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

// --- Pin Definitions ---
#define DS18B20_SUPPLY_PIN  4    // DS18B20 #1 (подавальний) - data pin
#define DS18B20_RETURN_PIN  15   // DS18B20 #2 (зворотний)  - data pin
#define OLED_SDA            21
#define OLED_SCL            22

// --- Constants ---
#define SCREEN_WIDTH        128
#define SCREEN_HEIGHT       64
#define OLED_RESET          -1
#define OLED_ADDR           0x3C

// Heat meter simulation constants
const float FLOW_RATE     = 0.5;    // м³/год (витрата теплоносія)
const float SPECIFIC_HEAT = 4186.0; // Дж/(кг·°C) (теплоємність води)
const float WATER_DENSITY = 1000.0; // кг/м³

// --- Objects ---
OneWire oneWireSupply(DS18B20_SUPPLY_PIN);
OneWire oneWireReturn(DS18B20_RETURN_PIN);
DallasTemperature sensorSupply(&oneWireSupply);
DallasTemperature sensorReturn(&oneWireReturn);
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// --- Variables ---
float totalEnergy = 0.0;        // Накопичена теплова енергія (кВт·год)
unsigned long lastMeasure = 0;   // Час останнього вимірювання
unsigned long measureCount = 0;  // Лічильник вимірювань

void setup() {
  Serial.begin(115200);
  Serial.println("====================================");
  Serial.println(" IoT Heat Meter - Simulation");
  Serial.println(" Kompiuternyi Praktykum #1");
  Serial.println("====================================");

  // Init I2C for OLED
  Wire.begin(OLED_SDA, OLED_SCL);

  // Init OLED
  if (!display.begin(SSD1306_SWITCHCAPVCC, OLED_ADDR)) {
    Serial.println("ERROR: SSD1306 OLED not found!");
    while (true) { delay(100); }
  }

  // Splash screen
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);
  display.setCursor(10, 5);
  display.println("IoT Heat Meter");
  display.setCursor(10, 20);
  display.println("Praktykum #1");
  display.setCursor(10, 40);
  display.println("Initializing...");
  display.display();

  // Init DS18B20 sensors
  sensorSupply.begin();
  sensorReturn.begin();

  Serial.print("Supply sensor count: ");
  Serial.println(sensorSupply.getDeviceCount());
  Serial.print("Return sensor count: ");
  Serial.println(sensorReturn.getDeviceCount());

  delay(2000);
  lastMeasure = millis();
}

void loop() {
  // Request temperatures from both sensors
  sensorSupply.requestTemperatures();
  sensorReturn.requestTemperatures();

  float tSupply = sensorSupply.getTempCByIndex(0);
  float tReturn = sensorReturn.getTempCByIndex(0);

  bool supplyOk = (tSupply != DEVICE_DISCONNECTED_C);
  bool returnOk = (tReturn != DEVICE_DISCONNECTED_C);

  // Calculate heat energy
  unsigned long now = millis();
  float dtSeconds = (now - lastMeasure) / 1000.0;
  lastMeasure = now;
  measureCount++;

  float deltaT = 0;
  float powerW = 0;

  if (supplyOk && returnOk) {
    deltaT = tSupply - tReturn;

    // P = G [м³/год] * ρ [кг/м³] * c [Дж/(кг·°C)] * ΔT [°C] / 3600
    // Result in Watts
    powerW = FLOW_RATE * WATER_DENSITY * SPECIFIC_HEAT * deltaT / 3600.0;
    if (powerW < 0) powerW = 0; // No negative heat

    // Accumulate energy: E += P * dt (convert to kWh)
    float energyIncrement = powerW * dtSeconds / 3600000.0; // W·s → kWh
    totalEnergy += energyIncrement;
  }

  // --- Display on OLED ---
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);

  // Header
  display.setCursor(0, 0);
  display.print("== HEAT METER ==");

  // Supply temperature
  display.setCursor(0, 12);
  display.print("T1(sup): ");
  if (supplyOk) {
    display.print(tSupply, 1);
    display.print(" C");
  } else {
    display.print("ERR!");
  }

  // Return temperature
  display.setCursor(0, 22);
  display.print("T2(ret): ");
  if (returnOk) {
    display.print(tReturn, 1);
    display.print(" C");
  } else {
    display.print("ERR!");
  }

  // Delta T
  display.setCursor(0, 32);
  display.print("dT: ");
  if (supplyOk && returnOk) {
    display.print(deltaT, 1);
    display.print(" C");
  } else {
    display.print("---");
  }

  // Thermal power
  display.setCursor(0, 42);
  display.print("Power: ");
  display.print(powerW, 1);
  display.print(" W");

  // Accumulated energy
  display.setCursor(0, 52);
  display.print("Energy: ");
  if (totalEnergy < 1.0) {
    display.print(totalEnergy * 1000, 1);
    display.print(" Wh");
  } else {
    display.print(totalEnergy, 3);
    display.print(" kWh");
  }

  display.display();

  // --- Serial output ---
  Serial.println("-----------------------------");
  Serial.print("Measurement #");
  Serial.println(measureCount);
  Serial.print("T1 (supply):  ");
  Serial.print(supplyOk ? String(tSupply, 2) + " C" : "ERROR");
  Serial.println();
  Serial.print("T2 (return):  ");
  Serial.print(returnOk ? String(tReturn, 2) + " C" : "ERROR");
  Serial.println();
  Serial.print("Delta T:      ");
  Serial.print(deltaT, 2);
  Serial.println(" C");
  Serial.print("Flow rate:    ");
  Serial.print(FLOW_RATE, 2);
  Serial.println(" m3/h");
  Serial.print("Thermal pwr:  ");
  Serial.print(powerW, 1);
  Serial.println(" W");
  Serial.print("Total energy: ");
  Serial.print(totalEnergy * 1000, 2);
  Serial.print(" Wh (");
  Serial.print(totalEnergy, 4);
  Serial.println(" kWh)");

  delay(2000);
}