main.go

package main

import (
	"code.google.com/p/goauth2/oauth"
	drive "code.google.com/p/google-api-go-client/drive/v2"
	"flag"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
)

// OAuth
var client *http.Client
var config = &oauth.Config{
	ClientId:     "", // Set by --clientid
	ClientSecret: "", // Set by --secret
	Scope:        "", // filled in per-API
	AuthURL:      "https://accounts.google.com/o/oauth2/auth",
	TokenURL:     "https://accounts.google.com/o/oauth2/token",
}

var service *drive.Service

// Flags
var (
	clientId   = flag.String("clientid", "", "OAuth Client ID")
	secret     = flag.String("secret", "", "OAuth Client Secret")
	mimeType   = flag.String("mimeType", "text/html", "MIME type to download")
	cacheToken = flag.Bool("cachetoken", true, "cache the OAuth token")
)

func usage() {
	fmt.Fprintf(os.Stderr, "Usage: gdriver [flags] <fileId>\n")
	os.Exit(2)
}

// DownloadFile downloads the content of a given file object
func DownloadFile(url string, out io.WriteCloser) {

	// Make the request.
	r, err := client.Get(url)
	if err != nil {
		log.Fatal("Get:", err)
	}
	defer r.Body.Close()

	// Write the response to standard output.
	io.Copy(out, r.Body)
}

func getExportLink(file *drive.File, mimeType string) string {
	// TODO - return file.ExportLinks[*mimeType]
	var format string
	switch mimeType {
	case "text/html":
		format = "html"
	}
	return fmt.Sprintf("https://docs.google.com/feeds/download/documents/export/Export?id=%s&exportFormat=%s", file.Id, format)
}

func renderFile(file *drive.File, outFile string) {
	downloadUrl := getExportLink(file, *mimeType)

	inFormat := "html"

	cmd := exec.Command("pandoc", "-f", inFormat, "-o", outFile)

	pandocIn, err := cmd.StdinPipe()
	if err != nil {
		log.Fatal(err)
	}

	if err := cmd.Start(); err != nil {
		log.Fatal(err)
	}

	log.Printf("Downloading %s ...", downloadUrl)
	DownloadFile(downloadUrl, pandocIn)
	pandocIn.Close()

	log.Printf("Creating %s ...", outFile)

	if err := cmd.Wait(); err != nil {
		log.Fatal(err)
	}
}

func renderFiles(fileId string, path string) {

	// Get the file
	file, _ := service.Files.Get(fileId).Do()

	//log.Printf("File: \n %#v", file)

	// Check if this is a folder
	if file.MimeType == "application/vnd.google-apps.folder" {

		path = filepath.Join(path, file.Title)

		log.Printf("Got folder %s", path)

		// create the directory
		os.Mkdir(path, 0700)

		childList, _ := service.Children.List(file.Id).Do()

		for _, ref := range childList.Items {
			renderFiles(ref.Id, path)
		}

	} else {
		log.Printf("Got file %s/%s", path, file.Title)

		outFile := filepath.Join(path, fmt.Sprintf("%s.pdf", file.Title))

		renderFile(file, outFile)
	}
}

func main() {
	flag.Parse()
	if flag.NArg() == 0 {
		usage()
	}

	fileId := flag.Arg(0)

	config.Scope = drive.DriveScope
	config.ClientId = *clientId
	config.ClientSecret = *secret

	client = getOAuthClient(config)

	service, _ = drive.New(client)

	renderFiles(fileId, ".")

}