TouchSensor+Relay

#include <ESP8266WiFi.h>
#include <FirebaseArduino.h>
#include <ESP8266HTTPClient.h>


// Settings
#define FINGERPRINT "7A 54 06 9B DC 7A 25 B3 86 8D 66 53 48 2C 0B 96 42 C7 B3 0A"
#define FIREBASE_HOST "****"
#define FIREBASE_AUTH "*****"
#define WIFI_SSID "***"
#define WIFI_PASSWORD "***"
#define UID "***"
#define URL "/users/KfNnT1xivpai8iCs1tAr6s2LIHD3/devices"


const int relay = D0; // 16
const int sensor = D7;
int relayState = HIGH;
void setup() {


  Serial.begin(9600);

  // relay settings
  pinMode(relay, OUTPUT); // set relay as output
  digitalWrite(relay, relayState); // set Relay OFF (It still confusing about High and low in nodeMcu :) )

  // button settings
  pinMode(sensor, INPUT);


  // connect to wifi.
  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
  Serial.print("Connecting to wifi");
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print(".");
    delay(500);
  }
  Serial.println();
  Serial.print("connected: ");
  Serial.println(WiFi.localIP());

  // Connect to the firebase server
  Firebase.begin(FIREBASE_HOST, FIREBASE_AUTH);


}

int lastSensorState = LOW;
bool lastServerState = false;

void loop() {

  // listen sensor
  if (sensorStateIsChange()) {
    // sensor is change
    int currentSensorState = digitalRead(sensor);
    lastSensorState = currentSensorState;
    int state = currentSensorState ? LOW : HIGH;
    digitalWrite(relay, state); // state LOW is on , State HIGH is OFF.

    // now need sync state to server
    serverSetState(currentSensorState ? true : false);
  }

  // listen for server state
  if (serverStateIsChange()) {
    // server state is change
    bool currentServerState = serverStateIsChange();
    int sState = currentServerState ? LOW : HIGH;
    digitalWrite(relay, sState); // state LOW is on , State HIGH is OFF.
  }

}

bool sensorStateIsChange() {
  bool returnValue = false;
  int currentSensorState = digitalRead(sensor);
  if (lastSensorState != currentSensorState) {
    // now we see sensor State change.
    returnValue = true;
  }
  return returnValue;
}

bool serverGetState() {
  return Firebase.getBool(URL "/0/state");
}

void serverSetState(bool state) {
  Firebase.setBool(URL "/0/state", state);
  lastServerState = state;
  delay(200);
}

bool serverStateIsChange() {
  bool returnValue = false;

  bool currentServerState = serverGetState();
  if (currentServerState != lastServerState) {
    returnValue = true;
  }

  return returnValue;
}