response.go

// Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.

package cfn

import (
	"bytes"
	"encoding/json"
	"errors"
	"io/ioutil"
	"net/http"
)

// StatusType represents a CloudFormation response status
type StatusType string

const (
	StatusSuccess StatusType = "SUCCESS"
	StatusFailed  StatusType = "FAILED"
)

// Response is a representation of a Custom Resource
// response expected by CloudFormation.
type Response struct {
	Status             StatusType             `json:"Status"`
	RequestID          string                 `json:"RequestId"`
	LogicalResourceID  string                 `json:"LogicalResourceId"`
	StackID            string                 `json:"StackId"`
	PhysicalResourceID string                 `json:"PhysicalResourceId"`
	Reason             string                 `json:"Reason,omitempty"`
	NoEcho             bool                   `json:"NoEcho,omitempty"`
	Data               map[string]interface{} `json:"Data,omitempty"`

	url string
}

// NewResponse creates a Response with the relevant verbatim copied
// data from a Event
func NewResponse(r *Event) *Response {
	return &Response{
		RequestID:         r.RequestID,
		LogicalResourceID: r.LogicalResourceID,
		StackID:           r.StackID,

		url: r.ResponseURL,
	}
}

type httpClient interface {
	Do(req *http.Request) (*http.Response, error)
}

func (r *Response) sendWith(client httpClient) error {
	body, err := json.Marshal(r)
	if err != nil {
		return err
	}

	req, err := http.NewRequest(http.MethodPut, r.url, bytes.NewBuffer(body))
	if err != nil {
		return err
	}
	req.Header.Del("Content-Type")

	res, err := client.Do(req)
	if err != nil {
		return err
	}

	body, err = ioutil.ReadAll(res.Body)
	if err != nil {
		return err
	}
	res.Body.Close()

	if res.StatusCode != 200 {
		return errors.New("invalid status code")
	}

	return nil

}

// Send will send the Response to the given URL using the
// default HTTP client
func (r *Response) Send() error {
	return r.sendWith(http.DefaultClient)
}