function truncateText(text: string, headChars: number, tailChars: number, label: string): { text: string; truncated: boolean } {
  if (text.length <= headChars + tailChars) {
    return { text, truncated: false };
  }

  const head = text.slice(0, Math.max(0, headChars));
  const tail = text.slice(Math.max(0, text.length - Math.max(0, tailChars)));
  return {
    text: `[${label}: ${text.length} chars, showing first ${head.length} and last ${tail.length}]\n${head}\n\n…\n\n${tail}`,
    truncated: true,
  };
}

export function truncateOversizedText(
  text: string,
  options: { headChars: number; tailChars: number; maxChars: number },
): { text: string; truncated: boolean } {
  if (text.length <= options.maxChars) {
    return { text, truncated: false };
  }

  return truncateText(text, options.headChars, options.tailChars, "message truncated");
}

export function compressToolResultText(
  text: string,
  options: { headLines: number; tailLines: number; maxChars: number },
): { text: string; truncated: boolean } {
  const lines = text.split("\n");
  const lineBudget = options.headLines + options.tailLines;

  if (text.length <= options.maxChars && lines.length <= lineBudget + 1) {
    return { text, truncated: false };
  }

  if (lines.length > lineBudget + 1) {
    const head = lines.slice(0, Math.max(0, options.headLines)).join("\n");
    const tail = lines.slice(Math.max(0, lines.length - Math.max(0, options.tailLines))).join("\n");
    const omitted = Math.max(0, lines.length - options.headLines - options.tailLines);
    return {
      text:
        `[tool result compressed: ${lines.length} lines, ${text.length} chars, omitted ${omitted} middle lines]\n` +
        head +
        "\n\n…\n\n" +
        tail,
      truncated: true,
    };
  }

  return truncateText(text, Math.floor(options.maxChars / 3), Math.floor((options.maxChars * 2) / 3), "tool result compressed");
}