fix: address code review findings

internal/musicbrainz/client.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"strings"
 	"time"
 
 	"golang.org/x/time/rate"
@@ -93,13 +94,27 @@ type mbArtistCredit struct {
 
 // mbReleaseGroup represents the XML structure of a single release-group
 // in the MusicBrainz release-group list response.
+//
+// Note: release groups do NOT carry a "status" attribute in ws/2 (status
+// belongs to individual releases, not release groups), so it is intentionally
+// absent here. Type classification is read from the authoritative
+// <primary-type> / <secondary-type-list> elements rather than the legacy
+// "type" attribute, which only reflects the primary type and cannot detect
+// e.g. a compilation whose primary type is Album.
 type mbReleaseGroup struct {
-	ID           string         `xml:"id,attr"`
-	Title        string         `xml:"title"`
-	Type         string         `xml:"type,attr"`
-	Status       string         `xml:"status,attr"`
-	ArtistCredit mbArtistCredit `xml:"artist-credit"`
-	ReleaseDate  string         `xml:"first-release-date"`
+	ID           string           `xml:"id,attr"`
+	Title        string           `xml:"title"`
+	TypeAttr     string           `xml:"type,attr"`
+	PrimaryType  string           `xml:"primary-type"`
+	Secondary    mbSecondaryTypes `xml:"secondary-type-list"`
+	ArtistCredit mbArtistCredit   `xml:"artist-credit"`
+	ReleaseDate  string           `xml:"first-release-date"`
+}
+
+// mbSecondaryTypes captures the <secondary-type-list> element, which holds
+// zero or more <secondary-type> children (e.g. Live, Compilation, Remix).
+type mbSecondaryTypes struct {
+	Types []string `xml:"secondary-type"`
 }
 
 // mbReleaseGroupListXML wraps the release-group-list element to properly
@@ -127,14 +142,22 @@ func ParseReleaseGroups(data []byte) (*ParsedReleaseGroups, error) {
 		Count: list.ReleaseGroupList.Count,
 	}
 	for _, rg := range list.ReleaseGroupList.ReleaseGroups {
+		// Prefer the authoritative <primary-type> element; fall back to the
+		// legacy "type" attribute (which reflects the primary type) when the
+		// element is absent. The attribute is space-separated primary+secondary,
+		// so take the first token as the primary type.
+		primary := rg.PrimaryType
+		if primary == "" && rg.TypeAttr != "" {
+			primary = strings.Fields(rg.TypeAttr)[0]
+		}
 		result.ReleaseGroups = append(result.ReleaseGroups, ReleaseGroup{
-			ID:          rg.ID,
-			Title:       rg.Title,
-			Type:        rg.Type,
-			Status:      rg.Status,
-			ArtistID:    rg.ArtistCredit.NameCredit.Artist.ID,
-			ArtistName:  rg.ArtistCredit.NameCredit.Artist.Name,
-			ReleaseDate: rg.ReleaseDate,
+			ID:             rg.ID,
+			Title:          rg.Title,
+			Type:           primary,
+			SecondaryTypes: rg.Secondary.Types,
+			ArtistID:       rg.ArtistCredit.NameCredit.Artist.ID,
+			ArtistName:     rg.ArtistCredit.NameCredit.Artist.Name,
+			ReleaseDate:    rg.ReleaseDate,
 		})
 	}
 	return result, nil