webfinger: add response encoding and decoding

go.mod

@@ -1,3 +1,11 @@
 module gitea.treehouse.systems/jejune/jejune
 
 go 1.19
+
+require github.com/stretchr/testify v1.8.1
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

pkg/webfinger/webfinger.go

@@ -0,0 +1,54 @@
+package webfinger
+
+import (
+	"encoding/json"
+	"io"
+)
+
+// Resource provides the fields for a JRD as specified in RFC7033.
+type Resource struct {
+	Subject    string            `json:"subject"`
+	Aliases    []string          `json:"aliases,omitempty"`
+	Properties map[string]string `json:"properties,omitempty"`
+	Links      []Link            `json:"links,omitempty"`
+}
+
+// Link provides the fields for a link entry in a JRD.
+type Link struct {
+	Rel  string `json:"rel"`
+	Href string `json:"href"`
+}
+
+// Decoder provides a context for decoding a JRD.
+type Decoder struct {
+	reader io.Reader
+}
+
+// NewDecoder creates a Decoder given an I/O reader.
+func NewDecoder(r io.Reader) (*Decoder, error) {
+	dec := &Decoder{reader: r}
+	return dec, nil
+}
+
+// Decode decodes a JRD into a Resource.
+func (dec *Decoder) Decode(rs *Resource) error {
+	jdec := json.NewDecoder(dec.reader)
+	return jdec.Decode(rs)
+}
+
+// Encoder provides a context for encoding a JRD.
+type Encoder struct {
+	writer io.Writer
+}
+
+// NewEncoder creates an Encoder given an I/O writer.
+func NewEncoder(w io.Writer) (*Encoder, error) {
+	enc := &Encoder{writer: w}
+	return enc, nil
+}
+
+// Encode encodes a Resource into a JRD.
+func (enc *Encoder) Encode(rs *Resource) error {
+	jenc := json.NewEncoder(enc.writer)
+	return jenc.Encode(*rs)
+}

pkg/webfinger/webfinger_test.go

@@ -0,0 +1,34 @@
+package webfinger
+
+import (
+	"bytes"
+	"testing"
+	"github.com/stretchr/testify/require"
+)
+
+func TestRoundTrip(t *testing.T) {
+	jrd := Resource{
+		Subject: "acct:ariadne@jejune.dev",
+		Links: []Link{
+			{Rel: "application/activity+json", Href: "https://jejune.dev/.jejune/ariadne"},
+		},
+	}
+
+	encbuf := &bytes.Buffer{}
+	enc, err := NewEncoder(encbuf)
+	require.NoErrorf(t, err, "got error while constructing the encoder: %s", err)
+
+	err = enc.Encode(&jrd)
+	require.NoErrorf(t, err, "got error while encoding: %s", err)
+
+	dec, err := NewDecoder(encbuf)
+	require.NoErrorf(t, err, "got error while constructing the decoder: %s", err)
+
+	var decjrd Resource
+	err = dec.Decode(&decjrd)
+	require.NoErrorf(t, err, "got error while decoding: %s", err)
+
+	require.Equal(t, jrd.Subject, decjrd.Subject)
+	require.Equal(t, 1, len(decjrd.Links))
+	require.Equal(t, jrd.Links[0], decjrd.Links[0])
+}