#include <LiquidCrystal.h>
#include <Keypad.h>

//unsigned int nums[8] = {0,0,0,0,0,0,0,0}; //stores number inputs
long nums[8] = {0,0,0,0,0,0,0,0}; //stores number inputs
char oper[7] = {' ',' ',' ',' ',' ',' ',' '}; //stores operations to be preformed
int num_index = 0; // prevents overflow of nums array
int op_index = 0; // prevents overflow of oper array
String temp = ""; //string to store input
int tnum; // stores temp num to append to nums array

//key pad setup
const byte KEYPAD_ROWS = 4;
const byte KEYPAD_COLS = 4;
byte rowPins[KEYPAD_ROWS] = {53, 51, 49, 47};
byte colPins[KEYPAD_COLS] = {52, 50, 48, 46};
char keys[KEYPAD_ROWS][KEYPAD_COLS] = {
  {'1', '2', '3', 'A'},
  {'4', '5', '6', 'B'},
  {'7', '8', '9', 'C'},
  {'*', '0', '#', 'D'}
};

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, KEYPAD_ROWS, KEYPAD_COLS);

void setup(){
    Serial.begin(9600); // startmonitor
    Serial.println("Started: ");
}

void loop() {
    if(num_index == 8){
        Serial.println("\nAt calc max");
        calc();
        clear();
    }

    char key = keypad.getKey(); // key from keypad press
  
    if(key){

        switch(key){
            case '#':
                Serial.println("=");
                save(' ');
                calc();
                clear();
                break;

            case 'C':
                Serial.print("*");
                save('*');
                break;

            case 'A':
                Serial.print("+");
                save('+');
                break;

            case 'D':
                Serial.print("/");
                save('/');
                break;

            case 'B':
                Serial.print("-");
                save('-');
                break;

            case '*':
                Serial.println("Clearing");
                clear();
                break;

            default:
                Serial.print(key);
                temp += key;
        }
    }
}

void save(char op){ // saves the data to the arrays
    oper[op_index] = op;
    tnum = temp.toInt();
    nums[num_index] = tnum;
    temp = "";
    if(op_index != 7){
        op_index += 1;
    }
    num_index += 1;
}

void clear(){
    for (int i =0; i < 8; i++){
      Serial.print(nums[i]);
      Serial.print(" , "); 
    }
    Serial.print("\n");

    for (int i =0; i < 7; i++){
      Serial.print(oper[i]);
      Serial.print(" , "); 
    }
    Serial.print("\n");
    
    //needed code
    num_index = 0;
    op_index = 0;

    for (int i =0; i < 8; i++){
        nums[i] = 0;
    }
    for (int i =0; i < 7; i++){
        oper[i] = ' ';
    }

    temp = "";
}

//int sgn(long x){
//  return x==0?1:abs(x)/x;
//}

void calc(){ // begins calculations
    long ans = nums[0];
    float rem = 0.0;//remainer
    //changed from int to long to support 9999*9999
    long tempans = 0;

    for (int i = 0; i < op_index; i++){

        switch(oper[i]){
            case '+':
                //ans += nums[i + 1];
                tempans = (ans+rem)+nums[i + 1];
                rem = (ans+rem)+nums[i + 1]-tempans;
                ans = tempans;
                break;

            case '-':
                //if (ans < nums[i + 1]){
                //  Serial.println("Ans Neg, Pos Only");
                //  return;
                //}
                //else{
                //ans -= nums[i + 1];
                tempans = (ans+rem)-nums[i + 1];
                rem = (ans+rem)-nums[i + 1]-tempans;
                ans = tempans;
                break;
                //}
            case '*':
                //ans *= nums[i + 1];
                if (rem > 0){
                  tempans = (ans+rem)*nums[i + 1];
                }
                else{
                  tempans=ans*nums[i + 1];
                }
                //tempans = (ans+rem)*nums[i + 1];
                rem = (ans+rem)*nums[i + 1]-tempans;
                ans = tempans;
                break;

            case '/':
                if (nums[i + 1] == 0){
                    Serial.println("Divide By zero!");
                    return;
                }
                else{
                    //ans /= nums[i + 1];
                    //float temprem=((ans+rem) % nums[i+1])/nums[i+1];
                    tempans = (ans+rem)/nums[i + 1];
                    rem = (ans+rem)/nums[i + 1]-tempans;
                    ans = tempans;
                    break;
                }
            case ' ':
                int tempdec = floor(rem*100+0.5);
                String outstring = "";
                if (tempdec > 0){
                  outstring = String(String(ans)+"."+String(tempdec));
                }
                else{
                  outstring = String(ans);
                }
                //Serial.println(ans+rem);
                Serial.println(outstring);
                //Serial.println("\n");
                //Serial.println(rem);
                return;
        }
    }
  Serial.println(ans);   
}