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

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET    -1 // Reset pin not used (I2C interface)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

#define READ_INTERVAL 500 // Interval between sensor readings in milliseconds
#define NUM_READINGS 100  // Number of readings to store for a 10-second average (100 readings at 100ms intervals)

int readings[NUM_READINGS]; // Array to store sensor readings
int readIndex = 0;          // Index of the current reading
long total = 0;             // Sum of the readings

void setup() {
  Serial.begin(9600);  // Initialize serial communication at 9600 baud

  // SSD1306 display initialization
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {  // Address 0x3C for 128x64
    Serial.println(F("SSD1306 allocation failed"));
    for(;;);
  }

  // Initialize readings array with 0s
  for (int i = 0; i < NUM_READINGS; i++) {
    readings[i] = 0;
  }

  // Clear the buffer
  display.clearDisplay();

  // Display initial message
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 0);
  display.println("Sensor Reading:");
  display.display();
  delay(2000);  // Pause for 2 seconds
}

void loop() {
  // Read the resistance from the potentiometer (simulating sensor)
  int sensorValue = analogRead(A0);  // Read analog input from pin A0

  // Update the rolling sum and replace the oldest reading
  total = total - readings[readIndex]; // Subtract the oldest reading from the total
  readings[readIndex] = sensorValue;   // Store the new reading
  total = total + readings[readIndex]; // Add the new reading to the total

  // Advance to the next position in the readings array
  readIndex = (readIndex + 1) % NUM_READINGS;

  // Calculate the average value over the last 10 seconds
  float average = total / (float)NUM_READINGS;

  // Map the sensor value (range 0 to 1023) to percentage (0% to 100%)
  float percentage = map(sensorValue, 0, 1023, 0, 100);
  float avgPercentage = map(average, 0, 1023, 0, 100);

  // Clear the previous content
  display.clearDisplay();

  // Print sensor resistance and percentage on OLED display
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 10);
  display.print("Resistance:");
  display.setCursor(0, 20);
  display.print(sensorValue);
  display.setCursor(0, 30);
  display.print("Percentage:");
  display.setCursor(0, 40);
  display.print(percentage);
  display.print("%");
  display.setCursor(0, 50);
  display.print("Avg (10 sec):");
  display.setCursor(0, 60);
  display.print(avgPercentage);
  display.print("%");

  // Display the content
  display.display();

  // Delay to match the read interval
  delay(READ_INTERVAL);
}