From 6fac56d2c99acf1037fd65abdacfc27b776509a8 Mon Sep 17 00:00:00 2001
From: Marshall Polaris <marshall@pol.rs>
Date: Thu, 9 Jun 2022 15:13:06 -0700
Subject: [PATCH] Make feed updating do much less work (#455)

---
 functions/src/get-feed-data.ts |  5 ++--
 functions/src/update-feed.ts   | 44 +++++++++++++++++++---------------
 2 files changed, 27 insertions(+), 22 deletions(-)

diff --git a/functions/src/get-feed-data.ts b/functions/src/get-feed-data.ts
index 75782fed..dc45f563 100644
--- a/functions/src/get-feed-data.ts
+++ b/functions/src/get-feed-data.ts
@@ -42,8 +42,8 @@ export async function getTaggedContracts(tag: string) {
   return taggedContracts.filter((c) => (c.closeTime ?? Infinity) > Date.now())
 }
 
-export async function getRecentBetsAndComments(contract: Contract) {
-  const contractDoc = firestore.collection('contracts').doc(contract.id)
+export async function getRecentBetsAndComments(contractId: string) {
+  const contractDoc = firestore.collection('contracts').doc(contractId)
 
   const [recentBets, recentComments] = await Promise.all([
     getValues<Bet>(
@@ -64,7 +64,6 @@ export async function getRecentBetsAndComments(contract: Contract) {
   ])
 
   return {
-    contract,
     recentBets,
     recentComments,
   }
diff --git a/functions/src/update-feed.ts b/functions/src/update-feed.ts
index 03b1666c..f19fda92 100644
--- a/functions/src/update-feed.ts
+++ b/functions/src/update-feed.ts
@@ -1,6 +1,6 @@
 import * as functions from 'firebase-functions'
 import * as admin from 'firebase-admin'
-import { shuffle, sortBy } from 'lodash'
+import { flatten, shuffle, sortBy, uniq, zip, zipObject } from 'lodash'
 
 import { getValue, getValues } from './utils'
 import { Contract } from '../../common/contract'
@@ -67,15 +67,16 @@ export const updateFeedBatch = functions.https.onCall(
   async (data: { users: User[] }) => {
     const { users } = data
     const contracts = await getFeedContracts()
-
+    const feeds = await getNewFeeds(users, contracts)
     await Promise.all(
-      users.map(async (user) => {
-        const feed = await computeFeed(user, contracts)
-        await getUserCacheCollection(user).doc('feed').set({ feed })
-      })
+      zip(users, feeds).map(([user, feed]) =>
+        /* eslint-disable-next-line @typescript-eslint/no-non-null-assertion */
+        getUserCacheCollection(user!).doc('feed').set({ feed })
+      )
     )
   }
 )
+
 export const updateCategoryFeed = functions.https.onCall(
   async (data: { category: string }) => {
     const { category } = data
@@ -96,16 +97,28 @@ export const updateCategoryFeedBatch = functions.https.onCall(
   async (data: { users: User[]; category: string }) => {
     const { users, category } = data
     const contracts = await getTaggedContracts(category)
-
+    const feeds = await getNewFeeds(users, contracts)
     await Promise.all(
-      users.map(async (user) => {
-        const feed = await computeFeed(user, contracts)
-        await getUserCacheCollection(user).doc(`feed-${category}`).set({ feed })
-      })
+      zip(users, feeds).map(([user, feed]) =>
+        /* eslint-disable-next-line @typescript-eslint/no-non-null-assertion */
+        getUserCacheCollection(user!).doc(`feed-${category}`).set({ feed })
+      )
     )
   }
 )
 
+const getNewFeeds = async (users: User[], contracts: Contract[]) => {
+  const feeds = await Promise.all(users.map((u) => computeFeed(u, contracts)))
+  const contractIds = uniq(flatten(feeds).map((c) => c.id))
+  const data = await Promise.all(contractIds.map(getRecentBetsAndComments))
+  const dataByContractId = zipObject(contractIds, data)
+  return feeds.map((feed) =>
+    feed.map((contract) => {
+      return { contract, ...dataByContractId[contract.id] }
+    })
+  )
+}
+
 const getUserCacheCollection = (user: User) =>
   firestore.collection(`private-users/${user.id}/cache`)
 
@@ -135,14 +148,7 @@ export const computeFeed = async (user: User, contracts: Contract[]) => {
 
   // console.log(sortedContracts.map(([c, score]) => c.question + ': ' + score))
 
-  const feedContracts = sortedContracts
-    .slice(0, MAX_FEED_CONTRACTS)
-    .map(([c]) => c)
-
-  const feed = await Promise.all(
-    feedContracts.map((contract) => getRecentBetsAndComments(contract))
-  )
-  return feed
+  return sortedContracts.slice(0, MAX_FEED_CONTRACTS).map(([c]) => c)
 }
 
 function scoreContract(