[#970] added Twitch OAuth2 provider

tools/auth/auth.go

@@ -101,6 +101,8 @@ func NewProviderByName(name string) (Provider, error) {
 		return NewSpotifyProvider(), nil
 	case NameKakao:
 		return NewKakaoProvider(), nil
+	case NameTwitch:
+		return NewTwitchProvider(), nil
 	default:
 		return nil, errors.New("Missing provider " + name)
 	}

tools/auth/auth_test.go

@@ -99,4 +99,13 @@ func TestNewProviderByName(t *testing.T) {
 	if _, ok := p.(*auth.Kakao); !ok {
 		t.Error("Expected to be instance of *auth.Kakao")
 	}
+
+	// twitch
+	p, err = auth.NewProviderByName(auth.NameTwitch)
+	if err != nil {
+		t.Errorf("Expected nil, got error %v", err)
+	}
+	if _, ok := p.(*auth.Twitch); !ok {
+		t.Error("Expected to be instance of *auth.Twitch")
+	}
 }

tools/auth/base_provider.go

@@ -108,9 +108,20 @@ func (p *baseProvider) Client(token *oauth2.Token) *http.Client {
 
 // FetchRawUserData implements Provider.FetchRawUserData interface.
 func (p *baseProvider) FetchRawUserData(token *oauth2.Token, result any) error {
+	req, err := http.NewRequest("GET", p.userApiUrl, nil)
+	if err != nil {
+		return err
+	}
+
+	return p.sendRawUserDataRequest(req, token, result)
+}
+
+// sendRawUserDataRequest sends the specified request and
+// unmarshal the response body into result.
+func (p *baseProvider) sendRawUserDataRequest(req *http.Request, token *oauth2.Token, result any) error {
 	client := p.Client(token)
 
-	response, err := client.Get(p.userApiUrl)
+	response, err := client.Do(req)
 	if err != nil {
 		return err
 	}

tools/auth/twitch.go

@@ -0,0 +1,75 @@
+package auth
+
+import (
+	"errors"
+	"net/http"
+
+	"golang.org/x/oauth2"
+	"golang.org/x/oauth2/twitch"
+)
+
+var _ Provider = (*Twitch)(nil)
+
+// NameTwitch is the unique name of the Twitch provider.
+const NameTwitch string = "twitch"
+
+// Twitch allows authentication via Twitch OAuth2.
+type Twitch struct {
+	*baseProvider
+}
+
+// NewTwitchProvider creates new Twitch provider instance with some defaults.
+func NewTwitchProvider() *Twitch {
+	return &Twitch{&baseProvider{
+		scopes:     []string{"user:read:email"},
+		authUrl:    twitch.Endpoint.AuthURL,
+		tokenUrl:   twitch.Endpoint.TokenURL,
+		userApiUrl: "https://api.twitch.tv/helix/users",
+	}}
+}
+
+// FetchAuthUser returns an AuthUser instance based the Twitch's user api.
+func (p *Twitch) FetchAuthUser(token *oauth2.Token) (*AuthUser, error) {
+	// https://dev.twitch.tv/docs/api/reference#get-users
+	rawData := struct {
+		Data []struct {
+			Id              string `json:"id"`
+			Login           string `json:"login"`
+			DisplayName     string `json:"display_name"`
+			Email           string `json:"email"`
+			ProfileImageUrl string `json:"profile_image_url"`
+		} `json:"data"`
+	}{}
+
+	if err := p.FetchRawUserData(token, &rawData); err != nil {
+		return nil, err
+	}
+
+	if len(rawData.Data) == 0 {
+		return nil, errors.New("Failed to fetch AuthUser data")
+	}
+
+	user := &AuthUser{
+		Id:        rawData.Data[0].Id,
+		Name:      rawData.Data[0].DisplayName,
+		Username:  rawData.Data[0].Login,
+		Email:     rawData.Data[0].Email,
+		AvatarUrl: rawData.Data[0].ProfileImageUrl,
+	}
+
+	return user, nil
+}
+
+// FetchRawUserData implements Provider.FetchRawUserData interface.
+//
+// This differ from baseProvider because Twitch requires the `Client-Id` header.
+func (p *Twitch) FetchRawUserData(token *oauth2.Token, result any) error {
+	req, err := http.NewRequest("GET", p.userApiUrl, nil)
+	if err != nil {
+		return err
+	}
+
+	req.Header.Set("Client-Id", p.clientId)
+
+	return p.sendRawUserDataRequest(req, token, result)
+}