/** Hauteur utile du corps d’un iframe d’aperçu mail (évite le scrollHeight fantôme). */

export const EMAIL_PREVIEW_MIN_IFRAME_HEIGHT = 120

const CONTENT_MEASURE_SELECTORS =
  "p,div,span,td,th,li,h1,h2,h3,h4,h5,h6,table,img,blockquote,pre,hr,a,section,article,footer,header"

export function measureEmailPreviewIframeHeight(doc: Document): number {
  const body = doc.body
  const view = doc.defaultView
  if (!body || !view) return EMAIL_PREVIEW_MIN_IFRAME_HEIGHT

  const scrollEstimate = Math.max(
    body.scrollHeight,
    body.offsetHeight,
    doc.documentElement?.scrollHeight ?? 0,
    doc.documentElement?.offsetHeight ?? 0
  )

  const bodyTop = body.getBoundingClientRect().top
  let contentBottom = bodyTop

  for (const el of body.querySelectorAll(CONTENT_MEASURE_SELECTORS)) {
    const cs = view.getComputedStyle(el)
    if (cs.display === "none" || cs.visibility === "hidden") continue
    const rect = el.getBoundingClientRect()
    if (rect.height < 1 && rect.width < 1) continue
    contentBottom = Math.max(contentBottom, rect.bottom)
  }

  const hasVisibleLayout = contentBottom > bodyTop + 8
  if (hasVisibleLayout) {
    const boundEstimate = Math.ceil(contentBottom - bodyTop) + 4
    if (boundEstimate < scrollEstimate * 0.92) {
      return Math.max(EMAIL_PREVIEW_MIN_IFRAME_HEIGHT, boundEstimate)
    }
  }

  return Math.max(EMAIL_PREVIEW_MIN_IFRAME_HEIGHT, scrollEstimate + 2)
}