serialization.go

/*
   Copyright 2014 CoreOS, 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 api

import (
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"strings"

	"github.com/coreos/fleet/log"
)

func validateContentType(req *http.Request) error {
	values := req.Header["Content-Type"]
	count := len(values)

	if count != 1 {
		return fmt.Errorf("expected 1 Content-Type, got %d", count)
	}

	val := strings.SplitN(values[0], ";", 2)[0]
	val = strings.TrimSpace(val)
	if val != "application/json" {
		return errors.New("only acceptable Content-Type is application/json")
	}

	return nil
}

// sendResponse attempts to marshal an arbitrary thing to JSON then write
// it to the http.ResponseWriter
func sendResponse(rw http.ResponseWriter, code int, resp interface{}) {
	enc, err := json.Marshal(resp)
	if err != nil {
		log.Errorf("Failed JSON-encoding HTTP response: %v", err)
		rw.WriteHeader(http.StatusInternalServerError)
		return
	}

	rw.Header().Set("Content-Type", "application/json")
	rw.WriteHeader(code)

	_, err = rw.Write(enc)
	if err != nil {
		log.Errorf("Failed sending HTTP response body: %v", err)
	}
}

// errorEntity is a fork of "google.golang.org/api/googleapi".Error
type errorEntity struct {
	// Code is the HTTP response status code and will always be populated.
	Code int `json:"code"`
	// Message is the server response message and is only populated when
	// explicitly referenced by the JSON server response.
	Message string `json:"message"`
}

type errorResponse struct {
	Error errorEntity `json:"error"`
}

// sendError builds an errorResponse entity from the given arguments, serializing
// the object into the provided http.ResponseWriter
func sendError(rw http.ResponseWriter, code int, err error) {
	resp := errorResponse{Error: errorEntity{Code: code}}
	if err != nil {
		resp.Error.Message = err.Error()
	}
	sendResponse(rw, code, resp)
}