utils.js

/**
 * js/utils.js
 * Utility functions for the rental car system.
 */

/**
 * Formats a date string into a more readable format (e.g., "DD/MM/YYYY").
 * @param {string} dateString - The date string (e.g., "YYYY-MM-DD").
 * @returns {string} Formatted date string.
 */
export function formatDate(dateString) {
    if (!dateString) return '';
    try {
        const date = new Date(dateString);
        const day = String(date.getDate()).padStart(2, '0');
        const month = String(date.getMonth() + 1).padStart(2, '0'); // Month is 0-indexed
        const year = date.getFullYear();
        return `${day}/${month}/${year}`;
    } catch (e) {
        console.error("Error formatting date:", e);
        return dateString; // Return original if invalid
    }
}

/**
 * Calculates the total rental price based on car price per day and rental duration.
 * @param {number} pricePerDay - The daily rental price of the car.
 * @param {string} startDateString - The start date (YYYY-MM-DD).
 * @param {string} endDateString - The end date (YYYY-MM-DD).
 * @returns {number | null} Total price or null if dates are invalid.
 */
export function calculateRentalPrice(pricePerDay, startDateString, endDateString) {
    if (!pricePerDay || !startDateString || !endDateString) {
        return null;
    }

    try {
        const startDate = new Date(startDateString);
        const endDate = new Date(endDateString);

        if (isNaN(startDate.getTime()) || isNaN(endDate.getTime())) {
            console.error("Invalid start or end date for price calculation.");
            return null;
        }

        // Calculate difference in days
        const diffTime = Math.abs(endDate - startDate);
        // Add 1 to include the last day. If pickup and return on same day, it's 1 day.
        const diffDays = Math.ceil(diffTime / (1000 * 60 * 60 * 24)) + 1; 

        if (diffDays <= 0) {
            return pricePerDay; // At least one day rental
        }

        return pricePerDay * diffDays;

    } catch (e) {
        console.error("Error calculating rental price:", e);
        return null;
    }
}