gcs-proxy.go

gcs-proxy.go

package main

import (
	"context"
	"fmt"
	"io/ioutil"
	"net/http"
	"strconv"
	"strings"
	"sync"

	"github.com/gorilla/mux"

	"cloud.google.com/go/storage"
)

type storageConnection struct {
	Client *storage.Client
}

var (
	client *storageConnection
	once   sync.Once
)

const (
	// GCSBucket name
	GCSBucket = "gcs-cdn-test-02"
	// ProjectID Google Project ID name
	ProjectID = "gcs-cdn-test-01"
	delimitor = "_"
)

// GetGCSClient gets singleton object for Google Storage
func GetGCSClient(ctx context.Context) (*storage.Client, error) {
	var clientErr error
	once.Do(func() {
		storageClient, err := storage.NewClient(ctx)
		if err != nil {
			clientErr = fmt.Errorf("Failed to create GCS client ERROR:%s", err.Error())
		} else {
			client = &storageConnection{
				Client: storageClient,
			}
		}
	})
	return client.Client, clientErr
}

// Download gets a file from GCS bucket, Takes file path as a path param from request
func Download(w http.ResponseWriter, r *http.Request) {
	fmt.Println("Calling download")
	clientCtx, cancel := context.WithCancel(context.Background())
	defer cancel()
	dir := mux.Vars(r)["dir"]
	filename := mux.Vars(r)["filename"]
	filePath := fmt.Sprintf("%s/%s", dir, filename)
	client, err := GetGCSClient(clientCtx)
	reader, err := client.Bucket(GCSBucket).UserProject(ProjectID).Object(filePath).NewReader(clientCtx)
	if err != nil {
		fmt.Println("Error ", err.Error())
		return
	}
	defer reader.Close()
	contentType := reader.ContentType()
	size := strconv.FormatInt(reader.Size(), 10)
	content, err := ioutil.ReadAll(reader)
	if err != nil {
		fmt.Println("Error ", err.Error())
		return
	}
	w.Header().Set("Content-Type", contentType)
	disposition := "attachment"
	if strings.Contains(contentType, "image") || strings.Contains(contentType, "pdf") {
		disposition = "inline"
	}
	// The header field Content-Disposition helps the client(Browser)
	// to decide whether the content can be rendered on the browser or downloaded.
	w.Header().Set("Content-Disposition", disposition+"; filename="+filename)
	w.Header().Set("Content-Length", size)
	w.Header().Set("Access-Control-Allow-Origin", "*")
	w.Header().Set("Access-Control-Allow-Methods", "POST, GET, OPTIONS, PUT, DELETE")
	w.WriteHeader(http.StatusOK)
	w.Write(content)
}

func healtcheck(w http.ResponseWriter, r *http.Request) {
	w.Write([]byte("OK"))
}

func main() {
	router := mux.NewRouter().StrictSlash(true)
	router.HandleFunc("/healthz", healtcheck).Methods("GET", "HEAD")
	router.HandleFunc("/file/{dir}/{filename}", Download).Methods("GET")
	http.ListenAndServe(":8081", router)
}