import { compareAbsolute, parseNumber } from "./utils";

/**

* Adds two numbers represented as strings.

* @param left

* @param right

* @returns

*/

export function add(left: string, right: string): string {

// Parse input numbers

let leftParsed = parseNumber(left);

let rightParsed = parseNumber(right);

if (leftParsed.sign === rightParsed.sign) {

// If signs are the same, perform addition

let sign = leftParsed.sign;

// Pad fractional parts to equal length

let maxFracLen = Math.max(

leftParsed.fractionalPart.length,

rightParsed.fractionalPart.length

);

leftParsed.fractionalPart = leftParsed.fractionalPart.padEnd(

maxFracLen,

"0"

);

rightParsed.fractionalPart = rightParsed.fractionalPart.padEnd(

maxFracLen,

"0"

);

// Pad integer parts to equal length

let maxIntLen = Math.max(

leftParsed.integerPart.length,

rightParsed.integerPart.length

);

leftParsed.integerPart = leftParsed.integerPart.padStart(maxIntLen, "0");

rightParsed.integerPart = rightParsed.integerPart.padStart(maxIntLen, "0");

// Combine integer and fractional parts

let leftCombined = leftParsed.integerPart + leftParsed.fractionalPart;

let rightCombined = rightParsed.integerPart + rightParsed.fractionalPart;

// Perform digit-by-digit addition

let result = "";

let carry = 0;

for (let i = leftCombined.length - 1; i >= 0; i--) {

let sum = parseInt(leftCombined[i]) + parseInt(rightCombined[i]) + carry;

carry = Math.floor(sum / 10);

result = (sum % 10).toString() + result;

}

if (carry > 0) {

result = carry.toString() + result;

}

// Restore decimal point

if (maxFracLen > 0) {

let integerResult = result.slice(0, -maxFracLen);

let fractionalResult = result.slice(-maxFracLen);

result = integerResult + "." + fractionalResult;

}

// Remove unnecessary zeros

result = result.replace(/^0+(?!\.|$)/, ""); // Remove leading zeros

result = result.replace(/(\.\d*?)0+$/, "$1"); // Remove trailing zeros in fractional part

result = result.replace(/\.$/, ""); // Remove decimal point if fractional part is empty

// Apply sign

if (sign === -1 && result !== "0") {

result = "-" + result;

}

return result;

} else {

// If signs are different, perform subtraction

let compare = compareAbsolute(leftParsed, rightParsed);

let sign = compare >= 0 ? leftParsed.sign : rightParsed.sign;

// Determine which number is larger in absolute value

let minuend = compare >= 0 ? leftParsed : rightParsed;

let subtrahend = compare >= 0 ? rightParsed : leftParsed;

// Pad fractional parts to equal length

let maxFracLen = Math.max(

minuend.fractionalPart.length,

subtrahend.fractionalPart.length

);

minuend.fractionalPart = minuend.fractionalPart.padEnd(maxFracLen, "0");

subtrahend.fractionalPart = subtrahend.fractionalPart.padEnd(

maxFracLen,

"0"

);

// Pad integer parts to equal length

let maxIntLen = Math.max(

minuend.integerPart.length,

subtrahend.integerPart.length

);

minuend.integerPart = minuend.integerPart.padStart(maxIntLen, "0");

subtrahend.integerPart = subtrahend.integerPart.padStart(maxIntLen, "0");

// Combine integer and fractional parts

let minuendCombined = minuend.integerPart + minuend.fractionalPart;

let subtrahendCombined = subtrahend.integerPart + subtrahend.fractionalPart;

// Perform digit-by-digit subtraction

let result = "";

let borrow = 0;

for (let i = minuendCombined.length - 1; i >= 0; i--) {

let diff =

parseInt(minuendCombined[i]) - parseInt(subtrahendCombined[i]) - borrow;

if (diff < 0) {

diff += 10;

borrow = 1;

} else {

borrow = 0;

}

result = diff.toString() + result;

}

// Restore decimal point

if (maxFracLen > 0) {

let integerResult = result.slice(0, -maxFracLen);

let fractionalResult = result.slice(-maxFracLen);

result = integerResult + "." + fractionalResult;

}

// Remove unnecessary zeros

result = result.replace(/^0+(?!\.|$)/, ""); // Remove leading zeros

result = result.replace(/(\.\d*?)0+$/, "$1"); // Remove trailing zeros in fractional part

result = result.replace(/\.$/, ""); // Remove decimal point if fractional part is empty

// Handle case where result is zero

if (result === "") {

result = "0";

}

// Apply sign

if (sign === -1 && result !== "0") {

result = "-" + result;

}

return result;

}

}

export default add;