Function createUsageNormalizer

src/api/transform/responses-api-stream.ts:117–148

(
	calculateCost?: (inputTokens: number, outputTokens: number, cacheReadTokens: number) => number,
)

 * @param calculateCost - Optional function to compute total cost from token counts
 */
export function createUsageNormalizer(
	calculateCost?: (inputTokens: number, outputTokens: number, cacheReadTokens: number) => number,
): (usage: any) => ApiStreamUsageChunk | undefined {
	return (usage: any): ApiStreamUsageChunk | undefined => {
		if (!usage) return undefined

		const inputDetails = usage.input_tokens_details ?? usage.prompt_tokens_details
		const cachedTokens = inputDetails?.cached_tokens ?? 0

		const inputTokens = usage.input_tokens ?? usage.prompt_tokens ?? 0
		const outputTokens = usage.output_tokens ?? usage.completion_tokens ?? 0
		const cacheReadTokens = usage.cache_read_input_tokens ?? cachedTokens ?? 0
		const cacheWriteTokens = usage.cache_creation_input_tokens ?? usage.cache_write_tokens ?? 0

		const reasoningTokens =
			typeof usage.output_tokens_details?.reasoning_tokens === "number"
				? usage.output_tokens_details.reasoning_tokens
				: undefined

		const totalCost = calculateCost ? calculateCost(inputTokens, outputTokens, cacheReadTokens) : undefined

		return {
			type: "usage",
			inputTokens,
			outputTokens,
			cacheWriteTokens,
			cacheReadTokens,
			...(typeof reasoningTokens === "number" ? { reasoningTokens } : {}),
			...(typeof totalCost === "number" ? { totalCost } : {}),
		}
	}
}