// Gemeinsame Logik fuer Kuendigungs- (§ 312k BGB) und Widerrufsbutton (§ 356a BGB).
// Oeffentlich, ohne Login. Zweistufig: Einstiegsbutton -> Formular -> Bestaetigungsbutton.
function initLegalForm({ endpoint, fields }) {
  const intro = document.getElementById('intro')
  const form = document.getElementById('decl-form')
  const done = document.getElementById('done')
  const errEl = document.getElementById('form-error')

  document.getElementById('start-btn').addEventListener('click', () => {
    intro.classList.add('hidden')
    form.classList.remove('hidden')
    form.querySelector('input').focus()
  })

  const reasonWrap = document.getElementById('reason-wrap')
  form.querySelectorAll('[name="kind"]').forEach((r) =>
    r.addEventListener('change', () => {
      reasonWrap?.classList.toggle('hidden', form.kind.value !== 'ausserordentlich')
    })
  )

  form.addEventListener('submit', async (ev) => {
    ev.preventDefault()
    errEl.classList.add('hidden')
    const payload = {}
    for (const f of fields) payload[f] = form.elements[f]?.value?.trim?.() ?? form.elements[f]?.value ?? ''
    const btn = form.querySelector('button[type="submit"]')
    btn.disabled = true
    try {
      const res = await fetch(endpoint, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify(payload),
      })
      const data = await res.json().catch(() => ({}))
      if (!res.ok) throw new Error(data.error || `Fehler ${res.status}`)
      const at = new Date(data.receivedAt).toLocaleString('de-DE', { dateStyle: 'full', timeStyle: 'short' })
      const esc = (s) => String(s || '').replace(/[&<>"]/g, (c) => ({ '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;' })[c])
      document.getElementById('done-at').textContent = at
      document.getElementById('done-list').innerHTML = fields
        .filter((f) => payload[f])
        .map((f) => `<dt>${esc(form.querySelector(`[data-label-for="${f}"]`)?.dataset.label || f)}</dt><dd>${esc(
          form.elements[f]?.type === 'radio' || form.elements[f] instanceof RadioNodeList
            ? form.querySelector(`[name="${f}"]:checked`)?.dataset.text || payload[f]
            : payload[f]
        )}</dd>`)
        .join('')
      form.classList.add('hidden')
      done.classList.remove('hidden')
      window.scrollTo({ top: 0, behavior: 'smooth' })
    } catch (err) {
      errEl.textContent = err.message
      errEl.classList.remove('hidden')
      btn.disabled = false
    }
  })
}