Implement Sequence extension

v2/extensions/sequence_extension.go

@@ -0,0 +1,69 @@
+/*
+ Copyright 2024 The CloudEvents Authors
+ SPDX-License-Identifier: Apache-2.0
+*/
+
+package extensions
+
+import (
+	"github.com/cloudevents/sdk-go/v2/binding"
+	"github.com/cloudevents/sdk-go/v2/event"
+	"github.com/cloudevents/sdk-go/v2/types"
+)
+
+const SequenceExtensionKey = "sequence"
+
+// SequenceExtension represents the CloudEvents Sequence extension,
+// which describes the position of an event in the ordered sequence
+// of events produced by a unique event source.
+// See https://github.com/cloudevents/spec/blob/main/cloudevents/extensions/sequence.md
+// for more info.
+type SequenceExtension struct {
+	Sequence string `json:"sequence"`
+}
+
+// AddSequenceExtension sets the sequence extension attribute on the event.
+// The value MUST be a non-empty, lexicographically-orderable string.
+func AddSequenceExtension(e *event.Event, sequence string) {
+	if sequence != "" {
+		e.SetExtension(SequenceExtensionKey, sequence)
+	}
+}
+
+// GetSequenceExtension extracts the sequence extension from a CloudEvent.
+// It returns the extension and true if found, or an empty extension and false otherwise.
+func GetSequenceExtension(e event.Event) (SequenceExtension, bool) {
+	if val, ok := e.Extensions()[SequenceExtensionKey]; ok {
+		if s, err := types.ToString(val); err == nil && s != "" {
+			return SequenceExtension{Sequence: s}, true
+		}
+	}
+	return SequenceExtension{}, false
+}
+
+// ReadTransformer returns a binding.TransformerFunc that reads the sequence
+// extension from a message into this SequenceExtension struct.
+func (s *SequenceExtension) ReadTransformer() binding.TransformerFunc {
+	return func(reader binding.MessageMetadataReader, writer binding.MessageMetadataWriter) error {
+		val := reader.GetExtension(SequenceExtensionKey)
+		if val != nil {
+			formatted, err := types.Format(val)
+			if err != nil {
+				return err
+			}
+			s.Sequence = formatted
+		}
+		return nil
+	}
+}
+
+// WriteTransformer returns a binding.TransformerFunc that writes the sequence
+// extension from this SequenceExtension struct into a message.
+func (s *SequenceExtension) WriteTransformer() binding.TransformerFunc {
+	return func(reader binding.MessageMetadataReader, writer binding.MessageMetadataWriter) error {
+		if s.Sequence != "" {
+			return writer.SetExtension(SequenceExtensionKey, s.Sequence)
+		}
+		return nil
+	}
+}

v2/extensions/sequence_extension_test.go

@@ -0,0 +1,161 @@
+/*
+ Copyright 2024 The CloudEvents Authors
+ SPDX-License-Identifier: Apache-2.0
+*/
+
+package extensions_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/cloudevents/sdk-go/v2/binding"
+	bindingtest "github.com/cloudevents/sdk-go/v2/binding/test"
+	"github.com/cloudevents/sdk-go/v2/event"
+	"github.com/cloudevents/sdk-go/v2/extensions"
+	"github.com/cloudevents/sdk-go/v2/test"
+)
+
+func TestAddSequenceExtension(t *testing.T) {
+	e := event.New()
+	e.SetSource("https://example.com/source")
+	e.SetType("com.example.test")
+	e.SetID("123")
+
+	extensions.AddSequenceExtension(&e, "001")
+
+	got, ok := e.Extensions()[extensions.SequenceExtensionKey]
+	require.True(t, ok)
+	require.Equal(t, "001", got)
+}
+
+func TestAddSequenceExtension_Empty(t *testing.T) {
+	e := event.New()
+	e.SetSource("https://example.com/source")
+	e.SetType("com.example.test")
+	e.SetID("123")
+
+	extensions.AddSequenceExtension(&e, "")
+
+	_, ok := e.Extensions()[extensions.SequenceExtensionKey]
+	require.False(t, ok)
+}
+
+func TestGetSequenceExtension(t *testing.T) {
+	e := event.New()
+	e.SetSource("https://example.com/source")
+	e.SetType("com.example.test")
+	e.SetID("123")
+	e.SetExtension(extensions.SequenceExtensionKey, "042")
+
+	ext, ok := extensions.GetSequenceExtension(e)
+	require.True(t, ok)
+	require.Equal(t, "042", ext.Sequence)
+}
+
+func TestGetSequenceExtension_NotPresent(t *testing.T) {
+	e := event.New()
+	e.SetSource("https://example.com/source")
+	e.SetType("com.example.test")
+	e.SetID("123")
+
+	ext, ok := extensions.GetSequenceExtension(e)
+	require.False(t, ok)
+	require.Equal(t, "", ext.Sequence)
+}
+
+func TestSequenceExtension_ReadTransformer_Empty(t *testing.T) {
+	e := test.MinEvent()
+	e.Context = e.Context.AsV1()
+
+	tests := []bindingtest.TransformerTestArgs{
+		{
+			Name:         "Read from Mock Structured message",
+			InputMessage: bindingtest.MustCreateMockStructuredMessage(t, e),
+			WantEvent:    e,
+		},
+		{
+			Name:         "Read from Mock Binary message",
+			InputMessage: bindingtest.MustCreateMockBinaryMessage(e),
+			WantEvent:    e,
+		},
+		{
+			Name:       "Read from Event message",
+			InputEvent: e,
+			WantEvent:  e,
+		},
+	}
+	for _, tt := range tests {
+		ext := extensions.SequenceExtension{}
+		tt.Transformers = binding.Transformers{ext.ReadTransformer()}
+		bindingtest.RunTransformerTests(t, context.TODO(), []bindingtest.TransformerTestArgs{tt})
+		require.Zero(t, ext.Sequence)
+	}
+}
+
+func TestSequenceExtension_ReadTransformer(t *testing.T) {
+	e := test.MinEvent()
+	e.Context = e.Context.AsV1()
+	wantExt := extensions.SequenceExtension{
+		Sequence: "00042",
+	}
+	extensions.AddSequenceExtension(&e, wantExt.Sequence)
+
+	tests := []bindingtest.TransformerTestArgs{
+		{
+			Name:         "Read from Mock Structured message",
+			InputMessage: bindingtest.MustCreateMockStructuredMessage(t, e),
+			WantEvent:    e,
+		},
+		{
+			Name:         "Read from Mock Binary message",
+			InputMessage: bindingtest.MustCreateMockBinaryMessage(e),
+			WantEvent:    e,
+		},
+		{
+			Name:       "Read from Event message",
+			InputEvent: e,
+			WantEvent:  e,
+		},
+	}
+	for _, tt := range tests {
+		haveExt := extensions.SequenceExtension{}
+		tt.Transformers = binding.Transformers{haveExt.ReadTransformer()}
+		bindingtest.RunTransformerTests(t, context.TODO(), []bindingtest.TransformerTestArgs{tt})
+		require.Equal(t, wantExt.Sequence, haveExt.Sequence)
+	}
+}
+
+func TestSequenceExtension_WriteTransformer(t *testing.T) {
+	e := test.MinEvent()
+	e.Context = e.Context.AsV1()
+
+	ext := extensions.SequenceExtension{
+		Sequence: "00042",
+	}
+	want := e.Clone()
+	extensions.AddSequenceExtension(&want, ext.Sequence)
+
+	bindingtest.RunTransformerTests(t, context.TODO(), []bindingtest.TransformerTestArgs{
+		{
+			Name:         "Write to Mock Structured message",
+			InputMessage: bindingtest.MustCreateMockStructuredMessage(t, e),
+			WantEvent:    want,
+			Transformers: binding.Transformers{ext.WriteTransformer()},
+		},
+		{
+			Name:         "Write to Mock Binary message",
+			InputMessage: bindingtest.MustCreateMockBinaryMessage(e),
+			WantEvent:    want,
+			Transformers: binding.Transformers{ext.WriteTransformer()},
+		},
+		{
+			Name:         "Write to Event message",
+			InputEvent:   e,
+			WantEvent:    want,
+			Transformers: binding.Transformers{ext.WriteTransformer()},
+		},
+	})
+}