@stellar/stellar-sdk/lib/esm/base/soroban.js

A library for working with the Stellar network, including communication with the Horizon and Soroban RPC servers.

class Soroban {
  /**
   * Given a whole number smart contract amount of a token and an amount of
   * decimal places (if the token has any), it returns a "display" value.
   *
   * All arithmetic inside the contract is performed on integers to avoid
   * potential precision and consistency issues of floating-point.
   *
   * @param amount - the token amount you want to display
   * @param decimals - specify how many decimal places a token has
   *
   * @throws if the given amount has a decimal point already
   * @example
   * ```ts
   * formatTokenAmount("123000", 4) === "12.3";
   * formatTokenAmount("123000", 3) === "123.0";
   * formatTokenAmount("123", 3) === "0.123";
   * ```
   */
  static formatTokenAmount(amount, decimals) {
    if (amount.includes(".")) {
      throw new TypeError("No decimals are allowed");
    }
    const negative = amount.startsWith("-");
    let formatted = negative ? amount.slice(1) : amount;
    if (decimals > 0) {
      if (decimals > formatted.length) {
        formatted = ["0", formatted.toString().padStart(decimals, "0")].join(
          "."
        );
      } else {
        formatted = [
          formatted.slice(0, -decimals),
          formatted.slice(-decimals)
        ].join(".");
      }
    }
    if (formatted.includes(".")) {
      formatted = formatted.replace(/0+$/, "");
      if (formatted.endsWith(".")) {
        formatted += "0";
      }
    }
    if (formatted.startsWith(".")) {
      formatted = `0${formatted}`;
    }
    return negative ? `-${formatted}` : formatted;
  }
  /**
   * Parse a token amount to use it on smart contract
   *
   * This function takes the display value and its decimals (if the token has
   * any) and returns a string that'll be used within the smart contract.
   *
   * Returns the whole number token amount represented by the display value
   * with the decimal places shifted over.
   *
   * @param value - the token amount you want to use on a smart contract
   *    which you've been displaying in a UI
   * @param decimals - the number of decimal places expected in the
   *    display value (different than the "actual" number, because suffix zeroes
   *    might not be present)
   *
   * @example
   * ```ts
   * const displayValueAmount = "123.4560"
   * const parsedAmtForSmartContract = parseTokenAmount(displayValueAmount, 5);
   * parsedAmtForSmartContract === "12345600"
   * ```
   */
  static parseTokenAmount(value, decimals) {
    const [whole, fraction, ...rest] = value.split(".").slice();
    if (rest.length) {
      throw new Error(`Invalid decimal value: ${value}`);
    }
    if (fraction?.length && fraction.length > decimals) {
      throw new Error(
        `Too many decimal places in "${value}": expected at most ${decimals}, got ${fraction.length}`
      );
    }
    const shifted = BigInt(
      whole + (fraction?.padEnd(decimals, "0") ?? "0".repeat(decimals))
    );
    return shifted.toString();
  }
}

export { Soroban };
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