create platform independent token file (fixes #4) (#5)

* create platform independent token file (fixes #4)

* uncapitalize error message strings

Since the release of Staticcheck 2019.1 ST1005 seems to be enabled which
triggers the error message: 'error strings should not be capitalized'.

* use filepath.Join() and set tokenFile as a flag

README.md

@@ -50,6 +50,7 @@ Flags:
   -d, --debug       enable debug logging (default: false)
   -e, --export      export existing filters (default: false)
   -f, --creds-file  Gmail credential file (or env var GMAIL_CREDENTIAL_FILE) (default: <none>)
+  -t, --token-file  Gmail oauth token file (default: /tmp/token.json)
 
 Commands:
 

gmail.go

@@ -12,7 +12,7 @@ import (
 )
 
 // getClient retrieves a token, saves the token, then returns the generated client.
-func getClient(ctx context.Context, config *oauth2.Config) (*http.Client, error) {
+func getClient(ctx context.Context, tokenFile string, config *oauth2.Config) (*http.Client, error) {
 	// Try reading the token from the file.
 	tok, err := tokenFromFile(tokenFile)
 	if err != nil {
@@ -41,12 +41,12 @@ func getTokenFromWeb(ctx context.Context, config *oauth2.Config) (*oauth2.Token,
 
 	var authCode string
 	if _, err := fmt.Scan(&authCode); err != nil {
-		return nil, fmt.Errorf("Unable to read authorization code: %v", err)
+		return nil, fmt.Errorf("unable to read authorization code: %v", err)
 	}
 
 	tok, err := config.Exchange(ctx, authCode)
 	if err != nil {
-		return nil, fmt.Errorf("Unable to retrieve token from web: %v", err)
+		return nil, fmt.Errorf("unable to retrieve token from web: %v", err)
 	}
 
 	return tok, nil
@@ -71,7 +71,7 @@ func saveToken(path string, token *oauth2.Token) error {
 
 	f, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0600)
 	if err != nil {
-		return fmt.Errorf("Unable to cache oauth token: %v", err)
+		return fmt.Errorf("unable to cache oauth token: %v", err)
 	}
 	defer f.Close()
 

main.go

@@ -8,6 +8,7 @@ import (
 	"io/ioutil"
 	"os"
 	"os/signal"
+	"path/filepath"
 	"syscall"
 
 	"github.com/genuinetools/pkg/cli"
@@ -18,13 +19,14 @@ import (
 )
 
 const (
-	tokenFile = "/tmp/token.json"
 	gmailUser = "me"
 )
 
 var (
 	credsFile string
 
+	tokenFile string
+
 	api *gmail.Service
 
 	debug bool
@@ -52,6 +54,9 @@ func main() {
 	p.FlagSet.StringVar(&credsFile, "creds-file", os.Getenv("GMAIL_CREDENTIAL_FILE"), "Gmail credential file (or env var GMAIL_CREDENTIAL_FILE)")
 	p.FlagSet.StringVar(&credsFile, "f", os.Getenv("GMAIL_CREDENTIAL_FILE"), "Gmail credential file (or env var GMAIL_CREDENTIAL_FILE)")
 
+	p.FlagSet.StringVar(&tokenFile, "token-file", filepath.Join(os.TempDir(), "token.json"), "Gmail oauth token file")
+	p.FlagSet.StringVar(&tokenFile, "t", filepath.Join(os.TempDir(), "token.json"), "Gmail oauth token file")
+
 	// Set the before function.
 	p.Before = func(ctx context.Context) error {
 		// Set the log level.
@@ -60,12 +65,12 @@ func main() {
 		}
 
 		if len(credsFile) < 1 {
-			return errors.New("Gmail credential file cannot be empty")
+			return errors.New("the Gmail credential file cannot be empty")
 		}
 
 		// Make sure the file exists.
 		if _, err := os.Stat(credsFile); os.IsNotExist(err) {
-			return fmt.Errorf("Credential file %s does not exist", credsFile)
+			return fmt.Errorf("credential file %s does not exist", credsFile)
 		}
 
 		// Read the credentials file.
@@ -85,7 +90,7 @@ func main() {
 		}
 
 		// Get the client from the config.
-		client, err := getClient(ctx, config)
+		client, err := getClient(ctx, tokenFile, config)
 		if err != nil {
 			return fmt.Errorf("creating client failed: %v", err)
 		}