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

// ---- OLED ----
#define OLED_WIDTH  128
#define OLED_HEIGHT  64
#define OLED_ADDR  0x3C
Adafruit_SSD1306 display(OLED_WIDTH, OLED_HEIGHT, &Wire, -1);

// ---- Pins ----
#define PIN_SPO2_ADC   34
#define PIN_TEMP_ADC   35
#define PIN_BP_ADC     32
#define PIN_LED_STATUS  2
#define PIN_LED_HR      4
#define PIN_BTN_MEASURE 25
#define PIN_BTN_RESET   26

// ---- Simulated vital sign values ----
float spo2    = 0;
float tempC   = 0;
int   sysBP   = 0;
int   diasBP  = 0;
int   heartRate = 0;

unsigned long lastBlink = 0;
unsigned long lastHRBeat = 0;
bool statusLed = false;

// ---- Read ADC and map to physiological range ----
float readSpO2() {
  int raw = analogRead(PIN_SPO2_ADC);
  return map(raw, 0, 4095, 880, 1000) / 10.0;  // 88.0 – 100.0 %
}

float readTemp() {
  int raw = analogRead(PIN_TEMP_ADC);
  return map(raw, 0, 4095, 350, 420) / 10.0;   // 35.0 – 42.0 °C
}

int readSysBP() {
  int raw = analogRead(PIN_BP_ADC);
  return map(raw, 0, 4095, 60, 180);            // 60 – 180 mmHg
}

int estimateDiasBP(int sys) {
  return (int)(sys * 0.63);                     // rough 2/3 ratio
}

int estimateHR(float spo2val) {
  // Simulate HR loosely correlated to SpO2 (low SpO2 -> slightly raised HR)
  return (int)(70 + (100.0 - spo2val) * 2.5);
}

void drawDisplay() {
  display.clearDisplay();

  // Header
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 0);
  display.print("VITAL SIGNS MONITOR");
  display.drawLine(0, 9, 127, 9, SSD1306_WHITE);

  // SpO2
  display.setCursor(0, 13);
  display.print("SpO2 : ");
  display.setTextSize(1);
  display.print(spo2, 1);
  display.print(" %");

  // Heart Rate
  display.setCursor(0, 24);
  display.print("HR   : ");
  display.print(heartRate);
  display.print(" bpm");

  // Temperature
  display.setCursor(0, 35);
  display.print("Temp : ");
  display.print(tempC, 1);
  display.print(" C");

  // Blood Pressure
  display.setCursor(0, 46);
  display.print("BP   : ");
  display.print(sysBP);
  display.print("/");
  display.print(diasBP);
  display.print(" mmHg");

  // Status bar
  display.drawLine(0, 56, 127, 56, SSD1306_WHITE);
  display.setCursor(0, 58);
  bool measuring = (digitalRead(PIN_BTN_MEASURE) == LOW);
  display.print(measuring ? ">> MEASURING... <<" : "  Press to measure");

  display.display();
}

void setup() {
  Serial.begin(115200);
  Serial.println("Vital Signs Monitor — Wokwi Simulation");

  pinMode(PIN_LED_STATUS,  OUTPUT);
  pinMode(PIN_LED_HR,      OUTPUT);
  pinMode(PIN_BTN_MEASURE, INPUT_PULLUP);
  pinMode(PIN_BTN_RESET,   INPUT_PULLUP);

  analogReadResolution(12);

  Wire.begin(21, 22);

  if (!display.begin(SSD1306_SWITCHCAPVCC, OLED_ADDR)) {
    Serial.println("SSD1306 not found — check wiring");
    while (true) { delay(100); }
  }
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);

  // Splash
  display.setTextSize(1);
  display.setCursor(10, 10);
  display.println("VITAL SIGNS MONITOR");
  display.setCursor(20, 28);
  display.println("Kyambogo University");
  display.setCursor(30, 42);
  display.println("Initialising...");
  display.display();
  delay(1500);
}

void loop() {
  unsigned long now = millis();

  // Read sensors (potentiometers in simulation)
  spo2      = readSpO2();
  tempC     = readTemp();
  sysBP     = readSysBP();
  diasBP    = estimateDiasBP(sysBP);
  heartRate = estimateHR(spo2);

  // Status LED blink (1 Hz)
  if (now - lastBlink >= 500) {
    statusLed = !statusLed;
    digitalWrite(PIN_LED_STATUS, statusLed);
    lastBlink = now;
  }

  // HR beat LED — flash at heartRate bpm
  long hrInterval = 60000L / heartRate;
  if (now - lastHRBeat >= (unsigned long)hrInterval) {
    digitalWrite(PIN_LED_HR, HIGH);
    delay(50);
    digitalWrite(PIN_LED_HR, LOW);
    lastHRBeat = now;
  }

  drawDisplay();

  // Serial output for plotter / monitor
  Serial.print("SpO2:");    Serial.print(spo2);
  Serial.print(",Temp:");   Serial.print(tempC);
  Serial.print(",SysBP:");  Serial.print(sysBP);
  Serial.print(",DiasBP:"); Serial.print(diasBP);
  Serial.print(",HR:");     Serial.println(heartRate);

  delay(200);
}