[CORL-836] Create activeStories endpoint (#2787)

* Create activeStories GraphQL query endpoint

Set lastCommentedAt on stories when they are
commented upon.
Use lastCommentedAt to retrieve the activeStories.
Create a migration to partial index
lastCommentedAt on stories to make retrieval fast.

CORL-836

* fix: adjusted query to use index, more @auth directives

Co-authored-by: Wyatt Johnson <accounts+github@wyattjoh.ca>

src/core/server/models/comment/comment.ts

@@ -6,12 +6,6 @@ import uuid from "uuid";
 import { Omit, Sub } from "coral-common/types";
 import { dotize } from "coral-common/utils/dotize";
 import { CommentNotFoundError } from "coral-server/errors";
-import {
-  GQLCOMMENT_SORT,
-  GQLCOMMENT_STATUS,
-  GQLCommentTagCounts,
-  GQLTAG,
-} from "coral-server/graph/schema/__generated__/types";
 import logger from "coral-server/logger";
 import {
   EncodedCommentActionCounts,
@@ -31,6 +25,13 @@ import {
 import { TenantResource } from "coral-server/models/tenant";
 import { comments as collection } from "coral-server/services/mongodb/collections";
 
+import {
+  GQLCOMMENT_SORT,
+  GQLCOMMENT_STATUS,
+  GQLCommentTagCounts,
+  GQLTAG,
+} from "coral-server/graph/schema/__generated__/types";
+
 import { PUBLISHED_STATUSES } from "./constants";
 import {
   CommentStatusCounts,

src/core/server/models/story/index.ts

@@ -7,10 +7,6 @@ import {
   DuplicateStoryIDError,
   DuplicateStoryURLError,
 } from "coral-server/errors";
-import {
-  GQLStoryMetadata,
-  GQLStorySettings,
-} from "coral-server/graph/schema/__generated__/types";
 import {
   Connection,
   ConnectionInput,
@@ -21,6 +17,11 @@ import { GlobalModerationSettings } from "coral-server/models/settings";
 import { TenantResource } from "coral-server/models/tenant";
 import { stories as collection } from "coral-server/services/mongodb/collections";
 
+import {
+  GQLStoryMetadata,
+  GQLStorySettings,
+} from "coral-server/graph/schema/__generated__/types";
+
 import { createEmptyCommentStatusCounts } from "../comment/helpers";
 import {
   createEmptyCommentModerationQueueCounts,
@@ -75,6 +76,11 @@ export interface Story extends TenantResource {
    * createdAt is the date that the Story was added to the Coral database.
    */
   createdAt: Date;
+
+  /**
+   * lastCommentedAt is the last time someone commented on this story.
+   */
+  lastCommentedAt?: Date;
 }
 
 export interface UpsertStoryInput {
@@ -455,3 +461,43 @@ async function retrieveConnection(
   // Return a connection.
   return resolveConnection(query, input, story => story.createdAt);
 }
+
+export async function retrieveActiveStories(
+  mongo: Db,
+  tenantID: string,
+  limit: number
+) {
+  const stories = await collection(mongo)
+    .find({
+      tenantID,
+      // We limit this query to stories that have the following field. This
+      // allows us to use the index.
+      lastCommentedAt: {
+        $exists: true,
+      },
+    })
+    .sort({ lastCommentedAt: -1 })
+    .limit(limit)
+    .toArray();
+
+  return stories;
+}
+
+export async function updateStoryLastCommentedAt(
+  mongo: Db,
+  tenantID: string,
+  storyID: string,
+  now: Date
+) {
+  await collection(mongo).updateOne(
+    {
+      tenantID,
+      id: storyID,
+    },
+    {
+      $set: {
+        lastCommentedAt: now,
+      },
+    }
+  );
+}