const dialogs = new Map(
  [...document.querySelectorAll('.legal-dialog')].map(dialog => [dialog.id, dialog]),
);
let returnFocus;

function syncDialog() {
  const next = dialogs.get(location.hash.slice(1));
  let closed = false;

  for (const dialog of dialogs.values()) {
    if (dialog.open && dialog !== next) {
      dialog.close();
      closed = true;
    }
  }

  if (next && !next.open) {
    returnFocus ??= document.querySelector(`[data-legal-open][aria-controls="${next.id}"]`);
    next.showModal();
    next.querySelector('.legal-copy').scrollTop = 0;
    next.querySelector('h1').focus({ preventScroll: true });
  } else if (!next && closed) {
    returnFocus?.focus({ preventScroll: true });
    returnFocus = undefined;
  }
}

function dismissDialog() {
  history.replaceState(null, '', location.pathname + location.search);
  syncDialog();
}

for (const link of document.querySelectorAll('[data-legal-open]')) {
  link.addEventListener('click', event => {
    if (event.button !== 0 || event.metaKey || event.ctrlKey || event.shiftKey || event.altKey) return;
    event.preventDefault();
    returnFocus = link;
    history.pushState(null, '', link.hash);
    syncDialog();
  });
}

for (const dialog of dialogs.values()) {
  dialog.querySelector('[data-legal-close]').addEventListener('click', event => {
    event.preventDefault();
    dismissDialog();
  });
  dialog.addEventListener('cancel', event => {
    event.preventDefault();
    dismissDialog();
  });
  dialog.addEventListener('keydown', event => {
    if (event.key !== 'Tab' || event.altKey || event.ctrlKey || event.metaKey) return;
    const controls = [...dialog.querySelectorAll('a[href], button:not([disabled]), [tabindex="0"]')];
    const first = controls[0];
    const last = controls.at(-1);
    const active = document.activeElement;
    if (!controls.includes(active) || (event.shiftKey && active === first)
      || (!event.shiftKey && active === last)) {
      event.preventDefault();
      (event.shiftKey ? last : first)?.focus();
    }
  });

  // Close only when both ends of a click are on the backdrop, not a text-selection drag.
  let startedOutside = false;
  const outside = event => {
    const rect = dialog.getBoundingClientRect();
    return event.clientX < rect.left || event.clientX > rect.right
      || event.clientY < rect.top || event.clientY > rect.bottom;
  };
  dialog.addEventListener('pointerdown', event => {
    startedOutside = event.target === dialog && outside(event);
  });
  dialog.addEventListener('click', event => {
    if (startedOutside && event.target === dialog && outside(event)) dismissDialog();
    startedOutside = false;
  });
}

window.addEventListener('hashchange', syncDialog);
window.addEventListener('popstate', syncDialog);
syncDialog();