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

//Global - OLED screen setup
#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
#define OLED_RESET     -1 // Reset pin # (or -1 if sharing Arduino reset pin)
#define SCREEN_ADDRESS 0x3C
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

//Global - Pin variables 
int buttonPin = 2; // recieves a signal from pin 2 (Button)
int buttonPin2 = 4; // recieves a signal from pin 4 (Button)
int buttonPin3 = 7; // recieves a signal from pin 7 (Button)
int ledPin = 13; // recieves a signal from pin 4 (LED)
int buttonState1 = 0; // Is the button currently pressed?
int buttonState2 = 0; // Is the button currently pressed?
int buttonState3 = 0; // Is the button currently pressed?

// Logic variables
int currentOperator = 0; // 0: OR, 1: AND 
char stateDisplay[] = "OR"; // Current operator 
int logicGate1 = 0;
int logicGate2 = 0;
char gateDisplay1[2];
char gateDisplay2[3];
bool switchLimiter;

//Global - recieves a string and a X, Y to DRAW a TEXT on screen 
void basicText(char text[], int xPos, int yPos){
  display.setCursor(xPos, yPos);
  display.println(text);
}

// Display information on screen
void updateDisplay (){
  
  switch(currentOperator) {
    case 0:
      sprintf(stateDisplay, "OR");
      break;
    case 1:
      sprintf(stateDisplay, "AND");
      break;
    case 2:
      sprintf(stateDisplay, "NOR");
      break;
    case 3:
      sprintf(stateDisplay, "NAND");
      break;      
  }

   // String setup - setup the string on display
   sprintf(gateDisplay1, "%d", logicGate1);
   sprintf(gateDisplay2, "%d", logicGate2);
   // Text setup 
   display.setTextSize(1);
   display.setTextColor(WHITE);
   // Display Text
   basicText("Logic Gate Simulator", 0, 0);
   basicText("Current Operat:", 0, 9);
   basicText(stateDisplay, 95, 9);
   basicText("Button 1 state:", 0, 20);
   basicText(gateDisplay1, 95, 20);
   basicText("Button 2 state:", 0, 30);
   basicText(gateDisplay2, 95, 30);
   basicText("Can you light up the LED?", 0, 45);
   display.display();

}

// Switch current LED state
void lightSwitch () {

    // Change LED state
    if(digitalRead(ledPin) == 0) {
      digitalWrite(ledPin, 1);
    } else {
      digitalWrite(ledPin, 0);
    }
    delay(500);
}

// switch state
int stateSwitch(int numb) {

    if(numb == 0) {
      numb = 1;
    } else {
      numb = 0;
    }
    return numb;
}

void setup() {

  Serial.begin(9600);

  // initialize digital pin LED_BUILTIN as an output.
  pinMode(ledPin, OUTPUT);
  pinMode(buttonPin, INPUT);
  pinMode(buttonPin2, INPUT); 
  pinMode(buttonPin3, INPUT);
  pinMode(9, OUTPUT); // recieves a signal from pin 7

  // initialize the OLED object
  if(!display.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS)) {
    Serial.println(F("SSD1306 allocation failed"));
    for(;;); // Don't proceed, loop forever
  }

}

// the loop function runs over and over again forever
void loop() {

  // Detects if buttons are pressed
  buttonState1 = digitalRead(buttonPin);
  buttonState2 = digitalRead(buttonPin2);
  buttonState3 = digitalRead(buttonPin3);

  // Logic when button 1 or 2 is pressed
  if(buttonState1 == HIGH || buttonState2 == HIGH){

  // Switch states in logic gates when a button is pressed    
  if(buttonState1 == HIGH){
    logicGate1 = stateSwitch(logicGate1);
    delay(100);
  }

  // Switch states in logic gates when a button is pressed 
  if(buttonState2 == HIGH){
    logicGate2 = stateSwitch(logicGate2);
    delay(100);
  }

  // Clear the buffer.
  display.clearDisplay();
  updateDisplay();

  // Light LED if conditions are met
  if(currentOperator == 0){ 
    // OR Operator
    if(logicGate1 == 1 || logicGate2 == 1){
      digitalWrite(ledPin, 1);
      delay(100);
    } else {
      digitalWrite(ledPin, 0);
      delay(100);
    }      
  }else if(currentOperator == 1){
    // AND Operator  
    if(logicGate1 == 1 && logicGate2 == 1){
      digitalWrite(ledPin, 1);
      delay(100);
    } else {
      digitalWrite(ledPin, 0);
      delay(100);
    }
  }

  // Logic when NO button is pressed
  } else {

    // Clear the buffer.
    display.clearDisplay();
    updateDisplay();

    // Light LED if conditions are met
    if(currentOperator == 2){
      // NOR
      if(!(logicGate1 == 1 && logicGate2 == 1)){
        digitalWrite(ledPin, 1);
      }else{
        digitalWrite(ledPin, 0);
      }
    }else if(currentOperator == 3){
      // NAND
      if(!(logicGate1 == 1 || logicGate2 == 1)){
        digitalWrite(ledPin, 1);
      } else {
        digitalWrite(ledPin, 0);
      }
    }    
  }

  // Logic when button 3 is pressed
  if(buttonState3 == HIGH){

    // Cycle between availiable logic operators
    if(currentOperator == 3){
      currentOperator = 0;
      digitalWrite(ledPin, 0);      
    } else if (currentOperator <= 4){
      currentOperator++;      
    }else {
      currentOperator = 0;
      digitalWrite(ledPin, 0);
    }

    delay(250);
  }

  // Nescessary delay for currently unknown reasons
  delay(1);
}