add Facebook provider for oauth2

oauth2/oauth2_test.go

@@ -12,6 +12,7 @@ import (
 
 	"golang.org/x/net/context"
 	"golang.org/x/oauth2"
+	"golang.org/x/oauth2/facebook"
 	"gopkg.in/authboss.v0"
 	"gopkg.in/authboss.v0/internal/mocks"
 )
@@ -27,6 +28,15 @@ var testProviders = map[string]authboss.OAuth2Provider{
 		Callback:         Google,
 		AdditionalParams: url.Values{"include_requested_scopes": []string{"true"}},
 	},
+	"facebook": authboss.OAuth2Provider{
+		OAuth2Config: &oauth2.Config{
+			ClientID:     `jazz`,
+			ClientSecret: `hands`,
+			Scopes:       []string{`email`},
+			Endpoint:     facebook.Endpoint,
+		},
+		Callback: Facebook,
+	},
 }
 
 func TestInitialize(t *testing.T) {

oauth2/providers.go

@@ -45,3 +45,35 @@ func Google(cfg oauth2.Config, token *oauth2.Token) (authboss.Attributes, error)
 		authboss.StoreEmail:     jsonResp.Email,
 	}, nil
 }
+
+type facebookMeResponse struct {
+	ID    string `json:"id"`
+	Email string `json:"email"`
+	Name  string `json:"name"`
+}
+
+const (
+	facebookInfoEndpoint = "https://graph.facebook.com/me?fields=name,email"
+)
+
+// Google is a callback appropriate for use with Google's OAuth2 configuration.
+func Facebook(cfg oauth2.Config, token *oauth2.Token) (authboss.Attributes, error) {
+	client := cfg.Client(oauth2.NoContext, token)
+	resp, err := clientGet(client, facebookInfoEndpoint)
+	if err != nil {
+		return nil, err
+	}
+
+	defer resp.Body.Close()
+	dec := json.NewDecoder(resp.Body)
+	var jsonResp facebookMeResponse
+	if err = dec.Decode(&jsonResp); err != nil {
+		return nil, err
+	}
+
+	return authboss.Attributes{
+		"name":                  jsonResp.Name,
+		authboss.StoreOAuth2UID: jsonResp.ID,
+		authboss.StoreEmail:     jsonResp.Email,
+	}, nil
+}

oauth2/providers_test.go

@@ -43,3 +43,39 @@ func TestGoogle(t *testing.T) {
 		t.Error("Email wrong:", email)
 	}
 }
+
+func TestFacebook(t *testing.T) {
+	saveClientGet := clientGet
+	defer func() {
+		clientGet = saveClientGet
+	}()
+
+	clientGet = func(_ *http.Client, url string) (*http.Response, error) {
+		return &http.Response{
+			Body: ioutil.NopCloser(strings.NewReader(`{"id":"id", "email":"email", "name":"name"}`)),
+		}, nil
+	}
+
+	cfg := *testProviders["facebook"].OAuth2Config
+	tok := &oauth2.Token{
+		AccessToken:  "token",
+		TokenType:    "Bearer",
+		RefreshToken: "refresh",
+		Expiry:       time.Now().Add(60 * time.Minute),
+	}
+
+	user, err := Facebook(cfg, tok)
+	if err != nil {
+		t.Error(err)
+	}
+
+	if uid, ok := user[authboss.StoreOAuth2UID]; !ok || uid != "id" {
+		t.Error("UID wrong:", uid)
+	}
+	if email, ok := user[authboss.StoreEmail]; !ok || email != "email" {
+		t.Error("Email wrong:", email)
+	}
+	if name, ok := user["name"]; !ok || name != "name" {
+		t.Error("Name wrong:", name)
+	}
+}