Paystack fee

fee.ts

class PaystackSetup {
  private readonly decimalFee: number = 0.015; // 1.5%
  private readonly feeCap: number = 2000; // Maximum fee per transaction
  private readonly flatFee: number = 100; // Flat fee applied for transactions >= NGN 2,500

  /// Calculates the total price to be charged to the customer, including transaction fees.
  calculateTotalPrice(price: number): number {
    if (price < 2500) {
      return this.calculateBelow2500(price);
    }
    return this.calculateAbove2500(price);
  }

  /// Calculates the final amount for transactions below NGN 2,500.
  private calculateBelow2500(price: number): number {
    const applicableFees = this.decimalFee * price;

    if (applicableFees > this.feeCap) {
      // If percentage fee exceeds the fee cap, add the fee cap to the price
      return this.roundToTwoDecimalPlaces(price + this.feeCap);
    }

    // Calculate the price including only the percentage fee
    return this.roundToTwoDecimalPlaces(price / (1 - this.decimalFee));
  }

  /// Calculates the final amount for transactions of NGN 2,500 and above.
  private calculateAbove2500(price: number): number {
    const applicableFees = (this.decimalFee * price) + this.flatFee;

    if (applicableFees > this.feeCap) {
      // If combined fees exceed the fee cap, add the fee cap to the price
      return this.roundToTwoDecimalPlaces(price + this.feeCap);
    }

    // Calculate the price including both percentage and flat fees
    return this.roundToTwoDecimalPlaces((price + this.flatFee) / (1 - this.decimalFee));
  }

  /// Rounds a number to two decimal places.
  private roundToTwoDecimalPlaces(value: number): number {
    return Math.ceil(value * 100) / 100;
  }
}