Add a hotness thread sort (#6649)

* Add a hotness thread sort

* Bump @atproto/api

6 files changed, 67 insertions, 4 deletions

diff --git a/package.json b/package.json
index 3ba944db7..91b091a1b 100644
--- a/package.json
+++ b/package.json
@@ -54,7 +54,7 @@
     "icons:optimize": "svgo -f ./assets/icons"
   },
   "dependencies": {
-    "@atproto/api": "^0.13.11",
+    "@atproto/api": "^0.13.18",
     "@braintree/sanitize-url": "^6.0.2",
     "@discord/bottom-sheet": "bluesky-social/react-native-bottom-sheet",
     "@emoji-mart/react": "^1.1.1",
diff --git a/src/screens/Settings/ThreadPreferences.tsx b/src/screens/Settings/ThreadPreferences.tsx
index c27cea7de..d29daa58b 100644
--- a/src/screens/Settings/ThreadPreferences.tsx
+++ b/src/screens/Settings/ThreadPreferences.tsx
@@ -56,6 +56,12 @@ export function ThreadPreferencesScreen({}: Props) {
                 values={sortReplies ? [sortReplies] : []}
                 onChange={values => setThreadViewPrefs({sort: values[0]})}>
                 <View style={[a.gap_sm, a.flex_1]}>
+                  <Toggle.Item name="hotness" label={_(msg`Hot replies first`)}>
+                    <Toggle.Radio />
+                    <Toggle.LabelText>
+                      <Trans>Hot replies first</Trans>
+                    </Toggle.LabelText>
+                  </Toggle.Item>
                   <Toggle.Item
                     name="oldest"
                     label={_(msg`Oldest replies first`)}>
diff --git a/src/state/queries/post-thread.ts b/src/state/queries/post-thread.ts
index 93e3a5c3b..4784a9d75 100644
--- a/src/state/queries/post-thread.ts
+++ b/src/state/queries/post-thread.ts
@@ -237,7 +237,11 @@ export function sortThread(
         }
       }
 
-      if (opts.sort === 'oldest') {
+      if (opts.sort === 'hotness') {
+        const aHotness = getHotness(a.post)
+        const bHotness = getHotness(b.post)
+        return bHotness - aHotness
+      } else if (opts.sort === 'oldest') {
         return a.post.indexedAt.localeCompare(b.post.indexedAt)
       } else if (opts.sort === 'newest') {
         return b.post.indexedAt.localeCompare(a.post.indexedAt)
@@ -269,6 +273,21 @@ export function sortThread(
 // internal methods
 // =
 
+// Inspired by https://join-lemmy.org/docs/contributors/07-ranking-algo.html
+// We want to give recent comments a real chance (and not bury them deep below the fold)
+// while also surfacing well-liked comments from the past. In the future, we can explore
+// something more sophisticated, but we don't have much data on the client right now.
+function getHotness(post: AppBskyFeedDefs.PostView) {
+  const hoursAgo =
+    (new Date().getTime() - new Date(post.indexedAt).getTime()) /
+    (1000 * 60 * 60)
+  const likeCount = post.likeCount ?? 0
+  const likeOrder = Math.log(3 + likeCount)
+  const timePenaltyExponent = 1.5 + 1.5 / (1 + Math.log(1 + likeCount))
+  const timePenalty = Math.pow(hoursAgo + 2, timePenaltyExponent)
+  return likeOrder / timePenalty
+}
+
 function responseToThreadNodes(
   node: ThreadViewNode,
   depth = 0,
diff --git a/src/state/queries/preferences/const.ts b/src/state/queries/preferences/const.ts
index e07f40ec5..549f7ce29 100644
--- a/src/state/queries/preferences/const.ts
+++ b/src/state/queries/preferences/const.ts
@@ -15,7 +15,7 @@ export const DEFAULT_HOME_FEED_PREFS: UsePreferencesQueryResponse['feedViewPrefs
   }
 
 export const DEFAULT_THREAD_VIEW_PREFS: ThreadViewPreferences = {
-  sort: 'newest',
+  sort: 'hotness',
   prioritizeFollowedUsers: true,
   lab_treeViewEnabled: false,
 }
diff --git a/src/state/queries/preferences/types.ts b/src/state/queries/preferences/types.ts
index 928bb90da..8f523fcf2 100644
--- a/src/state/queries/preferences/types.ts
+++ b/src/state/queries/preferences/types.ts
@@ -22,6 +22,6 @@ export type ThreadViewPreferences = Pick<
   BskyThreadViewPreference,
   'prioritizeFollowedUsers'
 > & {
-  sort: 'oldest' | 'newest' | 'most-likes' | 'random' | string
+  sort: 'hotness' | 'oldest' | 'newest' | 'most-likes' | 'random' | string
   lab_treeViewEnabled?: boolean
 }
diff --git a/yarn.lock b/yarn.lock
index acc9e0fc5..daa9a3de9 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -72,6 +72,20 @@
     tlds "^1.234.0"
     zod "^3.23.8"
 
+"@atproto/api@^0.13.18":
+  version "0.13.18"
+  resolved "https://registry.yarnpkg.com/@atproto/api/-/api-0.13.18.tgz#cc537cc3b4c8d03f258a373f4d893fea11a77cdd"
+  integrity sha512-rrl5HhzGYWZ7fiC965TPBUOVItq9M4dxMb6qz8IvAVQliSkrJrKc7UD0QWL89QiiXaOBuX8w+4i5r4wrfBGddg==
+  dependencies:
+    "@atproto/common-web" "^0.3.1"
+    "@atproto/lexicon" "^0.4.3"
+    "@atproto/syntax" "^0.3.1"
+    "@atproto/xrpc" "^0.6.4"
+    await-lock "^2.2.2"
+    multiformats "^9.9.0"
+    tlds "^1.234.0"
+    zod "^3.23.8"
+
 "@atproto/aws@^0.2.7":
   version "0.2.7"
   resolved "https://registry.yarnpkg.com/@atproto/aws/-/aws-0.2.7.tgz#2f3e05c897ef49b4c46452ec8c36870193952998"
@@ -269,6 +283,17 @@
     multiformats "^9.9.0"
     zod "^3.23.8"
 
+"@atproto/lexicon@^0.4.3":
+  version "0.4.3"
+  resolved "https://registry.yarnpkg.com/@atproto/lexicon/-/lexicon-0.4.3.tgz#d69f6bb363a6326df7766c48132bfa30e22622d9"
+  integrity sha512-lFVZXe1S1pJP0dcxvJuHP3r/a+EAIBwwU7jUK+r8iLhIja+ml6NmYv8KeFHmIJATh03spEQ9s02duDmFVdCoXg==
+  dependencies:
+    "@atproto/common-web" "^0.3.1"
+    "@atproto/syntax" "^0.3.1"
+    iso-datestring-validator "^2.2.2"
+    multiformats "^9.9.0"
+    zod "^3.23.8"
+
 "@atproto/oauth-provider@^0.2.5":
   version "0.2.5"
   resolved "https://registry.yarnpkg.com/@atproto/oauth-provider/-/oauth-provider-0.2.5.tgz#7358398125f840404bcc02c966fd2f333869ad2f"
@@ -411,6 +436,11 @@
   resolved "https://registry.yarnpkg.com/@atproto/syntax/-/syntax-0.3.0.tgz#fafa2dbea9add37253005cb663e7373e05e618b3"
   integrity sha512-Weq0ZBxffGHDXHl9U7BQc2BFJi/e23AL+k+i5+D9hUq/bzT4yjGsrCejkjq0xt82xXDjmhhvQSZ0LqxyZ5woxA==
 
+"@atproto/syntax@^0.3.1":
+  version "0.3.1"
+  resolved "https://registry.yarnpkg.com/@atproto/syntax/-/syntax-0.3.1.tgz#4346418728f9643d783d2ffcf7c77e132e1f53d4"
+  integrity sha512-fzW0Mg1QUOVCWUD3RgEsDt6d1OZ6DdFmbKcDdbzUfh0t4rhtRAC05KbZYmxuMPWDAiJ4BbbQ5dkAc/mNypMXkw==
+
 "@atproto/xrpc-server@^0.7.1":
   version "0.7.1"
   resolved "https://registry.yarnpkg.com/@atproto/xrpc-server/-/xrpc-server-0.7.1.tgz#e9750aab7bb531c3a82dc6048d47179de18dbdd9"
@@ -437,6 +467,14 @@
     "@atproto/lexicon" "^0.4.2"
     zod "^3.23.8"
 
+"@atproto/xrpc@^0.6.4":
+  version "0.6.4"
+  resolved "https://registry.yarnpkg.com/@atproto/xrpc/-/xrpc-0.6.4.tgz#4cf59774f7c72e5bc821bc5f1d57f0a6ae2014db"
+  integrity sha512-9ZAJ8nsXTqC4XFyS0E1Wlg7bAvonhXQNQ3Ocs1L1LIwFLXvsw/4fNpIHXxvXvqTCVeyHLbImOnE9UiO1c/qIYA==
+  dependencies:
+    "@atproto/lexicon" "^0.4.3"
+    zod "^3.23.8"
+
 "@aws-crypto/crc32@3.0.0":
   version "3.0.0"
   resolved "https://registry.yarnpkg.com/@aws-crypto/crc32/-/crc32-3.0.0.tgz#07300eca214409c33e3ff769cd5697b57fdd38fa"