const SLACK_MAX_LENGTH = 4000;

export function formatForSlack(text: string): string[] {
  let converted = text
    .replace(/\*\*(.+?)\*\*/g, "*$1*")
    .replace(/\[([^\]]+)\]\(([^)]+)\)/g, "<$2|$1>")
    .replace(/^#{1,6}\s+(.+)$/gm, "*$1*");

  return chunkText(converted, SLACK_MAX_LENGTH);
}

function chunkText(text: string, maxLen: number): string[] {
  if (text.length <= maxLen) return [text];

  const chunks: string[] = [];
  let remaining = text;

  while (remaining.length > maxLen) {
    let splitAt = maxLen;

    const newlineIdx = remaining.lastIndexOf("\n", maxLen);
    if (newlineIdx > maxLen * 0.5) {
      splitAt = newlineIdx + 1;
    } else {
      const spaceIdx = remaining.lastIndexOf(" ", maxLen);
      if (spaceIdx > maxLen * 0.5) {
        splitAt = spaceIdx + 1;
      }
    }

    chunks.push(remaining.slice(0, splitAt));
    remaining = remaining.slice(splitAt);
  }

  if (remaining) chunks.push(remaining);
  return chunks;
}