// Zalo rejects over-long texts. Split long replies, preferring paragraph
// boundaries when chunkMode is 'newline'.
export function chunk(text: string, limit: number, mode: 'length' | 'newline'): string[] {
  if (text.length <= limit) return [text]
  const out: string[] = []
  let rest = text
  while (rest.length > limit) {
    let cut = limit
    if (mode === 'newline') {
      // Prefer the last double-newline (paragraph), then single newline,
      // then space. Fall back to hard cut.
      const para = rest.lastIndexOf('\n\n', limit)
      const line = rest.lastIndexOf('\n', limit)
      const space = rest.lastIndexOf(' ', limit)
      cut = para > limit / 2 ? para : line > limit / 2 ? line : space > 0 ? space : limit
    }
    out.push(rest.slice(0, cut))
    rest = rest.slice(cut).replace(/^\n+/, '')
  }
  if (rest) out.push(rest)
  return out
}