[#1643] added Gitea OAuth2 provider

Co-authored-by: Steve MacLeod <sjmacleoddev@gmail.com>

tools/auth/gitea.go

@@ -0,0 +1,67 @@
+package auth
+
+import (
+	"encoding/json"
+	"strconv"
+
+	"golang.org/x/oauth2"
+)
+
+var _ Provider = (*Gitea)(nil)
+
+// NameGitea is the unique name of the Gitea provider.
+const NameGitea string = "gitea"
+
+// Gitea allows authentication via Gitea OAuth2.
+type Gitea struct {
+	*baseProvider
+}
+
+// NewGiteaProvider creates new Gitea provider instance with some defaults.
+func NewGiteaProvider() *Gitea {
+	return &Gitea{&baseProvider{
+		scopes:     []string{"read:user", "user:email"},
+		authUrl:    "https://gitea.com/login/oauth/authorize",
+		tokenUrl:   "https://gitea.com/login/oauth/access_token",
+		userApiUrl: "https://gitea.com/api/v1/user",
+	}}
+}
+
+// FetchAuthUser returns an AuthUser instance based on Gitea's user api.
+//
+// API reference: https://try.gitea.io/api/swagger#/user/userGetCurrent
+func (p *Gitea) FetchAuthUser(token *oauth2.Token) (*AuthUser, error) {
+	data, err := p.FetchRawUserData(token)
+	if err != nil {
+		return nil, err
+	}
+
+	rawUser := map[string]any{}
+	if err := json.Unmarshal(data, &rawUser); err != nil {
+		return nil, err
+	}
+
+	extracted := struct {
+		Id        int    `json:"id"`
+		Name      string `json:"full_name"`
+		Username  string `json:"login"`
+		Email     string `json:"email"`
+		AvatarUrl string `json:"avatar_url"`
+	}{}
+	if err := json.Unmarshal(data, &extracted); err != nil {
+		return nil, err
+	}
+
+	user := &AuthUser{
+		Id:           strconv.Itoa(extracted.Id),
+		Name:         extracted.Name,
+		Username:     extracted.Username,
+		Email:        extracted.Email,
+		AvatarUrl:    extracted.AvatarUrl,
+		RawUser:      rawUser,
+		AccessToken:  token.AccessToken,
+		RefreshToken: token.RefreshToken,
+	}
+
+	return user, nil
+}