Function createSseTransformStream

sdk/src/impl/chatgpt-backend-fetch.ts:212–450

()

// ============================================================================

function createSseTransformStream(): TransformStream<Uint8Array, Uint8Array> {
  const encoder = new TextEncoder()
  const decoder = new TextDecoder()

  let buffer = ''
  let responseId: string | null = null
  let responseModel: string | null = null
  let nextToolCallIndex = 0
  const outputIndexToToolIndex = new Map<number, number>()
  let emittedRole = false

  function emit(
    controller: TransformStreamDefaultController<Uint8Array>,
    chunk: Record<string, unknown>,
  ) {
    controller.enqueue(encoder.encode(`data: ${JSON.stringify(chunk)}\n\n`))
  }

  function processEvent(
    controller: TransformStreamDefaultController<Uint8Array>,
    data: Record<string, unknown>,
  ) {
    const type = data.type as string | undefined
    if (!type) return

    switch (type) {
      case 'response.created': {
        const resp = data.response as Record<string, unknown> | undefined
        responseId = (resp?.id as string) ?? null
        responseModel = (resp?.model as string) ?? null
        if (!emittedRole) {
          emit(controller, {
            id: responseId,
            model: responseModel,
            choices: [
              { index: 0, delta: { role: 'assistant' }, finish_reason: null },
            ],
          })
          emittedRole = true
        }
        break
      }

      case 'response.output_text.delta': {
        emit(controller, {
          id: responseId,
          choices: [
            {
              index: 0,
              delta: { content: data.delta as string },
              finish_reason: null,
            },
          ],
        })
        break
      }

      case 'response.reasoning_summary_text.delta': {