Initial commit

auth.go

@@ -0,0 +1,74 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"os"
+
+	"golang.org/x/net/context"
+	"golang.org/x/oauth2"
+)
+
+// Retrieve a token, saves the token, then returns the generated client.
+func getClient(config *oauth2.Config) (*http.Client, error) {
+	// 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, err = getTokenFromWeb(config)
+		if err != nil {
+			return nil, err
+		}
+
+		err = saveToken(tokFile, tok)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return config.Client(context.Background(), tok), nil
+}
+
+// Request a token from the web, then returns the retrieved token.
+func getTokenFromWeb(config *oauth2.Config) (*oauth2.Token, error) {
+	authURL := config.AuthCodeURL("state-token", oauth2.AccessTypeOffline)
+	log.Printf("Go to the following link in your browser then type the authorization code: \n%v", authURL)
+
+	var authCode string
+	if _, err := fmt.Scan(&authCode); err != nil {
+		return nil, err
+	}
+
+	tok, err := config.Exchange(context.TODO(), authCode)
+	if err != nil {
+		return nil, err
+	}
+	return tok, nil
+}
+
+// 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)
+	return tok, err
+}
+
+// Saves a token to a file path.
+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 err
+	}
+	defer f.Close()
+	json.NewEncoder(f).Encode(token)
+
+	return nil
+}