package core

import (
	"context"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"golang.org/x/oauth2"
	"golang.org/x/oauth2/google"
	"google.golang.org/api/gmail/v1"
	"google.golang.org/api/option"
	"io/ioutil"
	"log"
	"net/http"
	"os"
)

//<editor-fold name="secure gmail">

/*======================================================================================



                              secure gmail



======================================================================================*/

// 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)

	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)

	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()

	json.NewEncoder(f).Encode(token)
}

func getMailService() *gmail.Service {
	ctx := context.Background()
	b, err := ioutil.ReadFile("gmail-creds.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, gmail.GmailSendScope, gmail.GmailComposeScope)

	if err != nil {
		log.Fatalf("Unable to parse client secret file to config: %v", err)
	}

	client := getClient(config)

	srv, err := gmail.NewService(ctx, option.WithHTTPClient(client))

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

	return srv
}

func TestSend() {
	srv := getMailService()

	payload := []byte("testing")

	msg := gmail.Message{Raw: base64.URLEncoding.EncodeToString(payload)}

	msgResp, err := srv.Users.Messages.Send("me", &msg).Do()

	if err != nil {
		panic(err)
	}

	fmt.Printf("%#v\n", msgResp)
}

//</editor-fold>