scrape all upcoming events following cursor

scrape.js

@@ -17,27 +17,6 @@ const get_upcoming_events = pathOr(
 
 const merge_edges = unionWith(eqBy(prop('event_id')));
 
-const load_page = async (page, event_page) => {
-  try {
-    const graphql_data = new Promise((resolve, reject) => {
-      page.on('response', async (response) => {
-        if (graphql_endpoint === response.request().url()) {
-          const text = await response.json();
-          const upcoming_events = get_upcoming_events(text);
-          if (upcoming_events !== null) {
-            resolve(upcoming_events);
-          }
-        }
-      });
-    });
-    await page.goto(event_page);
-    await page.evaluate(() => window.scrollBy(0, window.innerHeight));
-    return await graphql_data;
-  } catch (e) {
-    console.error(e);
-  }
-};
-
 const load_event = async (page, event_id) => {
   try {
     const image_data = new Promise((resolve, reject) => {
@@ -174,6 +153,28 @@ const event_ids = pathOr('', ['event_ids'], argv)
   .filter((str) => str.length !== 0)
   .map((event_id) => `https://www.facebook.com/events/${event_id}`);
 
+const register_upcoming_events_listener = (endpoint, page) => {
+  let responses = [];
+  return new Promise((resolve, reject) => {
+    page.on('response', async (response) => {
+      if (endpoint === response.request().url()) {
+        try {
+          const json = await response.json();
+          const upcoming_events = get_upcoming_events(json);
+          if (upcoming_events !== null) {
+            responses = [upcoming_events, ...responses];
+            if (!upcoming_events.page_info.has_next_page) {
+              resolve(responses);
+            }
+          }
+        } catch (err) {
+          reject(err);
+        }
+      }
+    });
+  });
+};
+
 (async () => {
   create_images_directory('./events/img');
 
@@ -182,31 +183,33 @@ const event_ids = pathOr('', ['event_ids'], argv)
   let events = [];
 
   for (let page_id of page_ids) {
+    let scraping = true;
     const facebook_page = await browser.newPage();
-    const data = await load_page(facebook_page, page_id);
-    const edges = data.edges.map(map_event);
-    events = merge_edges(edges, events);
-
-    events = await Promise.all(
-      events.map(async (event) => {
-        const event_page = await browser.newPage();
-        const event_data = await load_event(event_page, event.event_id);
-        return {
-          ...event_data,
-          ...event,
-        };
-      }),
-    );
+    const upcoming_events = register_upcoming_events_listener(
+      graphql_endpoint,
+      facebook_page,
+    )
+      .then((upcoming_events) => {
+        scraping = false;
+        return upcoming_events;
+      })
+      .catch((err) => {
+        console.error(err);
+        scraping = false;
+      });
+
+    await facebook_page.goto(page_id);
+
+    while (scraping) {
+      await facebook_page.evaluate(() =>
+        window.scrollBy(0, window.innerHeight),
+      );
+    }
 
-    events = await Promise.all(
-      events.map(async (event) => {
-        const images = await save_images(event);
-        delete event.image;
-        return {
-          images,
-          ...event,
-        };
-      }),
+    const responses = await upcoming_events;
+    const nodes = responses.reduce(
+      (res, current) => [...res, ...current.edges],
+      [],
     );
   }
   console.log(JSON.stringify(events));