int buttonPin = D3;
int buttonState; // has the button been pushed
int lastPress = 0;
int buttonDelay = .5*1000;

int ledPin = D2;
bool ledOn = false;
int ledBrightness = 0;

int potPin = A1;
int potReading = 0;

void setup() {
    pinMode( ledPin, OUTPUT );
    pinMode( buttonPin, INPUT_PULLUP );
    // Add a pullup resistor to the pin (prevent floating pin, where button is connected to the digital pin)

    Particle.function("led", ledControl);
    Particle.variable("ledOn", ledOn);
}

void loop() {
    int elapsedTime = millis()-lastPress;

    buttonState = digitalRead(buttonPin);
    potReading = analogRead(potPin); // from 0 to 4095
    ledBrightness = map(potReading, 0, 4095, 0, 255);
    
    if ((buttonState == LOW) && (elapsedTime > buttonDelay)) {
        lastPress = millis();
        ledOn = !ledOn;
    }

    if (ledOn == true) {
        analogWrite(ledPin, ledBrightness);
    }
    else {
        digitalWrite(ledPin, LOW);
    }
}

int ledControl(String command) {
    // find out the state of the led
    if(command == "HIGH"){
        ledOn = true;
    }else if(command == "LOW"){ 
        ledOn = false;
    }else{
        return -1;
    }
    return 1;
}