/*
* From: https://github.com/serverless/event-gateway/blob/master/event/event.go
* Modified: Strip to handler requirements
*
* Copyright 2017 Serverless, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
package cloudevents
import (
"encoding/json"
"errors"
"fmt"
"mime"
"net/http"
"strings"
"time"
"unicode"
"github.com/google/uuid"
"github.com/oxtoacart/bpool"
validator "gopkg.in/go-playground/validator.v9"
)
var (
bufferPool = bpool.NewSizedBufferPool(1024, 8)
)
const (
// TransformationVersion is indicative of the revision of how Event Gateway transforms a request into CloudEvents format.
TransformationVersion = "0.1"
// CloudEventsVersion currently supported by Event Gateway
CloudEventsVersion = "0.1"
)
// Event is a default event structure. All data that passes through the Event Gateway
// is formatted to a format defined CloudEvents v0.1 spec.
type Event struct {
EventType string `json:"eventType" validate:"required"`
EventTypeVersion string `json:"eventTypeVersion,omitempty"`
CloudEventsVersion string `json:"cloudEventsVersion" validate:"required"`
Source string `json:"source" validate:"uri,required"`
EventID string `json:"eventID" validate:"required"`
EventTime *time.Time `json:"eventTime,omitempty"`
SchemaURL string `json:"schemaURL,omitempty"`
Extensions map[string]interface{} `json:"extensions,omitempty"`
ContentType string `json:"contentType,omitempty"`
Data interface{} `json:"data"`
}
// New return new instance of Event.
func New(eventType string, mimeType string, payload interface{}) *Event {
now := time.Now()
event := &Event{
EventType: eventType,
CloudEventsVersion: CloudEventsVersion,
Source: "https://micro.mu",
EventID: uuid.New().String(),
EventTime: &now,
ContentType: mimeType,
Data: payload,
Extensions: map[string]interface{}{
"eventgateway": map[string]interface{}{
"transformed": "true",
"transformation-version": TransformationVersion,
},
},
}
event.Data = normalizePayload(event.Data, event.ContentType)
return event
}
// FromRequest takes an HTTP request and returns an Event along with path. Most of the implementation
// is based on https://github.com/cloudevents/spec/blob/master/http-transport-binding.md.
// This function also supports legacy mode where event type is sent in Event header.
func FromRequest(r *http.Request) (*Event, error) {
contentType := r.Header.Get("Content-Type")
mimeType, _, err := mime.ParseMediaType(contentType)
if err != nil {
if err.Error() != "mime: no media type" {
return nil, err
}
mimeType = "application/octet-stream"
}
// Read request body
body := []byte{}
if r.Body != nil {
buf := bufferPool.Get()
defer bufferPool.Put(buf)
if _, err := buf.ReadFrom(r.Body); err != nil {
return nil, err
}
body = buf.Bytes()
}
var event *Event
if mimeType == mimeCloudEventsJSON { // CloudEvents Structured Content Mode
return parseAsCloudEvent(mimeType, body)
} else if isCloudEventsBinaryContentMode(r.Header) { // CloudEvents Binary Content Mode
return parseAsCloudEventBinary(r.Header, body)
} else if isLegacyMode(r.Header) {
if mimeType == mimeJSON { // CloudEvent in Legacy Mode
event, err = parseAsCloudEvent(mimeType, body)
if err != nil {
return New(string(r.Header.Get("event")), mimeType, body), nil
}
return event, err
}
return New(string(r.Header.Get("event")), mimeType, body), nil
}
return New("http.request", mimeJSON, newHTTPRequestData(r, body)), nil
}
// Validate Event struct
func (e *Event) Validate() error {
validate := validator.New()
err := validate.Struct(e)
if err != nil {
return fmt.Errorf("CloudEvent not valid: %v", err)
}
return nil
}
func isLegacyMode(headers http.Header) bool {
if headers.Get("Event") != "" {
return true
}
return false
}
func isCloudEventsBinaryContentMode(headers http.Header) bool {
if headers.Get("CE-EventType") != "" &&
headers.Get("CE-CloudEventsVersion") != "" &&
headers.Get("CE-Source") != "" &&
headers.Get("CE-EventID") != "" {
return true
}
return false
}
func parseAsCloudEventBinary(headers http.Header, payload interface{}) (*Event, error) {
event := &Event{
EventType: headers.Get("CE-EventType"),
EventTypeVersion: headers.Get("CE-EventTypeVersion"),
CloudEventsVersion: headers.Get("CE-CloudEventsVersion"),
Source: headers.Get("CE-Source"),
EventID: headers.Get("CE-EventID"),
ContentType: headers.Get("Content-Type"),
Data: payload,
}
err := event.Validate()
if err != nil {
return nil, err
}
if headers.Get("CE-EventTime") != "" {
val, err := time.Parse(time.RFC3339, headers.Get("CE-EventTime"))
if err != nil {
return nil, err
}
event.EventTime = &val
}
if val := headers.Get("CE-SchemaURL"); len(val) > 0 {
event.SchemaURL = val
}
event.Extensions = map[string]interface{}{}
for key, val := range flatten(headers) {
if strings.HasPrefix(key, "Ce-X-") {
key = strings.TrimLeft(key, "Ce-X-")
// Make first character lowercase
runes := []rune(key)
runes[0] = unicode.ToLower(runes[0])
event.Extensions[string(runes)] = val
}
}
event.Data = normalizePayload(event.Data, event.ContentType)
return event, nil
}
func flatten(h http.Header) map[string]string {
headers := map[string]string{}
for key, header := range h {
headers[key] = header[0]
if len(header) > 1 {
headers[key] = strings.Join(header, ", ")
}
}
return headers
}
func parseAsCloudEvent(mime string, payload interface{}) (*Event, error) {
body, ok := payload.([]byte)
if ok {
event := &Event{}
err := json.Unmarshal(body, event)
if err != nil {
return nil, err
}
err = event.Validate()
if err != nil {
return nil, err
}
event.Data = normalizePayload(event.Data, event.ContentType)
return event, nil
}
return nil, errors.New("couldn't cast to []byte")
}
const (
mimeJSON = "application/json"
mimeFormMultipart = "multipart/form-data"
mimeFormURLEncoded = "application/x-www-form-urlencoded"
mimeCloudEventsJSON = "application/cloudevents+json"
)
// normalizePayload takes anything, checks if it's []byte array and depending on provided mime
// type converts it to either string or map[string]interface to avoid having base64 string after
// JSON marshaling.
func normalizePayload(payload interface{}, mime string) interface{} {
if bytePayload, ok := payload.([]byte); ok && len(bytePayload) > 0 {
switch {
case mime == mimeJSON || strings.HasSuffix(mime, "+json"):
var result map[string]interface{}
err := json.Unmarshal(bytePayload, &result)
if err != nil {
return payload
}
return result
case strings.HasPrefix(mime, mimeFormMultipart), mime == mimeFormURLEncoded:
return string(bytePayload)
}
}
return payload
}
// HTTPRequestData is a event schema used for sending events to HTTP subscriptions.
type HTTPRequestData struct {
Headers map[string]string `json:"headers"`
Query map[string][]string `json:"query"`
Body interface{} `json:"body"`
Host string `json:"host"`
Path string `json:"path"`
Method string `json:"method"`
Params map[string]string `json:"params"`
}
// NewHTTPRequestData returns a new instance of HTTPRequestData
func newHTTPRequestData(r *http.Request, eventData interface{}) *HTTPRequestData {
req := &HTTPRequestData{
Headers: flatten(r.Header),
Query: r.URL.Query(),
Body: eventData,
Host: r.Host,
Path: r.URL.Path,
Method: r.Method,
}
req.Body = normalizePayload(req.Body, r.Header.Get("content-type"))
return req
}