clean up backend spotify import functionality

migrate/spotify.go

@@ -12,6 +12,8 @@ import (
 	"github.com/jackc/pgx/v5"
 )
 
+const batchSize = 1000
+
 type SpotifyTrack struct {
 	Timestamp string `json:"ts"`
 	Played    int    `json:"ms_played"`
@@ -20,25 +22,30 @@ type SpotifyTrack struct {
 	Album     string `json:"master_metadata_album_album_name"`
 }
 
-type existingTrack struct {
+type trackSource struct {
+	tracks       []SpotifyTrack
+	tracksToSkip map[string]struct{}
+	idx          int
+	userId       int
+}
+
+type dbTrack struct {
 	Timestamp time.Time
 	SongName  string
 	Artist    string
 }
 
-// trackSource implements pgx.CopyFromSource for efficient bulk inserts
-type trackSource struct {
-	tracks   []SpotifyTrack
-	existing map[string]struct{}
-	idx      int
-	userId   int
-}
-
 func (s *trackSource) Next() bool {
 	for s.idx < len(s.tracks) {
 		t := s.tracks[s.idx]
-		key := fmt.Sprintf("%s|%s|%s", t.Artist, t.Name, t.Timestamp)
-		if _, exists := s.existing[key]; exists {
+		ts, err := normalizeTs(t.Timestamp)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Error normalizing timestamp: %v\n", err)
+			s.idx++
+			continue
+		}
+		key := fmt.Sprintf("%s|%s|%s", t.Artist, t.Name, ts)
+		if _, shouldSkip := s.tracksToSkip[key]; shouldSkip {
 			s.idx++
 			continue
 		}
@@ -51,7 +58,6 @@ func (s *trackSource) Next() bool {
 func (s *trackSource) Values() ([]any, error) {
 	// idx is already incremented in Next(), so use idx-1
 	t := s.tracks[s.idx-1]
-	// parse spotify string timestamp to a real time object
 	ts, err := time.Parse(time.RFC3339Nano, t.Timestamp)
 	if err != nil {
 		return nil, err
@@ -71,48 +77,62 @@ func (s *trackSource) Err() error {
 	return nil
 }
 
-// find tracks with the same artist and name in a 20 second +- timeframe
-func getExistingTracks(
-	userId int,
-	tracks []SpotifyTrack,
-) (map[string]struct{}, error) {
-	// check for empty track import
-	if len(tracks) == 0 {
-		return map[string]struct{}{}, nil
-	}
-
-	// find min/max timestamps in this batch to create time window to
-	// search for duplicates
-	var minTs, maxTs time.Time
-	// go through each track (t) in the array
-	for _, t := range tracks {
-		// parse spotify timestamp into operational time datatype
-		ts, err := time.Parse(time.RFC3339Nano, t.Timestamp)
+func normalizeTs(ts string) (string, error) {
+	t, err := time.Parse(time.RFC3339Nano, ts)
 	if err != nil {
-			continue
-		}
-		// if minTs uninitialized or timestamp predates minTs
-		if minTs.IsZero() || ts.Before(minTs) {
-			minTs = ts
-		}
-		// if timestamp comes after maxTs
-		if ts.After(maxTs) {
-			maxTs = ts
-		}
+		return "", err
 	}
+	return t.Format(time.RFC3339Nano), nil
+}
 
-	// check if all parses failed, therefore no way to find duplicate by time
+func getExistingTracks(
+	userId int, tracks []SpotifyTrack,
+) (map[string]struct{}, error) {
+	minTs, maxTs := findTimeRange(tracks)
 	if minTs.IsZero() {
 		return map[string]struct{}{}, nil
 	}
 
-	// find all tracks within [min-20s, max+20s] window (duplicates)
+	dbTracks, err := fetchDbTracks(userId, minTs, maxTs)
+	if err != nil {
+		return nil, err
+	}
+
+	dbIndex := buildDbTrackIndex(dbTracks)
+
+	return findDuplicates(tracks, dbIndex), nil
+}
+
+// get the min/max timestamp range for a batch of tracks
+func findTimeRange(tracks []SpotifyTrack) (time.Time, time.Time) {
+	var minTs, maxTs time.Time
+	for _, t := range tracks {
+		ts, err := time.Parse(time.RFC3339Nano, t.Timestamp)
+		if err != nil {
+			continue
+		}
+		if minTs.IsZero() || ts.Before(minTs) {
+			minTs = ts
+		}
+		if ts.After(maxTs) {
+			maxTs = ts
+		}
+	}
+	return minTs, maxTs
+}
+
+/*
+	 get all tracks in the database for a user that have the same timestamp
+		range as the current batch
+*/
+func fetchDbTracks(userId int, minTs, maxTs time.Time) ([]dbTrack, error) {
 	rows, err := db.Pool.Query(context.Background(),
 		`SELECT song_name, artist, timestamp 
 		 FROM history 
 		 WHERE user_id = $1 
 		 AND timestamp BETWEEN $2 AND $3`,
 		userId,
+		// adjust 20 seconds to find duplicates on edges of batch
 		minTs.Add(-20*time.Second),
 		maxTs.Add(20*time.Second))
 	if err != nil {
@@ -120,102 +140,118 @@ func getExistingTracks(
 	}
 	defer rows.Close()
 
-	// prepare map to hold duplicate track keys
-	existing := make(map[string]struct{})
-	// create array of tracks
-	var existingTracks []existingTrack
-	// for each repeat play (-20s +20s)
+	var dbTracks []dbTrack
 	for rows.Next() {
-		// write the data from json to the track in memory
-		var t existingTrack
+		var t dbTrack
 		if err := rows.Scan(&t.SongName, &t.Artist, &t.Timestamp); err != nil {
 			continue
 		}
-		// add track in memory to existingTracks array
-		existingTracks = append(existingTracks, t)
+		dbTracks = append(dbTracks, t)
 	}
+	return dbTracks, nil
+}
 
-	// index existing tracks by artist|name for O(1) lookup
-	existingIndex := make(map[string][]time.Time)
-	for _, t := range existingTracks {
+func buildDbTrackIndex(tracks []dbTrack) map[string][]time.Time {
+	index := make(map[string][]time.Time)
+	for _, t := range tracks {
 		key := t.Artist + "|" + t.SongName
-		existingIndex[key] = append(existingIndex[key], t.Timestamp)
+		index[key] = append(index[key], t.Timestamp)
 	}
+	return index
+}
 
-	// check each new track against indexed existing tracks
-	for _, newTrack := range tracks {
-		newTs, err := time.Parse(time.RFC3339Nano, newTrack.Timestamp)
+func findDuplicates(tracks []SpotifyTrack, dbIndex map[string][]time.Time) map[string]struct{} {
+	duplicates := make(map[string]struct{})
+	seenInBatch := make(map[string]struct{})
+
+	for _, track := range tracks {
+		trackKey, err := createTrackKey(track)
 		if err != nil {
 			continue
 		}
 
-		lookupKey := newTrack.Artist + "|" + newTrack.Name
-		if timestamps, found := existingIndex[lookupKey]; found {
-			for _, existTs := range timestamps {
-				diff := newTs.Sub(existTs)
+		// in batch check
+		if _, seen := seenInBatch[trackKey]; seen {
+			duplicates[trackKey] = struct{}{}
+			continue
+		}
+		seenInBatch[trackKey] = struct{}{}
+
+		// in db check
+		lookupKey := fmt.Sprintf("%s|%s", track.Artist, track.Name)
+		if dbTimestamps, found := dbIndex[lookupKey]; found {
+			if isDuplicateWithinWindow(track, dbTimestamps) {
+				duplicates[trackKey] = struct{}{}
+			}
+		}
+	}
+
+	return duplicates
+}
+
+func createTrackKey(track SpotifyTrack) (string, error) {
+	ts, err := normalizeTs(track.Timestamp)
+	if err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("%s|%s|%s", track.Artist, track.Name, ts), nil
+}
+
+// check if a track timestamp falls < 20 seconds of another
+func isDuplicateWithinWindow(track SpotifyTrack, existingTimestamps []time.Time) bool {
+	trackTime, err := time.Parse(time.RFC3339Nano, track.Timestamp)
+	if err != nil {
+		return false
+	}
+	for _, existingTime := range existingTimestamps {
+		diff := trackTime.Sub(existingTime)
 		if diff < 0 {
 			diff = -diff
 		}
 		if diff < 20*time.Second {
-					key := fmt.Sprintf(
-						"%s|%s|%s",
-						newTrack.Artist,
-						newTrack.Name,
-						newTrack.Timestamp,
-					)
-					existing[key] = struct{}{}
-					break
+			return true
 		}
 	}
-		}
-	}
-
-	return existing, nil
+	return false
 }
 
 func ImportSpotify(tracks []SpotifyTrack, userId int) error {
 	totalImported := 0
-	batchSize := 1000
+	totalTracks := len(tracks)
+	batchStart := 0
 
-	for batchStart := 0; batchStart < len(tracks); batchStart += batchSize {
-		// get the limit of the current batch
-		batchEnd := batchStart + batchSize
-		// set limit to track array length in current batch too big
-		if batchEnd > len(tracks) {
-			batchEnd = len(tracks)
-		}
+	for batchStart < totalTracks {
+		// cap batchEnd at total track count on final batch to prevent OOB error
+		batchEnd := min(batchStart+batchSize, totalTracks)
 
-		// create array to hold valid listens
 		var validTracks []SpotifyTrack
 		for i := batchStart; i < batchEnd; i++ {
-			// if current track is listened to for 20 sec and name and artist is not
-			// blank, add to validTracks array
-			if tracks[i].Played >= 20000 && tracks[i].Name != "" && tracks[i].Artist != "" {
+			if tracks[i].Played >= 20000 && // 20 seconds
+				tracks[i].Name != "" &&
+				tracks[i].Artist != "" {
 				validTracks = append(validTracks, tracks[i])
 			}
 		}
 
-		// if there are no valid tracks in this batch, go to the next
 		if len(validTracks) == 0 {
+			batchStart += batchSize
 			continue
 		}
 
-		// find replayed tracks in the batch that was just gathered
-		existing, err := getExistingTracks(userId, validTracks)
+		tracksToSkip, err := getExistingTracks(userId, validTracks)
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "Error checking existing tracks: %v\n", err)
+			batchStart += batchSize
 			continue
 		}
 
-		// get data of struct pointer
 		src := &trackSource{
 			tracks:       validTracks,
-			existing: existing,
+			tracksToSkip: tracksToSkip,
 			idx:          0,
 			userId:       userId,
 		}
 
-		// insert all valid tracks from current batch into db
 		copyCount, err := db.Pool.CopyFrom(
 			context.Background(),
 			pgx.Identifier{"history"},
@@ -237,6 +273,7 @@ func ImportSpotify(tracks []SpotifyTrack, userId int) error {
 		} else {
 			totalImported += int(copyCount)
 		}
+		batchStart += batchSize
 	}
 	return nil
 }