CloudEvents I/O format support. (#948)

* CloudEvents I/O format support.

* Updated format doc.

* Remove log lines

* This adds support for CloudEvent ingestion at the http router layer.

* Updated per comments.

* Responds with full CloudEvent message.

* Fixed up per comments

* Fix tests

* Checks for cloudevent content-type

* doesn't error on missing content-type.

api/agent/call.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"mime"
 	"net/http"
 	"strings"
 	"time"
@@ -49,13 +50,34 @@ type Param struct {
 }
 type Params []Param
 
+const (
+	ceMimeType = "application/cloudevents+json"
+)
+
 func FromRequest(a Agent, app *models.App, path string, req *http.Request) CallOpt {
 	return func(c *call) error {
-		route, err := a.GetRoute(req.Context(), app.ID, path)
+		ctx := req.Context()
+		route, err := a.GetRoute(ctx, app.ID, path)
 		if err != nil {
 			return err
 		}
 
+		log := common.Logger(ctx)
+		// Check whether this is a CloudEvent, if coming in via HTTP router (only way currently), then we'll look for a special header
+		// Content-Type header: https://github.com/cloudevents/spec/blob/master/http-transport-binding.md#32-structured-content-mode
+		// Expected Content-Type for a CloudEvent: application/cloudevents+json; charset=UTF-8
+		contentType := req.Header.Get("Content-Type")
+		t, _, err := mime.ParseMediaType(contentType)
+		if err != nil {
+			// won't fail here, but log
+			log.Debugf("Could not parse Content-Type header: %v", err)
+		} else {
+			if t == ceMimeType {
+				c.IsCloudEvent = true
+				route.Format = models.FormatCloudEvent
+			}
+		}
+
 		if route.Format == "" {
 			route.Format = models.FormatDefault
 		}
@@ -258,6 +280,9 @@ func (a *agent) GetCall(opts ...CallOpt) (Call, error) {
 type call struct {
 	*models.Call
 
+	// IsCloudEvent flag whether this was ingested as a cloud event. This may become the default or only way.
+	IsCloudEvent bool `json:"is_cloud_event"`
+
 	da             DataAccess
 	w              io.Writer
 	req            *http.Request