/* VORÜBERGEHENDE MESSUNG (2026-10-29), wird nach der Klärung wieder entfernt: Am iPhone (App vom Home-Bildschirm) steht die Leiste zu hoch.
   Schickt Bildschirmwerte (Fenster, visualViewport, Bildschirm, Safe-Area, vh-Einheiten, Lage der Leiste) an
   /api/diag/hoehe; der Server schreibt sie ins Log (server/routes/diagHoehe.js). Keine Inhalte, keine Eingaben. Höchstens MAX Meldungen je Seite. */

const MAX = 80
const ZIEL = '/api/diag/hoehe'
const rund = (x) => (Number.isFinite(x) ? Math.round(x * 10) / 10 : null)

export function starteDiagHoehe({ win = window, doc = document }) {
  const t0 = Date.now()
  let n = 0
  const probe = (stil) => {
    const el = doc.createElement('div')
    el.setAttribute('aria-hidden', 'true')
    el.style.cssText = `position:fixed;left:0;top:0;width:0;visibility:hidden;pointer-events:none;${stil}`
    doc.body.append(el)
    return el
  }
  const sa = probe('height:0;padding:env(safe-area-inset-top) env(safe-area-inset-right) env(safe-area-inset-bottom) env(safe-area-inset-left)')
  const vh = probe('height:100vh'); const dvh = probe('height:100dvh'); const svh = probe('height:100svh'); const lvh = probe('height:100lvh')
  const unten = probe('top:auto;bottom:0;height:1px') // wo „bottom: 0“ eines festen Elements wirklich landet

  function messe(art, extra) {
    const vv = win.visualViewport
    const cs = win.getComputedStyle(sa)
    const leiste = doc.getElementById('kn-leiste')?.getBoundingClientRect()
    const huelle = doc.querySelector('.kn-huelle')?.getBoundingClientRect()
    const aktiv = doc.activeElement
    return {
      art, ms: Date.now() - t0, hash: win.location.hash,
      iw: win.innerWidth, ih: win.innerHeight, ow: win.outerWidth, oh: win.outerHeight,
      cw: doc.documentElement.clientWidth, ch: doc.documentElement.clientHeight, dh: doc.documentElement.scrollHeight,
      sw: win.screen?.width, sh: win.screen?.height, sah: win.screen?.availHeight, dpr: win.devicePixelRatio,
      vv: vv ? [rund(vv.width), rund(vv.height), rund(vv.offsetTop), rund(vv.pageTop), rund(vv.scale)] : null,
      sy: rund(win.scrollY),
      sa: [cs.paddingTop, cs.paddingRight, cs.paddingBottom, cs.paddingLeft].map((p) => rund(parseFloat(p))),
      vh: [vh.offsetHeight, dvh.offsetHeight, svh.offsetHeight, lvh.offsetHeight],
      unten: rund(unten.getBoundingClientRect().bottom),
      leiste: leiste ? [rund(leiste.top), rund(leiste.bottom), rund(leiste.height)] : null,
      huelle: huelle ? [rund(huelle.top), rund(huelle.height)] : null,
      app: Boolean(win.matchMedia?.('(display-mode: standalone)').matches), ns: win.navigator?.standalone ?? null,
      ori: win.screen?.orientation?.type ?? null,
      fokus: aktiv && aktiv !== doc.body ? aktiv.tagName : null,
      tast: doc.body.classList.contains('kn-tastatur'),
      ...(n === 0 ? { ua: String(win.navigator?.userAgent ?? '').slice(0, 200) } : {}),
      ...(extra ?? {}),
    }
  }

  function sende(art, extra) {
    if (n >= MAX) return
    let daten
    try { daten = messe(art, extra) } catch (fehler) { daten = { art, fehler: String(fehler?.message ?? fehler).slice(0, 200) } }
    n += 1
    try {
      win.fetch(ZIEL, { method: 'POST', credentials: 'same-origin', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify(daten), keepalive: true }).catch(() => {})
    } catch { /* Messung darf nie stören */ }
  }

  const spaeter = (fn, ms) => win.setTimeout(fn, ms)
  const entprellt = (art) => { let id = null; return () => { if (id) win.clearTimeout(id); id = spaeter(() => { id = null; sende(art) }, 250) } }
  sende('start')
  spaeter(() => sende('start+1s'), 1000)
  spaeter(() => sende('start+4s'), 4000)
  win.addEventListener('resize', entprellt('resize'))
  win.visualViewport?.addEventListener('resize', entprellt('vv-resize'))
  win.visualViewport?.addEventListener('scroll', entprellt('vv-scroll'))
  doc.addEventListener('focusin', (ev) => { if (ev.target?.matches?.('textarea, input')) sende('fokus') })
  doc.addEventListener('focusout', (ev) => { if (ev.target?.matches?.('textarea, input')) { spaeter(() => sende('unfokus+300ms'), 300); spaeter(() => sende('unfokus+1s'), 1000) } })
  doc.addEventListener('visibilitychange', () => { if (doc.visibilityState === 'visible') { sende('sichtbar'); spaeter(() => sende('sichtbar+1s'), 1000) } })
  win.addEventListener('hashchange', () => spaeter(() => sende('route'), 600))
  win.addEventListener('pageshow', (ev) => { if (ev.persisted) sende('pageshow') })
  return { sende }
}