#include <WiFi.h>

#include <PubSubClient.h>

#include <Adafruit_GFX.h>

#include <Adafruit_SSD1306.h>

#include <ESP32_SoftWire.h>



#define SCREEN_WIDTH 128

#define SCREEN_HEIGHT 64

#define OLED_RESET    -1

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);



const int ecgPin = 34; // Pin connected to the potentiometer simulating AD8232

const int potPin = 35; // Pin connected to the potentiometer for heart rate adjustment

const char* mqtt_server = "broker.hivemq.com";

const char* mqtt_topic = "ecg/warning";



WiFiClient espClient;

PubSubClient client(espClient);



int16_t displayBuffer[SCREEN_WIDTH];

uint8_t bufferIndex = 0;



// ECG Parameters

const int SAMPLE_RATE = 200;  // Higher sampling rate for better resolution

float heartRate = 60.0;       // Initial heart rate

float phase = 0.0;            // Phase of the ECG signal

const float PI_VAL = 3.14159;



// Time management

unsigned long lastUpdate = 0;

const int REFRESH_RATE = 5;  // Reduced refresh rate for smoother signal



void setup() {

  Serial.begin(115200);

  pinMode(ecgPin, INPUT);

  pinMode(potPin, INPUT);

  Wire.begin();



  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {

    Serial.println(F("SSD1306 allocation failed"));

    for(;;);

  }

  display.display();

  delay(2000);

  display.clearDisplay();



  // Connect to WiFi

  Serial.print("Connecting to WiFi");

  WiFi.begin("Wokwi-GUEST", "", 6); // Use Wokwi-GUEST for Wokwi simulator

  while (WiFi.status() != WL_CONNECTED) {

    delay(100);

    Serial.print(".");

  }

  Serial.println(" Connected!");



  // Connect to MQTT

  client.setServer(mqtt_server, 1883);

  while (!client.connected()) {

    Serial.println("Connecting to MQTT...");

    if (client.connect("ESP32Client")) {

      Serial.println("Connected to MQTT");

    } else {

      Serial.print("Failed with state ");

      Serial.print(client.state());

      delay(2000);

    }

  }



  // Initialize buffer with baseline

  for(int i = 0; i < SCREEN_WIDTH; i++) {

    displayBuffer[i] = SCREEN_HEIGHT / 2;

  }

}



float generateECGSample(float t) {

    float sample = 0;

    

    // P wave

    if(t >= 0.0 && t < 0.1) {

        sample += 0.15 * exp(-pow((t-0.05)/0.015, 2));  // Sharper P wave

    }



    // QRS Complex

    if(t >= 0.12 && t < 0.20) {

        sample -= 0.15 * exp(-pow((t-0.125)/0.005, 2)); // Q

        sample += 1.0 * exp(-pow((t-0.15)/0.01, 2));    // R

        sample -= 0.35 * exp(-pow((t-0.18)/0.005, 2));  // S

    }

    

    // T wave

    if(t >= 0.35 && t < 0.50) {

        sample += 0.25 * exp(-pow((t-0.43)/0.03, 2));  // T wave amplitude tweaked

    }



    // Baseline drift (to simulate some irregularities)

    sample += 0.02 * sin(2 * PI_VAL * t * 0.5); // Slow sinusoidal drift

    

    return sample;

}



void updateDisplay() {

    display.clearDisplay();

    

    // Show Heart Rate

    display.setCursor(0, 0);

    display.print("HR: ");

    display.print((int)heartRate);

    display.print(" BPM");

    

    // Draw ECG Wave

    for(int i = 0; i < SCREEN_WIDTH - 1; i++) {

        int x1 = i;

        int x2 = i + 1;

        int y1 = displayBuffer[i];

        int y2 = displayBuffer[i + 1];

        

        display.drawLine(x1, y1, x2, y2, SSD1306_WHITE);

    }

    

    display.display();

}



void loop() {

    unsigned long currentTime = millis();

    

    // Update heart rate from potentiometer

    int potValue = analogRead(potPin);

    heartRate = map(potValue, 0, 4095, 50, 150);  // Adjusted heart rate range for more realistic values

    

    if(currentTime - lastUpdate >= REFRESH_RATE) {

        lastUpdate = currentTime;

        

        // Calculate new phase based on heart rate

        float phaseIncrement = (heartRate / 30.0) / SAMPLE_RATE;  // Artificially speed up by factor of 2

        phase += phaseIncrement;

        if(phase >= 1.0) phase = 0;

        

        // Shift buffer left

        for(int i = 0; i < SCREEN_WIDTH - 1; i++) {

            displayBuffer[i] = displayBuffer[i + 1];

        }

        

        // Generate new sample

        float newSample = generateECGSample(phase);

        // Scale and offset for display

        displayBuffer[SCREEN_WIDTH - 1] = (SCREEN_HEIGHT / 2) - (newSample * SCREEN_HEIGHT / 3);

        

        // Update display

        updateDisplay();

    }



    Serial.print("ECG Value: ");

    Serial.println(displayBuffer[SCREEN_WIDTH - 1]);

    Serial.print("Heart Rate: ");

    Serial.println(heartRate);



    // Send warning message if heart rate is in dangerous zone

    if (heartRate < 60 || heartRate > 100) {

        String payload = "Warning: Heart rate out of safe range! Current HR: " + String(heartRate);

        client.publish(mqtt_topic, payload.c_str());

    }



    client.loop();

    delay(100);

}