SimonMayerhofer

/**
 * Calculates the remaining inventory, current average buy price, total cost and total gains using FIFO (First In First Out) method.
 * The function expects three parameters: transactionsType, transactionQuantities and transactionPrices sorted by date.
 *
 * Inspired by: https://www.allstacksdeveloper.com/2022/09/fifo-stock-portfolio-google-sheets.html
 * 
 * @param {string[] | string} transactionsType - An array or a single string representing transaction types. Each string should be either 'B' for buy or 'S' for sell.
 * @param {number[] | number} transactionQuantities - An array or a single number representing the quantities for each transaction.
 * @param {number[] | number} transactionPrices - An array or a single number representing the prices for each transaction.
 * @throws Will throw an error if transactionPrices and transactionQuantities are not arrays or if their lengths are not equal.