add EOSE envelope encoder with marshal/unmarshal support and tests

pkg/encoders/envelopes/eoseenvelope/eoseenvelope.go

@@ -0,0 +1,86 @@
+// Package eoseenvelope provides an encoder for the EOSE (End Of Stored
+// Events) event that signifies that a REQ has found all stored events and
+// from here on the request morphs into a subscription, until the limit, if
+// requested, or until CLOSE or CLOSED.
+package eoseenvelope
+
+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 = "EOSE"
+
+// T is an EOSE envelope (End of Stored Events), that signals the end of events
+// that are stored and the beginning of a subscription. This is necessitated by
+// the confusing multiplexing of websockets for multiple requests, and an ugly
+// merging of two distinct API calls, filter and subscribe.
+type T struct {
+	Subscription []byte
+}
+
+var _ codec.Envelope = (*T)(nil)
+
+// New creates a new eoseenvelope.T with a standard form subscription.Id.
+func New() *T {
+	return new(T)
+}
+
+// NewFrom creates a new  eoseenvelope.T using a provided subscription.Id.
+func NewFrom[V []byte | string](id V) *T { return &T{Subscription: []byte(id)} }
+
+// Label returns the label of a EOSE envelope.
+func (en *T) Label() string { return L }
+
+// Write the  eoseenvelope.T to a provided io.Writer.
+func (en *T) Write(w io.Writer) (err error) {
+	_, err = w.Write(en.Marshal(nil))
+	return
+}
+
+// Marshal a eoseenvelope.T envelope in minified JSON, appending to a provided
+// destination slice.
+func (en *T) Marshal(dst []byte) (b []byte) {
+	var err error
+	b = dst
+	b = envelopes.Marshal(
+		b, L,
+		func(bst []byte) (o []byte) {
+			o = bst
+			o = append(o, '"')
+			o = append(o, en.Subscription...)
+			o = append(o, '"')
+			return
+		},
+	)
+	_ = err
+	return
+}
+
+// Unmarshal a eoseenvelope.T from minified JSON, returning the remainder after
+// the end of the envelope.
+func (en *T) Unmarshal(b []byte) (r []byte, err error) {
+	r = b
+	if en.Subscription, r, err = text.UnmarshalQuoted(r); chk.E(err) {
+		return
+	}
+	if r, err = envelopes.SkipToTheEnd(r); chk.E(err) {
+		return
+	}
+	return
+}
+
+// Parse reads a EOSE envelope in minified JSON into a newly allocated
+// eoseenvelope.T.
+func Parse(b []byte) (t *T, rem []byte, err error) {
+	t = New()
+	if rem, err = t.Unmarshal(b); chk.E(err) {
+		return
+	}
+	return
+}

pkg/encoders/envelopes/eoseenvelope/eoseenvelope_test.go

@@ -0,0 +1,66 @@
+package eoseenvelope
+
+import (
+	"testing"
+
+	"lol.mleku.dev/chk"
+	"next.orly.dev/pkg/encoders/envelopes"
+	"next.orly.dev/pkg/utils"
+)
+
+func TestMarshalUnmarshal(t *testing.T) {
+	var err error
+	rb, rb1, rb2 := make([]byte, 0, 65535), make([]byte, 0, 65535), make(
+		[]byte, 0, 65535,
+	)
+	for i := range 1000 {
+		s := utils.NewSubscription(i)
+		req := NewFrom(s)
+		rb = req.Marshal(rb)
+		// log.I.Ln(req.ID)
+		rb1 = rb1[:len(rb)]
+		copy(rb1, rb)
+		var rem []byte
+		var l string
+		if l, rb, err = envelopes.Identify(rb); chk.E(err) {
+			t.Fatal(err)
+		}
+		if l != L {
+			t.Fatalf("invalid sentinel %s, expect %s", l, L)
+		}
+		req2 := New()
+		if rem, err = req2.Unmarshal(rb); chk.E(err) {
+			t.Fatal(err)
+		}
+		// log.I.Ln(req2.ID)
+		if len(rem) > 0 {
+			t.Fatalf(
+				"unmarshal failed, remainder\n%d %s",
+				len(rem), rem,
+			)
+		}
+		rb2 = req2.Marshal(rb2)
+		if !utils.FastEqual(rb1, rb2) {
+			if len(rb1) != len(rb2) {
+				t.Fatalf(
+					"unmarshal failed, different lengths\n%d %s\n%d %s\n",
+					len(rb1), rb1, len(rb2), rb2,
+				)
+			}
+			for i := range rb1 {
+				if rb1[i] != rb2[i] {
+					t.Fatalf(
+						"unmarshal failed, difference at position %d\n%d %s\n%s\n%d %s\n%s\n",
+						i, len(rb1), rb1[:i], rb1[i:], len(rb2), rb2[:i],
+						rb2[i:],
+					)
+				}
+			}
+			t.Fatalf(
+				"unmarshal failed\n%d %s\n%d %s\n",
+				len(rb1), rb1, len(rb2), rb2,
+			)
+		}
+		rb, rb1, rb2 = rb[:0], rb1[:0], rb2[:0]
+	}
+}

pkg/utils/subscription.go

@@ -0,0 +1,9 @@
+package utils
+
+import (
+	"fmt"
+)
+
+func NewSubscription(n int) []byte {
+	return []byte(fmt.Sprintf("sub:%d", n))
+}