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

// OLED display parameters
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET    -1

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// Pin definitions for buttons
const int buttonModePin = 2; // Pin for mode selection button
const int buttonUpPin = 3;   // Pin for range up button
const int buttonDownPin = 4; // Pin for range down button

// Variables to store button states
volatile bool modeChanged = false;
volatile bool upPressed = false;
volatile bool downPressed = false;
int mode = 0; // 0 for capacitance, 1 for inductance
int capacitanceRange = 0;
int inductanceRange = 0;
int currentRange = 0; // Holds current range (based on mode)

// Range descriptions
const char* capacitanceRanges[4] = {"1-999 pF", "1-999 nF", "1-999 uF", "1-10 mF"};
const char* inductanceRanges[3] = {"1-999 uH", "1-999 mH", "1-10 H"};

void setup() {
  // Initialize serial communication (for debugging purposes)
  Serial.begin(9600);

  // Initialize buttons
  pinMode(buttonModePin, INPUT_PULLUP); // Mode button with internal pull-up resistor
  pinMode(buttonUpPin, INPUT_PULLUP);   // Up button with internal pull-up resistor
  pinMode(buttonDownPin, INPUT_PULLUP); // Down button with internal pull-up resistor

  // Attach interrupts for button presses
  attachInterrupt(digitalPinToInterrupt(buttonModePin), modeButtonPressed, FALLING);
  attachInterrupt(digitalPinToInterrupt(buttonUpPin), upButtonPressed, FALLING);
  attachInterrupt(digitalPinToInterrupt(buttonDownPin), downButtonPressed, FALLING);

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

void loop() {
  // Handle mode change
  if (modeChanged) {
    modeChanged = false;
    mode = !mode; // Toggle mode (0 for capacitance, 1 for inductance)
    currentRange = (mode == 0) ? capacitanceRange : inductanceRange; // Set range for the new mode
    updateDisplay();
  }

  // Handle range increase
  if (upPressed) {
    upPressed = false;
    if (mode == 0) {
      capacitanceRange = (capacitanceRange + 1) % 4; // 4 ranges for capacitance (0-3)
      currentRange = capacitanceRange;
    } else {
      inductanceRange = (inductanceRange + 1) % 3; // 3 ranges for inductance (0-2)
      currentRange = inductanceRange;
    }
    updateDisplay();
  }

  // Handle range decrease
  if (downPressed) {
    downPressed = false;
    if (mode == 0) {
      capacitanceRange = (capacitanceRange - 1 + 4 ) % 4; // Ensure range wraps around (0-3)
      currentRange = capacitanceRange;
    } else {
      inductanceRange = (inductanceRange - 1 + 4 ) % 3; // Ensure range wraps around (0-2)
      currentRange = inductanceRange;
    }
    updateDisplay();
  }
}

// Interrupt service routine for mode button
void modeButtonPressed() {
  modeChanged = true;
}

// Interrupt service routine for up button
void upButtonPressed() {
  upPressed = true;
}

// Interrupt service routine for down button
void downButtonPressed() {
  downPressed = true;
}

// Function to update the OLED display
void updateDisplay() {
  display.clearDisplay();
  
  // Display mode
  display.setTextSize(2);
  display.setTextColor(SSD1306_WHITE);
  if (mode == 0) {
    display.setCursor(0, 0);
    display.println(F("Capacitance"));
  } else {
    display.setCursor(0, 0);
    display.println(F("Inductance"));
  }

  // Display current range
  display.setTextSize(1);
  display.setCursor(0, 40);
  display.print(F("Range: "));
  if (mode == 0) {
    display.println(capacitanceRanges[currentRange]);
  } else {
    display.println(inductanceRanges[currentRange]);
  }

  display.display();
}