export function validateAgeLive(inputEl, minAge = 5, maxAge = 18) {
  const dob = inputEl.value.trim();
  if (!dob) return false;

  const birthDate = parseDateOnly(dob);
  if (isNaN(birthDate.getTime())) {
    showFeedback(inputEl, false, "Invalid date format (Use YYYY-MM-DD)");
    return false;
  }

  const registrationAgeDeadline = window.appConfig?.registrationAgeDeadline;
  const schoolYearAgeDeadline = window.appConfig?.schoolYearAgeDeadline || registrationAgeDeadline;
  const minimumAgeDeadline = parseDateOnlyOrToday(registrationAgeDeadline);
  const ageDeadline = parseDateOnlyOrToday(schoolYearAgeDeadline);

  const minBirthDate = new Date(Date.UTC(ageDeadline.getUTCFullYear() - maxAge - 1, ageDeadline.getUTCMonth(), ageDeadline.getUTCDate() + 1)); // oldest
  const maxBirthDate = new Date(Date.UTC(minimumAgeDeadline.getUTCFullYear() - minAge, minimumAgeDeadline.getUTCMonth(), minimumAgeDeadline.getUTCDate())); // youngest

  const isValidAge = birthDate >= minBirthDate && birthDate <= maxBirthDate;

  // Format date as MM-DD-YYYY for error message (use original deadline, not adjusted)
  const formatDateMMDDYYYY = (dateStr) => {
    if (!dateStr) return dateStr;
    // Parse as UTC to avoid timezone issues that could shift the date
    const date = new Date(dateStr + 'T00:00:00.000Z');
    if (isNaN(date.getTime())) return dateStr;
    const month = String(date.getUTCMonth() + 1).padStart(2, '0');
    const day = String(date.getUTCDate()).padStart(2, '0');
    const year = date.getUTCFullYear();
    return `${month}-${day}-${year}`;
  };

  const errorMessage = isValidAge
    ? ""
    : `Must be at least ${minAge} years old by ${formatDateMMDDYYYY(registrationAgeDeadline)} and no older than ${maxAge} by ${formatDateMMDDYYYY(schoolYearAgeDeadline)}.`;

  showFeedback(inputEl, isValidAge, errorMessage);
  return isValidAge;
}

function normalize(date) {
  return new Date(Date.UTC(date.getFullYear(), date.getMonth(), date.getDate()));
}

function parseDateOnly(value) {
  const match = String(value || '').match(/^(\d{4})-(\d{2})-(\d{2})$/);
  if (!match) return new Date(NaN);

  const year = Number(match[1]);
  const monthIndex = Number(match[2]) - 1;
  const day = Number(match[3]);
  const date = new Date(Date.UTC(year, monthIndex, day));

  if (
    date.getUTCFullYear() !== year ||
    date.getUTCMonth() !== monthIndex ||
    date.getUTCDate() !== day
  ) {
    return new Date(NaN);
  }

  return date;
}

function parseDateOnlyOrToday(value) {
  const date = parseDateOnly(value);
  return isNaN(date.getTime()) ? normalize(new Date()) : date;
}


// Helper function (unchanged)
function showFeedback(inputEl, isValid, message) {
  inputEl.classList.toggle("is-invalid", !isValid);
  const feedbackEl = inputEl.nextElementSibling || document.createElement("div");
  feedbackEl.textContent = message;
  feedbackEl.className = `invalid-feedback ${isValid ? "d-none" : ""}`;
  inputEl.parentNode.appendChild(feedbackEl);
}

// Set max birthdate (2025 - minAge)
window.addEventListener("DOMContentLoaded", () => {
  const minAge = 5; // Must match validateAgeLive's default
  const deadline = parseDateOnlyOrToday(window.appConfig?.schoolYearAgeDeadline);
  const registrationAgeDeadline = parseDateOnly(window.appConfig?.registrationAgeDeadline);
  const maxDeadline = isNaN(registrationAgeDeadline.getTime()) ? deadline : registrationAgeDeadline;
  const maxBirthYear = maxDeadline.getUTCFullYear() - minAge;
  const maxDateStr = `${maxBirthYear}-12-31`; // Latest allowed birthdate for age-5 registration grace

  document.querySelectorAll(".dob-input").forEach((input) => {
    input.setAttribute("max", maxDateStr);
    input.setAttribute(
      "aria-label",
      `Born before ${maxBirthYear + 1} (${minAge}+ years by ${maxDeadline.getUTCFullYear()})`
    );
  });
});