OmniRoute/open-sse/handlers/usageExtractor.ts

/**
 * Extract usage from non-streaming response body
 * Handles different provider response formats
 */
export function extractUsageFromResponse(responseBody, provider) {
  if (!responseBody || typeof responseBody !== "object") return null;

  // OpenAI format (has prompt_tokens / completion_tokens)
  if (
    responseBody.usage &&
    typeof responseBody.usage === "object" &&
    responseBody.usage.prompt_tokens !== undefined
  ) {
    return {
      prompt_tokens: responseBody.usage.prompt_tokens || 0,
      completion_tokens: responseBody.usage.completion_tokens || 0,
      cached_tokens: responseBody.usage.prompt_tokens_details?.cached_tokens,
      reasoning_tokens: responseBody.usage.completion_tokens_details?.reasoning_tokens,
    };
  }

  // OpenAI Responses API format (input_tokens / output_tokens)
  const responsesUsage = responseBody.response?.usage || responseBody.usage;
  if (
    responsesUsage &&
    typeof responsesUsage === "object" &&
    (responsesUsage.input_tokens !== undefined || responsesUsage.output_tokens !== undefined)
  ) {
    return {
      prompt_tokens: responsesUsage.input_tokens || 0,
      completion_tokens: responsesUsage.output_tokens || 0,
      cache_read_input_tokens: responsesUsage.cache_read_input_tokens,
      cached_tokens:
        responsesUsage.input_tokens_details?.cached_tokens ??
        responsesUsage.cache_read_input_tokens,
      cache_creation_input_tokens: responsesUsage.cache_creation_input_tokens,
      reasoning_tokens:
        responsesUsage.reasoning_tokens || responsesUsage.output_tokens_details?.reasoning_tokens,
    };
  }

  // Claude format
  if (
    responseBody.usage &&
    typeof responseBody.usage === "object" &&
    (responseBody.usage.input_tokens !== undefined ||
      responseBody.usage.output_tokens !== undefined)
  ) {
    return {
      prompt_tokens: responseBody.usage.input_tokens || 0,
      completion_tokens: responseBody.usage.output_tokens || 0,
      cache_read_input_tokens: responseBody.usage.cache_read_input_tokens,
      cache_creation_input_tokens: responseBody.usage.cache_creation_input_tokens,
    };
  }

  // Gemini format
  if (responseBody.usageMetadata && typeof responseBody.usageMetadata === "object") {
    return {
      prompt_tokens: responseBody.usageMetadata.promptTokenCount || 0,
      completion_tokens: responseBody.usageMetadata.candidatesTokenCount || 0,
      reasoning_tokens: responseBody.usageMetadata.thoughtsTokenCount,
    };
  }

  return null;
}