add const

server/ids/ids.go

@@ -0,0 +1,59 @@
+package ids
+
+// this package is at such a high level in the hierarchy because
+// it's used by both `server/db` (for now) and `server/ctrlsubsonic`
+
+import (
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+var (
+	ErrBadSeparator = errors.New("bad separator")
+	ErrNotAnInt     = errors.New("not an int")
+	ErrBadPrefix    = errors.New("bad prefix")
+)
+
+type ID string
+
+const (
+	// type values copied from subsonic
+	Artist ID = "ar"
+	Album  ID = "al"
+	Track  ID = "tr"
+)
+
+var accepted = []ID{Artist,
+	Album,
+	Track,
+}
+
+type IDV struct {
+	Type  ID
+	Value int
+}
+
+func (i IDV) String() string {
+	return fmt.Sprintf("%s-%d", i.Type, i.Value)
+}
+
+func Parse(in string) (IDV, error) {
+	parts := strings.Split(in, "-")
+	if len(parts) != 2 {
+		return IDV{}, ErrBadSeparator
+	}
+	partType := parts[0]
+	partValue := parts[1]
+	val, err := strconv.Atoi(partValue)
+	if err != nil {
+		return IDV{}, fmt.Errorf("%q: %w", partValue, ErrNotAnInt)
+	}
+	for _, acc := range accepted {
+		if partType == string(acc) {
+			return IDV{Type: acc, Value: val}, nil
+		}
+	}
+	return IDV{}, fmt.Errorf("%q: %w", partType, ErrBadPrefix)
+}