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codec_v01.go
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codec_v01.go
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package http
import (
"context"
"encoding/json"
"fmt"
"net/http"
"net/textproto"
"strings"
"github.com/cloudevents/sdk-go/pkg/cloudevents"
cecontext "github.com/cloudevents/sdk-go/pkg/cloudevents/context"
"github.com/cloudevents/sdk-go/pkg/cloudevents/observability"
"github.com/cloudevents/sdk-go/pkg/cloudevents/transport"
"github.com/cloudevents/sdk-go/pkg/cloudevents/types"
)
// CodecV01 represents a http transport codec that uses CloudEvents spec v0.1
type CodecV01 struct {
CodecStructured
DefaultEncoding Encoding
}
// Adheres to Codec
var _ transport.Codec = (*CodecV01)(nil)
// Encode implements Codec.Encode
func (v CodecV01) Encode(ctx context.Context, e cloudevents.Event) (transport.Message, error) {
encoding := v.DefaultEncoding
strEnc := cecontext.EncodingFrom(ctx)
if strEnc != "" {
switch strEnc {
case Binary:
encoding = BinaryV01
case Structured:
encoding = StructuredV01
}
}
_, r := observability.NewReporter(context.Background(), CodecObserved{o: reportEncode, c: encoding.Codec()})
m, err := v.obsEncode(ctx, e, encoding)
if err != nil {
r.Error()
} else {
r.OK()
}
return m, err
}
func (v CodecV01) obsEncode(ctx context.Context, e cloudevents.Event, encoding Encoding) (transport.Message, error) {
switch encoding {
case Default:
fallthrough
case BinaryV01:
return v.encodeBinary(ctx, e)
case StructuredV01:
return v.encodeStructured(ctx, e)
default:
return nil, fmt.Errorf("unknown encoding: %d", encoding)
}
}
// Decode implements Codec.Decode
func (v CodecV01) Decode(ctx context.Context, msg transport.Message) (*cloudevents.Event, error) {
_, r := observability.NewReporter(ctx, CodecObserved{o: reportDecode, c: v.inspectEncoding(ctx, msg).Codec()}) // TODO: inspectEncoding is not free.
e, err := v.obsDecode(ctx, msg)
if err != nil {
r.Error()
} else {
r.OK()
}
return e, err
}
func (v CodecV01) obsDecode(ctx context.Context, msg transport.Message) (*cloudevents.Event, error) {
switch v.inspectEncoding(ctx, msg) {
case BinaryV01:
return v.decodeBinary(ctx, msg)
case StructuredV01:
return v.decodeStructured(ctx, cloudevents.CloudEventsVersionV01, msg)
default:
return nil, transport.NewErrMessageEncodingUnknown("v01", TransportName)
}
}
func (v CodecV01) encodeBinary(ctx context.Context, e cloudevents.Event) (transport.Message, error) {
header, err := v.toHeaders(e.Context.AsV01())
if err != nil {
return nil, err
}
body, err := e.DataBytes()
if err != nil {
panic("encode")
}
msg := &Message{
Header: header,
Body: body,
}
return msg, nil
}
func (v CodecV01) toHeaders(ec *cloudevents.EventContextV01) (http.Header, error) {
// Preserve case in v0.1, even though HTTP headers are case-insensitive.
h := http.Header{}
h["CE-CloudEventsVersion"] = []string{ec.CloudEventsVersion}
h["CE-EventID"] = []string{ec.EventID}
h["CE-EventType"] = []string{ec.EventType}
h["CE-Source"] = []string{ec.Source.String()}
if ec.EventTime != nil && !ec.EventTime.IsZero() {
h["CE-EventTime"] = []string{ec.EventTime.String()}
}
if ec.EventTypeVersion != nil {
h["CE-EventTypeVersion"] = []string{*ec.EventTypeVersion}
}
if ec.SchemaURL != nil {
h["CE-DataSchema"] = []string{ec.SchemaURL.String()}
}
if ec.ContentType != nil && *ec.ContentType != "" {
h.Set("Content-Type", *ec.ContentType)
}
// Regarding Extensions, v0.1 Spec says the following:
// * Each map entry name MUST be prefixed with "CE-X-"
// * Each map entry name's first character MUST be capitalized
for k, v := range ec.Extensions {
encoded, err := json.Marshal(v)
if err != nil {
return nil, err
}
h["CE-X-"+strings.Title(k)] = []string{string(encoded)}
}
return h, nil
}
func (v CodecV01) decodeBinary(ctx context.Context, msg transport.Message) (*cloudevents.Event, error) {
m, ok := msg.(*Message)
if !ok {
return nil, fmt.Errorf("failed to convert transport.Message to http.Message")
}
ca, err := v.fromHeaders(m.Header)
if err != nil {
return nil, err
}
var body interface{}
if len(m.Body) > 0 {
body = m.Body
}
return &cloudevents.Event{
Context: &ca,
Data: body,
DataEncoded: body != nil,
}, nil
}
func (v CodecV01) fromHeaders(h http.Header) (cloudevents.EventContextV01, error) {
// Normalize headers.
for k, v := range h {
ck := textproto.CanonicalMIMEHeaderKey(k)
if k != ck {
h[ck] = v
}
}
ec := cloudevents.EventContextV01{}
ec.CloudEventsVersion = h.Get("CE-CloudEventsVersion")
h.Del("CE-CloudEventsVersion")
ec.EventID = h.Get("CE-EventID")
h.Del("CE-EventID")
ec.EventType = h.Get("CE-EventType")
h.Del("CE-EventType")
source := types.ParseURLRef(h.Get("CE-Source"))
h.Del("CE-Source")
if source != nil {
ec.Source = *source
}
var err error
ec.EventTime, err = types.ParseTimestamp(h.Get("CE-EventTime"))
if err != nil {
return ec, err
}
h.Del("CE-EventTime")
etv := h.Get("CE-EventTypeVersion")
h.Del("CE-EventTypeVersion")
if etv != "" {
ec.EventTypeVersion = &etv
}
ec.SchemaURL = types.ParseURLRef(h.Get("CE-DataSchema"))
h.Del("CE-DataSchema")
et := h.Get("Content-Type")
if et != "" {
ec.ContentType = &et
}
extensions := make(map[string]interface{})
for k, v := range h {
if len(k) > len("CE-X-") && strings.EqualFold(k[:len("CE-X-")], "CE-X-") {
key := k[len("CE-X-"):]
var tmp interface{}
if err := json.Unmarshal([]byte(v[0]), &tmp); err == nil {
extensions[key] = tmp
} else {
// If we can't unmarshal the data, treat it as a string.
extensions[key] = v[0]
}
h.Del(k)
}
}
if len(extensions) > 0 {
ec.Extensions = extensions
}
return ec, nil
}
func (v CodecV01) inspectEncoding(ctx context.Context, msg transport.Message) Encoding {
version := msg.CloudEventsVersion()
if version != cloudevents.CloudEventsVersionV01 {
return Unknown
}
m, ok := msg.(*Message)
if !ok {
return Unknown
}
contentType := m.Header.Get("Content-Type")
if contentType == cloudevents.ApplicationCloudEventsJSON {
return StructuredV01
}
return BinaryV01
}