#include <Wire.h>                   // Built-in I2C library
#include <Adafruit_GFX.h>           // Core graphics library
#include <Adafruit_SSD1306.h>       // OLED screen library
#include <OneWire.h>                // 1-Wire protocol library
#include <DallasTemperature.h>      // DS18B20 sensor library

// --- Hardware Instantiations ---
#define ONE_WIRE_BUS 4
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature tempSensors(&oneWire);

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

// --- MUX Control Pins ---
#define MUX_SIG  34  // Analog read pin on ESP32
#define MUX_S0   13
#define MUX_S1   12
#define MUX_S2   14
#define MUX_S3   27

// --- Navigation ---
#define BTN_NEXT 18  // Pushbutton to switch views

// --- Data Structures ---
struct Breaker {
  float voltage;      // In Volts
  float current;      // In Amperes
  float temperature;  // In Celsius
  bool isTripped;     // Fault status
};

Breaker breakers[6];
int currentView = 0; // 0 = Summary Table, 1-6 = Individual Breaker Views
unsigned long lastButtonPress = 0;
unsigned long lastTempRequest = 0;

// Function Prototypes
float readMuxChannel(byte channel);
void updateSensors();
void renderUI();

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

  // Initialize I2C bus on GPIO 21 (SDA) and GPIO 22 (SCL)
  Wire.begin(21, 22);

  // Internal Pull-Up for DS18B20 DQ Line on GPIO 4
  pinMode(ONE_WIRE_BUS, INPUT_PULLUP);

  // Initialize MUX control pins
  pinMode(MUX_S0, OUTPUT);
  pinMode(MUX_S1, OUTPUT);
  pinMode(MUX_S2, OUTPUT);
  pinMode(MUX_S3, OUTPUT);
  pinMode(MUX_SIG, INPUT);

  // Initialize Navigation Button
  pinMode(BTN_NEXT, INPUT_PULLUP);

  // Initialize OLED Screen
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    for (;;);
  }

  // Initialize DS18B20 Temperature Sensors on 1-Wire bus
  tempSensors.begin();
  tempSensors.setWaitForConversion(false); // Non-blocking conversion

  // Trigger initial temperature conversion
  tempSensors.requestTemperatures();

  // Splash Screen
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);
  display.setCursor(15, 20);
  display.println(F("SMART SSCB PANEL"));
  display.setCursor(22, 38);
  display.println(F("System Ready"));
  display.display();
  delay(1000);
}

void loop() {
  // 1. Read sensor data across MUX & 1-Wire bus
  updateSensors();

  // 2. Handle button navigation (Debounced)
  if (digitalRead(BTN_NEXT) == LOW && (millis() - lastButtonPress > 250)) {
    lastButtonPress = millis();
    currentView = (currentView + 1) % 7; // Cycles 0 -> 1 -> ... -> 6 -> 0
  }

  // 3. Render User Interface
  renderUI();

  delay(30); // Display refresh rate
}

// Reads standard 16-channel MUX via binary control pins
float readMuxChannel(byte channel) {
  digitalWrite(MUX_S0, bitRead(channel, 0));
  digitalWrite(MUX_S1, bitRead(channel, 1));
  digitalWrite(MUX_S2, bitRead(channel, 2));
  digitalWrite(MUX_S3, bitRead(channel, 3));

  delayMicroseconds(10); // Settling delay for MUX switch
  int rawADC = analogRead(MUX_SIG);
  
  // Convert 12-bit ADC (0-4095) to 0.0V - 3.3V
  return (rawADC / 4095.0) * 3.3;
}

void updateSensors() {
  // 1. Fetch temperature readings every 1000ms
  if (millis() - lastTempRequest >= 1000) {
    lastTempRequest = millis();

    for (int i = 0; i < 6; i++) {
      float tempReading = tempSensors.getTempCByIndex(i);
      if (tempReading != DEVICE_DISCONNECTED_C && tempReading > -50.0) {
        breakers[i].temperature = tempReading;
      } else {
        breakers[i].temperature = 25.0; // Fallback if sensor index 'i' is missing
      }
    }

    // Trigger next conversion cycle
    tempSensors.requestTemperatures();
  }

  // 2. Read MUX channels and process trip logic
  for (int i = 0; i < 6; i++) {
    float rawVoltageSense = readMuxChannel(i * 2);        // Channels 0, 2, 4, 6, 8, 10
    float rawCurrentSense = readMuxChannel((i * 2) + 1);  // Channels 1, 3, 5, 7, 9, 11

    // 48V System Scaling
    breakers[i].voltage = (rawVoltageSense / 3.3) * 60.0; 
    breakers[i].current = (rawCurrentSense / 3.3) * 25.0;

    // Fault Trip Logic (48V nominal system)
    breakers[i].isTripped = (breakers[i].voltage > 56.0 || 
                             breakers[i].current > 15.0 || 
                             breakers[i].temperature > 80.0);
  }
}

// Draws the display screen based on current selection
void renderUI() {
  display.clearDisplay();

  if (currentView == 0) {
    // --- DASHBOARD OVERVIEW TABLE ---
    display.setTextSize(1);
    display.setCursor(0, 0);
    display.println(F("PANEL OVERVIEW   [NEXT>]"));
    display.drawLine(0, 9, 128, 9, SSD1306_WHITE);

    for (int i = 0; i < 6; i++) {
      int y = 13 + (i * 8);
      display.setCursor(0, y);
      display.print(F("B"));
      display.print(i + 1);
      display.print(F(": "));

      if (breakers[i].isTripped) {
        display.print(F("TRIPPED!"));
      } else {
        display.print(breakers[i].voltage, 1);
        display.print(F("V "));
        display.print(breakers[i].current, 1);
        display.print(F("A"));
      }
    }
  } else {
    // --- INDIVIDUAL BREAKER DETAILED VIEW ---
    int bIndex = currentView - 1;
    display.setTextSize(1);
    display.setCursor(0, 0);
    display.print(F("BREAKER #"));
    display.print(currentView);
    display.print(F(" DETAILS"));
    display.drawLine(0, 9, 128, 9, SSD1306_WHITE);

    display.setCursor(0, 14);
    display.print(F("Status:  "));
    if (breakers[bIndex].isTripped) {
      display.println(F("[ TRIPPED ]"));
    } else {
      display.println(F("[ NORMAL OK ]"));
    }

    display.setCursor(0, 24);
    display.print(F("Voltage: "));
    display.print(breakers[bIndex].voltage, 1);
    display.println(F(" V"));

    display.setCursor(0, 34);
    display.print(F("Current: "));
    display.print(breakers[bIndex].current, 1);
    display.println(F(" A"));

    display.setCursor(0, 44);
    display.print(F("Power:   "));
    float power = breakers[bIndex].voltage * breakers[bIndex].current;
    display.print(power, 1);
    display.println(F(" W"));

    display.setCursor(0, 54);
    display.print(F("Temp:    "));
    display.print(breakers[bIndex].temperature, 1);
    display.println(F(" C"));
  }

  display.display();
}