From 4216a7931aad0bbe2f990e228592d84648641c22 Mon Sep 17 00:00:00 2001
From: Alex Gleason <alex@alexgleason.me>
Date: Tue, 29 Aug 2023 12:55:00 -0500
Subject: [PATCH] Add `paginated` helper function, DRY pagination code

---
 src/controllers/api/accounts.ts      |  6 ++----
 src/controllers/api/notifications.ts |  6 ++----
 src/controllers/api/timelines.ts     | 20 +++++++-------------
 src/utils/web.ts                     | 26 +++++++++++++++++---------
 4 files changed, 28 insertions(+), 30 deletions(-)

diff --git a/src/controllers/api/accounts.ts b/src/controllers/api/accounts.ts
index 92445622..d84382af 100644
--- a/src/controllers/api/accounts.ts
+++ b/src/controllers/api/accounts.ts
@@ -6,7 +6,7 @@ import { booleanParamSchema } from '@/schema.ts';
 import { jsonMetaContentSchema } from '@/schemas/nostr.ts';
 import { toAccount, toRelationship, toStatus } from '@/transformers/nostr-to-mastoapi.ts';
 import { eventDateComparator, isFollowing, lookupAccount } from '@/utils.ts';
-import { buildLinkHeader, paginationSchema, parseBody } from '@/utils/web.ts';
+import { paginated, paginationSchema, parseBody } from '@/utils/web.ts';
 import { createEvent } from '@/utils/web.ts';
 
 const createAccountController: AppController = (c) => {
@@ -110,9 +110,7 @@ const accountStatusesController: AppController = async (c) => {
   }
 
   const statuses = await Promise.all(events.map(toStatus));
-
-  const link = buildLinkHeader(c.req.url, events);
-  return c.json(statuses, 200, link ? { link } : undefined);
+  return paginated(c, events, statuses);
 };
 
 const fileSchema = z.custom<File>((value) => value instanceof File);
diff --git a/src/controllers/api/notifications.ts b/src/controllers/api/notifications.ts
index 30c38597..dce75e4d 100644
--- a/src/controllers/api/notifications.ts
+++ b/src/controllers/api/notifications.ts
@@ -1,6 +1,6 @@
 import { type AppController } from '@/app.ts';
 import * as mixer from '@/mixer.ts';
-import { buildLinkHeader, paginationSchema } from '@/utils/web.ts';
+import { paginated, paginationSchema } from '@/utils/web.ts';
 import { toNotification } from '@/transformers/nostr-to-mastoapi.ts';
 import { Time } from '@/utils.ts';
 
@@ -14,9 +14,7 @@ const notificationsController: AppController = async (c) => {
   );
 
   const statuses = await Promise.all(events.map(toNotification));
-
-  const link = buildLinkHeader(c.req.url, events);
-  return c.json(statuses, 200, link ? { link } : undefined);
+  return paginated(c, events, statuses);
 };
 
 export { notificationsController };
diff --git a/src/controllers/api/timelines.ts b/src/controllers/api/timelines.ts
index 1b7c52b8..6f43034a 100644
--- a/src/controllers/api/timelines.ts
+++ b/src/controllers/api/timelines.ts
@@ -3,7 +3,7 @@ import * as mixer from '@/mixer.ts';
 import { getFeed, getPublicFeed } from '@/queries.ts';
 import { booleanParamSchema } from '@/schema.ts';
 import { toStatus } from '@/transformers/nostr-to-mastoapi.ts';
-import { buildLinkHeader, paginationSchema } from '@/utils/web.ts';
+import { paginated, paginationSchema } from '@/utils/web.ts';
 import { Time } from '@/utils.ts';
 
 import type { AppController } from '@/app.ts';
@@ -17,10 +17,8 @@ const homeTimelineController: AppController = async (c) => {
     return c.json([]);
   }
 
-  const statuses = (await Promise.all(events.map(toStatus))).filter(Boolean);
-
-  const link = buildLinkHeader(c.req.url, events);
-  return c.json(statuses, 200, link ? { link } : undefined);
+  const statuses = await Promise.all(events.map(toStatus));
+  return paginated(c, events, statuses);
 };
 
 const publicQuerySchema = z.object({
@@ -36,10 +34,8 @@ const publicTimelineController: AppController = async (c) => {
     return c.json([]);
   }
 
-  const statuses = (await Promise.all(events.map(toStatus))).filter(Boolean);
-
-  const link = buildLinkHeader(c.req.url, events);
-  return c.json(statuses, 200, link ? { link } : undefined);
+  const statuses = await Promise.all(events.map(toStatus));
+  return paginated(c, events, statuses);
 };
 
 const hashtagTimelineController: AppController = async (c) => {
@@ -55,10 +51,8 @@ const hashtagTimelineController: AppController = async (c) => {
     return c.json([]);
   }
 
-  const statuses = (await Promise.all(events.map(toStatus))).filter(Boolean);
-
-  const link = buildLinkHeader(c.req.url, events);
-  return c.json(statuses, 200, link ? { link } : undefined);
+  const statuses = await Promise.all(events.map(toStatus));
+  return paginated(c, events, statuses);
 };
 
 export { hashtagTimelineController, homeTimelineController, publicTimelineController };
diff --git a/src/utils/web.ts b/src/utils/web.ts
index 7044d04a..6d895231 100644
--- a/src/utils/web.ts
+++ b/src/utils/web.ts
@@ -89,6 +89,22 @@ function buildLinkHeader(url: string, events: Event[]): string | undefined {
   return `<${next}>; rel="next", <${prev}>; rel="prev"`;
 }
 
+type Entity = { id: string };
+type HeaderRecord = Record<string, string | string[]>;
+
+/** Return results with pagination headers. */
+function paginated(c: AppContext, events: Event[], entities: (Entity | undefined)[], headers: HeaderRecord = {}) {
+  const link = buildLinkHeader(c.req.url, events);
+
+  if (link) {
+    headers.link = link;
+  }
+
+  // Filter out undefined entities.
+  const results = entities.filter((entity): entity is Entity => Boolean(entity));
+  return c.json(results, 200, headers);
+}
+
 /** JSON-LD context. */
 type LDContext = (string | Record<string, string | Record<string, string>>)[];
 
@@ -107,12 +123,4 @@ function activityJson<T, P extends string>(c: Context<any, P>, object: T) {
   return response;
 }
 
-export {
-  activityJson,
-  buildLinkHeader,
-  createAdminEvent,
-  createEvent,
-  type PaginationParams,
-  paginationSchema,
-  parseBody,
-};
+export { activityJson, createAdminEvent, createEvent, paginated, type PaginationParams, paginationSchema, parseBody };