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

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET    -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

int button = 8;
int button2 = 7;
int button3 = 4;
int wheel = A0;
int scroll = A1;
int func = 0;
int counteraxes1 = 0;
int counteraxes2 = 0;
int counterarea = 0;
int counterfunc = 1;
int temppointvalue=0;

void setup() {
  Serial.begin(9600);
   if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { 
    Serial.println(F("SSD1306 allocation failed"));
    for(;;);
  }
  // for (int i : pins) {
  //   pinMode(i,INPUT);
  // }
  display.clearDisplay();
  display.display();

  pinMode(button,INPUT);
  pinMode(button2,INPUT);
  pinMode(wheel,INPUT);
  pinMode(scroll,INPUT);
  pinMode(button3,INPUT);
  
}

void axes(){
  for (int i=0; i<64;i++){
    int j = map(i,0,63,0,127);
    display.drawPixel(63,i,SSD1306_WHITE);
    display.drawPixel(j,32,SSD1306_WHITE);
  }
    display.display();
}

void area(int x , float m){
  float a = 0;
  if (x>0){
    for (int i=0; i<x+1 ; i++){
      if (func==1){
        float y2 = m*(i+1);
        //Serial.println(y2);
        float y1 = m*(i);
        //Serial.println(y1);
        a = (y1+y2)/2+a;
      }
      else if (func==2){
        int y2=m*pow(i+1,2);
        int y1=m*pow(i,2);
        a = (y1+y2)/2+a;
      }
      else if (func==3){
        float y2 = sin(i+1);
        float y1 = sin(i);
        a = (y1+y2)/2+a;
      }
      else if (func==4){
        int y2 = pow(m,i+1);
        int y1 = pow(m,i);
        a = (y1+y2)/2+a;
      }
    }
    Serial.print("The area under the curve from x = 0 to x = ");
    Serial.print(x);
    Serial.print(" is ");
    Serial.println(a);
  }
  else {
    for (int i=x; i<0 ; i++){
      if (func==1){
        float y2 = m*(i-1);
        //Serial.println(y2);
        float y1 = m*(i);
        //Serial.println(y1);
        a = (y1+y2)/2+a;
      }
      else if (func==2){
        int y2=m*pow(i-1,2);
        int y1=m*pow(i,2);
        a = (y1+y2)/2+a;
      }
      else if (func==3){
        float y2 = sin(i-1);
        float y1 = sin(i);
        a = (y1+y2)/2+a;
      }
      else if (func==4){
        int y2 = pow(m,i-1);
        int y1 = pow(m,i);
        a = (y1+y2)/2+a;
      }
    }
    Serial.print("The area under the curve from x = ");
    Serial.print(x);
    Serial.print(" to x = 0 is ");
    Serial.println(a);
  }
}

void derivative(int x ,float m){
  if (func==1){
    float y2 = m*(x+1-64)+64;
    //Serial.println(y2);
    float y1 = m*(x-64)+64;
    //Serial.println(y1);
    float d = (y2-y1);
    Serial.print("The derivative at x = ");
    Serial.print(x);
    Serial.print(" is ");
    Serial.println(d);
  }
  else if (func==2){
    int y2=m*pow(x+1,2);
    int y1=m*pow(x,2);
    float d = (y2-y1);
    Serial.print("The derivative at x = ");
    Serial.print(x);
    Serial.print(" is ");
    Serial.println(d);
    
  }
  else if (func==3){
    float rawx2 = (x+1)/20.0;
    float y2 = 32-sin(rawx2)*31;
    float rawx1 = (x)/20.0;
    float y1 = 32-sin(rawx1)*31;
    float d = -(y2-y1)*20.0/31.0;
    Serial.print("The derivative at x = ");
    Serial.print(x);
    Serial.print(" is ");
    Serial.println(d);
  }
  else if (func==4){
    float max_rawy = pow(m, 127.0 / 32.0);
    float denominator = max_rawy - 1.0;
    if (abs(denominator) < 0.0001) {
      return 0.0; 
    }

    float exponent1 = (float)(-x + 1.0) / 32.0;  
    float rawy1 = pow(m, exponent1);
    float y1 = 63.0 - ((rawy1 - 1.0) * 63.0 / (max_rawy - 1.0));

    float exponent2 = (float)(-x) / 32.0;  
    float rawy2 = pow(m, exponent2);
    float y2 = 63.0 - ((rawy2 - 1.0) * 63.0 / (max_rawy - 1.0));

    float d = y2-y1;
    Serial.print("The derivative at x = ");
    Serial.print(x);
    Serial.print(" is ");
    Serial.println(d, 4);
  }
}

void linear(float m){
  display.clearDisplay();
  for (int x=0; x<128; x++){
    int rawy = m*(x-64)+64;
    int y = map(rawy,0,127,63,0);
    display.drawPixel(x,y,SSD1306_WHITE);
  }
  func = 1;
  display.display();
}

void quadratic(float m){
  display.clearDisplay();
  for (int x=-64;x<65;x++){
    int rawy=m*pow(x,2);
    int y = map(rawy,0,4096,32,0);
    display.drawPixel(x+64,y,SSD1306_WHITE);
  }
  func=2;
  display.display();
}

void sine(float m) {
  display.clearDisplay();
  for (int x=-128;x<65;x++){
    float rawx = x/20.0;
    float rawy=sin(rawx);
    int y = 32-rawy*31;
    display.drawPixel(x+64+m,y,SSD1306_WHITE);
  }
  func=3;
  display.display();
}

void exponential(float m) {
  display.clearDisplay();
  
  for (int x = 0; x < 128; x++) {
    float exponent = (float)x / 32.0; 
    
    float rawy = pow(m, exponent);
    
    float max_rawy = pow(m, 127.0 / 32.0);
    int y = 63 - (int)((rawy - 1.0) * 63.0 / (max_rawy - 1.0));
    if (y >= 0 && y < 64) {
      display.drawPixel(x, y-32, SSD1306_WHITE);
    }
  }
  
  func = 4;
  display.display();
}



void loop() {

  int funcchange = digitalRead(button);
  int axestoggle = digitalRead(button2);
  int wheelvalue = analogRead(wheel);
  int pointvalue = analogRead(scroll);
  int areavalue = digitalRead(button3);

  //Serial.println(wheelvalue/1023.0);
  //Serial.println(wheelvalue);
  //Serial.println(wheelvalue/102);

  if (funcchange==HIGH){
    if (counterfunc==1){
      Serial.println("drawing linear graph");
      linear(wheelvalue/1023.0);
      counterfunc++;
    }
    else if (counterfunc==2){
      Serial.println("drawing quadratic graph");
      quadratic(wheelvalue/1023.0*4.0);
      counterfunc++;
    }
    else if (counterfunc==3){
      Serial.println("drawing sine graph");
      sine(wheelvalue/1023.0*63);
      counterfunc++;
    }
    else if (counterfunc==4){
      Serial.println("drawing exponential graph");
      exponential(wheelvalue/51+1);
      counterfunc=1;
    }
  }

  // if (pointvalue!=temppointvalue){
  //   derivative(pointvalue/1023.0*128 - 64.0 ,wheelvalue/1023.0);
  // }

  if (func==1){
    linear(wheelvalue/1023.0);
    if (counteraxes1==1){
      axes();
    }
  }
  else if (func==2){
    quadratic(wheelvalue/1023.0*4.0);
    if (counteraxes1==1){
      axes();
    }
  }
  else if (func==3){
    sine(wheelvalue/1023.0*63);
    if (counteraxes1==1){
      axes();
    }
  }
  else if (func==4){
    exponential(wheelvalue/51+1);
    if (counteraxes1==1){
      axes();
    }
  }

  //Area & Derivative
  if (areavalue==HIGH){
    //Serial.println("Working");
    if (counterarea == 0){
      area(pointvalue/1023.0*128 - 64.0 ,wheelvalue/1023.0);
      derivative(pointvalue/1023.0*128 - 64.0 ,wheelvalue/1023.0);
      counterarea=1;
    }
  }
  else{
    counterarea=0;
  }

  //Axis toggling
  if (axestoggle==HIGH){
    if (counteraxes1==0 && counteraxes2==0){
      counteraxes2=1;
      counteraxes1=1;
      Serial.println("drawing axes");
      // Serial.print(counteraxes1);
      // Serial.println(counteraxes2);
    }
    else if (counteraxes1==1 && counteraxes2==0){
      Serial.println("removing axes");
      counteraxes1=0;
      counteraxes2=1;
      display.clearDisplay();
      // Serial.print(counteraxes1);
      // Serial.println(counteraxes2);
    }
  }
  else{
    counteraxes2=0;
    if (counteraxes1==1){
      axes();
    }
  }

  delay(10);
  temppointvalue = pointvalue;
}