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

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 32
#define OLED_RESET -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

#define VOLTAGE_PIN A0
#define RED_LED_PIN 2
#define GREEN_LED_PIN 3

// Define battery icon parameters
#define BATTERY_WIDTH 110
#define BATTERY_HEIGHT 26
#define BATTERY_X 0
#define BATTERY_Y 6
#define BATTERY_MARGIN 4
#define BATTERY_SEGMENT_HEIGHT 18

// Function prototype
void drawBatteryIcon(int percentage);

void setup() {
  Serial.begin(9600);
  pinMode(RED_LED_PIN, OUTPUT);
  pinMode(GREEN_LED_PIN, OUTPUT);
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("failed"));
    for(;;);
  }
  display.display(); 
  delay(500); 
  display.clearDisplay(); 
}

void loop() {
  int sensorValue = analogRead(VOLTAGE_PIN);
  float voltage = sensorValue * (4.2 / 1023.0);
  int percentage;
  if (voltage <= 0) { // Lower Voltage Value
    percentage = 0;
  } else if (voltage >= 4.2) { // Upper Voltage Value
    percentage = 100;
  } else {
    percentage = map(voltage * 1000, 500, 4500, 0, 100); 
  }
  if (percentage <= 25) {
    digitalWrite(RED_LED_PIN, HIGH); 
    digitalWrite(GREEN_LED_PIN, LOW); 
  } else if (percentage >= 26 && percentage <= 100) {
    digitalWrite(RED_LED_PIN, LOW); 
    digitalWrite(GREEN_LED_PIN, HIGH); 
  } else {
    digitalWrite(RED_LED_PIN, LOW); 
    digitalWrite(GREEN_LED_PIN, LOW); 
  }
  display.clearDisplay();
  drawBatteryIcon(percentage);
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setRotation(1); // Rotate text 90 degrees clockwise
  display.setCursor(6,0); // Set cursor position for the percentage value
  display.print(percentage);
  display.print("%");
  display.display();
  delay(500); 
}

// Function to draw battery icon with capacity bars
void drawBatteryIcon(int percentage) {
  // Rotate the display content 90 degrees clockwise
  display.setRotation(0);
  // Draw battery outline
  display.drawRect(BATTERY_X, BATTERY_Y, BATTERY_WIDTH, BATTERY_HEIGHT, SSD1306_WHITE);
  // Calculate number of bars based on percentage
  int numBars = map(percentage, 0, 100, 0, 10);
  // Draw capacity bars
  for (int i = 0; i < numBars; i++) {
    int barX = BATTERY_X + BATTERY_MARGIN + i * (BATTERY_WIDTH - 2 * BATTERY_MARGIN) / 10;
    int barY = BATTERY_Y + BATTERY_MARGIN;
    display.fillRect(barX, barY, (BATTERY_WIDTH - 2 * BATTERY_MARGIN) / 10, BATTERY_SEGMENT_HEIGHT, SSD1306_WHITE);
  }
}