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feed.go
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feed.go
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package bangers
import (
"context"
"errors"
"fmt"
"strconv"
"time"
"encoding/json"
appbsky "github.com/bluesky-social/indigo/api/bsky"
"github.com/ericvolp12/bsky-experiments/pkg/consumer/store"
"github.com/ericvolp12/bsky-experiments/pkg/consumer/store/store_queries"
"github.com/ericvolp12/bsky-experiments/pkg/search"
"github.com/redis/go-redis/v9"
"go.opentelemetry.io/otel"
)
const (
atBangersKey = "at-bangers"
atBangersTTL = 30 * time.Minute
userTTL = 10 * time.Minute
maxPosts = 3000
)
type BangersFeed struct {
FeedActorDID string
Store *store.Store
Redis *redis.Client
}
type NotFoundError struct {
error
}
func NewBangersFeed(ctx context.Context, feedActorDID string, store *store.Store, redis *redis.Client) (*BangersFeed, []string, error) {
return &BangersFeed{
FeedActorDID: feedActorDID,
Store: store,
Redis: redis,
}, []string{"bangers", "at-bangers"}, nil
}
var tracer = otel.Tracer("bangers-feed")
type postRef struct {
ActorDid string `json:"did"`
Rkey string `json:"rkey"`
}
func (f *BangersFeed) fetchAndCachePosts(ctx context.Context, userDID string, feed string) ([]postRef, error) {
var posts []store_queries.Post
var err error
if feed == "bangers" {
posts, err = f.Store.Queries.GetTopPostsForActor(ctx, store_queries.GetTopPostsForActorParams{
ActorDid: userDID,
Limit: maxPosts,
Offset: 0,
})
} else {
posts, err = f.Store.Queries.GetTopPosts(ctx, store_queries.GetTopPostsParams{
Limit: maxPosts,
Offset: 0,
})
}
if err != nil {
return nil, err
}
cacheKey := feed
if feed == "bangers" {
cacheKey += ":" + userDID
}
p := f.Redis.Pipeline()
postRefs := []postRef{}
for _, post := range posts {
postRef := postRef{
ActorDid: post.ActorDid,
Rkey: post.Rkey,
}
cacheValue, err := json.Marshal(postRef)
if err != nil {
return nil, fmt.Errorf("error marshalling post: %w", err)
}
p.RPush(ctx, cacheKey, cacheValue)
postRefs = append(postRefs, postRef)
}
ttl := atBangersTTL
if feed == "bangers" {
ttl = userTTL
}
p.Expire(ctx, cacheKey, ttl)
_, err = p.Exec(ctx)
if err != nil {
return nil, fmt.Errorf("error caching posts for feed (%s): %w", feed, err)
}
return postRefs, nil
}
func (f *BangersFeed) GetPage(ctx context.Context, feed string, userDID string, limit int64, cursor string) ([]*appbsky.FeedDefs_SkeletonFeedPost, *string, error) {
ctx, span := tracer.Start(ctx, "GetPage")
defer span.End()
offset := int64(0)
var err error
if cursor != "" {
offset, err = strconv.ParseInt(cursor, 10, 64)
if err != nil {
return nil, nil, fmt.Errorf("error parsing cursor: %w", err)
}
}
var posts []postRef
cacheKey := feed
if feed == "bangers" {
if userDID == "" {
return nil, nil, fmt.Errorf("authorization required for feed: %s", feed)
}
cacheKey += ":" + userDID
}
cached, err := f.Redis.LRange(ctx, cacheKey, offset, offset+limit-1).Result()
if err == redis.Nil || len(cached) == 0 {
posts, err = f.fetchAndCachePosts(ctx, userDID, feed)
if err != nil {
if errors.As(err, &search.NotFoundError{}) {
return nil, nil, NotFoundError{fmt.Errorf("posts not found for feed %s", feed)}
}
return nil, nil, fmt.Errorf("error getting posts from registry for feed (%s): %w", feed, err)
}
// Truncate the posts to the limit and offset
if len(posts) > int(limit) {
posts = posts[offset : offset+limit]
}
} else if err == nil {
posts = make([]postRef, len(cached))
for i, cachedValue := range cached {
json.Unmarshal([]byte(cachedValue), &posts[i])
}
} else {
return nil, nil, fmt.Errorf("error getting posts from cache for feed (%s): %w", feed, err)
}
// Serve posts from the cache if within the 3k window
if offset+limit > maxPosts {
var dbPosts []store_queries.Post
switch feed {
case "bangers":
dbPosts, err = f.Store.Queries.GetTopPostsForActor(ctx, store_queries.GetTopPostsForActorParams{
ActorDid: userDID,
Limit: int32(limit),
Offset: int32(offset),
})
case "at-bangers":
// Fetch posts beyond the 3k window from the database
dbPosts, err = f.Store.Queries.GetTopPosts(ctx, store_queries.GetTopPostsParams{
Limit: int32(limit),
Offset: int32(offset),
})
}
if err != nil {
if errors.As(err, &search.NotFoundError{}) {
return nil, nil, NotFoundError{fmt.Errorf("posts not found for feed %s", feed)}
}
return nil, nil, fmt.Errorf("error getting posts from registry for feed (%s): %w", feed, err)
}
posts = []postRef{}
for _, post := range dbPosts {
posts = append(posts, postRef{
ActorDid: post.ActorDid,
Rkey: post.Rkey,
})
}
}
feedPosts := []*appbsky.FeedDefs_SkeletonFeedPost{}
for _, post := range posts {
postAtURL := fmt.Sprintf("at://%s/app.bsky.feed.post/%s", post.ActorDid, post.Rkey)
feedPosts = append(feedPosts, &appbsky.FeedDefs_SkeletonFeedPost{
Post: postAtURL,
})
}
if int64(len(posts)) < limit {
return feedPosts, nil, nil
}
newCursor := strconv.FormatInt(offset+limit, 10)
return feedPosts, &newCursor, nil
}
func (f *BangersFeed) Describe(ctx context.Context) ([]appbsky.FeedDescribeFeedGenerator_Feed, error) {
ctx, span := tracer.Start(ctx, "Describe")
defer span.End()
feeds := []appbsky.FeedDescribeFeedGenerator_Feed{
{
Uri: "at://" + f.FeedActorDID + "/app.bsky.feed.generator/" + "bangers",
},
{
Uri: "at://" + f.FeedActorDID + "/app.bsky.feed.generator/" + "at-bangers",
},
}
return feeds, nil
}