[#335] added Discord OAuth2 provider

tools/auth/discord.go

@@ -0,0 +1,61 @@
+package auth
+
+import (
+	"fmt"
+
+	"golang.org/x/oauth2"
+)
+
+var _ Provider = (*Discord)(nil)
+
+// NameDiscord is the unique name of the Discord provider.
+const NameDiscord string = "discord"
+
+// Discord allows authentication via Discord OAuth2.
+type Discord struct {
+	*baseProvider
+}
+
+// NewDiscordProvider creates a new Discord provider instance with some defaults.
+func NewDiscordProvider() *Discord {
+	// https://discord.com/developers/docs/topics/oauth2
+	// https://discord.com/developers/docs/resources/user#get-current-user
+	return &Discord{&baseProvider{
+		scopes:     []string{"identify", "email"},
+		authUrl:    "https://discord.com/api/oauth2/authorize",
+		tokenUrl:   "https://discord.com/api/oauth2/token",
+		userApiUrl: "https://discord.com/api/users/@me",
+	}}
+}
+
+// FetchAuthUser returns an AuthUser instance from Discord's user api.
+func (p *Discord) FetchAuthUser(token *oauth2.Token) (*AuthUser, error) {
+	// https://discord.com/developers/docs/resources/user#user-object
+	rawData := struct {
+		Id            string `json:"id"`
+		Username      string `json:"username"`
+		Discriminator string `json:"discriminator"`
+		Email         string `json:"email"`
+		Avatar        string `json:"avatar"`
+	}{}
+
+	if err := p.FetchRawUserData(token, &rawData); err != nil {
+		return nil, err
+	}
+
+	// Build a full avatar URL using the avatar hash provided in the API response
+	// https://discord.com/developers/docs/reference#image-formatting
+	avatarUrl := fmt.Sprintf("https://cdn.discordapp.com/avatars/%s/%s.png", rawData.Id, rawData.Avatar)
+
+	// Concatenate the user's username and discriminator into a single username string
+	username := fmt.Sprintf("%s#%s", rawData.Username, rawData.Discriminator)
+
+	user := &AuthUser{
+		Id:        rawData.Id,
+		Name:      username,
+		Email:     rawData.Email,
+		AvatarUrl: avatarUrl,
+	}
+
+	return user, nil
+}