Maintenance: improve error wrapping

internal/publicip/publicip.go

@@ -3,6 +3,7 @@ package publicip
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"math/rand"
@@ -27,6 +28,8 @@ func NewIPGetter(client *http.Client) IPGetter {
 	}
 }
 
+var ErrParseIP = errors.New("cannot parse IP address")
+
 func (i *ipGetter) Get(ctx context.Context) (ip net.IP, err error) {
 	urls := []string{
 		"https://ifconfig.me/ip",
@@ -63,7 +66,7 @@ func (i *ipGetter) Get(ctx context.Context) (ip net.IP, err error) {
 	s := strings.ReplaceAll(string(content), "\n", "")
 	ip = net.ParseIP(s)
 	if ip == nil {
-		return nil, fmt.Errorf("cannot parse IP address from %q", s)
+		return nil, fmt.Errorf("%w: %s", ErrParseIP, s)
 	}
 	return ip, nil
 }

internal/publicip/state.go

@@ -1,6 +1,7 @@
 package publicip
 
 import (
+	"errors"
 	"fmt"
 	"net"
 	"reflect"
@@ -32,6 +33,8 @@ func (l *looper) GetStatus() (status models.LoopStatus) {
 	return l.state.status
 }
 
+var ErrInvalidStatus = errors.New("invalid status")
+
 func (l *looper) SetStatus(status models.LoopStatus) (outcome string, err error) {
 	l.state.statusMu.Lock()
 	defer l.state.statusMu.Unlock()
@@ -67,8 +70,8 @@ func (l *looper) SetStatus(status models.LoopStatus) (outcome string, err error)
 		l.state.status = status
 		return status.String(), nil
 	default:
-		return "", fmt.Errorf("status %q can only be %q or %q",
-			status, constants.Running, constants.Stopped)
+		return "", fmt.Errorf("%w: %s: it can only be one of: %s, %s",
+			ErrInvalidStatus, status, constants.Running, constants.Stopped)
 	}
 }