// From https://randomnerdtutorials.com/esp32-mqtt-publish-subscribe-arduino-ide
// https://randomnerdtutorials.com/esp32-adc-analog-read-arduino-ide
// Compatible with https://github.com/pixavier/mqtt4snap request/response and request reporter blocks

#include <WiFi.h>
#include "PubSubClient.h"

const char* ssid = "Wokwi-GUEST";
const char* password = "";
const char* mqttServer = "broker.emqx.io";
int port = 1883;
String stMac;
char mac[50];
char clientId[50];

WiFiClient espClient;
PubSubClient client(espClient);

const int ldrPin = 35;

void setup() {
  Serial.begin(115200);
  randomSeed(analogRead(0));

  delay(10);
  Serial.println();
  Serial.print("Connecting to ");
  Serial.println(ssid);

  wifiConnect();

  Serial.println("");
  Serial.println("WiFi connected");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
  Serial.println(WiFi.macAddress());
  stMac = WiFi.macAddress();
  stMac.replace(":", "_");
  Serial.println(stMac);
  
  client.setServer(mqttServer, port);
  client.setCallback(callback);
  client.setKeepAlive(10);
  pinMode(ldrPin, INPUT);
}

void wifiConnect() {
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
}

void mqttReconnect() {
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    long r = random(1000);
    sprintf(clientId, "clientId-%ld", r);
    if (client.connect(clientId)) {
      Serial.print(clientId);
      Serial.println(" connected");
      client.subscribe("name/ldr/#");
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      delay(5000);
    }
  }
}

void callback(char* topic, byte* payload, unsigned int length) {
  char topicBuf[50];
  char payloadBuf[20];

  String strTopic = String(topic);  // topic example: topicName/ldr/lux/idCall-1032.3
  Serial.print("topic: ");
  Serial.println(strTopic);
  int lastPos = strTopic.lastIndexOf("@");  // callbackTopic (cback): Last subtopic
  if (lastPos > 0) {
    String topic = strTopic.substring(0, lastPos - 1);   // cback example:  idCall-1032.3
    String cback = strTopic.substring(lastPos + 1);   // cback example:  idCall-1032.3
    Serial.print("cack: ");
    Serial.println(cback);
    int len = cback.length() + 1; 
    cback.toCharArray(topicBuf, len);

    if (topic.equals("name/ldr/get/lux")) {
      int lux = analogRead(ldrPin);
      sprintf(payloadBuf, "%d", lux);
      Serial.println(payloadBuf);
      client.publish(topicBuf, payloadBuf, len);
    }
  }
}

void loop() {
  delay(10);
  if (!client.connected()) {
    mqttReconnect();
  }
  client.loop();
}