Add database schema, ERD, and repository layer

internal/database/track_repository.go

@@ -0,0 +1,68 @@
+package database
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+type Track struct {
+	ID          string
+	ExternalID  string
+	AlbumID     string
+	Title       string
+	DurationMS  int
+	ISRC        string
+	DiscNumber  int
+	TrackNumber int
+	CreatedAt   time.Time
+}
+
+type TrackRepository struct {
+	pool *pgxpool.Pool
+}
+
+func NewTrackRepository(pool *pgxpool.Pool) *TrackRepository {
+	return &TrackRepository{pool: pool}
+}
+
+func (r *TrackRepository) Create(ctx context.Context, t *Track) error {
+	_, err := r.pool.Exec(ctx,
+		`INSERT INTO tracks (external_id, album_id, title, duration_ms, isrc, disc_number, track_number)
+		 VALUES ($1, $2, $3, $4, $5, $6, $7)
+		 ON CONFLICT (external_id) DO UPDATE SET
+		   title = EXCLUDED.title,
+		   duration_ms = EXCLUDED.duration_ms,
+		   isrc = EXCLUDED.isrc,
+		   disc_number = EXCLUDED.disc_number,
+		   track_number = EXCLUDED.track_number`,
+		t.ExternalID, t.AlbumID, t.Title, t.DurationMS, t.ISRC, t.DiscNumber, t.TrackNumber,
+	)
+	if err != nil {
+		return fmt.Errorf("creating track: %w", err)
+	}
+	return nil
+}
+
+func (r *TrackRepository) GetByAlbumID(ctx context.Context, albumID string) ([]*Track, error) {
+	rows, err := r.pool.Query(ctx,
+		`SELECT id, external_id, album_id, title, duration_ms, isrc, disc_number, track_number, created_at
+		 FROM tracks WHERE album_id = $1 ORDER BY disc_number, track_number`, albumID,
+	)
+	if err != nil {
+		return nil, fmt.Errorf("listing tracks: %w", err)
+	}
+	defer rows.Close()
+
+	var tracks []*Track
+	for rows.Next() {
+		t := &Track{}
+		if err := rows.Scan(&t.ID, &t.ExternalID, &t.AlbumID, &t.Title, &t.DurationMS, &t.ISRC, &t.DiscNumber, &t.TrackNumber, &t.CreatedAt); err != nil {
+			return nil, fmt.Errorf("scanning track: %w", err)
+		}
+		tracks = append(tracks, t)
+	}
+	return tracks, nil
+}