package cloudfunction

import (

"encoding/json"

"fmt"

"io/ioutil"

"net/http"

"os"

"strings"

"time"

"github.com/CodeLinkIO/go-cloudfunction-auth/internal"

"golang.org/x/oauth2"

"golang.org/x/oauth2/google"

)

const GOOGLE_TOKEN_URL = "https://oauth2.googleapis.com/token"

func JWTAccessTokenSourceFromJSON(jsonKey []byte, audience string) (oauth2.TokenSource, error) {

cfg, err := google.JWTConfigFromJSON(jsonKey)

if err != nil {

return nil, fmt.Errorf("google: could not parse JSON key: %v", err)

}

pk, err := internal.ParseKey(cfg.PrivateKey)

if err != nil {

return nil, fmt.Errorf("google: could not parse key: %v", err)

}

ts := &jwtAccessTokenSource{

email: cfg.Email,

audience: audience,

pk: pk,

pkID: cfg.PrivateKeyID,

}

tok, err := ts.Token()

if err != nil {

return nil, err

}

return oauth2.ReuseTokenSource(tok, ts), nil

}

type TokenResponse struct {

IdToken string `json:"id_token"`

}

func Authenticate(tokenSource oauth2.TokenSource) (token oauth2.Token, err error) {

jwt, err := tokenSource.Token()

if err != nil {

return

}

client := &http.Client{Timeout: time.Second * 10}

payload := strings.NewReader("grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Ajwt-bearer&assertion=" + jwt.AccessToken)

req, _ := http.NewRequest("POST", GOOGLE_TOKEN_URL, payload)

req.Header.Add("Content-Type", "application/x-www-form-urlencoded")

res, err := client.Do(req)

if err != nil {

return

}

defer res.Body.Close()

body, err := ioutil.ReadAll(res.Body)

if err != nil {

return

}

tokenRes := &TokenResponse{}

err = json.Unmarshal(body, tokenRes)

if err != nil {

fmt.Println(err.Error())

}

token = oauth2.Token{

AccessToken: tokenRes.IdToken,

}

return

}

func NewClient(jwtSource oauth2.TokenSource) *http.Client {

token, err := Authenticate(jwtSource)

if err != nil {

fmt.Printf("cannot authenticate with google: %v", err)

os.Exit(1)

}

return &http.Client{

Transport: &oauth2.Transport{

Base: http.DefaultClient.Transport,

Source: &googleTokenSource{

GoogleToken: &token,

},

},

}

}