#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);  // set the LCD address to 0x27 for a 16x2 display

int i = 0;
unsigned long previousMillis = 0;  // will store last time
unsigned long backlightMillis = 0;  // stores time of last backlight change
bool backlightState = true;  // stores the current state of the backlight (on or off)

const long interval = 3000;  // interval at which to change the info on LCD (milliseconds)
const long backlightOffDelay = 10000;  // time after which the backlight turns off (milliseconds)
const long backlightOnDelay = 10000;  // time to keep the backlight on (milliseconds)

const int buttonPin = 19;  // GPIO pin for the button
bool lastButtonState = LOW;  // previous button state
bool buttonPressed = false;  // flag for button press

float voltageBattery = 0.0; // VBatt
float voltageOut = 0.0; // VOut
float currentBattery = 0.0; // IBatt
float currentOut = 0.0; // IOut
float powerBattery = 0.0; // PBatt
float powerOut = 0.0; // POut

void setup() {
  pinMode(buttonPin, INPUT_PULLUP);  // set button pin as input with pull-up
  lcd.init();
  lcd.backlight();
  lcd.print("DIY UPS project");
  delay(2000);
}

void loop() {
  unsigned long currentMillis = millis();
  bool buttonState = digitalRead(buttonPin);  // read the state of the button
  
  // Check for button press to toggle backlight on/off
  if (buttonState == LOW && lastButtonState == HIGH) {
    // Button pressed, toggle backlight
    backlightState = !backlightState;
    if (backlightState) {
      lcd.backlight();  // turn backlight on
      backlightMillis = currentMillis;  // reset backlight timer
    } else {
      lcd.noBacklight();  // turn backlight off
    }
    delay(200);  // debounce delay
  }
  
  lastButtonState = buttonState;  // update last button state

  // Manage backlight off after 10 seconds if no button press
  if (backlightState && currentMillis - backlightMillis >= backlightOffDelay) {
    lcd.noBacklight();  // turn off backlight after 10 seconds
    backlightState = false;
  }

  // Keep backlight on for 10 seconds after button press
  if (!backlightState && currentMillis - backlightMillis >= backlightOnDelay && currentMillis - backlightMillis < backlightOffDelay) {
    lcd.backlight();  // turn on backlight for 10 seconds
    backlightState = true;
    backlightMillis = currentMillis;  // reset the timer
  }

  // Change the LCD display every 3 seconds
  if (currentMillis - previousMillis >= interval) {
      previousMillis = currentMillis;

      measure();

      switch(i) {
          case 0:
              infoOne();
              break;
          case 1:
              infoTwo();
              break;
          case 2:
              infoThree();
              break;
      }
      i = (i + 1) % 3;
  }
  delay(100);
}

void measure() { // TODO: Replace with INA219 code
  voltageBattery = (random(1200, 1350) / 100);
  voltageOut = (random(1200, 1350) / 100);
}

void infoOne() {
  lcd.clear();
  lcd.print("Vbat: ");
  lcd.print(voltageBattery);  // example
  lcd.print("V");
  lcd.setCursor(0, 1);
  lcd.print("Ibat: ");
  lcd.print("-500");  // example
  lcd.print("mA");
  lcd.setCursor(15, 1);
  lcd.print("1");
}

void infoTwo() {
  lcd.clear();
  lcd.print("Vout: ");
  lcd.print(voltageOut);  // example
  lcd.print("V");
  lcd.setCursor(0, 1);
  lcd.print("Iout: ");
  lcd.print("480");  // example
  lcd.print("mA");
  lcd.setCursor(15, 1);
  lcd.print("2");
}

void infoThree() {
  lcd.clear();
  lcd.print("Pbat: ");
  lcd.print("-6200");  // example
  lcd.print("mW");
  lcd.setCursor(0, 1);
  lcd.print("Pout: ");
  lcd.print("5856");  // example
  lcd.print("mW");
  lcd.setCursor(15, 1);
  lcd.print("3");
}