Function applyMessagePage

packages/app/src/context/server-session.ts:528–560

(
    sessionID: string,
    page: MessagePage,
    load: MessageLoadState | undefined,
    preserveUnfetched: boolean | ((message: Message) => boolean),
    cleanupOrphans: boolean,
  )

  }

  const applyMessagePage = (
    sessionID: string,
    page: MessagePage,
    load: MessageLoadState | undefined,
    preserveUnfetched: boolean | ((message: Message) => boolean),
    cleanupOrphans: boolean,
  ) => {
    const merged = mergeOptimisticPage(page, [...(optimistic.get(sessionID)?.values() ?? [])])
    merged.observed.forEach((item) => {
      if (!load?.clearedMessageParts.has(item.messageID)) confirmOptimistic(sessionID, item.messageID, item.parts)
    })
    const touchedMessages = new Set([...(load?.touchedMessages ?? []), ...(removedMessages.get(sessionID) ?? [])])
    const messages = reconcileFetched(merged.session, data.message[sessionID] ?? [], {
      touched: touchedMessages,
      retained: load?.retainedMessages,
      preserveUnfetched,
    })
    batch(() => {
      const messageIDs = replaceMessages(sessionID, messages)
      replaceParts(sessionID, merged.part, messageIDs, load)
      const orphans = orphanParts.get(sessionID)
      if (cleanupOrphans && page.complete && orphans) {
        for (const messageID of orphans) {
          if (!messageIDs.has(messageID)) setData(produce((draft) => deleteMessageParts(draft, messageID)))
        }
        orphanParts.delete(sessionID)
      }
      setMeta("limit", sessionID, messages.length)
      setMeta("cursor", sessionID, merged.cursor)
      setMeta("complete", sessionID, merged.complete)
      setMeta("at", sessionID, Date.now())
    })
  }

  const loadMessages = async (sessionID: string, limit: number, before?: string, mode?: "replace" | "prepend") => {
    if (meta.loading[sessionID]) return