source: imaps-frontend/node_modules/es-abstract/2021/StringPad.js

'use strict';

var $TypeError = require('es-errors/type');

var callBound = require('call-bind/callBound');

var ToLength = require('./ToLength');
var ToString = require('./ToString');

var $strSlice = callBound('String.prototype.slice');

// https://262.ecma-international.org/11.0/#sec-stringpad

module.exports = function StringPad(O, maxLength, fillString, placement) {
        if (placement !== 'start' && placement !== 'end') {
                throw new $TypeError('Assertion failed: `placement` must be "start" or "end"');
        }
        var S = ToString(O);
        var intMaxLength = ToLength(maxLength);
        var stringLength = S.length;
        if (intMaxLength <= stringLength) {
                return S;
        }
        var filler = typeof fillString === 'undefined' ? ' ' : ToString(fillString);
        if (filler === '') {
                return S;
        }
        var fillLen = intMaxLength - stringLength;

        // the String value consisting of repeated concatenations of filler truncated to length fillLen.
        var truncatedStringFiller = '';
        while (truncatedStringFiller.length < fillLen) {
                truncatedStringFiller += filler;
        }
        truncatedStringFiller = $strSlice(truncatedStringFiller, 0, fillLen);

        if (placement === 'start') {
                return truncatedStringFiller + S;
        }
        return S + truncatedStringFiller;
};