oups

internal/panel/auth/oauth.go

@@ -0,0 +1,74 @@
+package auth
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+
+	"golang.org/x/oauth2"
+)
+
+// DiscordEndpoint is the Discord OAuth2 endpoint.
+var DiscordEndpoint = oauth2.Endpoint{
+	AuthURL:  "https://discord.com/api/oauth2/authorize",
+	TokenURL: "https://discord.com/api/oauth2/token",
+}
+
+// DiscordUser holds the data returned by /users/@me.
+type DiscordUser struct {
+	ID       string `json:"id"`
+	Username string `json:"username"`
+	Avatar   string `json:"avatar"`
+}
+
+// AvatarURL returns the full Discord CDN URL for the user's avatar.
+func (u *DiscordUser) AvatarURL() string {
+	if u.Avatar == "" {
+		return ""
+	}
+	return fmt.Sprintf("https://cdn.discordapp.com/avatars/%s/%s.png?size=128", u.ID, u.Avatar)
+}
+
+// NewOAuthConfig builds an oauth2.Config for Discord.
+func NewOAuthConfig(clientID, clientSecret, callbackURL string) *oauth2.Config {
+	return &oauth2.Config{
+		ClientID:     clientID,
+		ClientSecret: clientSecret,
+		RedirectURL:  callbackURL,
+		Scopes:       []string{"identify"},
+		Endpoint:     DiscordEndpoint,
+	}
+}
+
+// AuthURL returns the Discord authorization URL with the given state.
+func AuthURL(cfg *oauth2.Config, state string) string {
+	return cfg.AuthCodeURL(state, oauth2.AccessTypeOnline)
+}
+
+// FetchDiscordUser exchanges the authorization code for a token, then calls /users/@me.
+func FetchDiscordUser(ctx context.Context, cfg *oauth2.Config, code string) (*DiscordUser, error) {
+	token, err := cfg.Exchange(ctx, code)
+	if err != nil {
+		return nil, fmt.Errorf("exchange oauth code: %w", err)
+	}
+
+	client := cfg.Client(ctx, token)
+	resp, err := client.Get("https://discord.com/api/v10/users/@me")
+	if err != nil {
+		return nil, fmt.Errorf("fetch discord user: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		body, _ := io.ReadAll(resp.Body)
+		return nil, fmt.Errorf("discord api %d: %s", resp.StatusCode, body)
+	}
+
+	var user DiscordUser
+	if err := json.NewDecoder(resp.Body).Decode(&user); err != nil {
+		return nil, fmt.Errorf("decode discord user: %w", err)
+	}
+	return &user, nil
+}