/**
 * Text shaping for the call reader. Model summaries arrive as dense
 * paragraphs; on a wide pane they are a wall. Splitting them into one point
 * per sentence and setting the figures in bold is what makes them scannable.
 */

/**
 * Sentence boundaries, minus the periods inside abbreviations ("U.S.",
 * "Inc.", "vs.") and figures ("$27.8 million").
 */
const SENTENCE_BOUNDARY =
  /(?<!\b(?:[A-Z]|Inc|Ltd|Co|Corp|vs|Mr|Ms|Mrs|Dr|No|St|Jr|Sr|U\.S|e\.g|i\.e|approx))[.!?]["”')]?\s+(?=["“(]?[A-Z0-9$])/;

/**
 * Phrases a speaker uses to start a new topic; a paragraph break before one
 * lands where an editor would put it.
 */
const TOPIC_SHIFT =
  /^(?:Turning to|Moving (?:on )?to|Now,? (?:let me|let's|turning|moving|I'll|I want)|Let me (?:now |also |briefly )?(?:turn|move|shift|start|close|wrap|touch)|With that|Next,|Finally,|In (?:summary|closing)|Before I|Looking (?:ahead|forward)|Lastly,|First,|Second,|Third,|Fourth,|As for|Regarding|Switching to|Shifting to|To (?:wrap|close|summarize))/;

/**
 * A speaking turn as paragraphs of about `targetWords`, for transcripts the
 * server produced before it cut paragraphs itself. Sentences are grouped and
 * the group closes early where the speaker changes topic.
 */
export function splitParagraphs(text: string, targetWords = 80): string[] {
  const paragraphs: string[] = [];
  let current: string[] = [];
  let words = 0;
  const flush = () => {
    if (current.length > 0) paragraphs.push(current.join(" "));
    current = [];
    words = 0;
  };
  for (const sentence of splitSentences(text)) {
    const count = sentence.split(/\s+/).length;
    if (words >= targetWords * 0.4 && TOPIC_SHIFT.test(sentence)) flush();
    if (words > 0 && words + count > targetWords * 1.25) flush();
    current.push(sentence);
    words += count;
    if (words >= targetWords) flush();
  }
  flush();
  return paragraphs;
}

export function splitSentences(text: string): string[] {
  const out: string[] = [];
  let rest = text.trim();
  while (rest.length > 0) {
    const match = SENTENCE_BOUNDARY.exec(rest);
    if (!match) {
      out.push(rest);
      break;
    }
    // Keep the closing punctuation, drop the whitespace that followed it.
    const cut = match.index + match[0].trimEnd().length;
    out.push(rest.slice(0, cut).trim());
    rest = rest.slice(match.index + match[0].length);
  }
  return out.filter(Boolean);
}