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

const char *mqtt_server =
    "bme.vsb.cz"; // Replace with your MQTT broker IP address or hostname
const int mqtt_port =
    1883; // Replace with your MQTT broker port (default: 1883)
const char *mqtt_topic =
    "test/json-data" ; // Replace with the MQTT topic to

// Analog-digital conversion constants
const int ecgPin = 35;
const int tempPin = 34;
const float vref = 3.3; // adc voltage range

// Time reference constants
const int measurementPeriod = 50;
int timeOfLastMeasurement = 0;

// Measurements buffer
const int ecgBufferLength = 20;
int ecgBufferIndex = 0;
float ecgBuffer[ecgBufferLength];

// WIfi and MQTT libs
WiFiClient espClient;
PubSubClient mqtt_client(espClient);

void setup() {
  Serial.begin(115200);
  pinMode(ecgPin, INPUT);
  pinMode(tempPin,INPUT);

  // Connect to WiFi network
  WiFi.begin("Wokwi-GUEST", "", 6);
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to WiFi...");
  }

  Serial.println("Connected to WiFi");

  // Connect to MQTT broker
  mqtt_client.setServer(mqtt_server, mqtt_port);

  while (!mqtt_client.connected()) {
    if (mqtt_client.connect("ESP32")) {
      Serial.println("Connected to MQTT broker");
    } else {
      delay(1000);
    }
  }
}

void loop() {

  int currentTime = millis();
  if(currentTime - timeOfLastMeasurement < measurementPeriod) {
    delay(1);
    return;
  }

  // Read the analog input and calculate the voltage
  int adc_value = analogRead(ecgPin);
  float voltage = adc_value * (vref / 4096);
  ecgBuffer[ecgBufferIndex++] = voltage;

  if(ecgBufferIndex >= ecgBufferLength) {

    // Get value from the temp adc pin
    int rawTemp = analogRead(tempPin);

    // Reset the buffer index
    ecgBufferIndex = 0;

    // Create general document
    DynamicJsonDocument jsonToSend(2048);

    // Fill in the values
    jsonToSend["measurement period"] = measurementPeriod;
    jsonToSend["temperature"] = rawTemp;
    for (int i = 0; i < ecgBufferLength; i++) {
      jsonToSend["ecg"][i] = ecgBuffer[i];
    }

    // Serialize created structure into a String type
    String json = "";
    serializeJson(jsonToSend, json);

    // Publish the voltage to the MQTT topic
    mqtt_client.publish(mqtt_topic, json.c_str());
    delay(2000);
  }
}