nfs: implement Guest mountpoint

Author: djdv

internal/filesystem/nfs/mountpoint.go

@@ -24,9 +24,17 @@ type (
 	Host struct {
 		Maddr multiaddr.Multiaddr `json:"maddr,omitempty"`
 	}
+	// Guest holds metadata required to establish
+	// a client connection to an NFS server.
+	Guest struct {
+		Maddr multiaddr.Multiaddr
+	}
 )
 
-const HostID filesystem.Host = "NFS"
+const (
+	HostID  filesystem.Host = "NFS"
+	GuestID filesystem.ID   = "NFS"
+)
 
 func (*Host) HostID() filesystem.Host { return HostID }
 
@@ -76,3 +84,21 @@ func (nh *Host) Mount(fsys fs.FS) (io.Closer, error) {
 	go func() { errsCh <- nfs.Serve(goListener, cachedHandler) }()
 	return closerFn, nil
 }
+
+func (*Guest) GuestID() filesystem.ID { return GuestID }
+func (gn *Guest) UnmarshalJSON(b []byte) error {
+	// multiformats/go-multiaddr issue #100
+	var maddrWorkaround struct {
+		Maddr maddrc.Multiaddr `json:"maddr,omitempty"`
+	}
+	if err := json.Unmarshal(b, &maddrWorkaround); err != nil {
+		return err
+	}
+	gn.Maddr = maddrWorkaround.Maddr.Multiaddr
+	return nil
+}
+
+func (gn *Guest) MakeFS() (fs.FS, error) {
+	// TODO: fields to options.
+	return NewNFSGuest(gn.Maddr)
+}