//Quinton Chapman
//CS 2336
//Lab 46

#include <iostream>
#include <string>
#include <deque>
#include <iostream>
#include <lab46.h>

using namespace std;

BigInt BigInt::operator+(const BigInt& rhs) const{
    BigInt zero(0);
    if(*this==zero){
        return rhs;
    }
    else if(rhs==zero){
        return *this;
    }
    else if(this->sign == rhs.sign){
        BigInt left(*this);
        BigInt right(rhs);
        BigInt ans;

        while (left.digits.size() < right.digits.size()){
            left.digits.push_back('0');
        }
        while (left.digits.size() > right.digits.size()){
            right.digits.push_back('0');
        }

        int carry=0;
        for(uint i=0;i<left.digits.size();i++){
            int sum=carry+((left.digits.back()-'0')+(right.digits.back()-'0'));
            carry=sum/10;
            sum%=10;
            ans.digits.push_back('0'+sum);
            left.digits.pop_front();
            right.digits.pop_front();
        }

        ans.sign=this->sign;
        return ans;
    }//end if they are the same signs
    else{
        BigInt left(*this);
        BigInt right(rhs);
        BigInt ans;
        left.sign=POSITIVE;
        right.sign=POSITIVE;
        ans.sign=this->sign;

        while (left.digits.size() < right.digits.size()){
            left.digits.push_back('0');
        }
        while (left.digits.size() > right.digits.size()){
            right.digits.push_back('0');
        }

        int sub=0;
        if(left<right){
            left.digits.swap(right.digits);
            ans.sign=rhs.sign;
        }

            for(uint i=left.digits.size(); i > 0; i--){
                int sum=(right.digits.back()-'0')-(left.digits.back()-'0')+sub;
                if(sum<0){
                    sum+=10;
                    sub=-1;
                }
                else
                    sub=0;
                ans.digits.push_back(sum+'0');
                left.digits.pop_front();
                right.digits.pop_front();
            }

            while(digits.size()>1 && digits.back()=='0')
                ans.digits.pop_back();

        return ans;
    }//end if they are different signs
}//end plus

BigInt BigInt::operator-(const BigInt& rhs) const{
    BigInt sub(rhs);
    if(sub.sign==NEGATIVE)
        sub.sign=POSITIVE;
    else if(sub.sign==POSITIVE)
        sub.sign=NEGATIVE;
    return *this + sub;
}//end minus