/**
 * Shared utilities for OpenAI-compatible API paths.
 *
 * Both the OpenAI path (queryModelOpenAI) and Grok path (queryModelGrok) use
 * the same adapters (openaiStreamAdapter, openaiConvertMessages), so the event
 * processing logic should be shared rather than duplicated.
 */

/**
 * Merge a delta usage into the accumulated usage, preserving cache-related
 * fields from previous values when the delta carries explicit zeroes or
 * undefined values.
 *
 * Mirrors updateUsage() in claude.ts: a future adapter change that omits
 * cache fields from certain streaming events should not silently zero the
 * accumulated counters.
 */
export function updateOpenAIUsage(
  current: {
    input_tokens: number
    output_tokens: number
    cache_creation_input_tokens: number
    cache_read_input_tokens: number
  },
  delta: {
    input_tokens?: number
    output_tokens?: number
    cache_creation_input_tokens?: number
    cache_read_input_tokens?: number
  },
): typeof current {
  return {
    input_tokens: delta.input_tokens ?? current.input_tokens,
    output_tokens: delta.output_tokens ?? current.output_tokens,
    cache_creation_input_tokens:
      delta.cache_creation_input_tokens !== undefined &&
      delta.cache_creation_input_tokens > 0
        ? delta.cache_creation_input_tokens
        : current.cache_creation_input_tokens,
    cache_read_input_tokens:
      delta.cache_read_input_tokens !== undefined &&
      delta.cache_read_input_tokens > 0
        ? delta.cache_read_input_tokens
        : current.cache_read_input_tokens,
  }
}