parking-calculator-library/src/ParkingFeeCalculator.js

A library to calculate parking fees based on duration, with discounts for early bird, weekend, and loyalty members.

export class ParkingFeeCalculator {
  constructor() {
    this.rates = {
      shortTerm: 10000, // Per hour for the first 2 hours (UGX)
      midTerm: 7000, // Per hour for 2-6 hours (UGX)
      longTerm: 5000, // Per hour after 6 hours (UGX)
      dailyCap: 50000, // Maximum fee for 24 hours (UGX)
    };
    this.thresholds = {
      shortTermLimit: 2, // Short-term duration limit in hours
      midTermLimit: 6, // Mid-term duration limit in hours
    };
  }

  calculateParkingDuration(entryTime, exitTime) {
    if (!(entryTime instanceof Date) || !(exitTime instanceof Date)) {
      throw new Error("Invalid timestamp input");
    }

    if (exitTime < entryTime) {
      throw new Error("Exit time cannot be before entry time");
    }

    const durationMs = exitTime - entryTime;
    return durationMs / (1000 * 60 * 60); // Convert milliseconds to hours
  }

  calculateParkingFee(entryTime, exitTime) {
    const duration = this.calculateParkingDuration(entryTime, exitTime);
    let totalFee = 0;

    if (duration <= this.thresholds.shortTermLimit) {
      totalFee = duration * this.rates.shortTerm;
    } else if (duration <= this.thresholds.midTermLimit) {
      totalFee =
        this.thresholds.shortTermLimit * this.rates.shortTerm +
        (duration - this.thresholds.shortTermLimit) * this.rates.midTerm;
    } else {
      totalFee = Math.min(
        this.thresholds.shortTermLimit * this.rates.shortTerm +
          (this.thresholds.midTermLimit - this.thresholds.shortTermLimit) *
            this.rates.midTerm +
          (duration - this.thresholds.midTermLimit) * this.rates.longTerm,
        this.rates.dailyCap
      );
    }

    return Number(totalFee.toFixed(2));
  }

  applyDiscounts(originalFee, options = {}) {
    let discountedFee = originalFee;
    let appliedDiscounts = [];

    if (options.earlyBird && options.entryTime.getHours() < 9) {
      discountedFee *= 0.8;
      appliedDiscounts.push("Early Bird (20% off)");
    }

    if (
      options.weekendDiscount &&
      [0, 6].includes(options.entryTime.getDay())
    ) {
      discountedFee *= 0.9;
      appliedDiscounts.push("Weekend (10% off)");
    }

    if (options.loyaltyMember) {
      discountedFee *= 0.95;
      appliedDiscounts.push("Loyalty Member (5% off)");
    }

    return {
      fee: Number(discountedFee.toFixed(2)),
      discounts: appliedDiscounts,
    };
  }
}