camper/web/static/booking-dates.js

(function () {
    'use strict';

    function updateDepartureDate(arrivalDateField) {
        const arrivalDate = new Date(arrivalDateField.value);
        if (isNaN(arrivalDate)) {
            return;
        }
        const departureDateField = document.querySelector('[name="departure_date"]');
        if (!departureDateField) {
            return;
        }

        const minNights = Math.max(1, parseInt(departureDateField.dataset.minNights, 10));
        arrivalDate.setUTCDate(arrivalDate.getUTCDate() + minNights);
        const minDate = formatDate(arrivalDate);

        departureDateField.setAttribute('min', minDate);
        const departureDate = new Date(departureDateField.value);
        if (isNaN(departureDate) || departureDate < arrivalDate) {
            departureDateField.value = minDate;
        }

        const maxNights = parseInt(departureDateField.dataset.maxNights, 10);
        if (maxNights > 0) {
            arrivalDate.setUTCDate(arrivalDate.getUTCDate() + maxNights - minNights);
            const maxDate = formatDate(arrivalDate);
            departureDateField.setAttribute('max', maxDate);
            if (!isNaN(departureDate) && departureDate >= arrivalDate) {
                departureDateField.value = maxDate;
            }
        }
    }

    function formatDate(date) {
        return `${date.getFullYear()}-${zeroPad(date.getMonth() + 1)}-${zeroPad(date.getDate())}`;
    }

    function zeroPad(num) {
        return `${num < 10 ? '0' : ''}${num}`
    }

    const arrivalDateField = document.querySelector('[name="arrival_date"]');
    if (!arrivalDateField) {
        return;
    }
    arrivalDateField.addEventListener('change', function (event) {
        updateDepartureDate(event.target);
    });

    updateDepartureDate(arrivalDateField);
})();