IOT Push Button (Like Amazon Dash)

#define DEVICE_ID         "YOUR_USERNAME"
#define DEVICE_NAME       "iot-" DEVICE_ID
#define WIFI_SSID         "mad-" DEVICE_ID
#define WIFI_PASSWORD     DEVICE_ID
#define MQTT_SERVER       "YOUR_SERVER"
#define MQTT_USERNAME     DEVICE_ID
#define MQTT_PASSWORD     "YOUR_PASSWORD"
#define MQTT_SEND_CHANNEL "pushbutton"
#define MQTT_RECV_CHANNEL DEVICE_NAME




#define BUTTON_MODE 1
#define USE_SSL 1
#define GPIO2 2
#define BUTTON_TIMEOUT 30000


#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <ESP8266WebServer.h>
#include <ESP8266mDNS.h>
#include <PubSubClient.h>
#include <DNSServer.h>
#include <WiFiManager.h>
#include <ArduinoJson.h>
#include <stdarg.h>


#if USE_SSL
#   include <WiFiClientSecure.h>
//    WiFiClientSecure client;
#   define PORT 443
#else
// WiFiClient client;
#   define PORT 80
#endif


void reconnect();
void sendMessage(String action, String data, char* num = "", ...);
char* stringToChar(String str);

WiFiClient espClient;
PubSubClient client(espClient);
WiFiManager wifiManager;


long lastMsg = 0;
char msg[50];
int value = 0;
String DEVICE_FEATURES = "";

void setup() {

  DEVICE_FEATURES += "pushbutton;";
  pinMode(GPIO2, OUTPUT);
  digitalWrite(GPIO2, HIGH);


  //Serial.begin(9600);

  //  wifiManager.resetSettings();
  if (!wifiManager.autoConnect(WIFI_SSID, WIFI_PASSWORD)) {
    //Serial.println("failed to connect, we should reset as see if it connects");
    delay(1000);
    ESP.reset();
    delay(1000);
  }
  client.setServer(MQTT_SERVER, 1883);

}
void loop() {

  //if button mode, & time since start is greater than TIMEOUT close the time.
  if (millis() > BUTTON_TIMEOUT)
    digitalWrite(GPIO2, LOW);
  //if MQTT Client not connect connect it back.
  if (!client.connected())
    reconnect();
  client.loop();

}



/**
   Send message to server
   example: sendMessage("hello", DEVICE_NAME,"ksks","mac",getMacAddress(),"localIP",WiFi.localIP().toString());
   k for key
   d : double, f : float, s : string, l : long,
   No char type
*/
void sendMessage(String action, String data, char *types, ...) {
  StaticJsonBuffer<200> jsonBuffer;
  JsonObject& root = jsonBuffer.createObject();
  root["action"] = action;
  root["data"] = data;

  //find length
  int count = 0;
  while (types[count++] != '\0');
  --count;

  //if not even args
  if (count % 2 != 0)
    return;

  //for argument parsing.
  va_list arguments;
  va_start ( arguments, types );

  String key;

  //even length validated already
  for (int i = 0; types[i] != '\0'; i += 2) {
    //this is intentionally done, default key as type k can be used, but developer might mistake, causing lot of debugging
    if (types[i] != 'k')
      continue;
    key =  va_arg ( arguments, char *  );

    switch (types[i + 1])
    {
      case 'd': root[key] = (va_arg(arguments, int));
        break;
      case 'l': root[key] = (va_arg(arguments, long));
        break;
      case 'f': root[key] = (va_arg(arguments, double));
        break;
      case 's': root[key] = (va_arg(arguments, char *));
        break;
      default:  ;
    };
  }

  va_end ( arguments );                  // Cleans up the list

  char tmp[root.measureLength() + 2];
  root.printTo(tmp, sizeof(tmp));
  client.publish(MQTT_SEND_CHANNEL, tmp);
}



void reconnect() {
  // Loop until we're reconnected
  while (!client.connected()) {
    //Serial.print("Attempting MQTT connection...");
    // Attempt to connect
    if (client.connect(DEVICE_NAME, MQTT_USERNAME, MQTT_PASSWORD)) {
      //Serial.println("connected");
      // Once connected, publish an announcement...
      sendMessage("hello", DEVICE_NAME, "ksks", "features", (DEVICE_FEATURES).c_str() , "localIP", (WiFi.localIP().toString().c_str()));
      digitalWrite(GPIO2, LOW);
    } else {
      //Serial.print("failed, rc=");
      //Serial.print(client.state());
      //Serial.println(" try again in 5 seconds");
      // Wait 5 seconds before retrying
      delay(2000);
    }
  }
}