MORE REFACTORING!! + some improvements

Signed-off-by: ari melody <ari@arimelody.me>

music/credit.go

@@ -0,0 +1,92 @@
+package music
+
+import (
+	"fmt"
+
+	"github.com/jmoiron/sqlx"
+)
+
+type (
+    Credit struct {
+        Artist  *Artist `json:"artist"`
+        Role    string  `json:"role"`
+        Primary bool    `json:"primary"`
+    }
+
+    PostCreditBody struct {
+        Artist  string  `json:"artist"`
+        Role    string  `json:"role"`
+        Primary bool    `json:"primary"`
+    }
+)
+
+// GETTERS
+
+func (credit Credit) GetArtist() Artist {
+	return *credit.Artist
+}
+
+func (credit Credit) GetRole() string {
+	return credit.Role
+}
+
+func (credit Credit) IsPrimary() bool {
+	return credit.Primary
+}
+
+// SETTERS
+
+func (credit Credit) SetArtist(artist *Artist) error {
+	// TODO: update DB
+	credit.Artist = artist
+	return nil
+}
+
+func (credit Credit) SetRole(role string) error {
+	// TODO: update DB
+	credit.Role = role
+	return nil
+}
+
+func (credit Credit) SetPrimary(primary bool) error {
+	// TODO: update DB
+	credit.Primary = primary
+	return nil
+}
+
+// DATABASE
+
+func PullReleaseCredits(db *sqlx.DB, releaseID string) ([]Credit, error) {
+    var credits = []Credit{}
+
+    credit_rows, err := db.Query("SELECT artist, role, is_primary FROM musiccredits WHERE release=$1", releaseID)
+    if err != nil {
+        return []Credit{}, err
+    }
+
+    for credit_rows.Next() {
+        var artistID string
+        var credit = Credit{}
+        err = credit_rows.Scan(
+            &artistID,
+            &credit.Role,
+            &credit.Primary,
+        )
+        if err != nil {
+            fmt.Printf("Error while pulling credit for release %s: %s\n", releaseID, err)
+            continue
+        }
+
+        credit.Artist = GetArtist(artistID)
+        if credit.Artist == nil {
+            // this should absolutely not happen ever due to foreign key
+            // constraints, but it doesn't hurt to be sure!
+            fmt.Printf("Error while pulling credit for release %s: Artist %s does not exist\n", releaseID, artistID)
+            continue
+        }
+
+        credits = append(credits, credit)
+    }
+
+    return credits, nil
+}