Refractor and optimize AP collections

Only display urls in general object, and paginate video comments, shares, likes and
dislikes

server/lib/activitypub/crawl.ts

@@ -0,0 +1,40 @@
+import { ACTIVITY_PUB, JOB_REQUEST_TIMEOUT } from '../../initializers'
+import { doRequest } from '../../helpers/requests'
+import { logger } from '../../helpers/logger'
+
+async function crawlCollectionPage <T> (uri: string, handler: (items: T[]) => Promise<any>) {
+  logger.info('Crawling ActivityPub data on %s.', uri)
+
+  const options = {
+    method: 'GET',
+    uri,
+    json: true,
+    activityPub: true,
+    timeout: JOB_REQUEST_TIMEOUT
+  }
+
+  const response = await doRequest(options)
+  const firstBody = response.body
+
+  let limit = ACTIVITY_PUB.FETCH_PAGE_LIMIT
+  let i = 0
+  let nextLink = firstBody.first
+  while (nextLink && i < limit) {
+    options.uri = nextLink
+
+    const { body } = await doRequest(options)
+    nextLink = body.next
+    i++
+
+    if (Array.isArray(body.orderedItems)) {
+      const items = body.orderedItems
+      logger.info('Processing %i ActivityPub items for %s.', items.length, nextLink)
+
+      await handler(items)
+    }
+  }
+}
+
+export {
+  crawlCollectionPage
+}