feat: T-AUTH-5 — Facebook OAuth provider (#32)

internal/step_oauth.go

@@ -21,12 +21,16 @@ const (
 	googleOAuthAuthorizationURL = "https://accounts.google.com/o/oauth2/v2/auth"
 	googleOAuthTokenURL         = "https://oauth2.googleapis.com/token"
 	googleOAuthUserinfoURL      = "https://openidconnect.googleapis.com/v1/userinfo"
+	facebookOAuthAuthorizationURL = "https://www.facebook.com/v18.0/dialog/oauth"
+	facebookOAuthTokenURL         = "https://graph.facebook.com/v18.0/oauth/access_token"
+	facebookOAuthUserinfoURL      = "https://graph.facebook.com/me?fields=id,email,name"
 	oauthDefaultReturnTo        = "/auth/callback"
 	oauthDefaultStateTTL        = 15 * time.Minute
 	oauthJSONBodyLimit          = 1 << 20
 )
 
 var googleOAuthScopes = []string{"openid", "email", "profile"}
+var facebookOAuthScopes = []string{"email", "public_profile"}
 
 type oauthProviderConfigStep struct {
 	name   string
@@ -290,7 +294,37 @@ func oauthProviderConfig(config map[string]any, provider string) (oauthProviderC
 			cfg.userinfoURL = override
 		}
 		return cfg, ""
-	case "facebook", "instagram", "x", "bluesky":
+	case "facebook":
+		cfg := oauthProviderConfigData{
+			provider:         "facebook",
+			clientID:         oauthString(config, "facebook_oauth_client_id"),
+			clientSecret:     oauthString(config, "facebook_oauth_client_secret"),
+			redirectURL:      oauthString(config, "facebook_oauth_redirect_url"),
+			authorizationURL: facebookOAuthAuthorizationURL,
+			tokenURL:         facebookOAuthTokenURL,
+			userinfoURL:      facebookOAuthUserinfoURL,
+			scopes:           append([]string(nil), facebookOAuthScopes...),
+		}
+		if cfg.clientID == "" || cfg.clientSecret == "" || cfg.redirectURL == "" {
+			return cfg, "facebook oauth is not fully configured"
+		}
+		if override, ok := oauthEndpointURL(config, "facebook_oauth_authorization_url", facebookOAuthAuthorizationURL, "www.facebook.com"); !ok {
+			return cfg, "facebook authorization_url must use https and the expected Facebook hostname unless test endpoints are explicitly enabled"
+		} else {
+			cfg.authorizationURL = override
+		}
+		if override, ok := oauthEndpointURL(config, "facebook_oauth_token_url", facebookOAuthTokenURL, "graph.facebook.com"); !ok {
+			return cfg, "facebook token_url must use https and the expected Facebook hostname unless test endpoints are explicitly enabled"
+		} else {
+			cfg.tokenURL = override
+		}
+		if override, ok := oauthEndpointURL(config, "facebook_oauth_userinfo_url", facebookOAuthUserinfoURL, "graph.facebook.com"); !ok {
+			return cfg, "facebook userinfo_url must use https and the expected Facebook hostname unless test endpoints are explicitly enabled"
+		} else {
+			cfg.userinfoURL = override
+		}
+		return cfg, ""
+	case "instagram", "x", "bluesky":
 		return oauthProviderConfigData{provider: provider}, provider + " oauth provider is disabled in this release"
 	case "":
 		return oauthProviderConfigData{}, "missing oauth provider"

internal/step_oauth_test.go

@@ -386,3 +386,51 @@ func googleOAuthTestConfig(extra map[string]any) map[string]any {
 	}
 	return config
 }
+
+func facebookOAuthTestConfig(extra map[string]any) map[string]any {
+	config := map[string]any{
+		"facebook_oauth_client_id":     "fb-client",
+		"facebook_oauth_client_secret": "fb-secret",
+		"facebook_oauth_redirect_url":  "https://app.example.com/auth/facebook/callback",
+	}
+	for k, v := range extra {
+		config[k] = v
+	}
+	return config
+}
+
+func TestOAuthProviderConfig_FacebookAvailable(t *testing.T) {
+	step := newOAuthProviderConfigStep("test", facebookOAuthTestConfig(nil))
+	result, err := step.Execute(context.Background(), nil, nil, map[string]any{"provider": "facebook"}, nil, nil)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if result.Output["available"] != true {
+		t.Fatalf("expected available=true, got %v", result.Output["available"])
+	}
+	if result.Output["provider"] != "facebook" {
+		t.Fatalf("expected provider=facebook, got %v", result.Output["provider"])
+	}
+	if result.Output["client_id"] != "fb-client" {
+		t.Fatalf("expected client_id=fb-client, got %v", result.Output["client_id"])
+	}
+	if scopes, ok := result.Output["scopes"].([]string); !ok || len(scopes) == 0 {
+		t.Fatalf("expected scopes, got %v", result.Output["scopes"])
+	}
+}
+
+func TestOAuthProviderConfig_FacebookIncompleteUnavailable(t *testing.T) {
+	step := newOAuthProviderConfigStep("test", map[string]any{
+		"facebook_oauth_client_id": "fb-client",
+	})
+	result, err := step.Execute(context.Background(), nil, nil, map[string]any{"provider": "facebook"}, nil, nil)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if result.Output["available"] != false {
+		t.Fatalf("expected available=false, got %v", result.Output["available"])
+	}
+	if result.Output["disabled_reason"] == "" || result.Output["disabled_reason"] == nil {
+		t.Fatalf("expected disabled_reason, got %v", result.Output["disabled_reason"])
+	}
+}