let aqitext = aqi.toString()
	console.log(aqi)
  	console.log(level.level)
  
  		wg.backgroundColor = level.color
  
  		let content = wg.addText(aqitext)
  		content.textSize = 50
  		content.textColor = Color.black()
  
 		let wordLevel = wg.addText(level.level)
  		wordLevel.textSize = 15
  		wordLevel.textColor = Color.black()
  
  		let id = wg.addText(data.loc)
		id.textSize = 10
  		id.textColor = Color.black()
  
  		let updatedAt = new Date(data.ts*1000).toLocaleTimeString("en-US", { timeZone: "PST" })
  		let ts = wg.addText(`Updated ${updatedAt}`)
  		ts.textSize = 10
  		ts.textColor = Color.black()
    
	} catch (e) {
  		console.log(e)
  		let err = wg.addText(`error: ${e}`)
  		err.textSize = 10
  		err.textColor = Color.red()
  		err.textOpacity = 30
	}


	Script.setWidget(wg)
	Script.complete()
}

await run()