#ifdef LED_RED
#undef LED_RED  // Prevent conflict with MAX30105 enum
#endif

#include        // Graphics support for OLED
#include    // OLED screen library
#include                // I2C communication
#include "MAX30105.h"           // Sensor library
#include "heartRate.h"          // Heartbeat detection algorithm

// OLED screen setup
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET -1
#define SCREEN_ADDRESS 0x3C     // I2C address for most 0.96" OLEDs

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

// Heart rate variables
MAX30105 particleSensor;
const byte RATE_SIZE = 4;       // Number of readings to average
byte rates[RATE_SIZE];          // Store recent BPM values
byte rateSpot = 0;
long lastBeat = 0;              // Time of the last detected beat
float beatsPerMinute;
int beatAvg = 0;                // Averaged BPM

// Heart icon (small)
static const unsigned char PROGMEM beat1_bmp[] = {
  // 24x21 bitmap data
  0x03, 0xC0, 0xF0, 0x06, 0x71, 0x8C, 0x0C, 0x1B, 0x06, 0x18, 0x0E, 0x02, 0x10, 0x0C, 0x03, 0x10,
  0x04, 0x01, 0x10, 0x04, 0x01, 0x10, 0x40, 0x01, 0x10, 0x40, 0x01, 0x10, 0xC0, 0x03, 0x08, 0x88,
  0x02, 0x08, 0xB8, 0x04, 0xFF, 0x37, 0x08, 0x01, 0x30, 0x18, 0x01, 0x90, 0x30, 0x00, 0xC0, 0x60,
  0x00, 0x60, 0xC0, 0x00, 0x31, 0x80, 0x00, 0x1B, 0x00, 0x00, 0x0E, 0x00, 0x00, 0x04, 0x00
};

// Heart icon (large)
static const unsigned char PROGMEM beat2_bmp[] = {
  // 32x32 bitmap data
  0x01, 0xF0, 0x0F, 0x80, 0x06, 0x1C, 0x38, 0x60, 0x18, 0x06, 0x60, 0x18, 0x10, 0x01, 0x80, 0x08,
  0x20, 0x01, 0x80, 0x04, 0x40, 0x00, 0x00, 0x02, 0x40, 0x00, 0x00, 0x02, 0xC0, 0x00, 0x08, 0x03,
  0x80, 0x00, 0x08, 0x01, 0x80, 0x00, 0x18, 0x01, 0x80, 0x00, 0x1C, 0x01, 0x80, 0x00, 0x14, 0x00,
  0x80, 0x00, 0x14, 0x00, 0x80, 0x00, 0x14, 0x00, 0x40, 0x10, 0x12, 0x00, 0x40, 0x10, 0x12, 0x00,
  0x7E, 0x1F, 0x23, 0xFE, 0x03, 0x31, 0xA0, 0x04, 0x01, 0xA0, 0xA0, 0x0C, 0x00, 0xA0, 0xA0, 0x08,
  0x00, 0x60, 0xE0, 0x10, 0x00, 0x20, 0x60, 0x20, 0x06, 0x00, 0x40, 0x60, 0x03, 0x00, 0x40, 0xC0,
  0x01, 0x80, 0x01, 0x80, 0x00, 0xC0, 0x03, 0x00, 0x00, 0x60, 0x06, 0x00, 0x00, 0x30, 0x0C, 0x00,
  0x00, 0x08, 0x10, 0x00, 0x00, 0x06, 0x60, 0x00, 0x00, 0x03, 0xC0, 0x00, 0x00, 0x01, 0x80, 0x00
};

void setup() {
  Wire.setClock(400000);            // Use fast I2C speed (400kHz)
  Serial.begin(9600);               // Serial monitor for debugging

  // Start OLED display
  if (!display.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS)) {
    Serial.println("OLED not found");
    while (true);                   // Stop if display is not found
  }
  display.display();

  // Start MAX30102 sensor
  if (!particleSensor.begin(Wire, I2C_SPEED_FAST)) {
    Serial.println("MAX30102 not found");
    while (true);                   // Stop if sensor is not found
  }

  // Sensor configuration
  particleSensor.setup();                 // Use default settings
  particleSensor.setPulseAmplitudeRed(0x0A);  // Low red LED pulse
  particleSensor.setPulseAmplitudeGreen(0);   // Disable green LED

  Serial.println("Place your finger on the sensor.");
}

void loop() {
  long irValue = particleSensor.getIR();  // Get infrared value

  // Check if finger is detected
  if (irValue > 50000) {
    // Detect heartbeat
    if (checkForBeat(irValue)) {
      // Display small heart and current average BPM
      display.clearDisplay();
      display.drawBitmap(23, 15, beat1_bmp, 24, 21, WHITE);
      display.setTextSize(2);
      display.setTextColor(WHITE);
      display.setCursor(60, 10);
      display.println("BPM");
      display.setCursor(60, 28);
      display.println(beatAvg);
      display.display();

      // Calculate BPM based on time between beats
      long delta = millis() - lastBeat;
      lastBeat = millis();
      beatsPerMinute = 60 / (delta / 1000.0);

      // Keep only valid readings
      if (beatsPerMinute < 255 && beatsPerMinute > 20) {
        rates[rateSpot++] = (byte)beatsPerMinute;
        rateSpot %= RATE_SIZE;

        // Average the last few readings
        beatAvg = 0;
        for (byte x = 0; x < RATE_SIZE; x++) {
          beatAvg += rates[x];
        }
        beatAvg /= RATE_SIZE;

        delay(100);  // Small delay before drawing again

        // Display large heart and updated BPM
        display.clearDisplay();
        display.drawBitmap(18, 10, beat2_bmp, 32, 32, WHITE);
        display.setTextSize(2);
        display.setTextColor(WHITE);
        display.setCursor(60, 10);
        display.println("BPM");
        display.setCursor(60, 28);
        display.println(beatAvg);
        display.display();
      }

      // Print info to Serial Monitor
      Serial.print("IR=");
      Serial.print(irValue);
      Serial.print(", BPM=");
      Serial.print(beatsPerMinute);
      Serial.print(", Avg BPM=");
      Serial.println(beatAvg);
    }
  } else {
    // Finger not detected - show message
    Serial.println("Place your finger on the sensor");

    display.clearDisplay();
    display.setTextSize(1);
    display.setTextColor(WHITE);
    display.setCursor(30, 5);
    display.println("Please place ");
    display.setCursor(30, 15);
    display.println("your finger ");
    display.setCursor(30, 25);
    display.println("and wait... ");
    display.display();
  }
}