/**
 * Formatted text for text blocks.
 *
 * Two views on the same value: a formatting view with a toolbar and an HTML view with the markup.
 * Whatever is typed here is a *proposal* – the server filters it against its allowlist when it is
 * stored, so this file never decides what is allowed. It only offers what the allowlist accepts.
 *
 * execCommand is deprecated but is still the only thing every browser implements for this job, and
 * the alternative would be a selection engine of our own. The formatting it produces is normalised
 * on the server anyway, so a browser quirk cannot store something unexpected.
 */

/** Mirrors RichText::ALLOWED. Only used for the hint text and for cleaning up on paste. */
export const ALLOWED_TAGS = ['p', 'br', 'strong', 'b', 'em', 'i', 'u', 's', 'code', 'mark', 'sup', 'sub', 'ul', 'ol', 'li', 'a'];

const COMMANDS = [
  { command: 'bold', label: 'B', title: 'Fett (Strg+B)', style: 'font-weight:700' },
  { command: 'italic', label: 'I', title: 'Kursiv (Strg+I)', style: 'font-style:italic' },
  { command: 'underline', label: 'U', title: 'Unterstrichen (Strg+U)', style: 'text-decoration:underline' },
  { command: 'strikeThrough', label: 'S', title: 'Durchgestrichen', style: 'text-decoration:line-through' },
  { command: 'insertUnorderedList', label: '•', title: 'Liste' },
  { command: 'insertOrderedList', label: '1.', title: 'Nummerierte Liste' },
  { command: 'removeFormat', label: '⌫', title: 'Formatierung entfernen' },
];

function button(label, title, onClick, className = 'rt-button') {
  const node = document.createElement('button');
  node.type = 'button';
  node.className = className;
  node.textContent = label;
  node.title = title;
  node.setAttribute('aria-label', title);
  node.addEventListener('mousedown', event => event.preventDefault()); // keep the selection
  node.addEventListener('click', onClick);
  return node;
}

/**
 * Builds the control. `apply` is called with the markup whenever it changes; the caller decides
 * what to do with it (history entry, preview refresh).
 */
export function createRichText(value, apply, { label = 'Text', plain = false } = {}) {
  const wrap = document.createElement('div');
  wrap.className = 'rich-text';

  const bar = document.createElement('div');
  bar.className = 'rt-bar';
  bar.setAttribute('role', 'toolbar');
  bar.setAttribute('aria-label', `${label} formatieren`);

  const surface = document.createElement('div');
  surface.className = 'rt-surface';
  surface.contentEditable = 'true';
  surface.spellcheck = true;
  surface.setAttribute('role', 'textbox');
  surface.setAttribute('aria-multiline', 'true');
  surface.setAttribute('aria-label', label);
  // Unter Schema v12 ist der Text Klartext: "Preis <b>5 Euro</b>" ist dann eine Zeichenfolge, kein
  // Markup, und darf beim Oeffnen nicht als HTML gelesen werden.
  if (plain) surface.textContent = value ?? '';
  else surface.innerHTML = value ?? '';

  const source = document.createElement('textarea');
  source.className = 'rt-source';
  source.hidden = true;
  source.setAttribute('aria-label', `${label} als HTML`);
  source.value = plain ? surface.innerHTML : (value ?? '');

  const push = markup => { source.value = markup; apply(markup); };

  for (const entry of COMMANDS) {
    const node = button(entry.label, entry.title, () => {
      surface.focus();
      document.execCommand(entry.command);
      push(surface.innerHTML);
    });
    if (entry.style) node.style.cssText = entry.style;
    bar.append(node);
  }

  // Link insertion without a browser prompt: a field appears in the bar and takes the target.
  const linkRow = document.createElement('div');
  linkRow.className = 'rt-link';
  linkRow.hidden = true;
  const linkInput = document.createElement('input');
  linkInput.type = 'text';
  linkInput.placeholder = '/kontakt, #abschnitt, https://…, mailto:…';
  linkInput.setAttribute('aria-label', 'Linkziel');
  const newTabLabel = document.createElement('label'); newTabLabel.className = 'check-label';
  const newTab = document.createElement('input'); newTab.type = 'checkbox';
  newTabLabel.append(newTab, document.createTextNode(' In neuem Tab öffnen'));
  let savedRange = null, currentLink = null;
  const confirmLink = () => {
    const target = linkInput.value.trim();
    linkRow.hidden = true;
    surface.focus();
    if (savedRange) {
      const selection = window.getSelection();
      selection.removeAllRanges();
      selection.addRange(savedRange);
    }
    if (target) {
      if (currentLink && surface.contains(currentLink)) currentLink.setAttribute('href', target);
      else document.execCommand('createLink', false, target);
      const range = window.getSelection().rangeCount ? window.getSelection().getRangeAt(0) : null;
      for (const anchor of surface.querySelectorAll('a')) {
        if (anchor !== currentLink && !(anchor.getAttribute('href') === target && range?.intersectsNode(anchor))) continue;
        if (newTab.checked) { anchor.setAttribute('target', '_blank'); anchor.setAttribute('rel', 'noopener'); }
        else { anchor.removeAttribute('target'); anchor.removeAttribute('rel'); }
      }
    } else document.execCommand('unlink');
    push(surface.innerHTML);
    linkInput.value = '';
  };
  linkInput.addEventListener('keydown', event => {
    if ('Enter' === event.key) { event.preventDefault(); confirmLink(); }
    if ('Escape' === event.key) { event.preventDefault(); linkRow.hidden = true; surface.focus(); }
  });
  linkRow.append(linkInput, newTabLabel, button('Übernehmen', 'Linkziel übernehmen', confirmLink, 'text-button'));

  bar.append(button('🔗', 'Link setzen oder entfernen', () => {
    const selection = window.getSelection();
    savedRange = selection.rangeCount > 0 && surface.contains(selection.getRangeAt(0).commonAncestorContainer) ? selection.getRangeAt(0).cloneRange() : null;
    const node = savedRange?.startContainer;
    currentLink = (node?.nodeType === Node.ELEMENT_NODE ? node : node?.parentElement)?.closest('a');
    if (currentLink && (!surface.contains(currentLink) || !currentLink.contains(savedRange.endContainer))) currentLink = null;
    linkInput.value = currentLink?.getAttribute('href') || '';
    newTab.checked = currentLink?.getAttribute('target') === '_blank';
    linkRow.hidden = false;
    linkInput.focus();
  }));
  linkRow.addEventListener('keydown', event => { if (event.key === 'Escape') { event.preventDefault(); linkRow.hidden = true; surface.focus(); } });

  const toggle = button('HTML', 'Zwischen Formatierung und HTML wechseln', () => {
    const toSource = source.hidden;
    if (toSource) {
      source.value = surface.innerHTML;
    } else {
      surface.innerHTML = source.value;
      apply(source.value);
    }
    source.hidden = !toSource;
    surface.hidden = toSource;
    toggle.setAttribute('aria-pressed', String(toSource));
    (toSource ? source : surface).focus();
  }, 'rt-button rt-toggle');
  toggle.setAttribute('aria-pressed', 'false');
  bar.append(toggle);

  surface.addEventListener('input', () => push(surface.innerHTML));
  // Paste as plain text: pasted markup would be stripped on the server anyway, and pasting a
  // whole web page into a text block is never what someone means.
  surface.addEventListener('paste', event => {
    event.preventDefault();
    const text = event.clipboardData?.getData('text/plain') ?? '';
    document.execCommand('insertText', false, text);
  });
  source.addEventListener('change', () => { surface.innerHTML = source.value; apply(source.value); });

  wrap.append(bar, linkRow, surface, source);
  return { element: wrap, focus: () => surface.focus() };
}