#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <WiFi.h>
#include <PubSubClient.h>
#define LEDPIN 12
#define BUTTONPIN 15
#define DELAYTIME 50
#define BAUDRATE 9600
boolean ledState;
unsigned long timePrevious, timeCurrent;

#define OLED_RESET 4
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

const char* ssid = "Wokwi-GUEST";
const char* pass = "";
const char* broker = "mqtt.eclipseprojects.io";
const char* subs_led_action = "mqtttest/led_action";
const char* pub_led_status = "mqtttest/led_status";
const char* pub_led_action = "mqtttest/led_action";

const int brokerPort = 1883;

long MQTTLastPublishTime;
long MQTTPublishInterval = 10000;

String macAddr;
String ipAddr;

WiFiClient wifiClient;
PubSubClient mqtt(wifiClient);

void WifiSetup(){
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, pass);
  while(WiFi.status() != WL_CONNECTED){
    Serial.print(".");
    display.setTextColor(WHITE);
    display.setTextSize(2);
    display.setCursor(0,0);
    display.println(".");
    display.display();
    display.clearDisplay();
    delay(500);
  }

  ipAddr = WiFi.localIP().toString().c_str();
  macAddr = WiFi.macAddress();

  Serial.print("Connected at: ");
  Serial.println(ipAddr);
  Serial.println(WiFi.localIP());
  Serial.print("MAC: ");
  Serial.println(macAddr);

  display.setTextColor(WHITE);
  display.setTextSize(2);
  display.setCursor(0,0);
  display.println("WIFI Connected.");
  display.display();
  display.clearDisplay();

}
void MqttSetup(){
  mqtt.setServer(broker, brokerPort);
  mqtt.setCallback(Callback);
}

void Reconnect(){
  Serial.println("Connecting to MQTT Broker...");
  while (!mqtt.connected()) {
      Serial.println("Reconnecting to MQTT Broker..");
      String clientId = "ESP32Client-";
      clientId += String(random(0xffff), HEX);
      
      if (mqtt.connect(clientId.c_str())) {
        Serial.print("ID: ");
        Serial.println(clientId);
        Serial.println("Connected.");
        display.setTextColor(WHITE);
        display.setTextSize(2);
        display.setCursor(0,0);
        display.println("MQTT Broker Connected.");
        display.display();
        display.clearDisplay();
        mqtt.subscribe(subs_led_action);
      }      
      else {
        Serial.print("failed, rc=");
        Serial.print(mqtt.state());
        Serial.println(" try again in 5 seconds");
        display.setTextColor(WHITE);
        display.setTextSize(2);
        display.setCursor(0,0);
        display.println("MQTT Broker Connecting fail,  try again in 5 seconds.");
        display.display();
        display.clearDisplay();
        delay(5000);
      }
  }
}

// for mqtt-subscriber
void Callback(char* topic, byte* message, unsigned int length){

  Serial.print("Incoming topic: ");
  Serial.println(topic);
  
  String _messageStr;

  for (int i = 0; i < length; i++) {
    Serial.print((char)message[i]);
    _messageStr += (char)message[i];
  }

  Serial.println();

  if(String(topic) == subs_led_action){
    _messageStr.toLowerCase();
    if( _messageStr == "change"){
      Serial.println("By MQTT:");
      updateLed();
      if(ledState) {
        Serial.println("The light is on!");
        display.setTextColor(WHITE);
        display.setTextSize(2);
        display.setCursor(0,0);
        display.println("The light is turn ON by MQTT.");
        display.display();
        display.clearDisplay();
      }else {
        Serial.println("The light is off");
        display.setTextColor(WHITE);
        display.setTextSize(2);
        display.setCursor(0,0);
        display.println("The light is turn OFF by MQTT.");
        display.display();
        display.clearDisplay();
      }
    }
  }
}


void setup() {
  Serial.begin(BAUDRATE);
  pinMode(LEDPIN, OUTPUT);
  pinMode(BUTTONPIN, INPUT_PULLUP);
  ledState = LOW;
  digitalWrite(LEDPIN, ledState);

  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  display.clearDisplay();
  delay(1000);
  WifiSetup();
  delay(1000);
  MqttSetup();
}

void updateLed() { 
  timeCurrent = millis();
  if((timeCurrent - timePrevious) > DELAYTIME) {
    timePrevious = timeCurrent;
    ledState = !ledState;
    digitalWrite(LEDPIN, ledState);
  }
}

void loop() {
  char* receivedChar = "0";
  if(Serial.available()>0) {
    //receivedChar = Serial.read();
    //Serial.println(receivedChar);
    static char str[34]; // For strings of max length=33
    delay(64);
    memset(str,0,sizeof(str));
    byte count=0;
    while (Serial.available())
    {
      char c=Serial.read();
      if (c>=32 && count<sizeof(str)-1)
      {
        str[count]=c;
        count++;
      }
    }
    receivedChar = str;
  }
  boolean buttonPrevious, buttonCurrent;
  buttonPrevious = digitalRead(BUTTONPIN);
  delay(DELAYTIME);
  buttonCurrent = digitalRead(BUTTONPIN);

  if (buttonCurrent == LOW && buttonCurrent != buttonPrevious) {
    updateLed();
    Serial.println("Change by Pushbutton: ");
    if(ledState) {
      Serial.println("The light is on");
      display.setTextColor(WHITE);
      display.setTextSize(2);
      display.setCursor(0,0);
      display.println("The light is turn ON by Pushbutton.");
      display.display();
      display.clearDisplay();
    }else {
      Serial.println("The light is off");
      display.setTextColor(WHITE);
      display.setTextSize(2);
      display.setCursor(0,0);
      display.println("The light is turn OFF by Pushbutton.");
      display.display();
      display.clearDisplay();
    }
  }

  if( !mqtt.connected()){
    Reconnect();
  }

  if ((millis() - MQTTLastPublishTime) >= MQTTPublishInterval ) {
    if(ledState) {
      mqtt.publish(pub_led_status, String("ON").c_str());
    }else {
      mqtt.publish(pub_led_status, String("OFF").c_str());
    }
    Serial.println("Publish LED Ststus to MQTT Broker");
    MQTTLastPublishTime = millis();
  }
  mqtt.loop();

  if(strcmp(receivedChar,"input") == 0) {
    Serial.println("By Command:");
    updateLed();
    if(ledState) {
      Serial.println("The light is on!");
      display.setTextColor(WHITE);
      display.setTextSize(2);
      display.setCursor(0,0);
      display.println("The light is turn ON by Command.");
      display.display();
      display.clearDisplay();
    }else {
      Serial.println("The light is off");
      display.setTextColor(WHITE);
      display.setTextSize(2);
      display.setCursor(0,0);
      display.println("The light is turn OFF by Command.");
      display.display();
      display.clearDisplay();
    }
  }

}