boolean relayOn = false; // true when relay energized
boolean relayJustTurnedON = false; // true when relay just turned on by push button
boolean wifiTurnRelayON = false; // set true if WiFi connection commands relay ON
boolean wifiTurnRelayOFF = false; //  set true if WiFi connection commands relay OFF
boolean GPIO2wasLOW = false; // set true if last debouced read of GPIO2 as an input was LOW, false if GPIO2 is an output

boolean configMode = false;  // not in config mode normally
void setup() {
  pinMode(0, OUTPUT);
  digitalWrite(0, LOW); // make GPIO0 output low
  // check GPIO2 input to see if push button pressed connecting it to GPIO0
  configMode = (digitalRead(2) == LOW);
  if (configMode) {
    // start AP and get ready to serve config web page
    // leave relay on to indicate in config mode
    //......
  } else {
    // normal usage
    // make GPIO0 HIGH to turn off the relay
    digitalWrite(0, HIGH);
    // set up GPIO0 / GPIO2 to detect user push button
    // relay ALWAYS starts in OFF state
    // NOTE: push button is ALWAYS open here
    // because if it was pushed then we would be
    // in config mode and not here
    pinMode(0, INPUT);
    pinMode(2, OUTPUT);
    digitalWrite(2, LOW);
    //.....
  }
  // rest of setup()
}

void loop() {
  // put your main code here, to run repeatedly:

  if (!relayOn) {
    // case i)
    // check if GPIO0 is being pulled LOW by push button being pressed and GPIO2 Output LOW
    if (digitalRead(0) == LOW) {
      // hold relay ON with GPIO0
      pinMode(2, INPUT);
      pinMode(0, OUTPUT);
      digitalWrite(0, LOW); // make GPIO0 output low
      // make GPIO2 an input
      relayJustTurnedON = true;
      relayOn = true; 
      GPIO2wasLOW = true;
    }
  } else {
    // relay is ON, held by GPIO0 output LOW
    // case ii)
    if (relayJustTurnedON) {
      // look for GPIO2 going high on push button release from turn ON
      if (digitalRead(2) == HIGH) {
        relayJustTurnedON = false;
        GPIO2wasLOW = false;
      } // else keep looking for push button release
    } else {
      // check GPIO2 for LOW then HIGH
      if (GPIO2wasLOW) {
        // check for release
        if (digitalRead(2) == HIGH) {
          // turn relay off
          pinMode(0, INPUT); // turns relay off
          pinMode(2, OUTPUT); // set GPIO2 as Output LOW
          digitalWrite(2, LOW);
          relayOn = false;
        }
      } else {
        // not was low check if push button has been pressed
        if (digitalRead(2) == LOW) {
          GPIO2wasLOW = true;
          // hold relay ON with GPIO0 until release of push button
        } // else loop and keep looking for LOW input
      }
    }
  }

  if (wifiTurnRelayON) {
    pinMode(2, INPUT);
    pinMode(0, OUTPUT);
    digitalWrite(0, LOW);
    wifiTurnRelayON = false; // finished this
    relayJustTurnedON = false;
  }
  if (wifiTurnRelayOFF) {
    pinMode(0, INPUT);
    pinMode(2, OUTPUT);
    digitalWrite(2, LOW);
    wifiTurnRelayOFF = false; // finished this
  }

  // ...
  // code for WiFi connection to control relay
  // should set either wifiTurnRelayOFF or wifiTurnRelayON to true
  // ...

}