#define pinCLK 1       // CLK pin connected to GPIO 1
#define pinDT  2       // DT pin connected to GPIO 2
#define pinSW  3       // SW pin connected to GPIO 3

#include <U8g2lib.h>
#include <Wire.h>

// OLED display constructor
U8G2_SSD1306_128X64_NONAME_F_HW_I2C u8g2(U8G2_R0, /* reset=*/ U8X8_PIN_NONE, /* clock=*/ 6, /* data=*/ 5);

int count = 0;    // Var to know how many clicks occured (increment clockwise and decrement counter_clockwise)
int previousStateSW;           // Var to memorize previous SW state to compare it with actual state
int previousStateCLK;          // Var to memorize previous CL state to compare it with actual state

void setup() {

    Serial.begin(9600);

    // Initialize the OLED display
    u8g2.begin();

    u8g2.setFont(u8g2_font_ncenB14_tr);
    u8g2.setCursor(0, 20); // Set position (x, y)
            // Write text to the screen
    u8g2.print("Starting Display");

    pinMode(pinSW, INPUT_PULLUP);         // INPUT_PULLUP to avoid 'floating'
    pinMode(pinDT, INPUT);
    pinMode(pinCLK, INPUT);

    previousStateSW  = digitalRead(pinSW);    // initial value for SW
    previousStateCLK = digitalRead(pinCLK);   // initial value for CLK

    delay(200); // delay to stabilize signal before the loop
}

void loop() {

    int actualStateCLK = digitalRead(pinCLK); // reading CLK value
    int actualStateDT  = digitalRead(pinDT);  // reading DT value
    int actualStateSW  = digitalRead(pinSW);  // reading SW value

    // Clear the screen
    u8g2.clearBuffer();

    // *************************
    // Push Button verification
    // *************************

    if (actualStateSW != previousStateSW) {    // Checking if SW state has changed
        previousStateSW = actualStateSW;      // Save new state

        if (actualStateSW == LOW) {
            Serial.println(F("SW Button pushed"));     // Display State on serial monitor
            
            // Set font and position
            u8g2.setFont(u8g2_font_ncenB14_tr);
            u8g2.setCursor(0, 20); // Set position (x, y)
            // Write text to the screen
            u8g2.print("SW Button :");

            u8g2.setCursor(0, 40); // Set position (x, y)
            // Write text to the screen
            u8g2.print("Pushed");

        } else {
            Serial.println(F("SW Button released"));
            
            u8g2.setFont(u8g2_font_ncenB14_tr);
            u8g2.setCursor(0, 20); // Set position (x, y)
            // Write text to the screen
            u8g2.print("SW Button :");

            u8g2.setCursor(0, 40); // Set position (x, y)
            // Write text to the screen
            u8g2.print("Released");
        }
        // Send the buffer to the display
        u8g2.sendBuffer();

        delay(10); // Delay to avoid rebounce
    }

    // ***************************
    // Rotary encoder verification
    // ***************************

    if (actualStateCLK != previousStateCLK) {       // Checking if SW state has changed
        previousStateCLK = actualStateCLK;           // Save new state

        if (actualStateCLK == LOW) {

            if (actualStateCLK != actualStateDT) {   // comparing CLK and DT, if they're different, direction is counter-clockwise          
                count--;                            // decrement counter
                Serial.print(F("Direction = counter-clockwise | Counter value = "));   // Display value on Serial Monitor
                Serial.println(count);

                u8g2.setFont(u8g2_font_ncenB10_tr);
                u8g2.setCursor(0, 15); // Set position (x, y)

                // Write text to the screen
                u8g2.print("Direction :");
                
                u8g2.setFont(u8g2_font_ncenB08_tr);
                u8g2.setCursor(0, 28); // Set position (x, y)
                u8g2.print("counter-clockwise");

                u8g2.setFont(u8g2_font_ncenB10_tr);
                u8g2.setCursor(0, 45); // Set position (x, y)
                // Write text to the screen
                u8g2.print("Counter value = ");

                u8g2.setCursor(0, 60); // Set position (x, y)
                u8g2.println(count);

                // Send the buffer to the display
                u8g2.sendBuffer();
            }
            else {                                   // when CLK and DT are similar, direction is clockwise            
                count++;                             // increment counter
                Serial.print(F("Direction = clockwise | Counter value = "));   // Display value on Serial Monitor
                Serial.println(count);

                 u8g2.setFont(u8g2_font_ncenB10_tr);
                u8g2.setCursor(0, 15); // Set position (x, y)

                // Write text to the screen
                u8g2.print("Direction :");
                

                u8g2.setCursor(0, 30); // Set position (x, y)
                u8g2.print("clockwise");

                u8g2.setCursor(0, 45); // Set position (x, y)
                // Write text to the screen
                u8g2.print("Counter value = ");

                u8g2.setCursor(0, 60); // Set position (x, y)
                u8g2.println(count);

                // Send the buffer to the display
                u8g2.sendBuffer();
            }

            delay(1);   // delay to avoid CLK rebounce      
        }
    }
}