Form — Unsaved-changes leave guard

:root {
  --brand: #5b5bf0;
  --brand-d: #4646d6;
  --brand-700: #3a3ab8;
  --brand-50: #eef0ff;
  --accent: #00b4a6;
  --accent-soft: #d8f5f2;
  --ink: #101322;
  --ink-2: #3a4060;
  --muted: #6c7393;
  --bg: #f6f7fb;
  --white: #ffffff;
  --surface: #ffffff;
  --line: rgba(16, 19, 34, 0.1);
  --line-2: rgba(16, 19, 34, 0.16);
  --ok: #2f9e6f;
  --ok-soft: #e7f6ee;
  --warn: #d98a2b;
  --warn-soft: #fdf2e3;
  --danger: #d4503e;
  --danger-d: #b23e2e;
  --danger-soft: #fbeeec;
  --r-sm: 8px;
  --r-md: 14px;
  --r-lg: 20px;
  --sh-1: 0 1px 2px rgba(16, 19, 34, 0.08);
  --sh-2: 0 8px 24px rgba(16, 19, 34, 0.08);
  --sh-3: 0 24px 60px rgba(16, 19, 34, 0.22);
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  align-items: flex-start;
  justify-content: center;
  padding: 48px 20px 64px;
  background:
    radial-gradient(1200px 460px at 14% -8%, var(--brand-50), transparent 60%),
    radial-gradient(900px 420px at 100% 0%, var(--accent-soft), transparent 55%),
    var(--bg);
  color: var(--ink);
  font-family: "Inter", system-ui, -apple-system, "Segoe UI", sans-serif;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.page {
  width: 100%;
  max-width: 760px;
  display: grid;
  grid-template-columns: 188px 1fr;
  gap: 20px;
  align-items: start;
}

/* ── Side rail (guarded route links) ───────────────── */
.rail {
  position: sticky;
  top: 0;
  display: flex;
  flex-direction: column;
  gap: 2px;
  padding: 16px 12px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--r-lg);
  box-shadow: var(--sh-2);
}

.rail__brand {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 4px 8px 12px;
  margin-bottom: 6px;
  font-size: 14px;
  font-weight: 800;
  letter-spacing: -0.01em;
  color: var(--ink);
  border-bottom: 1px solid var(--line);
}

.rail__brand svg {
  color: var(--brand);
}

.rail__link {
  display: block;
  padding: 9px 12px;
  border-radius: var(--r-sm);
  font-size: 14px;
  font-weight: 600;
  color: var(--ink-2);
  text-decoration: none;
  transition:
    background 0.15s ease,
    color 0.15s ease;
}

.rail__link:hover {
  background: var(--brand-50);
  color: var(--brand-700);
}

.rail__link:focus-visible {
  outline: none;
  box-shadow: 0 0 0 3px var(--brand-50);
}

.rail__link.is-current {
  background: var(--brand);
  color: var(--white);
}

.rail__link.is-current:hover {
  background: var(--brand-d);
  color: var(--white);
}

/* ── Card ───────────────────────────────────────────── */
.card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--r-lg);
  box-shadow: var(--sh-2);
  padding: 32px;
}

.card__head {
  margin-bottom: 22px;
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  padding: 5px 11px;
  border-radius: 999px;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.02em;
  transition:
    background 0.18s ease,
    color 0.18s ease;
}

.eyebrow[data-state="clean"] {
  background: var(--ok-soft);
  color: var(--ok);
}

.eyebrow[data-state="dirty"] {
  background: var(--warn-soft);
  color: var(--warn);
}

.eyebrow[data-state="dirty"] svg {
  animation: pulse 1.8s ease-in-out infinite;
}

@keyframes pulse {
  0%,
  100% {
    opacity: 1;
  }
  50% {
    opacity: 0.4;
  }
}

.card__title {
  margin: 14px 0 8px;
  font-size: 27px;
  font-weight: 800;
  letter-spacing: -0.02em;
  line-height: 1.18;
}

.card__lede {
  margin: 0;
  color: var(--muted);
  font-size: 15px;
  max-width: 52ch;
}

/* ── Form grid ──────────────────────────────────────── */
.form {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 18px;
}

.field {
  grid-column: 1 / -1;
  min-width: 0;
  border: 0;
  margin: 0;
  padding: 0;
}

.field--half {
  grid-column: span 1;
}

.field--group {
  padding: 0;
}

.field__label {
  display: block;
  margin-bottom: 4px;
  padding: 0;
  font-size: 14px;
  font-weight: 600;
  color: var(--ink);
}

legend.field__label {
  float: left;
}

.req {
  color: var(--danger);
  font-weight: 700;
}

.field__hint {
  margin: 0 0 8px;
  font-size: 13px;
  color: var(--muted);
}

.field__error {
  margin: 0 0 8px;
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 13px;
  font-weight: 600;
  color: var(--danger);
}

.field__error::before {
  content: "";
  flex: none;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: var(--danger);
  -webkit-mask: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24'%3E%3Cpath fill='white' d='M12 2a10 10 0 100 20 10 10 0 000-20zm0 5a1 1 0 011 1v5a1 1 0 11-2 0V8a1 1 0 011-1zm0 9.5a1.2 1.2 0 110 2.4 1.2 1.2 0 010-2.4z'/%3E%3C/svg%3E")
    center / contain no-repeat;
  mask: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24'%3E%3Cpath fill='white' d='M12 2a10 10 0 100 20 10 10 0 000-20zm0 5a1 1 0 011 1v5a1 1 0 11-2 0V8a1 1 0 011-1zm0 9.5a1.2 1.2 0 110 2.4 1.2 1.2 0 010-2.4z'/%3E%3C/svg%3E")
    center / contain no-repeat;
}

.field__count {
  margin: 6px 0 0;
  font-size: 12px;
  font-weight: 600;
  color: var(--muted);
  text-align: right;
}

.field__count.is-max {
  color: var(--warn);
}

/* ── Inputs ─────────────────────────────────────────── */
.input {
  width: 100%;
  padding: 11px 13px;
  font: inherit;
  font-size: 15px;
  color: var(--ink);
  background: var(--white);
  border: 1.5px solid var(--line-2);
  border-radius: var(--r-sm);
  box-shadow: var(--sh-1);
  transition:
    border-color 0.15s ease,
    box-shadow 0.15s ease,
    background 0.15s ease;
}

.input::placeholder {
  color: #9aa0bd;
}

.textarea {
  resize: vertical;
  min-height: 76px;
  line-height: 1.5;
}

.select {
  appearance: none;
  -webkit-appearance: none;
  padding-right: 38px;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='20' height='20' viewBox='0 0 24 24' fill='none' stroke='%236c7393' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M6 9l6 6 6-6'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 11px center;
  cursor: pointer;
}

.input:hover:not(:disabled) {
  border-color: var(--ink-2);
}

.input:focus-visible {
  outline: none;
  border-color: var(--brand);
  box-shadow: 0 0 0 4px var(--brand-50);
}

.input:disabled {
  background: #f1f2f7;
  color: var(--muted);
  cursor: not-allowed;
  box-shadow: none;
}

/* Error / success states on the wrapping .field */
.field.is-error .input {
  border-color: var(--danger);
  background: #fffafa;
}

.field.is-error .input:focus-visible {
  box-shadow: 0 0 0 4px color-mix(in srgb, var(--danger) 20%, transparent);
}

.field.is-valid .input {
  border-color: var(--ok);
}

.field.is-valid .input:focus-visible {
  box-shadow: 0 0 0 4px color-mix(in srgb, var(--ok) 18%, transparent);
}

/* ── Checkboxes ─────────────────────────────────────── */
.checks {
  clear: both;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
}

.check {
  display: flex;
  align-items: center;
  gap: 11px;
  padding: 11px 13px;
  border: 1.5px solid var(--line-2);
  border-radius: var(--r-sm);
  background: var(--white);
  cursor: pointer;
  font-size: 14px;
  font-weight: 500;
  color: var(--ink-2);
  transition:
    border-color 0.15s ease,
    background 0.15s ease;
}

.check:hover {
  border-color: var(--ink-2);
}

.check:has(input:checked) {
  border-color: var(--brand);
  background: var(--brand-50);
}

.check input {
  position: absolute;
  opacity: 0;
  width: 1px;
  height: 1px;
}

.check__box {
  flex: none;
  display: grid;
  place-items: center;
  width: 22px;
  height: 22px;
  border: 1.5px solid var(--line-2);
  border-radius: 6px;
  background: var(--white);
  color: var(--white);
  transition:
    background 0.15s ease,
    border-color 0.15s ease,
    box-shadow 0.15s ease;
}

.check__box svg {
  opacity: 0;
  transform: scale(0.6);
  transition:
    opacity 0.12s ease,
    transform 0.12s ease;
}

.check input:checked ~ .check__box {
  background: var(--brand);
  border-color: var(--brand);
}

.check input:checked ~ .check__box svg {
  opacity: 1;
  transform: scale(1);
}

.check input:focus-visible ~ .check__box {
  box-shadow: 0 0 0 4px var(--brand-50);
}

/* ── Actions ────────────────────────────────────────── */
.form__actions {
  grid-column: 1 / -1;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 12px;
  margin-top: 6px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 20px;
  font: inherit;
  font-size: 15px;
  font-weight: 600;
  border-radius: var(--r-sm);
  border: 1.5px solid transparent;
  cursor: pointer;
  transition:
    transform 0.12s ease,
    box-shadow 0.15s ease,
    background 0.15s ease,
    border-color 0.15s ease,
    opacity 0.15s ease;
}

.btn:active {
  transform: translateY(1px);
}

.btn:focus-visible {
  outline: none;
  box-shadow: 0 0 0 4px var(--brand-50);
}

.btn--primary {
  background: var(--brand);
  color: var(--white);
  box-shadow: var(--sh-1);
}

.btn--primary:hover:not(:disabled) {
  background: var(--brand-d);
}

.btn--primary:disabled {
  background: #c3c5e8;
  color: #eef0ff;
  cursor: not-allowed;
  box-shadow: none;
}

.btn--ghost {
  background: var(--white);
  color: var(--ink-2);
  border-color: var(--line-2);
}

.btn--ghost:hover {
  border-color: var(--ink-2);
  background: #fafbff;
}

.btn--danger {
  background: var(--danger);
  color: var(--white);
  box-shadow: var(--sh-1);
}

.btn--danger:hover {
  background: var(--danger-d);
}

.btn--danger:focus-visible {
  box-shadow: 0 0 0 4px color-mix(in srgb, var(--danger) 28%, transparent);
}

.form__status {
  margin: 0;
  font-size: 13px;
  font-weight: 600;
  color: var(--muted);
}

.form__status.is-ok {
  color: var(--ok);
}

.form__status.is-error {
  color: var(--danger);
}

/* ── Modal (leave guard) ────────────────────────────── */
.modal {
  position: fixed;
  inset: 0;
  z-index: 80;
  display: grid;
  place-items: center;
  padding: 20px;
}

.modal__backdrop {
  position: absolute;
  inset: 0;
  background: rgba(16, 19, 34, 0.5);
  backdrop-filter: blur(2px);
  animation: fadeIn 0.18s ease;
}

.modal__dialog {
  position: relative;
  width: 100%;
  max-width: 420px;
  background: var(--surface);
  border-radius: var(--r-lg);
  box-shadow: var(--sh-3);
  padding: 26px 26px 22px;
  text-align: center;
  animation: dialogIn 0.22s cubic-bezier(0.2, 0.9, 0.3, 1.2);
}

.modal__dialog:focus-visible {
  outline: none;
}

.modal__icon {
  display: inline-grid;
  place-items: center;
  width: 56px;
  height: 56px;
  border-radius: 50%;
  background: var(--warn-soft);
  color: var(--warn);
  margin-bottom: 12px;
}

.modal__title {
  margin: 0 0 8px;
  font-size: 20px;
  font-weight: 800;
  letter-spacing: -0.01em;
}

.modal__desc {
  margin: 0 auto 20px;
  max-width: 38ch;
  color: var(--muted);
  font-size: 14.5px;
}

.modal__desc strong {
  color: var(--ink-2);
}

.modal__actions {
  display: flex;
  gap: 12px;
}

.modal__actions .btn {
  flex: 1;
}

@keyframes fadeIn {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

@keyframes dialogIn {
  from {
    opacity: 0;
    transform: translateY(10px) scale(0.97);
  }
  to {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
}

/* ── Toast ──────────────────────────────────────────── */
.toast {
  position: fixed;
  left: 50%;
  bottom: 26px;
  transform: translateX(-50%) translateY(16px);
  max-width: calc(100vw - 40px);
  padding: 12px 18px;
  background: var(--ink);
  color: var(--white);
  font-size: 14px;
  font-weight: 600;
  border-radius: var(--r-md);
  box-shadow: var(--sh-2);
  opacity: 0;
  pointer-events: none;
  transition:
    opacity 0.22s ease,
    transform 0.22s ease;
  z-index: 90;
}

.toast.is-visible {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}

/* ── Responsive ─────────────────────────────────────── */
@media (max-width: 720px) {
  .page {
    grid-template-columns: 1fr;
  }

  .rail {
    position: static;
    flex-direction: row;
    flex-wrap: wrap;
    align-items: center;
    gap: 6px;
    padding: 12px 14px;
  }

  .rail__brand {
    width: 100%;
    margin-bottom: 2px;
    padding-bottom: 10px;
  }
}

@media (max-width: 520px) {
  body {
    padding: 18px 14px 48px;
  }

  .card {
    padding: 22px 18px;
    border-radius: var(--r-md);
  }

  .card__title {
    font-size: 23px;
  }

  .form {
    grid-template-columns: 1fr;
    gap: 16px;
  }

  .field--half {
    grid-column: 1 / -1;
  }

  .checks {
    grid-template-columns: 1fr;
  }

  .form__actions {
    flex-direction: column;
    align-items: stretch;
  }

  .form__actions .btn {
    width: 100%;
  }

  .form__status {
    text-align: center;
  }

  .modal__actions {
    flex-direction: column-reverse;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
  }
}

/* Form — Unsaved-changes leave guard
 * ------------------------------------------------------------------
 * Tracks a "dirty" state once any field diverges from its saved
 * baseline. Any guarded navigation (in-page route links, the Cancel
 * button) is intercepted while dirty and routed through an accessible
 * confirm modal: Leave & discard / Stay. Saving validates, re-baselines
 * the form, and clears the guard. The native `beforeunload` event is
 * wired too so tab close / refresh / external links also warn — see the
 * note where it's registered (browsers show their own generic dialog;
 * the custom modal can't replace it for that event).
 */
(function () {
  "use strict";

  var form = document.getElementById("profile-form");
  var saveBtn = document.getElementById("save-btn");
  var cancelBtn = document.getElementById("cancel-btn");
  var status = document.getElementById("form-status");
  var badge = document.getElementById("dirty-badge");
  var badgeText = document.getElementById("dirty-badge-text");
  var toastEl = document.getElementById("toast");

  var modal = document.getElementById("guard-modal");
  var dialog = modal.querySelector(".modal__dialog");
  var modalDest = document.getElementById("modal-dest");
  var stayBtn = document.getElementById("stay-btn");
  var leaveBtn = document.getElementById("leave-btn");

  var bio = document.getElementById("bio");
  var bioNow = document.getElementById("bio-now");
  var bioCount = document.getElementById("bio-count");

  // Validation runs only on these required fields.
  var REQUIRED = ["displayName", "email"];

  var dirty = false; // does the form diverge from baseline?
  var baseline = snapshot(); // serialized saved state
  var pendingAction = null; // function to run if the user confirms "Leave"
  var lastFocused = null; // element to restore focus to on modal close

  /* ── Snapshot / dirty detection ─────────────────────────────── */

  // Serialize current form values into a comparable string.
  function snapshot() {
    var data = new FormData(form);
    var parts = [];
    var keys = ["displayName", "email", "role", "timezone", "bio"];
    keys.forEach(function (k) {
      parts.push(k + "=" + (data.get(k) || ""));
    });
    // Checkbox group → sorted list of checked values.
    var notify = data.getAll("notify").sort().join(",");
    parts.push("notify=" + notify);
    return parts.join("|");
  }

  function recomputeDirty() {
    var nowDirty = snapshot() !== baseline;
    if (nowDirty === dirty) return;
    dirty = nowDirty;
    saveBtn.disabled = !dirty;
    badge.dataset.state = dirty ? "dirty" : "clean";
    badgeText.textContent = dirty ? "Unsaved changes" : "All changes saved";
    if (!dirty) {
      status.textContent = "";
      status.className = "form__status";
    }
  }

  /* ── Field-level validation ─────────────────────────────────── */

  function setError(name, message) {
    var field = form.querySelector('[data-field="' + name + '"]');
    var input = document.getElementById(name);
    var err = document.getElementById(name + "-error");
    field.classList.add("is-error");
    field.classList.remove("is-valid");
    input.setAttribute("aria-invalid", "true");
    input.setAttribute("aria-describedby", name + "-hint " + name + "-error");
    err.textContent = message;
    err.hidden = false;
  }

  function setValid(name) {
    var field = form.querySelector('[data-field="' + name + '"]');
    var input = document.getElementById(name);
    var err = document.getElementById(name + "-error");
    field.classList.remove("is-error");
    field.classList.add("is-valid");
    input.removeAttribute("aria-invalid");
    input.setAttribute("aria-describedby", name + "-hint");
    err.hidden = true;
    err.textContent = "";
  }

  function clearState(name) {
    var field = form.querySelector('[data-field="' + name + '"]');
    var input = document.getElementById(name);
    var err = document.getElementById(name + "-error");
    field.classList.remove("is-error", "is-valid");
    input.removeAttribute("aria-invalid");
    input.setAttribute("aria-describedby", name + "-hint");
    err.hidden = true;
  }

  var EMAIL_RE = /^[^\s@]+@[^\s@]+\.[^\s@]{2,}$/;

  function validateField(name, markValid) {
    var value = (document.getElementById(name).value || "").trim();
    if (name === "displayName") {
      if (!value) return fail(name, "Enter a display name.");
      if (value.length < 2) return fail(name, "Use at least 2 characters.");
    }
    if (name === "email") {
      if (!value) return fail(name, "Enter your email address.");
      if (!EMAIL_RE.test(value)) return fail(name, "Enter a valid email, e.g. name@atlas.dev.");
    }
    if (markValid) setValid(name);
    return true;

    function fail(n, msg) {
      setError(n, msg);
      return false;
    }
  }

  function validateAll() {
    var firstInvalid = null;
    REQUIRED.forEach(function (name) {
      var ok = validateField(name, true);
      if (!ok && !firstInvalid) firstInvalid = document.getElementById(name);
    });
    return firstInvalid;
  }

  /* ── Toast helper ───────────────────────────────────────────── */

  var toastTimer = null;
  function toast(msg) {
    toastEl.hidden = false;
    toastEl.textContent = msg;
    // Force reflow so the transition replays on rapid calls.
    void toastEl.offsetWidth;
    toastEl.classList.add("is-visible");
    clearTimeout(toastTimer);
    toastTimer = setTimeout(function () {
      toastEl.classList.remove("is-visible");
    }, 2600);
  }

  /* ── Modal (accessible, focus-trapped) ──────────────────────── */

  function focusable() {
    return Array.prototype.slice.call(
      dialog.querySelectorAll("button:not([disabled])")
    );
  }

  function openModal(destLabel, onLeave) {
    pendingAction = onLeave;
    modalDest.textContent = destLabel;
    lastFocused = document.activeElement;
    modal.hidden = false;
    document.body.style.overflow = "hidden";
    // Move focus into the dialog; "Stay" is the safe default.
    stayBtn.focus();
    document.addEventListener("keydown", onKeydown, true);
  }

  function closeModal() {
    modal.hidden = true;
    document.body.style.overflow = "";
    document.removeEventListener("keydown", onKeydown, true);
    pendingAction = null;
    if (lastFocused && typeof lastFocused.focus === "function") {
      lastFocused.focus();
    }
    lastFocused = null;
  }

  function onKeydown(e) {
    if (e.key === "Escape") {
      e.preventDefault();
      closeModal(); // Esc == Stay
      return;
    }
    if (e.key !== "Tab") return;
    // Focus trap: keep Tab / Shift+Tab inside the dialog.
    var items = focusable();
    if (!items.length) return;
    var first = items[0];
    var last = items[items.length - 1];
    var active = document.activeElement;
    if (e.shiftKey && active === first) {
      e.preventDefault();
      last.focus();
    } else if (!e.shiftKey && active === last) {
      e.preventDefault();
      first.focus();
    } else if (items.indexOf(active) === -1) {
      e.preventDefault();
      first.focus();
    }
  }

  // Backdrop or any [data-close="stay"] element == Stay.
  modal.addEventListener("click", function (e) {
    if (e.target.getAttribute("data-close") === "stay") closeModal();
  });

  leaveBtn.addEventListener("click", function () {
    var action = pendingAction;
    closeModal();
    if (typeof action === "function") action();
  });

  /* ── Guarded navigation ─────────────────────────────────────── */

  // Run `proceed` immediately when clean; otherwise confirm first.
  function guard(destLabel, proceed) {
    if (!dirty) {
      proceed();
      return;
    }
    openModal(destLabel, proceed);
  }

  // Intercept the mock in-page route links.
  var railLinks = document.querySelectorAll(".rail__link");
  railLinks.forEach(function (link) {
    link.addEventListener("click", function (e) {
      e.preventDefault();
      var dest = link.dataset.route || "this page";
      guard(dest, function () {
        // Simulated client-side route change.
        railLinks.forEach(function (l) {
          l.classList.remove("is-current");
          l.removeAttribute("aria-current");
        });
        link.classList.add("is-current");
        link.setAttribute("aria-current", "page");
        // Leaving discards edits → reset to baseline values, clear guard.
        form.reset();
        REQUIRED.forEach(clearState);
        baseline = snapshot();
        recomputeDirty();
        updateBioCount();
        toast("Switched to " + dest + " — edits discarded.");
      });
    });
  });

  // Cancel button: same guard, "leaving" the editor.
  cancelBtn.addEventListener("click", function () {
    guard("the editor", function () {
      form.reset();
      REQUIRED.forEach(clearState);
      baseline = snapshot();
      recomputeDirty();
      updateBioCount();
      status.textContent = "Changes discarded.";
      status.className = "form__status";
      toast("Changes discarded.");
    });
  });

  /* ── beforeunload (tab close / refresh / external links) ────── */
  // The browser shows its OWN generic confirmation for this event; a
  // custom modal cannot be substituted here. We only opt in while dirty
  // by calling preventDefault() and setting returnValue.
  window.addEventListener("beforeunload", function (e) {
    if (!dirty) return;
    e.preventDefault();
    e.returnValue = ""; // required for the prompt in most browsers
  });

  /* ── Live input wiring ──────────────────────────────────────── */

  form.addEventListener("input", function (e) {
    recomputeDirty();
    var name = e.target.name;
    // Re-validate a required field live once it has shown an error.
    if (REQUIRED.indexOf(name) !== -1) {
      var field = form.querySelector('[data-field="' + name + '"]');
      if (field && field.classList.contains("is-error")) validateField(name, true);
    }
    if (e.target === bio) updateBioCount();
  });

  form.addEventListener("change", recomputeDirty);

  // Blur validation for required fields.
  REQUIRED.forEach(function (name) {
    document.getElementById(name).addEventListener("blur", function () {
      if (document.getElementById(name).value.trim()) validateField(name, true);
    });
  });

  function updateBioCount() {
    var len = bio.value.length;
    bioNow.textContent = String(len);
    bioCount.classList.toggle("is-max", len >= 160);
  }

  /* ── Save ───────────────────────────────────────────────────── */

  form.addEventListener("submit", function (e) {
    e.preventDefault();
    var firstInvalid = validateAll();
    if (firstInvalid) {
      status.textContent = "Fix the highlighted fields before saving.";
      status.className = "form__status is-error";
      firstInvalid.focus();
      return;
    }
    // Simulated save: re-baseline and clear the guard.
    saveBtn.disabled = true;
    status.textContent = "Saving…";
    status.className = "form__status";
    setTimeout(function () {
      baseline = snapshot();
      recomputeDirty(); // dirty → false, guard now inert
      status.textContent = "Profile saved.";
      status.className = "form__status is-ok";
      toast("Profile saved — the leave guard is now off.");
    }, 420);
  });

  // Initialize counters / state on load.
  updateBioCount();
  recomputeDirty();
})();

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <title>Form — Unsaved-changes leave guard</title>
    <link rel="preconnect" href="https://fonts.googleapis.com" />
    <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
    <link
      href="https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700;800&display=swap"
      rel="stylesheet"
    />
    <link rel="stylesheet" href="style.css" />
  </head>
  <body>
    <main class="page">
      <!-- Mock app shell: the in-page nav links are guarded route links -->
      <nav class="rail" aria-label="Account settings sections">
        <span class="rail__brand">
          <svg viewBox="0 0 24 24" width="18" height="18" aria-hidden="true">
            <circle cx="12" cy="9" r="3.4" fill="none" stroke="currentColor" stroke-width="2" />
            <path
              fill="none"
              stroke="currentColor"
              stroke-width="2"
              stroke-linecap="round"
              d="M5 19.2c1.4-3 4-4.4 7-4.4s5.6 1.4 7 4.4"
            />
          </svg>
          Atlas&nbsp;ID
        </span>
        <a class="rail__link is-current" href="#profile" data-route="Profile" aria-current="page">
          Profile
        </a>
        <a class="rail__link" href="#billing" data-route="Billing">Billing</a>
        <a class="rail__link" href="#security" data-route="Security">Security</a>
        <a class="rail__link" href="#team" data-route="Team">Team</a>
      </nav>

      <section class="card" aria-labelledby="form-title">
        <header class="card__head">
          <span class="eyebrow" data-state="clean" id="dirty-badge" role="status" aria-live="polite">
            <svg viewBox="0 0 24 24" width="14" height="14" aria-hidden="true">
              <path
                fill="none"
                stroke="currentColor"
                stroke-width="2"
                stroke-linecap="round"
                stroke-linejoin="round"
                d="M9 12.5l2 2 4-4M12 3l8 4v5c0 5-3.5 8-8 9-4.5-1-8-4-8-9V7l8-4z"
              />
            </svg>
            <span id="dirty-badge-text">All changes saved</span>
          </span>
          <h1 id="form-title" class="card__title">Edit your profile</h1>
          <p class="card__lede">
            Change a field, then try a nav link, Cancel, or closing the tab — a guard
            asks before you lose unsaved work. Saving clears the guard.
          </p>
        </header>

        <form id="profile-form" class="form" novalidate>
          <div class="field" data-field="displayName">
            <label class="field__label" for="displayName">
              Display name <span class="req" aria-hidden="true">*</span>
            </label>
            <p class="field__hint" id="displayName-hint">Shown across Atlas, e.g. Marisol Quintero.</p>
            <p class="field__error" id="displayName-error" hidden></p>
            <input
              class="input"
              id="displayName"
              name="displayName"
              type="text"
              autocomplete="name"
              value="Marisol Quintero"
              aria-describedby="displayName-hint"
              required
            />
          </div>

          <div class="field" data-field="email">
            <label class="field__label" for="email">
              Email address <span class="req" aria-hidden="true">*</span>
            </label>
            <p class="field__hint" id="email-hint">Used for sign-in and account notices.</p>
            <p class="field__error" id="email-error" hidden></p>
            <input
              class="input"
              id="email"
              name="email"
              type="email"
              autocomplete="email"
              inputmode="email"
              value="marisol@atlas.dev"
              aria-describedby="email-hint"
              required
            />
          </div>

          <div class="field field--half" data-field="role">
            <label class="field__label" for="role">Job title</label>
            <p class="field__hint" id="role-hint">Optional — appears on your team card.</p>
            <p class="field__error" id="role-error" hidden></p>
            <input
              class="input"
              id="role"
              name="role"
              type="text"
              autocomplete="organization-title"
              value="Product Designer"
              placeholder="e.g. Product Designer"
              aria-describedby="role-hint"
            />
          </div>

          <div class="field field--half" data-field="timezone">
            <label class="field__label" for="timezone">Time zone</label>
            <p class="field__hint" id="timezone-hint">We schedule digests in your local time.</p>
            <p class="field__error" id="timezone-error" hidden></p>
            <select class="input select" id="timezone" name="timezone" aria-describedby="timezone-hint">
              <option value="utc-8">Pacific (UTC−8)</option>
              <option value="utc-6">Central (UTC−6)</option>
              <option value="utc-5" selected>Eastern (UTC−5)</option>
              <option value="utc+0">London (UTC+0)</option>
              <option value="utc+1">Central Europe (UTC+1)</option>
            </select>
          </div>

          <div class="field" data-field="bio">
            <label class="field__label" for="bio">Short bio</label>
            <p class="field__hint" id="bio-hint">Up to 160 characters.</p>
            <p class="field__error" id="bio-error" hidden></p>
            <textarea
              class="input textarea"
              id="bio"
              name="bio"
              rows="3"
              maxlength="160"
              placeholder="A line about what you do."
              aria-describedby="bio-hint bio-count"
            >Designing calm, fast tools for small teams.</textarea>
            <p class="field__count" id="bio-count" aria-live="polite"><span id="bio-now">43</span>/160</p>
          </div>

          <fieldset class="field field--group" data-field="notify">
            <legend class="field__label">Email me about</legend>
            <p class="field__hint" id="notify-hint">Toggle the digests you want.</p>
            <div class="checks" aria-describedby="notify-hint">
              <label class="check">
                <input type="checkbox" name="notify" value="product" checked />
                <span class="check__box" aria-hidden="true">
                  <svg viewBox="0 0 24 24" width="14" height="14" aria-hidden="true">
                    <path
                      fill="none"
                      stroke="currentColor"
                      stroke-width="3"
                      stroke-linecap="round"
                      stroke-linejoin="round"
                      d="M5 12.5l4.5 4.5L19 7"
                    />
                  </svg>
                </span>
                <span class="check__text">Product updates</span>
              </label>
              <label class="check">
                <input type="checkbox" name="notify" value="weekly" />
                <span class="check__box" aria-hidden="true">
                  <svg viewBox="0 0 24 24" width="14" height="14" aria-hidden="true">
                    <path
                      fill="none"
                      stroke="currentColor"
                      stroke-width="3"
                      stroke-linecap="round"
                      stroke-linejoin="round"
                      d="M5 12.5l4.5 4.5L19 7"
                    />
                  </svg>
                </span>
                <span class="check__text">Weekly digest</span>
              </label>
            </div>
          </fieldset>

          <div class="form__actions">
            <button type="submit" class="btn btn--primary" id="save-btn" disabled>
              Save changes
              <svg viewBox="0 0 24 24" width="18" height="18" aria-hidden="true">
                <path
                  fill="none"
                  stroke="currentColor"
                  stroke-width="2"
                  stroke-linecap="round"
                  stroke-linejoin="round"
                  d="M5 12.5l4.5 4.5L19 6"
                />
              </svg>
            </button>
            <!-- Cancel is itself guarded: it tries to "leave" the editor -->
            <button type="button" class="btn btn--ghost" id="cancel-btn">Cancel</button>
            <p class="form__status" id="form-status" role="status" aria-live="polite"></p>
          </div>
        </form>
      </section>
    </main>

    <!-- Accessible confirm modal: focus-trapped, Esc = Stay -->
    <div class="modal" id="guard-modal" hidden>
      <div class="modal__backdrop" data-close="stay"></div>
      <div
        class="modal__dialog"
        role="alertdialog"
        aria-modal="true"
        aria-labelledby="modal-title"
        aria-describedby="modal-desc"
        tabindex="-1"
      >
        <span class="modal__icon" aria-hidden="true">
          <svg viewBox="0 0 24 24" width="26" height="26">
            <path
              fill="none"
              stroke="currentColor"
              stroke-width="2"
              stroke-linecap="round"
              stroke-linejoin="round"
              d="M12 3l9.5 16.5H2.5L12 3zM12 9.5v4.5M12 17.2v.2"
            />
          </svg>
        </span>
        <h2 class="modal__title" id="modal-title">You have unsaved changes</h2>
        <p class="modal__desc" id="modal-desc">
          If you leave <strong id="modal-dest">this page</strong> now, your edits to the
          profile form will be discarded. Save them first, or leave anyway.
        </p>
        <div class="modal__actions">
          <button type="button" class="btn btn--ghost" id="stay-btn" data-close="stay">
            Stay on page
          </button>
          <button type="button" class="btn btn--danger" id="leave-btn">Leave &amp; discard</button>
        </div>
      </div>
    </div>

    <!-- Toast region -->
    <div class="toast" id="toast" role="status" aria-live="polite" hidden></div>

    <script src="script.js"></script>
  </body>
</html>