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

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

// Common I2C addresses: 0x3C or 0x3D ???
#define OLED_ADDR 0x3C

// -------------------- DHT22 --------------------
#define DHTPIN   16
#define DHTTYPE  DHT22
DHT dht(DHTPIN, DHTTYPE);

// -------------------- NTC ADC pins (ADC1) --------------------
#define NTC1_PIN 34
#define NTC2_PIN 35

// -------------------- NTC / divider constants --------------------
// If you don't know your exact thermistor spec, these are common defaults for "10k NTC 3950"
const float R_FIXED = 10000.0;   // fixed resistor value in ohms (10k)
const float R0      = 10000.0;   // thermistor resistance at T0_K (10k at 25C)
const float T0_K      = 25.0 + 273.15; // 25C in Kelvin
const float BETA    = 3950.0;    // beta value

// -------------------- ADC settings --------------------
const int   ADC_MAX = 4095;  // 12-bit ADC on ESP32
const float VCC     = 3.3;   // reference / supply

int readAdcAvg(int pin, int samples = 10) {
  long sum = 0;
  for (int i = 0; i < samples; i++) {
    sum += analogRead(pin);
    delay(2);
  }
  return (int)(sum / samples);
}

float readNTC_C(int pin) {
  int raw = readAdcAvg(pin, 12);

  raw = constrain(raw, 1, ADC_MAX - 1);

  float v = (raw * VCC) / ADC_MAX;

  // Guard against divide-by-near-zero (wiring fault / saturation)
  if (v <= 0.001) return NAN;
  if (v >= (VCC - 0.001)) return NAN;

  float r_ntc = (R_FIXED * v) / (VCC - v);

  float invT = (1.0 / T0_K) + (1.0 / BETA) * log(r_ntc / R0);
  float tempK = 1.0 / invT;
  return tempK - 273.15;
}



void oledPrintLine(int y, const String &s) {
  display.setCursor(0, y);
  display.print(s);
}

void setup() {
  Serial.begin(115200);

  // I2C on requested pins
  Wire.begin(21, 22);

  // OLED init
  if (!display.begin(SSD1306_SWITCHCAPVCC, OLED_ADDR)) {
    Serial.println("OLED init failed (check address 0x3C/0x3D and wiring).");
    while (true) delay(100);
  }
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);

  // DHT init
  dht.begin();

  // ADC setup
  analogReadResolution(12);               // 0..4095
  analogSetAttenuation(ADC_11db);         // good range up to ~3.3V (practical)

  display.clearDisplay();
  oledPrintLine(0, "ESP32 Temp Monitor");
  oledPrintLine(16, "Starting sensors...");
  display.display();

  delay(1500);
}

void loop() {
  // --- Read DHT22 ---
  float dhtT = dht.readTemperature(); // C
  float dhtH = dht.readHumidity();

  // --- Read NTCs ---
  float ntc1C = readNTC_C(NTC1_PIN);
  float ntc2C = readNTC_C(NTC2_PIN);
  oledPrintLine(30, isnan(ntc1C) ? "NTC1 : read fail" : "NTC1 : " + String(ntc1C, 1) + "C");
  oledPrintLine(44, isnan(ntc2C) ? "NTC2 : read fail" : "NTC2 : " + String(ntc2C, 1) + "C");

  // Handle DHT read failures (common if wiring/pullup is off)
  bool dhtOk = !(isnan(dhtT) || isnan(dhtH));

  // --- OLED ---
  display.clearDisplay();
  oledPrintLine(0, "Temps (C)");
  display.drawLine(0, 10, 127, 10, SSD1306_WHITE);

  if (dhtOk) {
    oledPrintLine(14, "DHT22: " + String(dhtT, 1) + "C  " + String(dhtH, 0) + "%");
  } else {
    oledPrintLine(14, "DHT22: read fail");
  }

  //oledPrintLine(30, "NTC1 : " + String(ntc1C, 1) + "C");
  //oledPrintLine(44, "NTC2 : " + String(ntc2C, 1) + "C");

// Bottom row Y position
int y = 54;   // Adjust if your font is taller

// Left temperature
oledPrintXY(0, y, "NTC1: " + String(ntc1C, 1) + "C");

// Right temperature (roughly half the screen)
oledPrintXY(64, y, "NTC2: " + String(ntc2C, 1) + "C");

  display.display();

  // --- Serial debug ---
  Serial.print("DHT22: ");
  if (dhtOk) {
    Serial.print(dhtT); Serial.print("C, ");
    Serial.print(dhtH); Serial.print("%");
  } else {
    Serial.print("FAIL");
  }
  Serial.print(" | NTC1: "); Serial.print(ntc1C);
  Serial.print("C | NTC2: "); Serial.print(ntc2C);
  Serial.println("C");

  delay(1000);
}