add NOTICE and OK envelope encoders with marshal/unmarshal support and comprehensive tests

pkg/encoders/envelopes/noticeenvelope/noticeenvelope.go

@@ -0,0 +1,84 @@
+// Package noticeenvelope is a codec for the NOTICE envelope, which is used to
+// serve (mostly ignored) messages that are supposed to be shown to a user in
+// the client.
+package noticeenvelope
+
+import (
+	"io"
+
+	"lol.mleku.dev/chk"
+	"next.orly.dev/pkg/encoders/envelopes"
+	"next.orly.dev/pkg/encoders/text"
+	"next.orly.dev/pkg/interfaces/codec"
+)
+
+// L is the label associated with this type of codec.Envelope.
+const L = "NOTICE"
+
+// T is a NOTICE envelope, intended to convey information to the user about the
+// state of the relay connection. This thing is rarely displayed on clients
+// except sometimes in event logs.
+type T struct {
+	Message []byte
+}
+
+var _ codec.Envelope = (*T)(nil)
+
+// New creates a new empty NOTICE noticeenvelope.T.
+func New() *T { return &T{} }
+
+// NewFrom creates a new noticeenvelope.T with a provided message.
+func NewFrom[V string | []byte](msg V) *T { return &T{Message: []byte(msg)} }
+
+// Label returns the label of a NOTICE envelope.
+func (en *T) Label() string { return L }
+
+// Write the NOTICE T to a provided io.Writer.
+func (en *T) Write(w io.Writer) (err error) {
+	_, err = w.Write(en.Marshal(nil))
+	return
+}
+
+// Marshal a NOTICE envelope in minified JSON into an noticeenvelope.T,
+// appending to a provided destination slice. Note that this ensures correct
+// string escaping on the Reason field.
+func (en *T) Marshal(dst []byte) (b []byte) {
+	var err error
+	_ = err
+	b = dst
+	b = envelopes.Marshal(
+		b, L,
+		func(bst []byte) (o []byte) {
+			o = bst
+			o = append(o, '"')
+			o = text.NostrEscape(o, en.Message)
+			o = append(o, '"')
+			return
+		},
+	)
+	return
+}
+
+// Unmarshal a noticeenvelope.T from minified JSON, returning the remainder
+// after the end of the envelope. Note that this ensures the Reason string is
+// correctly unescaped by NIP-01 escaping rules.
+func (en *T) Unmarshal(b []byte) (r []byte, err error) {
+	r = b
+	if en.Message, r, err = text.UnmarshalQuoted(r); chk.E(err) {
+		return
+	}
+	if r, err = envelopes.SkipToTheEnd(r); chk.E(err) {
+		return
+	}
+	return
+}
+
+// Parse reads a NOTICE envelope in minified JSON into a newly allocated
+// noticeenvelope.T.
+func Parse(b []byte) (t *T, rem []byte, err error) {
+	t = New()
+	if rem, err = t.Unmarshal(b); chk.E(err) {
+		return
+	}
+	return
+}