Support updating docker image for a server from the frontend

app/Http/Controllers/Api/Client/Servers/SettingsController.php

@@ -2,13 +2,16 @@
 
 namespace Pterodactyl\Http\Controllers\Api\Client\Servers;
 
+use Illuminate\Http\Request;
 use Illuminate\Http\Response;
 use Pterodactyl\Models\Server;
 use Illuminate\Http\JsonResponse;
 use Pterodactyl\Repositories\Eloquent\ServerRepository;
 use Pterodactyl\Services\Servers\ReinstallServerService;
 use Pterodactyl\Http\Controllers\Api\Client\ClientApiController;
+use Symfony\Component\HttpKernel\Exception\BadRequestHttpException;
 use Pterodactyl\Http\Requests\Api\Client\Servers\Settings\RenameServerRequest;
+use Pterodactyl\Http\Requests\Api\Client\Servers\Settings\SetDockerImageRequest;
 use Pterodactyl\Http\Requests\Api\Client\Servers\Settings\ReinstallServerRequest;
 
 class SettingsController extends ClientApiController
@@ -73,4 +76,26 @@ class SettingsController extends ClientApiController
 
         return new JsonResponse([], Response::HTTP_ACCEPTED);
     }
+
+    /**
+     * Changes the Docker image in use by the server.
+     *
+     * @param \Pterodactyl\Http\Requests\Api\Client\Servers\Settings\SetDockerImageRequest $request
+     * @param \Pterodactyl\Models\Server $server
+     * @return \Illuminate\Http\JsonResponse
+     *
+     * @throws \Throwable
+     */
+    public function dockerImage(SetDockerImageRequest $request, Server $server)
+    {
+        if (!in_array($server->image, $server->egg->docker_images)) {
+            throw new BadRequestHttpException(
+                'This server\'s Docker image has been manually set by an administrator and cannot be updated.'
+            );
+        }
+
+        $server->forceFill(['image' => $request->input('docker_image')])->saveOrFail();
+
+        return new JsonResponse([], Response::HTTP_NO_CONTENT);
+    }
 }

app/Http/Controllers/Api/Client/Servers/StartupController.php

@@ -62,6 +62,7 @@ class StartupController extends ClientApiController
             ->transformWith($this->getTransformer(EggVariableTransformer::class))
             ->addMeta([
                 'startup_command' => $startup,
+                'docker_images' => $server->egg->docker_images,
                 'raw_startup_command' => $server->startup,
             ])
             ->toArray();

app/Http/Requests/Api/Client/Servers/Settings/SetDockerImageRequest.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace Pterodactyl\Http\Requests\Api\Client\Servers\Settings;
+
+use Webmozart\Assert\Assert;
+use Pterodactyl\Models\Server;
+use Illuminate\Validation\Rule;
+use Pterodactyl\Models\Permission;
+use Pterodactyl\Contracts\Http\ClientPermissionsRequest;
+use Pterodactyl\Http\Requests\Api\Client\ClientApiRequest;
+
+class SetDockerImageRequest extends ClientApiRequest implements ClientPermissionsRequest
+{
+    /**
+     * @return string
+     */
+    public function permission(): string
+    {
+        return Permission::ACTION_STARTUP_DOCKER_IMAGE;
+    }
+
+    /**
+     * @return array[]
+     */
+    public function rules(): array
+    {
+        /** @var \Pterodactyl\Models\Server $server */
+        $server = $this->route()->parameter('server');
+
+        Assert::isInstanceOf($server, Server::class);
+
+        return [
+            'docker_image' => ['required', 'string', Rule::in($server->egg->docker_images)],
+        ];
+    }
+}