refactor: use a helper type to decode AddrInfo from JSON (#178)

This saves us a bunch of error prone manual decode/encode logic.
Co-authored-by: Marten Seemann <martenseemann@gmail.com>

peer/addrinfo_serde.go

@@ -6,33 +6,38 @@ import (
 	ma "github.com/multiformats/go-multiaddr"
 )
 
+// Helper struct for decoding as we can't unmarshal into an interface (Multiaddr).
+type addrInfoJson struct {
+	ID    ID
+	Addrs []string
+}
+
 func (pi AddrInfo) MarshalJSON() ([]byte, error) {
-	out := make(map[string]interface{})
-	out["ID"] = pi.ID.Pretty()
-	var addrs []string
-	for _, a := range pi.Addrs {
-		addrs = append(addrs, a.String())
+	addrs := make([]string, len(pi.Addrs))
+	for i, addr := range pi.Addrs {
+		addrs[i] = addr.String()
 	}
-	out["Addrs"] = addrs
-	return json.Marshal(out)
+	return json.Marshal(&addrInfoJson{
+		ID:    pi.ID,
+		Addrs: addrs,
+	})
 }
 
 func (pi *AddrInfo) UnmarshalJSON(b []byte) error {
-	var data map[string]interface{}
-	err := json.Unmarshal(b, &data)
-	if err != nil {
+	var data addrInfoJson
+	if err := json.Unmarshal(b, &data); err != nil {
 		return err
 	}
-	pid, err := IDB58Decode(data["ID"].(string))
-	if err != nil {
-		return err
-	}
-	pi.ID = pid
-	addrs, ok := data["Addrs"].([]interface{})
-	if ok {
-		for _, a := range addrs {
-			pi.Addrs = append(pi.Addrs, ma.StringCast(a.(string)))
+	addrs := make([]ma.Multiaddr, len(data.Addrs))
+	for i, addr := range data.Addrs {
+		maddr, err := ma.NewMultiaddr(addr)
+		if err != nil {
+			return err
 		}
+		addrs[i] = maddr
 	}
+
+	pi.ID = data.ID
+	pi.Addrs = addrs
 	return nil
 }

peer/addrinfo_test.go

@@ -133,3 +133,21 @@ func TestAddrInfosFromP2pAddrs(t *testing.T) {
 		delete(expected, info.ID.Pretty())
 	}
 }
+
+func TestAddrInfoJSON(t *testing.T) {
+	ai := AddrInfo{ID: testID, Addrs: []ma.Multiaddr{maddrFull}}
+	out, err := ai.MarshalJSON()
+	if err != nil {
+		t.Fatal(err)
+	}
+	var addrInfo AddrInfo
+	if err := addrInfo.UnmarshalJSON(out); err != nil {
+		t.Fatal(err)
+	}
+	if addrInfo.ID != testID {
+		t.Fatalf("expected ID to equal %s, got %s", testID.Pretty(), addrInfo.ID.Pretty())
+	}
+	if len(addrInfo.Addrs) != 1 || !addrInfo.Addrs[0].Equal(maddrFull) {
+		t.Fatalf("expected addrs to match %v, got %v", maddrFull, addrInfo.Addrs)
+	}
+}