grain.social is a photo sharing platform built on atproto.
grain.social
atproto
photography
appview
feat: add For You feed with collaborative filtering algorithm
Reverse-engineered from spacecowboy17's Bluesky For You feed playground.
Algorithm: find user's favorites → find co-likers → surface their other
favorites, scored with half-life decay, smoothing, and popularity penalty.
Falls back to most-favorited galleries for cold start users.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
+566
-2
+2
-1
app/lib/components/molecules/FeedTabs.svelte
+2
-1
app/lib/components/molecules/FeedTabs.svelte
···
3
3
import { pinnedFeeds } from '$lib/preferences'
4
4
import { isAuthenticated } from '$lib/stores'
5
5
6
+
const authOnlyFeeds = new Set(['following', 'foryou'])
6
7
const tabFeeds = $derived(
7
-
$isAuthenticated ? $pinnedFeeds : $pinnedFeeds.filter((f) => f.id !== 'following')
8
+
$isAuthenticated ? $pinnedFeeds : $pinnedFeeds.filter((f) => !authOnlyFeeds.has(f.id))
8
9
)
9
10
</script>
10
11
+3
-1
app/lib/preferences.ts
+3
-1
app/lib/preferences.ts
···
1
1
import { writable, get } from "svelte/store";
2
2
import { callXrpc } from "$hatk/client";
3
-
import { Images, Users, Camera, MapPin, Hash, Pin } from "lucide-svelte";
3
+
import { Images, Users, Camera, MapPin, Hash, Pin, Sparkles } from "lucide-svelte";
4
4
5
5
export interface PinnedFeed {
6
6
id: string;
···
12
12
export const DEFAULT_PINNED: PinnedFeed[] = [
13
13
{ id: "recent", label: "Recent", type: "feed", path: "/" },
14
14
{ id: "following", label: "Following", type: "feed", path: "/feeds/following" },
15
+
{ id: "foryou", label: "For You", type: "feed", path: "/feeds/for-you" },
15
16
];
16
17
17
18
/* eslint-disable @typescript-eslint/no-explicit-any */
18
19
const CORE_ICONS: Record<string, any> = {
19
20
recent: Images,
20
21
following: Users,
22
+
foryou: Sparkles,
21
23
};
22
24
23
25
const TYPE_ICONS: Record<string, any> = {
+7
app/lib/queries.ts
+7
app/lib/queries.ts
···
19
19
staleTime: 60_000,
20
20
});
21
21
22
+
export const forYouFeedQuery = (did: string, limit = 50, f?: Fetch) =>
23
+
queryOptions({
24
+
queryKey: ["getFeed", "foryou", did],
25
+
queryFn: () => callXrpc("dev.hatk.getFeed", { feed: "foryou", actor: did, limit }, f),
26
+
staleTime: 60_000,
27
+
});
28
+
22
29
export const actorFeedQuery = (did: string, limit = 50, f?: Fetch) =>
23
30
queryOptions({
24
31
queryKey: ["getFeed", "actor", did],
+29
app/routes/feeds/for-you/+page.svelte
+29
app/routes/feeds/for-you/+page.svelte
···
1
+
<script lang="ts">
2
+
import { createQuery } from '@tanstack/svelte-query'
3
+
import FeedList from '$lib/components/organisms/FeedList.svelte'
4
+
import FeedTabs from '$lib/components/molecules/FeedTabs.svelte'
5
+
import { forYouFeedQuery } from '$lib/queries'
6
+
import { viewer } from '$lib/stores'
7
+
import OGMeta from '$lib/components/atoms/OGMeta.svelte'
8
+
9
+
const feed = createQuery(() => forYouFeedQuery($viewer?.did ?? ''))
10
+
</script>
11
+
12
+
<OGMeta title="For You - grain" />
13
+
<FeedTabs />
14
+
{#if !$viewer?.did}
15
+
<div class="empty">Log in to get personalized gallery recommendations.</div>
16
+
{:else if feed.isLoading}
17
+
<FeedList feed="foryou" params={{ actor: $viewer.did }} skeleton />
18
+
{:else}
19
+
<FeedList feed="foryou" params={{ actor: $viewer.did }} initialItems={feed.data?.items ?? []} initialCursor={feed.data?.cursor} />
20
+
{/if}
21
+
22
+
<style>
23
+
.empty {
24
+
text-align: center;
25
+
color: var(--text-muted);
26
+
padding: 48px 16px;
27
+
font-size: 14px;
28
+
}
29
+
</style>
+11
app/routes/feeds/for-you/+page.ts
+11
app/routes/feeds/for-you/+page.ts
···
1
+
import { browser } from "$app/environment";
2
+
import { forYouFeedQuery } from "$lib/queries";
3
+
import type { PageLoad } from "./$types";
4
+
5
+
export const load: PageLoad = async ({ parent, fetch }) => {
6
+
const { queryClient, viewer } = await parent();
7
+
if (viewer?.did) {
8
+
const prefetch = queryClient.prefetchQuery(forYouFeedQuery(viewer.did, 50, fetch));
9
+
if (!browser) await prefetch;
10
+
}
11
+
};
+60
docs/plans/2026-04-08-for-you-feed-design.md
+60
docs/plans/2026-04-08-for-you-feed-design.md
···
1
+
# For You Feed Design
2
+
3
+
Collaborative filtering feed for Grain, reverse-engineered from the Bluesky For You feed playground by spacecowboy17.
4
+
5
+
## Algorithm
6
+
7
+
### Personalized mode (user has favorites)
8
+
9
+
1. **Seed**: Get user's 500 most recent favorites
10
+
2. **Co-likers**: Find other users who also favorited those same galleries
11
+
3. **Candidates**: Collect galleries those co-likers favorited (excluding user's own favorites and own galleries)
12
+
4. **Score** each candidate:
13
+
14
+
```
15
+
For each path (co-liker → candidate gallery):
16
+
path_score = 1 / (co_liker_total_likes ^ divisor_power)
17
+
path_score *= (1 - corater_decay) ^ (items_from_this_corater - 1)
18
+
19
+
base_score = sum(path_scores)
20
+
smoothed = base_score * (num_paths ^ smoothing_factor)
21
+
time_factor = 0.5 ^ (age_hours / half_life) // half_life=0 disables decay
22
+
final_score = smoothed * time_factor / (total_favorites ^ popularity_penalty)
23
+
```
24
+
25
+
5. **Rank** by final_score descending, paginate with cursor
26
+
27
+
### Cold start fallback (no favorites)
28
+
29
+
Return galleries ordered by favorite count descending, filtered to last 30 days.
30
+
31
+
## Default Parameters
32
+
33
+
| Parameter | Default | Description |
34
+
|-----------|---------|-------------|
35
+
| half_life | 6 | Hours; demotes older posts |
36
+
| smoothing_factor | 0.5 | Boosts multi-path posts |
37
+
| popularity_penalty | 0.3 | Demotes generally popular posts |
38
+
| divisor_power | 1.0 | Divides by co-liker's total likes |
39
+
| corater_decay | 0 | Decay for same co-liker (0=none) |
40
+
| time_shift | 24 | Hours; co-like contribution window |
41
+
| seed_limit | 500 | Max seed favorites |
42
+
43
+
## Files
44
+
45
+
- `server/feeds/foryou.ts` — feed generator with scoring logic
46
+
- `app/lib/queries.ts` — add forYouFeedQuery
47
+
- `app/routes/feeds/for-you/+page.ts` — page load
48
+
- `app/routes/feeds/for-you/+page.svelte` — feed UI
49
+
- `app/lib/preferences.ts` — add to DEFAULT_PINNED
50
+
51
+
## Pagination
52
+
53
+
Score-based cursor: encode `score:rkey` as cursor string. Since scores are computed in JS (not SQL), fetch all candidates, score, sort, then slice by cursor position. For v1, use offset-based cursor to keep it simple.
54
+
55
+
## Filters
56
+
57
+
- Exclude galleries user already favorited
58
+
- Exclude user's own galleries
59
+
- Respect takedown status and hidden labels
60
+
- Require gallery to have at least 1 item
+198
seeds/seed.ts
+198
seeds/seed.ts
···
461
461
{ rkey: "exif-portrait" },
462
462
);
463
463
464
+
// ── Additional galleries for For You feed testing ──
465
+
466
+
// Bob's second gallery: "Mountain Dawn"
467
+
const mountainDawn = await createRecord(
468
+
bob,
469
+
"social.grain.gallery",
470
+
{
471
+
title: "Mountain Dawn",
472
+
description: "First light on the peaks #nature #landscape",
473
+
createdAt: ago(15),
474
+
},
475
+
{ rkey: "mountain-dawn" },
476
+
);
477
+
const mdPhoto = await createRecord(
478
+
bob,
479
+
"social.grain.photo",
480
+
{ photo: forest, alt: "Mountain at sunrise", aspectRatio: { width: 4, height: 3 }, createdAt: ago(15) },
481
+
{ rkey: "photo-mountain" },
482
+
);
483
+
await createRecord(
484
+
bob,
485
+
"social.grain.gallery.item",
486
+
{ gallery: mountainDawn.uri, item: mdPhoto.uri, position: 0, createdAt: ago(15) },
487
+
{ rkey: "gi-mountain" },
488
+
);
489
+
490
+
// Carol's second gallery: "Rainy Days"
491
+
const rainyDays = await createRecord(
492
+
carol,
493
+
"social.grain.gallery",
494
+
{
495
+
title: "Rainy Days",
496
+
description: "Puddles and reflections #streetphotography #film",
497
+
createdAt: ago(12),
498
+
},
499
+
{ rkey: "rainy-days" },
500
+
);
501
+
const rdPhoto = await createRecord(
502
+
carol,
503
+
"social.grain.photo",
504
+
{ photo: filmCafe, alt: "Rain on cobblestones", aspectRatio: { width: 3, height: 4 }, createdAt: ago(12) },
505
+
{ rkey: "photo-rain" },
506
+
);
507
+
await createRecord(
508
+
carol,
509
+
"social.grain.gallery.item",
510
+
{ gallery: rainyDays.uri, item: rdPhoto.uri, position: 0, createdAt: ago(12) },
511
+
{ rkey: "gi-rain" },
512
+
);
513
+
514
+
// Carol's third gallery: "Golden Hour Portraits"
515
+
const goldenPortraits = await createRecord(
516
+
carol,
517
+
"social.grain.gallery",
518
+
{
519
+
title: "Golden Hour Portraits",
520
+
description: "Warm light and soft shadows #portrait #film",
521
+
createdAt: ago(8),
522
+
},
523
+
{ rkey: "golden-portraits" },
524
+
);
525
+
const gpPhoto = await createRecord(
526
+
carol,
527
+
"social.grain.photo",
528
+
{ photo: filmPortrait, alt: "Portrait in golden light", aspectRatio: { width: 3, height: 4 }, createdAt: ago(8) },
529
+
{ rkey: "photo-golden" },
530
+
);
531
+
await createRecord(
532
+
carol,
533
+
"social.grain.gallery.item",
534
+
{ gallery: goldenPortraits.uri, item: gpPhoto.uri, position: 0, createdAt: ago(8) },
535
+
{ rkey: "gi-golden" },
536
+
);
537
+
538
+
// Dave's gallery: "Concrete Jungle"
539
+
const concreteJungle = await createRecord(
540
+
dave,
541
+
"social.grain.gallery",
542
+
{
543
+
title: "Concrete Jungle",
544
+
description: "Brutalist architecture up close #architecture #city",
545
+
createdAt: ago(18),
546
+
},
547
+
{ rkey: "concrete-jungle" },
548
+
);
549
+
const cjPhoto = await uploadBlob(dave, "./seeds/images/skyline.jpg");
550
+
const cjPhotoRec = await createRecord(
551
+
dave,
552
+
"social.grain.photo",
553
+
{ photo: cjPhoto, alt: "Concrete facade", aspectRatio: { width: 4, height: 3 }, createdAt: ago(18) },
554
+
{ rkey: "photo-concrete" },
555
+
);
556
+
await createRecord(
557
+
dave,
558
+
"social.grain.gallery.item",
559
+
{ gallery: concreteJungle.uri, item: cjPhotoRec.uri, position: 0, createdAt: ago(18) },
560
+
{ rkey: "gi-concrete" },
561
+
);
562
+
563
+
// Dave's second gallery: "Night Architecture"
564
+
const nightArch = await createRecord(
565
+
dave,
566
+
"social.grain.gallery",
567
+
{
568
+
title: "Night Architecture",
569
+
description: "Buildings after dark #architecture #city #night",
570
+
createdAt: ago(7),
571
+
},
572
+
{ rkey: "night-architecture" },
573
+
);
574
+
const naPhoto = await uploadBlob(dave, "./seeds/images/city-night.jpg");
575
+
const naPhotoRec = await createRecord(
576
+
dave,
577
+
"social.grain.photo",
578
+
{ photo: naPhoto, alt: "Building lit up at night", aspectRatio: { width: 4, height: 3 }, createdAt: ago(7) },
579
+
{ rkey: "photo-night-arch" },
580
+
);
581
+
await createRecord(
582
+
dave,
583
+
"social.grain.gallery.item",
584
+
{ gallery: nightArch.uri, item: naPhotoRec.uri, position: 0, createdAt: ago(7) },
585
+
{ rkey: "gi-night-arch" },
586
+
);
587
+
464
588
// ── Favorites ──
589
+
// Create a web of favorites that gives the collaborative filtering algorithm signal.
590
+
//
591
+
// Alice favorites: Bob's Forest Trail, Carol's Kodak Moments
592
+
// Bob favorites: Alice's City Lights, Carol's Rainy Days, Dave's Concrete Jungle
593
+
// Carol favorites: Alice's City Lights, Bob's Forest Trail, Dave's Night Architecture
594
+
// Dave favorites: Alice's City Lights, Bob's Forest Trail, Bob's Mountain Dawn, Carol's Golden Portraits
595
+
//
596
+
// For Alice: co-likers on Forest Trail = Carol, Dave. Co-likers on Kodak Moments = (none extra).
597
+
// Carol also liked: City Lights (Alice's own, skip), Dave's Night Architecture → candidate!
598
+
// Dave also liked: City Lights (Alice's own, skip), Mountain Dawn → candidate!, Golden Portraits → candidate!
465
599
466
600
// Alice favorites Bob's gallery
467
601
await createRecord(
···
471
605
{ rkey: "fav-forest" },
472
606
);
473
607
608
+
// Alice favorites Carol's gallery
609
+
await createRecord(
610
+
alice,
611
+
"social.grain.favorite",
612
+
{ subject: carolGallery.uri, createdAt: ago(6) },
613
+
{ rkey: "fav-kodak" },
614
+
);
615
+
474
616
// Bob favorites Alice's gallery
475
617
await createRecord(
476
618
bob,
···
479
621
{ rkey: "fav-city" },
480
622
);
481
623
624
+
// Bob favorites Carol's Rainy Days
625
+
await createRecord(
626
+
bob,
627
+
"social.grain.favorite",
628
+
{ subject: rainyDays.uri, createdAt: ago(10) },
629
+
{ rkey: "fav-rainy" },
630
+
);
631
+
632
+
// Bob favorites Dave's Concrete Jungle
633
+
await createRecord(
634
+
bob,
635
+
"social.grain.favorite",
636
+
{ subject: concreteJungle.uri, createdAt: ago(14) },
637
+
{ rkey: "fav-concrete" },
638
+
);
639
+
482
640
// Carol favorites Alice's gallery
483
641
await createRecord(
484
642
carol,
···
493
651
"social.grain.favorite",
494
652
{ subject: bobGallery.uri, createdAt: ago(20) },
495
653
{ rkey: "fav-forest-2" },
654
+
);
655
+
656
+
// Carol favorites Dave's Night Architecture
657
+
await createRecord(
658
+
carol,
659
+
"social.grain.favorite",
660
+
{ subject: nightArch.uri, createdAt: ago(5) },
661
+
{ rkey: "fav-night-arch" },
662
+
);
663
+
664
+
// Dave favorites Alice's gallery
665
+
await createRecord(
666
+
dave,
667
+
"social.grain.favorite",
668
+
{ subject: aliceGallery.uri, createdAt: ago(16) },
669
+
{ rkey: "fav-city-3" },
670
+
);
671
+
672
+
// Dave favorites Bob's Forest Trail
673
+
await createRecord(
674
+
dave,
675
+
"social.grain.favorite",
676
+
{ subject: bobGallery.uri, createdAt: ago(14) },
677
+
{ rkey: "fav-forest-3" },
678
+
);
679
+
680
+
// Dave favorites Bob's Mountain Dawn
681
+
await createRecord(
682
+
dave,
683
+
"social.grain.favorite",
684
+
{ subject: mountainDawn.uri, createdAt: ago(11) },
685
+
{ rkey: "fav-mountain" },
686
+
);
687
+
688
+
// Dave favorites Carol's Golden Hour Portraits
689
+
await createRecord(
690
+
dave,
691
+
"social.grain.favorite",
692
+
{ subject: goldenPortraits.uri, createdAt: ago(4) },
693
+
{ rkey: "fav-golden" },
496
694
);
497
695
498
696
// ── Comments ──
+256
server/feeds/foryou.ts
+256
server/feeds/foryou.ts
···
1
+
import { defineFeed } from "$hatk";
2
+
import { hydrateGalleries } from "../hydrate/galleries.ts";
3
+
import { hideLabelsFilter } from "../labels/_hidden.ts";
4
+
5
+
// ─── Scoring parameters (spacecowboy17's optimized A/B values) ───────
6
+
const HALF_LIFE_HOURS = 6;
7
+
const SMOOTHING_FACTOR = 0.5;
8
+
const POPULARITY_PENALTY = 0.3;
9
+
const DIVISOR_POWER = 1.0;
10
+
const CORATER_DECAY = 0;
11
+
const TIME_SHIFT_HOURS = 24;
12
+
const SEED_LIMIT = 500;
13
+
const MAX_COLIKERS = 1000;
14
+
const PAGE_SIZE = 50;
15
+
16
+
export default defineFeed({
17
+
collection: "social.grain.gallery",
18
+
label: "For You",
19
+
20
+
hydrate: hydrateGalleries,
21
+
22
+
async generate(ctx) {
23
+
const actor = ctx.params.actor;
24
+
if (!actor) return ctx.ok({ uris: [] });
25
+
26
+
const limit = Math.min(Number(ctx.params.limit) || PAGE_SIZE, PAGE_SIZE);
27
+
const offset = Number(ctx.params.cursor) || 0;
28
+
29
+
// Step 1: Get user's recent favorites (seed)
30
+
const seedRows = (await ctx.db.query(
31
+
`SELECT f.subject AS gallery_uri, f.created_at
32
+
FROM "social.grain.favorite" f
33
+
WHERE f.did = $1
34
+
ORDER BY f.created_at DESC
35
+
LIMIT $2`,
36
+
[actor, SEED_LIMIT],
37
+
)) as { gallery_uri: string; created_at: string }[];
38
+
39
+
// Cold start: fall back to popular galleries
40
+
if (seedRows.length === 0) {
41
+
return coldStartFeed(ctx, actor, limit, offset);
42
+
}
43
+
44
+
const seedUris = seedRows.map((r) => r.gallery_uri);
45
+
46
+
// Build a map of seed gallery → when the user liked it
47
+
const seedLikeTime = new Map<string, number>();
48
+
for (const row of seedRows) {
49
+
seedLikeTime.set(row.gallery_uri, new Date(row.created_at).getTime());
50
+
}
51
+
52
+
// Step 2: Find co-likers (people who favorited the same galleries)
53
+
const placeholders = seedUris.map((_, i) => `$${i + 2}`).join(", ");
54
+
const colikerRows = (await ctx.db.query(
55
+
`SELECT f.did AS coliker, f.subject AS gallery_uri, f.created_at
56
+
FROM "social.grain.favorite" f
57
+
WHERE f.subject IN (${placeholders})
58
+
AND f.did != $1
59
+
ORDER BY f.created_at DESC`,
60
+
[actor, ...seedUris],
61
+
)) as { coliker: string; gallery_uri: string; created_at: string }[];
62
+
63
+
// Filter co-likers: only those who liked before the user (unless ignore_order)
64
+
// + apply time_shift window
65
+
const validColikers = new Set<string>();
66
+
const colikerSeedPairs = new Map<string, Set<string>>(); // coliker → set of shared galleries
67
+
68
+
for (const row of colikerRows) {
69
+
const userLikeTime = seedLikeTime.get(row.gallery_uri);
70
+
if (!userLikeTime) continue;
71
+
72
+
const colikeTime = new Date(row.created_at).getTime();
73
+
// Only consider likes before the user's like (+ time_shift window)
74
+
if (colikeTime <= userLikeTime + TIME_SHIFT_HOURS * 3600_000) {
75
+
validColikers.add(row.coliker);
76
+
if (!colikerSeedPairs.has(row.coliker)) {
77
+
colikerSeedPairs.set(row.coliker, new Set());
78
+
}
79
+
colikerSeedPairs.get(row.coliker)!.add(row.gallery_uri);
80
+
}
81
+
}
82
+
83
+
if (validColikers.size === 0) {
84
+
return coldStartFeed(ctx, actor, limit, offset);
85
+
}
86
+
87
+
// Step 3: Get co-likers' other favorites (candidates) + their total like counts
88
+
// Cap co-likers, preferring those with more overlap
89
+
const colikerList = [...validColikers]
90
+
.sort((a, b) => (colikerSeedPairs.get(b)?.size ?? 0) - (colikerSeedPairs.get(a)?.size ?? 0))
91
+
.slice(0, MAX_COLIKERS);
92
+
93
+
const colikerPlaceholders = colikerList.map((_, i) => `$${i + 2}`).join(", ");
94
+
const seedPlaceholders = seedUris.map((_, i) => `$${i + 2 + colikerList.length}`).join(", ");
95
+
96
+
const likeCountPlaceholders = colikerList.map((_, i) => `$${i + 1}`).join(", ");
97
+
98
+
const [candidateRows, likeCounts] = await Promise.all([
99
+
ctx.db.query(
100
+
`SELECT f.did AS coliker, f.subject AS gallery_uri, t.created_at AS gallery_created_at
101
+
FROM "social.grain.favorite" f
102
+
JOIN "social.grain.gallery" t ON t.uri = f.subject
103
+
LEFT JOIN _repos r ON t.did = r.did
104
+
WHERE f.did IN (${colikerPlaceholders})
105
+
AND f.subject NOT IN (${seedPlaceholders})
106
+
AND t.did != $1
107
+
AND (r.status IS NULL OR r.status != 'takendown')
108
+
AND ${hideLabelsFilter("t.uri")}
109
+
AND (SELECT count(*) FROM "social.grain.gallery.item" gi WHERE gi.gallery = t.uri) > 0`,
110
+
[actor, ...colikerList, ...seedUris],
111
+
) as Promise<{ coliker: string; gallery_uri: string; gallery_created_at: string }[]>,
112
+
113
+
ctx.db.query(
114
+
`SELECT did, COUNT(*) as cnt
115
+
FROM "social.grain.favorite"
116
+
WHERE did IN (${likeCountPlaceholders})
117
+
GROUP BY did`,
118
+
colikerList,
119
+
) as Promise<{ did: string; cnt: number }[]>,
120
+
]);
121
+
122
+
// Build co-liker total likes map
123
+
const colikerTotalLikes = new Map<string, number>();
124
+
for (const row of likeCounts) {
125
+
colikerTotalLikes.set(row.did, Number(row.cnt));
126
+
}
127
+
128
+
// Step 4: Score each candidate gallery
129
+
const now = Date.now();
130
+
const galleryScores = new Map<
131
+
string,
132
+
{ score: number; paths: number; created_at: string; coratersSeenCount: Map<string, number> }
133
+
>();
134
+
135
+
// Get popularity (total favorites) for candidate galleries
136
+
const candidateUris = [...new Set(candidateRows.map((r) => r.gallery_uri))];
137
+
138
+
const popularityMap = new Map<string, number>();
139
+
if (candidateUris.length > 0) {
140
+
const popPlaceholders = candidateUris.map((_, i) => `$${i + 1}`).join(", ");
141
+
const popRows = (await ctx.db.query(
142
+
`SELECT subject, COUNT(*) as cnt
143
+
FROM "social.grain.favorite"
144
+
WHERE subject IN (${popPlaceholders})
145
+
GROUP BY subject`,
146
+
candidateUris,
147
+
)) as { subject: string; cnt: number }[];
148
+
for (const row of popRows) {
149
+
popularityMap.set(row.subject, Number(row.cnt));
150
+
}
151
+
}
152
+
153
+
for (const row of candidateRows) {
154
+
const totalLikes = colikerTotalLikes.get(row.coliker) || 1;
155
+
156
+
let entry = galleryScores.get(row.gallery_uri);
157
+
if (!entry) {
158
+
entry = {
159
+
score: 0,
160
+
paths: 0,
161
+
created_at: row.gallery_created_at,
162
+
coratersSeenCount: new Map(),
163
+
};
164
+
galleryScores.set(row.gallery_uri, entry);
165
+
}
166
+
167
+
// Track how many items we've seen from this corater (for decay)
168
+
const seenCount = entry.coratersSeenCount.get(row.coliker) || 0;
169
+
entry.coratersSeenCount.set(row.coliker, seenCount + 1);
170
+
171
+
// Path score: 1 / total_likes^divisor_power
172
+
let pathScore = 1 / Math.pow(totalLikes, DIVISOR_POWER);
173
+
174
+
// Corater decay
175
+
if (CORATER_DECAY > 0) {
176
+
pathScore *= Math.pow(1 - CORATER_DECAY, seenCount);
177
+
}
178
+
179
+
entry.score += pathScore;
180
+
entry.paths += 1;
181
+
}
182
+
183
+
// Apply smoothing, time decay, and popularity penalty
184
+
const scored: { uri: string; score: number }[] = [];
185
+
186
+
for (const [uri, entry] of galleryScores) {
187
+
let score = entry.score;
188
+
189
+
// Smoothing: boost multi-path galleries
190
+
if (SMOOTHING_FACTOR > 0) {
191
+
score *= Math.pow(entry.paths, SMOOTHING_FACTOR);
192
+
}
193
+
194
+
// Time decay
195
+
if (HALF_LIFE_HOURS > 0) {
196
+
const ageHours = (now - new Date(entry.created_at).getTime()) / 3_600_000;
197
+
score *= Math.pow(0.5, ageHours / HALF_LIFE_HOURS);
198
+
}
199
+
200
+
// Popularity penalty
201
+
if (POPULARITY_PENALTY > 0) {
202
+
const popularity = popularityMap.get(uri) || 1;
203
+
score /= Math.pow(popularity, POPULARITY_PENALTY);
204
+
}
205
+
206
+
scored.push({ uri, score });
207
+
}
208
+
209
+
// Sort by score descending
210
+
scored.sort((a, b) => b.score - a.score);
211
+
212
+
// Paginate
213
+
const page = scored.slice(offset, offset + limit);
214
+
const nextCursor = offset + limit < scored.length ? String(offset + limit) : undefined;
215
+
216
+
return ctx.ok({
217
+
uris: page.map((r) => r.uri),
218
+
cursor: nextCursor,
219
+
});
220
+
},
221
+
});
222
+
223
+
// ─── Cold start: most-favorited galleries from last 30 days ──────────
224
+
async function coldStartFeed(
225
+
ctx: Parameters<Parameters<typeof defineFeed>[0]["generate"]>[0],
226
+
actor: string,
227
+
limit: number,
228
+
offset: number,
229
+
) {
230
+
const thirtyDaysAgo = new Date(Date.now() - 30 * 24 * 3600_000).toISOString();
231
+
232
+
const rows = (await ctx.db.query(
233
+
`SELECT t.uri, COUNT(f.did) as fav_count
234
+
FROM "social.grain.gallery" t
235
+
LEFT JOIN "social.grain.favorite" f ON f.subject = t.uri
236
+
LEFT JOIN _repos r ON t.did = r.did
237
+
WHERE (r.status IS NULL OR r.status != 'takendown')
238
+
AND t.did != $1
239
+
AND t.created_at > $2
240
+
AND ${hideLabelsFilter("t.uri")}
241
+
AND (SELECT count(*) FROM "social.grain.gallery.item" gi WHERE gi.gallery = t.uri) > 0
242
+
GROUP BY t.uri
243
+
ORDER BY fav_count DESC, t.created_at DESC
244
+
LIMIT $3 OFFSET $4`,
245
+
[actor, thirtyDaysAgo, limit, offset],
246
+
)) as { uri: string; fav_count: number }[];
247
+
248
+
// Check if there are more results
249
+
const hasMore = rows.length === limit;
250
+
const nextCursor = hasMore ? String(offset + limit) : undefined;
251
+
252
+
return ctx.ok({
253
+
uris: rows.map((r) => r.uri),
254
+
cursor: nextCursor,
255
+
});
256
+
}