//20x4 LCD
#include <LiquidCrystal_I2C.h> //SDA = B7[A4], SCL = B6[A5] STM32/[Arduino]
LiquidCrystal_I2C lcd(0x27, 20, 4);

int menuCounter = 0; //counts the clicks of the rotary encoder between menu items (0-3 in this case)

int menu1_Value = 0; //value within menu 1
int menu2_Value = 0; //value within menu 2

bool menu1_selected = false; //enable/disable to change the value of menu item
bool menu2_selected = false;
//Note: if a menu is selected ">" becomes "X".

//Defining pins
//Arduino interrupt pins: 2, 3.
const int RotaryCLK = 2; //CLK pin on the rotary encoder
const int RotaryDT = 4; //DT pin on the rotary encoder
const int PushButton = 3; //Button to enter/exit menu

//Statuses for the rotary encoder
int CLKNow;
int CLKPrevious;

int DTNow;
int DTPrevious;

bool refreshLCD = true; //refreshes values
bool refreshSelection = false; //refreshes selection (> / X)

void setup() 
{
  pinMode(RotaryCLK, INPUT_PULLUP); //RotaryCLK
  pinMode(RotaryDT, INPUT_PULLUP); //RotaryDT
  pinMode(PushButton, INPUT_PULLUP); //Button

  //------------------------------------------------------
  lcd.init(); // initialize the lcd   
  lcd.backlight();
  lcd.clear(); //clear the whole LCD
  printLCD(); //print the stationary parts on the screen
  //------------------------------------------------------
  //Store states of the rotary encoder
  CLKPrevious = digitalRead(RotaryCLK);
  DTPrevious = digitalRead(RotaryDT);
      
  attachInterrupt(digitalPinToInterrupt(RotaryCLK), rotate, CHANGE); //CLK pin is an interrupt pin
  attachInterrupt(digitalPinToInterrupt(PushButton), pushButton, FALLING); //PushButton pin is an interrupt pin

}

void loop() {
  if(refreshLCD == true){ //If we are allowed to update the LCD ...

    updateLCD(); // ... we update the LCD ...
    //... also, if one of the menus are already selected...
    if(menu1_selected == true || menu2_selected == true){
     // do nothing
    } else {
      updateCursorPosition(); //update the position
    }
    refreshLCD = false; //reset the variable - wait for a new trigger
  }

  if(refreshSelection == true){ //if the selection is changed
    updateSelection(); //update the selection on the LCD
    refreshSelection = false; // reset the variable - wait for a new trigger
  }
}

void rotate(){  
  //-----MENU1--------------------------------------------------------------
  if(menu1_selected == true){
  CLKNow = digitalRead(RotaryCLK);  
  if (CLKNow != CLKPrevious  && CLKNow == 1){
    if (digitalRead(RotaryDT) != CLKNow) {
      if(menu1_Value < 6000){ //we do not go above 6000
        menu1_Value++;  
      } else {
        menu1_Value = 0;  
      }      
    } else {
      if(menu1_Value < 1) {//we do not go below 0
        menu1_Value = 6000;
      } else {
      menu1_Value--;      
      }      
    }    
  }
  CLKPrevious = CLKNow;  // Store last CLK state
  }
  //---MENU2---------------------------------------------------------------
  else if(menu2_selected == true) {
    CLKNow = digitalRead(RotaryCLK); 
  if (CLKNow != CLKPrevious  && CLKNow == 1){
    if (digitalRead(RotaryDT) != CLKNow) {
      if(menu2_Value < 6000){ //we do not go above 6000
        menu2_Value++;  
      } else {
        menu2_Value = 0;  
      }      
    } else {
      if(menu2_Value < 1){ //we do not go below 0
          menu2_Value = 6000;
      } else {
      menu2_Value--;      
      }      
    }    
  }
  CLKPrevious = CLKNow;  // Store last CLK state
  } else {//MENU COUNTER----------------------------------------------------------------------------
  
  CLKNow = digitalRead(RotaryCLK); //Read the state of the CLK pin
  // If last and current state of CLK are different, then a pulse occurred  
  if (CLKNow != CLKPrevious  && CLKNow == 1){
    // If the DT state is different than the CLK state then
    // the encoder is rotating in A direction, so we increase
    if (digitalRead(RotaryDT) != CLKNow) {
      if(menuCounter < 1){ //we do not go above 3
        menuCounter++;  
      } else {
        menuCounter = 0;  
      }      
    } else {
        if(menuCounter < 1){ //we do not go below 0
          menuCounter = 1;
      } else {
      // Encoder is rotating CW so decrease
      menuCounter--;      
      }      
    }    
  }
  CLKPrevious = CLKNow;  // Store last CLK state
  }
  //Refresh LCD after changing the counter's value
  refreshLCD = true;
}

void pushButton(){
  switch(menuCounter){
     case 0:
     menu1_selected = !menu1_selected;  //we change the status of the variable to the opposite
     break;

     case 1:
     menu2_selected = !menu2_selected;
     break;
  } 
  
  refreshLCD = true; //Refresh LCD after changing the value of the menu
  refreshSelection = true; //refresh the selection ("X")
}

void printLCD(){
  //These are the values which are not changing the operation
  
  lcd.setCursor(1,0); //1st line, 2nd block
  lcd.print("Menu 1"); //text
  //----------------------
  lcd.setCursor(1,1); //2nd line, 2nd block
  lcd.print("Menu 2"); //text
}

void updateLCD(){

  lcd.setCursor(9,0); //1st line, 10th block
  lcd.print("    "); //erase the content by printing space over it
  lcd.setCursor(9,0); //1st line, 10th block
  lcd.print(menu1_Value); //print the value of menu1_Value variable

  lcd.setCursor(9,1);
  lcd.print("    ");
  lcd.setCursor(9,1);
  lcd.print(menu2_Value); //  
}

void updateCursorPosition(){
  //Clear display's ">" parts 
  lcd.setCursor(0,0); //1st line, 1st block
  lcd.print(" "); //erase by printing a space
  lcd.setCursor(0,1);
  lcd.print(" "); 
     
  //Place cursor to the new position
  switch(menuCounter){ //this checks the value of the counter (0, 1, 2 or 3)
  
    case 0:
    lcd.setCursor(0,0); //1st line, 1st block
    lcd.print(">"); 
    break;
    //-------------------------------
    case 1:
    lcd.setCursor(0,1); //2nd line, 1st block
    lcd.print(">"); 
    break;
  }
}

void updateSelection(){
  //When a menu is selected ">" becomes "X"

  if(menu1_selected == true){
    lcd.setCursor(0,0); //1st line, 1st block
    lcd.print("X"); 
  }
  //-------------------
  if(menu2_selected == true){
    lcd.setCursor(0,1); //2nd line, 1st block
    lcd.print("X"); 
  }
}