/** Remove marketing preheader blocks before display (bluemonday strips display:none). */

const HIDDEN_STYLE =
  /display\s*:\s*none|mso-hide\s*:\s*all|max-height\s*:\s*0|opacity\s*:\s*0|font-size\s*:\s*0|visibility\s*:\s*hidden/i

const HIDDEN_CLASS = /mcnPreviewText|preheader|preview-text/i

const INVISIBLE_RUN = /[\u034f\u200b-\u200f\ufeff\u00a0]{4,}/g

function shouldStripElement(el: Element): boolean {
  if (el.hasAttribute("hidden")) return true
  if (el.getAttribute("aria-hidden") === "true") return true
  const cls = el.className?.toString() ?? ""
  if (HIDDEN_CLASS.test(cls)) return true
  const style = el.getAttribute("style") ?? ""
  if (!style) return false
  const compact = style.replace(/\s+/g, "")
  return (
    HIDDEN_STYLE.test(style) ||
    (compact.includes("overflow:hidden") && /max-height\s*:\s*0/.test(style))
  )
}

export function stripHiddenEmailHtml(html: string): string {
  if (!html.trim() || typeof DOMParser === "undefined") {
    return html
  }
  try {
    const doc = new DOMParser().parseFromString(html, "text/html")
    const remove: Element[] = []
    doc.body.querySelectorAll("*").forEach((el) => {
      if (shouldStripElement(el)) remove.push(el)
    })
    for (const el of remove) el.remove()
    return doc.body.innerHTML
  } catch {
    return html
  }
}

export function stripInvisibleTextRuns(text: string): string {
  return text.replace(INVISIBLE_RUN, " ").replace(/\s+/g, " ").trim()
}