Update CloudEvents SDK to support most recent spec change to extensio…

…ns (#2)

* Updates CloudEvents SDK to support top level extension with various serializers/deserializers

README.md

@@ -7,12 +7,13 @@ Package cloudevents provides primitives to work with CloudEvents specification:
 Parsing Event from HTTP Request:
 ```go
 import "github.com/dispatchframework/cloudevents-go-sdk"
+	marshaller := v01.NewDefaultHTTPMarshaller()
 	// req is *http.Request
-	event, err := cloudEvents.FromHTTPRequest(req)
+	event, err := marshaller.FromRequest(req)
 	if err != nil {
 		panic("Unable to parse event from http Request: " + err.String())
 	}
-	fmt.Printf("eventType: %s", event.EventType)
+	fmt.Printf("eventType: %s", event.Get("eventType")
 ```
 
 Creating a minimal CloudEvent in version 0.1:
@@ -27,8 +28,9 @@ import "github.com/dispatchframework/cloudevents-go-sdk/v01"
 
 Creating HTTP request from CloudEvent:
 ```
+marshaller := v01.NewDefaultHTTPMarshaller()
 var req *http.Request
-err := event.ToHTTPRequest(req)
+err := event.ToRequest(req)
 if err != nil {
 	panic("Unable to marshal event into http Request: " + err.String())
 }

errors.go

@@ -28,3 +28,10 @@ type ContentTypeNotSupportedError string
 func (e ContentTypeNotSupportedError) Error() string {
 	return "provided content type " + string(e) + " is not supported"
 }
+
+// IllegalArgumentError is returned when an argument passed to a method is an illegal value
+type IllegalArgumentError string
+
+func (e IllegalArgumentError) Error() string {
+	return "argument " + string(e) + "is illegal"
+}

http.go

@@ -2,15 +2,19 @@ package cloudevents
 
 import (
 	"net/http"
-
-	"github.com/dispatchframework/cloudevents-go-sdk/v01"
+	"reflect"
 )
 
-// FromHTTPRequest parses a CloudEvent from any known encoding.
-func FromHTTPRequest(req *http.Request) (Event, error) {
-	// TODO: this should check the version of incoming CloudVersion header and create an appropriate event structure.
-	e := &v01.Event{}
-	err := e.FromHTTPRequest(req)
-	return e, err
+// HTTPMarshaller an interface with methods for creating CloudEvents
+type HTTPMarshaller interface {
+	FromRequest(req *http.Request) (Event, error)
+	ToRequest(req *http.Request, event Event) error
+}
 
+// HTTPCloudEventConverter an interface for defining converters that can read/write CloudEvents from HTTP requests
+type HTTPCloudEventConverter interface {
+	CanRead(t reflect.Type, mediaType string) bool
+	CanWrite(t reflect.Type, mediaType string) bool
+	Read(t reflect.Type, req *http.Request) (Event, error)
+	Write(t reflect.Type, req *http.Request, event Event) error
 }

v01/converter.go

@@ -0,0 +1,190 @@
+package v01
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"mime"
+	"net/http"
+	"reflect"
+
+	"github.com/dispatchframework/cloudevents-go-sdk"
+)
+
+// HTTPMarshaller A struct representing the v01 version of the HTTPMarshaller
+type HTTPMarshaller struct {
+	converters []cloudevents.HTTPCloudEventConverter
+}
+
+// NewDefaultHTTPMarshaller creates a new v01 HTTPMarshaller prepopulated with the Binary and JSON
+// CloudEvent converters
+func NewDefaultHTTPMarshaller() cloudevents.HTTPMarshaller {
+	return NewHTTPMarshaller(
+		NewJSONHTTPCloudEventConverter(),
+		NewBinaryHTTPCloudEventConverter())
+}
+
+// NewHTTPMarshaller creates a new HTTPMarshaller with the given HTTPCloudEventConverters
+func NewHTTPMarshaller(converters ...cloudevents.HTTPCloudEventConverter) cloudevents.HTTPMarshaller {
+	return &HTTPMarshaller{
+		converters: converters,
+	}
+}
+
+// FromRequest creates a new CloudEvent from an http Request
+func (e HTTPMarshaller) FromRequest(req *http.Request) (cloudevents.Event, error) {
+	if req == nil {
+		return nil, cloudevents.IllegalArgumentError("req")
+	}
+
+	mimeType, _, err := mime.ParseMediaType(req.Header.Get("Content-Type"))
+	if err != nil {
+		return nil, fmt.Errorf("error parsing request content type: %s", err.Error())
+	}
+
+	for _, v := range e.converters {
+		if v.CanRead(reflect.TypeOf(Event{}), mimeType) {
+			return v.Read(reflect.TypeOf(Event{}), req)
+		}
+	}
+	return nil, cloudevents.ContentTypeNotSupportedError(mimeType)
+}
+
+// ToRequest populates an http Request with the given CloudEvent
+func (e HTTPMarshaller) ToRequest(req *http.Request, event cloudevents.Event) error {
+	if req == nil {
+		return cloudevents.IllegalArgumentError("req")
+	}
+
+	if event == nil {
+		return cloudevents.IllegalArgumentError("event")
+	}
+
+	v01Event := event.(*Event)
+
+	contentType := v01Event.ContentType
+	if contentType == "" {
+		contentType = "application/cloudevents+json"
+	}
+
+	mimeType, _, err := mime.ParseMediaType(contentType)
+	if err != nil {
+		return fmt.Errorf("error parsing event content type: %s", err.Error())
+	}
+
+	for _, v := range e.converters {
+		if v.CanWrite(reflect.TypeOf(Event{}), mimeType) {
+			err := v.Write(reflect.TypeOf(Event{}), req, event)
+			if err != nil {
+				return err
+			}
+
+			return nil
+		}
+	}
+
+	return cloudevents.ContentTypeNotSupportedError(mimeType)
+}
+
+// jsonhttpCloudEventConverter new converter for reading/writing CloudEvents to JSON
+type jsonhttpCloudEventConverter struct {
+	supportedMediaTypes      map[string]bool
+	supportedMediaTypesSlice []string
+}
+
+// NewJSONHTTPCloudEventConverter creates a new JSONHTTPCloudEventConverter
+func NewJSONHTTPCloudEventConverter() cloudevents.HTTPCloudEventConverter {
+	mediaTypes := map[string]bool{
+		"application/cloudevents+json": true,
+	}
+
+	return &jsonhttpCloudEventConverter{
+		supportedMediaTypes: mediaTypes,
+	}
+}
+
+// CanRead specifies if this converter can read the given mediaType into a given reflect.Type
+func (j *jsonhttpCloudEventConverter) CanRead(t reflect.Type, mediaType string) bool {
+	return reflect.TypeOf(Event{}) == t && j.supportedMediaTypes[mediaType]
+}
+
+// CanWrite specifies if this converter can write the given Type into the given mediaType
+func (j *jsonhttpCloudEventConverter) CanWrite(t reflect.Type, mediaType string) bool {
+	return reflect.TypeOf(Event{}) == t && j.supportedMediaTypes[mediaType]
+}
+
+func (j *jsonhttpCloudEventConverter) Read(t reflect.Type, req *http.Request) (cloudevents.Event, error) {
+	e := reflect.New(t).Interface()
+	err := json.NewDecoder(req.Body).Decode(e)
+
+	if err != nil {
+		return nil, fmt.Errorf("error parsing request: %s", err.Error())
+	}
+
+	ret := e.(*Event)
+	return ret, nil
+}
+
+func (j *jsonhttpCloudEventConverter) Write(t reflect.Type, req *http.Request, event cloudevents.Event) error {
+	buffer := bytes.Buffer{}
+	if err := json.NewEncoder(&buffer).Encode(event); err != nil {
+		return err
+	}
+
+	req.Body = ioutil.NopCloser(&buffer)
+	req.ContentLength = int64(buffer.Len())
+	req.GetBody = func() (io.ReadCloser, error) {
+		reader := bytes.NewReader(buffer.Bytes())
+		return ioutil.NopCloser(reader), nil
+	}
+
+	req.Header.Set("Content-Type", "application/cloudevents+json")
+	return nil
+}
+
+// BinaryHTTPCloudEventConverter a converter for reading/writing CloudEvents into the binary format
+type binaryHTTPCloudEventConverter struct {
+	supportedMediaTypes map[string]bool
+}
+
+// NewBinaryHTTPCloudEventConverter creates a new BinaryHTTPCloudEventConverter
+func NewBinaryHTTPCloudEventConverter() cloudevents.HTTPCloudEventConverter {
+	mediaTypes := map[string]bool{
+		"application/json":         true,
+		"application/xml":          true,
+		"application/octet-stream": true,
+	}
+
+	return &binaryHTTPCloudEventConverter{
+		supportedMediaTypes: mediaTypes,
+	}
+}
+
+// CanRead specifies if this converter can read the given mediaType into a given reflect.Type
+func (b *binaryHTTPCloudEventConverter) CanRead(t reflect.Type, mediaType string) bool {
+	return reflect.TypeOf(Event{}) == t && b.supportedMediaTypes[mediaType]
+}
+
+// CanWrite specifies if this converter can write the given Type into the given mediaType
+func (b *binaryHTTPCloudEventConverter) CanWrite(t reflect.Type, mediaType string) bool {
+	return reflect.TypeOf(Event{}) == t && b.supportedMediaTypes[mediaType]
+}
+
+func (b *binaryHTTPCloudEventConverter) Read(t reflect.Type, req *http.Request) (cloudevents.Event, error) {
+	var event Event
+	if err := event.UnmarshalBinary(req); err != nil {
+		return nil, err
+	}
+
+	return &event, nil
+}
+
+func (b *binaryHTTPCloudEventConverter) Write(t reflect.Type, req *http.Request, event cloudevents.Event) error {
+	e := event.(*Event)
+	if err := e.MarshalBinary(req); err != nil {
+		return err
+	}
+	return nil
+}