Function xhrServerSentEvents

packages/ai-client/src/connection-adapters.ts:825–890

(
  url: string | (() => string),
  options: XhrConnectionOptionsResolver = {},
)

 * Create an XMLHttpRequest-backed Server-Sent Events connection adapter.
 */
export function xhrServerSentEvents(
  url: string | (() => string),
  options: XhrConnectionOptionsResolver = {},
): ConnectConnectionAdapter {
  return {
    async *connect(messages, data, abortSignal, runContext) {
      const resolvedUrl = typeof url === 'function' ? url() : url
      const resolvedOptions = await resolveXhrConnectionOptions(options)
      const signal = abortSignal || resolvedOptions.signal
      const request = createConfiguredXhrRequest(
        resolvedUrl,
        resolvedOptions,
        messages,
        data,
        runContext,
      )
      const lines = readXhrLines(request.xhr, signal)
      if (signal?.aborted) {
        await lines.next()
        return
      }
      request.xhr.send(request.body)
      let lastThreadId: string | undefined
      let lastRunId: string | undefined
      let lastModel: string | undefined

      for await (const line of lines) {
        if (
          line.startsWith(':') ||
          line.startsWith('event:') ||
          line.startsWith('id:') ||
          line.startsWith('retry:')
        ) {
          continue
        }

        const chunkData = parseSseDataLine(line)
        if (chunkData === '[DONE]') {
          const synthetic: RunFinishedEvent = {
            type: EventType.RUN_FINISHED,
            threadId: lastThreadId ?? runContext?.threadId ?? '',
            runId: lastRunId ?? runContext?.runId ?? '',
            model: lastModel ?? '',
            timestamp: Date.now(),
            finishReason: 'stop',
          }
          request.xhr.abort()
          yield synthetic
          return
        }

        const chunk = JSON.parse(chunkData) as StreamChunk
        if ('threadId' in chunk && typeof chunk.threadId === 'string') {
          lastThreadId = chunk.threadId
        }
        if ('runId' in chunk && typeof chunk.runId === 'string') {
          lastRunId = chunk.runId
        }