export type Usage = {
  inputTokens: number;
  outputTokens: number;
  totalTokens: number;
  estimated: boolean;
};

export const estimateTokens = (text: string) => {
  if (!text.trim()) {
    return 0;
  }

  const ascii = text.match(/[\x00-\x7F]/g)?.length ?? 0;
  const nonAscii = text.length - ascii;
  return Math.max(1, Math.ceil(ascii / 4 + nonAscii / 1.7));
};

export const normalizeUsage = (
  prompt: string,
  output: string,
  usage?: Partial<Usage> | null
): Usage => {
  const inputTokens = usage?.inputTokens ?? estimateTokens(prompt);
  const outputTokens = usage?.outputTokens ?? estimateTokens(output);

  return {
    inputTokens,
    outputTokens,
    totalTokens: usage?.totalTokens ?? inputTokens + outputTokens,
    estimated: usage?.estimated ?? !usage
  };
};