/*
 * IoT Health Monitor - WOKWI SIMULATION VERSION
 * MAX30100 is replaced by 2 potentiometers:
 *   POT1 (GPIO 34) = Simulated Heart Rate (BPM)
 *   POT2 (GPIO 35) = Simulated SpO2 (%)
 * DS18B20 = Real temperature simulation (click sensor to change temp)
 * OLED + Buzzer = Fully simulated
 */

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <OneWire.h>
#include <DallasTemperature.h>

// --- OLED Setup ---
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET    -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// --- DS18B20 Setup ---
#define DS18B20_PIN 4
OneWire oneWire(DS18B20_PIN);
DallasTemperature tempSensor(&oneWire);

// --- Potentiometer Pins (simulate BPM & SpO2) ---
#define POT_BPM_PIN  34
#define POT_SPO2_PIN 35

// --- Buzzer ---
#define BUZZER_PIN 15

// --- Thresholds ---
#define MIN_BPM   50
#define MAX_BPM   120
#define MIN_SPO2  90
#define MAX_TEMP  38.5

unsigned long lastUpdate = 0;

void setup() {
  Serial.begin(115200);
  pinMode(BUZZER_PIN, OUTPUT);
  digitalWrite(BUZZER_PIN, LOW);

  Wire.begin(21, 22);

  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println("OLED failed!");
    while (true);
  }

  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);
  display.setCursor(15, 20);
  display.println("Health Monitor");
  display.setCursor(20, 35);
  display.println("Initializing...");
  display.display();
  delay(2000);

  tempSensor.begin();
  Serial.println("System Ready!");
}

void loop() {
  if (millis() - lastUpdate > 1000) {
    lastUpdate = millis();

    // --- Read BPM from Potentiometer 1 (maps 0-4095 → 30-200 BPM) ---
    int rawBPM = analogRead(POT_BPM_PIN);
    float heartRate = map(rawBPM, 0, 4095, 30, 200);

    // --- Read SpO2 from Potentiometer 2 (maps 0-4095 → 80-100 %) ---
    int rawSpO2 = analogRead(POT_SPO2_PIN);
    float spO2 = map(rawSpO2, 0, 4095, 80, 100);

    // --- Read Temperature from DS18B20 ---
    tempSensor.requestTemperatures();
    float tempC = tempSensor.getTempCByIndex(0);

    // --- Print to Serial Monitor ---
    Serial.print("BPM: ");    Serial.print(heartRate);
    Serial.print(" | SpO2: "); Serial.print(spO2);
    Serial.print("% | Temp: "); Serial.print(tempC);
    Serial.println(" C");

    // --- Check Thresholds ---
    bool alert = false;
    String alertMsg = "Status: NORMAL";

    if (heartRate < MIN_BPM || heartRate > MAX_BPM) {
      alert = true;
      alertMsg = "!! Abnormal BPM !!";
    }
    if (spO2 < MIN_SPO2) {
      alert = true;
      alertMsg = "!! Low SpO2 !!";
    }
    if (tempC > MAX_TEMP && tempC < 85) {  // 85 = DS18B20 error value
      alert = true;
      alertMsg = "!! High Temp !!";
    }

    // --- Buzzer Control ---
    digitalWrite(BUZZER_PIN, alert ? HIGH : LOW);

    // --- Update OLED ---
    display.clearDisplay();
    display.setTextSize(1);
    display.setCursor(0, 0);
    display.println("== Health Monitor ==");
    display.drawLine(0, 9, 127, 9, WHITE);

    display.setCursor(0, 13);
    display.print("Heart Rate: ");
    display.print((int)heartRate);
    display.println(" BPM");

    display.setCursor(0, 27);
    display.print("SpO2     : ");
    display.print((int)spO2);
    display.println(" %");

    display.setCursor(0, 41);
    display.print("Temp     : ");
    display.print(tempC, 1);
    display.println(" C");

    display.drawLine(0, 54, 127, 54, WHITE);
    display.setCursor(0, 57);
    if (alert) {
      display.setTextColor(SSD1306_BLACK, SSD1306_WHITE); // inverted = highlight
      display.println(alertMsg);
      display.setTextColor(SSD1306_WHITE);
    } else {
      display.println(alertMsg);
    }
    display.display();
  }
}