4 files changed, 160 insertions, 0 deletions
diff --git a/internal/api/client/admin/admin.go b/internal/api/client/admin/admin.go
index 3d8e88c42..16c5fa8f8 100644
--- a/internal/api/client/admin/admin.go
+++ b/internal/api/client/admin/admin.go
@@ -20,6 +20,7 @@ package admin
 import (
 	"net/http"
 
+	"codeberg.org/gruf/go-debug"
 	"github.com/gin-gonic/gin"
 	"github.com/superseriousbusiness/gotosocial/internal/processing"
 )
@@ -46,6 +47,8 @@ const (
 	EmailTestPath           = EmailPath + "/test"
 	InstanceRulesPath       = BasePath + "/instance/rules"
 	InstanceRulesPathWithID = InstanceRulesPath + "/:" + IDKey
+	DebugPath               = BasePath + "/debug"
+	DebugAPUrlPath          = DebugPath + "/apurl"
 
 	IDKey                 = "id"
 	FilterQueryKey        = "filter"
@@ -116,4 +119,9 @@ func (m *Module) Route(attachHandler func(method string, path string, f ...gin.H
 	attachHandler(http.MethodPost, InstanceRulesPath, m.RulePOSTHandler)
 	attachHandler(http.MethodPatch, InstanceRulesPathWithID, m.RulePATCHHandler)
 	attachHandler(http.MethodDelete, InstanceRulesPathWithID, m.RuleDELETEHandler)
+
+	// debug stuff
+	if debug.DEBUG {
+		attachHandler(http.MethodGet, DebugAPUrlPath, m.DebugAPUrlHandler)
+	}
 }
diff --git a/internal/api/client/admin/debug_off.go b/internal/api/client/admin/debug_off.go
new file mode 100644
index 000000000..bc6e4001c
--- /dev/null
+++ b/internal/api/client/admin/debug_off.go
@@ -0,0 +1,75 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+//go:build !debug && !debugenv
+// +build !debug,!debugenv
+
+package admin
+
+import (
+	"github.com/gin-gonic/gin"
+)
+
+// #######################################################
+// # goswagger is generated using empty / off debug by   #
+// # default, so put all the swagger documentation here! #
+// #######################################################
+
+// DebugAPUrlHandler swagger:operation GET /api/v1/admin/debug/apurl debugAPUrl
+//
+// Perform a GET to the specified ActivityPub URL and return detailed debugging information.
+//
+// Only enabled / exposed if GoToSocial was built and is running with flag DEBUG=1.
+//
+//	---
+//	tags:
+//	- debug
+//
+//	produces:
+//	- application/json
+//
+//	parameters:
+//	-
+//		name: url
+//		type: string
+//		description: >-
+//			The URL / ActivityPub ID to dereference.
+//			This should be a full URL, including protocol.
+//			Eg., `https://example.org/users/someone`
+//		in: query
+//		required: true
+//
+//	security:
+//	- OAuth2 Bearer:
+//		- admin
+//
+//	responses:
+//		'200':
+//			name: Debug response.
+//			schema:
+//				"$ref": "#/definitions/debugAPUrlResponse"
+//		'400':
+//			description: bad request
+//		'401':
+//			description: unauthorized
+//		'404':
+//			description: not found
+//		'406':
+//			description: not acceptable
+//		'500':
+//			description: internal server error
+func (m *Module) DebugAPUrlHandler(c *gin.Context) {}
diff --git a/internal/api/client/admin/debug_on.go b/internal/api/client/admin/debug_on.go
new file mode 100644
index 000000000..c6dfa11ff
--- /dev/null
+++ b/internal/api/client/admin/debug_on.go
@@ -0,0 +1,58 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+//go:build debug || debugenv
+// +build debug debugenv
+
+package admin
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	apiutil "github.com/superseriousbusiness/gotosocial/internal/api/util"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"github.com/superseriousbusiness/gotosocial/internal/oauth"
+)
+
+func (m *Module) DebugAPUrlHandler(c *gin.Context) {
+	authed, err := oauth.Authed(c, true, true, true, true)
+	if err != nil {
+		apiutil.ErrorHandler(c, gtserror.NewErrorUnauthorized(err, err.Error()), m.processor.InstanceGetV1)
+		return
+	}
+
+	if !*authed.User.Admin {
+		err := fmt.Errorf("user %s not an admin", authed.User.ID)
+		apiutil.ErrorHandler(c, gtserror.NewErrorForbidden(err, err.Error()), m.processor.InstanceGetV1)
+		return
+	}
+
+	if _, err := apiutil.NegotiateAccept(c, apiutil.JSONAcceptHeaders...); err != nil {
+		apiutil.ErrorHandler(c, gtserror.NewErrorNotAcceptable(err, err.Error()), m.processor.InstanceGetV1)
+		return
+	}
+
+	resp, errWithCode := m.processor.Admin().DebugAPUrl(c.Request.Context(), authed.Account, c.Query("url"))
+	if errWithCode != nil {
+		apiutil.ErrorHandler(c, errWithCode, m.processor.InstanceGetV1)
+		return
+	}
+
+	c.JSON(http.StatusOK, resp)
+}
diff --git a/internal/api/model/admin.go b/internal/api/model/admin.go
index ca4aa32da..60036c19f 100644
--- a/internal/api/model/admin.go
+++ b/internal/api/model/admin.go
@@ -210,3 +210,22 @@ type AdminInstanceRule struct {
 	UpdatedAt string `json:"updated_at"` // when was item last updated
 	Text      string `json:"text"`       // text content of the rule
 }
+
+// DebugAPUrlResponse provides detailed debug
+// information for an AP URL dereference request.
+//
+// swagger:model debugAPUrlResponse
+type DebugAPUrlResponse struct {
+	// Remote AP URL that was requested.
+	RequestURL string `json:"request_url"`
+	// HTTP headers used in the outgoing request.
+	RequestHeaders map[string][]string `json:"request_headers"`
+	// HTTP headers returned from the remote instance.
+	ResponseHeaders map[string][]string `json:"response_headers"`
+	// HTTP response code returned from the remote instance.
+	ResponseCode int `json:"response_code"`
+	// Body returned from the remote instance.
+	// Will be stringified bytes; may be JSON,
+	// may be an error, may be both!
+	ResponseBody string `json:"response_body"`
+}