···
"Coves/internal/core/communityFeeds"
-
"Coves/internal/core/posts"
type postgresFeedRepo struct {
// sortClauses maps sort types to safe SQL ORDER BY clauses
// This whitelist prevents SQL injection via dynamic ORDER BY construction
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var sortClauses = map[string]string{
"hot": `(p.score / POWER(EXTRACT(EPOCH FROM (NOW() - p.created_at))/3600 + 2, 1.5)) DESC, p.created_at DESC, p.uri DESC`,
"top": `p.score DESC, p.created_at DESC, p.uri DESC`,
"new": `p.created_at DESC, p.uri DESC`,
···
// NOTE: Uses NOW() which means hot_rank changes over time - this is expected behavior
// for hot sorting (posts naturally age out). Slight time drift between cursor creation
// and usage may cause minor reordering but won't drop posts entirely (unlike using raw score).
-
const hotRankExpression = `(p.score / POWER(EXTRACT(EPOCH FROM (NOW() - p.created_at))/3600 + 2, 1.5))`
// NewCommunityFeedRepository creates a new PostgreSQL feed repository
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func NewCommunityFeedRepository(db *sql.DB) communityFeeds.Repository {
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return &postgresFeedRepo{db: db}
// GetCommunityFeed retrieves posts from a community with sorting and pagination
// Single query with JOINs for optimal performance
func (r *postgresFeedRepo) GetCommunityFeed(ctx context.Context, req communityFeeds.GetCommunityFeedRequest) ([]*communityFeeds.FeedViewPost, *string, error) {
// Build ORDER BY clause based on sort type
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orderBy, timeFilter := r.buildSortClause(req.Sort, req.Timeframe)
// Build cursor filter for pagination
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cursorFilter, cursorValues, err := r.parseCursor(req.Cursor, req.Sort)
return nil, nil, communityFeeds.ErrInvalidCursor
···
p.author_did, u.handle as author_handle,
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p.community_did, c.name as community_name, c.avatar_cid as community_avatar,
p.title, p.content, p.content_facets, p.embed, p.content_labels,
p.created_at, p.edited_at, p.indexed_at,
p.upvote_count, p.downvote_count, p.score, p.comment_count,
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FROM posts p`, hotRankExpression)
p.author_did, u.handle as author_handle,
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p.community_did, c.name as community_name, c.avatar_cid as community_avatar,
p.title, p.content, p.content_facets, p.embed, p.content_labels,
p.created_at, p.edited_at, p.indexed_at,
p.upvote_count, p.downvote_count, p.score, p.comment_count,
···
var feedPosts []*communityFeeds.FeedViewPost
var hotRanks []float64 // Store hot ranks for cursor building
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feedPost, hotRank, err := r.scanFeedViewPost(rows)
return nil, nil, fmt.Errorf("failed to scan feed post: %w", err)
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feedPosts = append(feedPosts, feedPost)
hotRanks = append(hotRanks, hotRank)
···
hotRanks = hotRanks[:req.Limit]
lastPost := feedPosts[len(feedPosts)-1].Post
lastHotRank := hotRanks[len(hotRanks)-1]
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cursorStr := r.buildCursor(lastPost, req.Sort, lastHotRank)
return feedPosts, cursor, nil
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// buildSortClause returns the ORDER BY SQL and optional time filter
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func (r *postgresFeedRepo) buildSortClause(sort, timeframe string) (string, string) {
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// Use whitelist map for ORDER BY clause (defense-in-depth against SQL injection)
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orderBy := sortClauses[sort]
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orderBy = sortClauses["hot"] // safe default
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// Add time filter for "top" sort
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timeFilter = r.buildTimeFilter(timeframe)
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return orderBy, timeFilter
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// buildTimeFilter returns SQL filter for timeframe
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func (r *postgresFeedRepo) buildTimeFilter(timeframe string) string {
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if timeframe == "" || timeframe == "all" {
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return fmt.Sprintf("AND p.created_at > NOW() - INTERVAL '%s'", interval)
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// parseCursor decodes pagination cursor
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func (r *postgresFeedRepo) parseCursor(cursor *string, sort string) (string, []interface{}, error) {
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if cursor == nil || *cursor == "" {
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// Decode base64 cursor
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decoded, err := base64.StdEncoding.DecodeString(*cursor)
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return "", nil, fmt.Errorf("invalid cursor encoding")
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// Parse cursor based on sort type using :: delimiter (Bluesky convention)
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parts := strings.Split(string(decoded), "::")
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// Cursor format: timestamp::uri
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return "", nil, fmt.Errorf("invalid cursor format")
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// Validate timestamp format
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if _, err := time.Parse(time.RFC3339Nano, createdAt); err != nil {
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return "", nil, fmt.Errorf("invalid cursor timestamp")
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// Validate URI format (must be AT-URI)
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if !strings.HasPrefix(uri, "at://") {
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return "", nil, fmt.Errorf("invalid cursor URI")
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filter := `AND (p.created_at < $3 OR (p.created_at = $3 AND p.uri < $4))`
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return filter, []interface{}{createdAt, uri}, nil
-
// Cursor format: score::timestamp::uri
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return "", nil, fmt.Errorf("invalid cursor format for %s sort", sort)
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// Validate score is numeric
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if _, err := fmt.Sscanf(scoreStr, "%d", &score); err != nil {
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return "", nil, fmt.Errorf("invalid cursor score")
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// Validate timestamp format
-
if _, err := time.Parse(time.RFC3339Nano, createdAt); err != nil {
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return "", nil, fmt.Errorf("invalid cursor timestamp")
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// Validate URI format (must be AT-URI)
-
if !strings.HasPrefix(uri, "at://") {
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return "", nil, fmt.Errorf("invalid cursor URI")
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filter := `AND (p.score < $3 OR (p.score = $3 AND p.created_at < $4) OR (p.score = $3 AND p.created_at = $4 AND p.uri < $5))`
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return filter, []interface{}{score, createdAt, uri}, nil
-
// Cursor format: hot_rank::timestamp::uri
-
// CRITICAL: Must use computed hot_rank, not raw score, to prevent pagination bugs
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return "", nil, fmt.Errorf("invalid cursor format for hot sort")
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// Validate hot_rank is numeric (float)
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if _, err := fmt.Sscanf(hotRankStr, "%f", &hotRank); err != nil {
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return "", nil, fmt.Errorf("invalid cursor hot rank")
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// Validate timestamp format
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if _, err := time.Parse(time.RFC3339Nano, createdAt); err != nil {
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return "", nil, fmt.Errorf("invalid cursor timestamp")
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// Validate URI format (must be AT-URI)
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if !strings.HasPrefix(uri, "at://") {
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return "", nil, fmt.Errorf("invalid cursor URI")
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// CRITICAL: Compare against the computed hot_rank expression, not p.score
-
// This prevents dropping posts with higher raw scores but lower hot ranks
-
// NOTE: We exclude the exact cursor post by URI to handle time drift in hot_rank
-
// (hot_rank changes with NOW(), so the same post may have different ranks over time)
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filter := fmt.Sprintf(`AND ((%s < $3 OR (%s = $3 AND p.created_at < $4) OR (%s = $3 AND p.created_at = $4 AND p.uri < $5)) AND p.uri != $6)`,
-
hotRankExpression, hotRankExpression, hotRankExpression)
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return filter, []interface{}{hotRank, createdAt, uri, uri}, nil
-
// buildCursor creates pagination cursor from last post
-
func (r *postgresFeedRepo) buildCursor(post *posts.PostView, sort string, hotRank float64) string {
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// Use :: as delimiter following Bluesky convention
-
// Safe because :: doesn't appear in ISO timestamps or AT-URIs
-
// Format: timestamp::uri (following Bluesky pattern)
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cursorStr = fmt.Sprintf("%s%s%s", post.CreatedAt.Format(time.RFC3339Nano), delimiter, post.URI)
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// Format: score::timestamp::uri
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score = post.Stats.Score
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cursorStr = fmt.Sprintf("%d%s%s%s%s", score, delimiter, post.CreatedAt.Format(time.RFC3339Nano), delimiter, post.URI)
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// Format: hot_rank::timestamp::uri
-
// CRITICAL: Use computed hot_rank with full precision to prevent pagination bugs
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// Using 'g' format with -1 precision gives us full float64 precision without trailing zeros
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// This prevents posts being dropped when hot ranks differ by <1e-6
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hotRankStr := strconv.FormatFloat(hotRank, 'g', -1, 64)
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cursorStr = fmt.Sprintf("%s%s%s%s%s", hotRankStr, delimiter, post.CreatedAt.Format(time.RFC3339Nano), delimiter, post.URI)
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return base64.StdEncoding.EncodeToString([]byte(cursorStr))
-
// scanFeedViewPost scans a row into FeedViewPost
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// Alpha: No viewer state - basic community feed only
-
func (r *postgresFeedRepo) scanFeedViewPost(rows *sql.Rows) (*communityFeeds.FeedViewPost, float64, error) {
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postView posts.PostView
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authorView posts.AuthorView
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communityRef posts.CommunityRef
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title, content sql.NullString
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facets, embed sql.NullString
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labelsJSON sql.NullString
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communityAvatar sql.NullString
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hotRank sql.NullFloat64
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&postView.URI, &postView.CID, &postView.RKey,
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&authorView.DID, &authorView.Handle,
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&communityRef.DID, &communityRef.Name, &communityAvatar,
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&title, &content, &facets, &embed, &labelsJSON,
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&postView.CreatedAt, &editedAt, &postView.IndexedAt,
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&postView.UpvoteCount, &postView.DownvoteCount, &postView.Score, &postView.CommentCount,
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// Build author view (no display_name or avatar in users table yet)
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postView.Author = &authorView
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communityRef.Avatar = nullStringPtr(communityAvatar)
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postView.Community = &communityRef
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postView.Title = nullStringPtr(title)
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postView.Text = nullStringPtr(content)
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var facetArray []interface{}
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if err := json.Unmarshal([]byte(facets.String), &facetArray); err == nil {
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postView.TextFacets = facetArray
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var embedData interface{}
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if err := json.Unmarshal([]byte(embed.String), &embedData); err == nil {
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postView.Embed = embedData
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postView.Stats = &posts.PostStats{
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Upvotes: postView.UpvoteCount,
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Downvotes: postView.DownvoteCount,
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CommentCount: postView.CommentCount,
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// Alpha: No viewer state for basic feed
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// TODO(feed-generator): Implement viewer state (saved, voted, blocked) in feed generator skeleton
-
// Build the record (required by lexicon - social.coves.community.post structure)
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record := map[string]interface{}{
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"$type": "social.coves.community.post",
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"community": communityRef.DID,
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"author": authorView.DID,
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"createdAt": postView.CreatedAt.Format(time.RFC3339),
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// Add optional fields to record if present
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record["title"] = title.String
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record["content"] = content.String
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var facetArray []interface{}
-
if err := json.Unmarshal([]byte(facets.String), &facetArray); err == nil {
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record["facets"] = facetArray
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var embedData interface{}
-
if err := json.Unmarshal([]byte(embed.String), &embedData); err == nil {
-
record["embed"] = embedData
-
// Labels are stored as JSONB containing full com.atproto.label.defs#selfLabels structure
-
// Deserialize and include in record
-
var selfLabels posts.SelfLabels
-
if err := json.Unmarshal([]byte(labelsJSON.String), &selfLabels); err == nil {
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record["labels"] = selfLabels
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postView.Record = record
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// Wrap in FeedViewPost
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feedPost := &communityFeeds.FeedViewPost{
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// Reason: nil, // TODO(feed-generator): Implement pinned posts
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// Reply: nil, // TODO(feed-generator): Implement reply context
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// Return the computed hot_rank (0.0 if NULL for non-hot sorts)
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hotRankValue = hotRank.Float64
-
return feedPost, hotRankValue, nil
-
// Helper function to convert sql.NullString to *string
-
func nullStringPtr(ns sql.NullString) *string {
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