main.go

package main

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"os"

	"golang.org/x/net/context"
	"golang.org/x/oauth2"
	"golang.org/x/oauth2/google"
	"google.golang.org/api/drive/v3"
	"google.golang.org/api/option"
)

/* // Retrieve a token, saves the token, then returns the generated client.
func getClient(config *oauth2.Config) *http.Client {
	// The file token.json stores the user's access and refresh tokens, and is
	// created automatically when the authorization flow completes for the first
	// time.
	tokFile := "token.json"
	tok, err := tokenFromFile(tokFile)
	if err != nil {
		tok = getTokenFromWeb(config)
		saveToken(tokFile, tok)
	}
	return config.Client(context.Background(), tok)
} */

// Request a token from the web, then returns the retrieved token.
/* func getTokenFromWeb(config *oauth2.Config) *oauth2.Token {
	authURL := config.AuthCodeURL("state-token", oauth2.AccessTypeOffline)
	fmt.Printf("Go to the following link in your browser then type the "+
		"authorization code: \n%v\n", authURL)
ß
	var authCode string
	if _, err := fmt.Scan(&authCode); err != nil {
		log.Fatalf("Unable to read authorization code %v", err)
	}

	tok, err := config.Exchange(context.TODO(), authCode)
	if err != nil {
		log.Fatalf("Unable to retrieve token from web %v", err)
	}
	return tok
} */

// Retrieves a token from a local file.
func tokenFromFile(file string) (*oauth2.Token, error) {
	f, err := os.Open(file)
	if err != nil {
		return nil, err
	}
	defer f.Close()
	tok := &oauth2.Token{}
	err = json.NewDecoder(f).Decode(tok)
	if err != nil {
		log.Fatalf("Unable %v", err)
	}
	return tok, err
}

/* // Saves a token to a file path.
func saveToken(path string, token *oauth2.Token) {
	fmt.Printf("Saving credential file to: %s\n", path)
	f, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0600)
	if err != nil {
		log.Fatalf("Unable to cache oauth token: %v", err)
	}
	defer f.Close()
	err = json.NewEncoder(f).Encode(token)
	if err != nil {
		log.Fatalf("Unable %v", err)
	}
} */

/*
func getToken() {
	b, err := ioutil.ReadFile("credentials.json")
	if err != nil {
		log.Fatalf("Unable to read client secret file: %v", err)
	}

	// If modifying these scopes, delete your previously saved token.json.
	config, err := google.ConfigFromJSON(b, drive.DriveFileScope)
	if err != nil {
		log.Fatalf("Unable to parse client secret file to config: %v", err)
	}
	client := getClient(config)

	srv, err := drive.New(client)
	if err != nil {
		log.Fatalf("Unable to retrieve Drive client: %v", err)
	}

	r, err := srv.Files.List().PageSize(10).
		Fields("nextPageToken, files(id, name)").Do()
	if err != nil {
		log.Fatalf("Unable to retrieve files: %v", err)
	}
	fmt.Println("Files:")
	if len(r.Files) == 0 {
		fmt.Println("No files found.")
	} else {
		for _, i := range r.Files {
			fmt.Printf("%s (%s)\n", i.Name, i.Id)
		}
	}
}

func getService() (*drive.Service, error) {
	b, err := ioutil.ReadFile("credentials.json")
	if err != nil {
		fmt.Printf("Unable to read credentials.json file. Err: %v\n", err)
		return nil, err
	}

	// If modifying these scopes, delete your previously saved token.json.
	config, err := google.ConfigFromJSON(b, drive.DriveFileScope)

	if err != nil {
		return nil, err
	}

	client := getClient(config)

	service, err := drive.New(client)

	if err != nil {
		fmt.Printf("Cannot create the Google Drive service: %v\n", err)
		return nil, err
	}

	return service, err
}

func createDir(service *drive.Service, name string, parentId string) (*drive.File, error) {
	d := &drive.File{
		Name:     name,
		MimeType: "application/vnd.google-apps.folder",
		Parents:  []string{parentId},
	}

	file, err := service.Files.Create(d).Do()

	if err != nil {
		log.Println("Could not create dir: " + err.Error())
		return nil, err
	}

	return file, nil
}

func createFile(service *drive.Service, name string, mimeType string, content io.Reader, parentId string) (*drive.File, error) {
	f := &drive.File{
		MimeType: mimeType,
		Name:     name,
		Parents:  []string{parentId},
	}
	file, err := service.Files.Create(f).Media(content).Do()

	if err != nil {
		log.Println("Could not create file: " + err.Error())
		return nil, err
	}

	return file, nil
}
*/

func main() {

	b, err := ioutil.ReadFile("credentials.json")
	if err != nil {
		log.Fatalf("Unable to read client secret file: %v", err)
	}
	ctx := context.Background()

	// If modifying these scopes, delete your previously saved token.json.
	config, err := google.ConfigFromJSON(b, drive.DriveMetadataScope)
	if err != nil {
		log.Fatalf("Unable to parse client secret file to config: %v", err)
	}

	//client := getClient(config)
	tokFile := "token.json"
	tok, err := tokenFromFile(tokFile)
	if err != nil {
		log.Fatalf("Unable to read client secret file: %v", err)
	}

	srv, err := drive.NewService(ctx, option.WithTokenSource(config.TokenSource(ctx, tok)))
	if err != nil {
		log.Fatalf("Unable to retrieve Drive client: %v", err)
	}

	r, err := srv.Files.List().PageSize(10).
		Fields("nextPageToken, files(id, name)").Do()
	if err != nil {
		log.Fatalf("Unable to retrieve files: %v", err)
	}

	fmt.Println("Files:")
	if len(r.Files) == 0 {
		fmt.Println("No files found.")
	} else {
		for _, i := range r.Files {
			fmt.Printf("%s (%s)\n", i.Name, i.Id)
		}
	}
	/*
		// Step 1. Open the file
		f, err := os.Open("go.mod")

		if err != nil {
			panic(fmt.Sprintf("cannot open file: %v", err))
		}

		defer f.Close()

		// Step 2. Get the Google Drive service
		service, err := getService()

		// Step 3. Create the directory
		dir, err := createDir(service, "My Folder", "root")

		if err != nil {
			panic(fmt.Sprintf("Could not create dir: %v\n", err))
		}

		// Step 4. Create the file and upload its content
		file, err := createFile(service, "uploaded-image.png", "image/png", f, dir.Id)

		if err != nil {
			panic(fmt.Sprintf("Could not create file: %v\n", err))
		}

		fmt.Printf("File '%s' successfully uploaded in '%s' directory", file.Name,  dir.Name)*/
}