feat(api-docs): document versioned response headers

Co-Authored-By: Virgil <virgil@lethean.io>

src/php/src/Api/Documentation/Extensions/VersionExtension.php

@@ -0,0 +1,126 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Core\Api\Documentation\Extensions;
+
+use Core\Api\Documentation\Extension;
+use Illuminate\Routing\Route;
+
+/**
+ * API Version Extension.
+ *
+ * Documents the X-API-Version response header and version-driven deprecation
+ * metadata for routes using the api.version middleware.
+ */
+class VersionExtension implements Extension
+{
+    /**
+     * Extend the complete OpenAPI specification.
+     */
+    public function extend(array $spec, array $config): array
+    {
+        if (! (bool) config('api.headers.include_version', true)) {
+            return $spec;
+        }
+
+        $spec['components']['headers'] = $spec['components']['headers'] ?? [];
+        $spec['components']['headers']['xapiversion'] = [
+            'description' => 'API version used to process the request.',
+            'schema' => [
+                'type' => 'string',
+            ],
+        ];
+
+        return $spec;
+    }
+
+    /**
+     * Extend an individual operation.
+     */
+    public function extendOperation(array $operation, Route $route, string $method, array $config): array
+    {
+        $version = $this->versionMiddlewareVersion($route);
+        if ($version === null) {
+            return $operation;
+        }
+
+        $includeVersion = (bool) config('api.headers.include_version', true);
+        $includeDeprecation = (bool) config('api.headers.include_deprecation', true);
+
+        $deprecatedVersions = array_map('intval', config('api.versioning.deprecated', []));
+        $sunsetDates = config('api.versioning.sunset', []);
+        $isDeprecatedVersion = in_array($version, $deprecatedVersions, true);
+        $sunsetDate = $sunsetDates[$version] ?? null;
+
+        if ($isDeprecatedVersion) {
+            $operation['deprecated'] = true;
+        }
+
+        foreach ($operation['responses'] as $status => &$response) {
+            if (! is_numeric($status) || (int) $status < 200 || (int) $status >= 600) {
+                continue;
+            }
+
+            $response['headers'] = $response['headers'] ?? [];
+
+            if ($includeVersion && ! isset($response['headers']['X-API-Version'])) {
+                $response['headers']['X-API-Version'] = [
+                    '$ref' => '#/components/headers/xapiversion',
+                ];
+            }
+
+            if (! $includeDeprecation || ! $isDeprecatedVersion) {
+                continue;
+            }
+
+            $response['headers']['Deprecation'] = [
+                '$ref' => '#/components/headers/deprecation',
+            ];
+            $response['headers']['X-API-Warn'] = [
+                '$ref' => '#/components/headers/xapiwarn',
+            ];
+
+            if ($sunsetDate !== null && $sunsetDate !== '') {
+                $response['headers']['Sunset'] = [
+                    '$ref' => '#/components/headers/sunset',
+                ];
+            }
+        }
+        unset($response);
+
+        return $operation;
+    }
+
+    /**
+     * Extract the version number from api.version middleware.
+     */
+    protected function versionMiddlewareVersion(Route $route): ?int
+    {
+        foreach ($route->middleware() as $middleware) {
+            if (! str_starts_with($middleware, 'api.version') && ! str_contains($middleware, 'ApiVersion')) {
+                continue;
+            }
+
+            if (! str_contains($middleware, ':')) {
+                return null;
+            }
+
+            [, $arguments] = explode(':', $middleware, 2);
+            $arguments = trim($arguments);
+            if ($arguments === '') {
+                return null;
+            }
+
+            $parts = explode(',', $arguments, 2);
+            $version = ltrim(trim($parts[0] ?? ''), 'vV');
+            if ($version === '' || ! is_numeric($version)) {
+                return null;
+            }
+
+            return (int) $version;
+        }
+
+        return null;
+    }
+}

src/php/src/Api/Documentation/OpenApiBuilder.php

@@ -12,6 +12,7 @@ use Core\Api\Documentation\Attributes\ApiTag;
 use Core\Api\Documentation\Extensions\ApiKeyAuthExtension;
 use Core\Api\Documentation\Extensions\RateLimitExtension;
 use Core\Api\Documentation\Extensions\SunsetExtension;
+use Core\Api\Documentation\Extensions\VersionExtension;
 use Core\Api\Documentation\Extensions\WorkspaceHeaderExtension;
 use Illuminate\Http\Resources\Json\JsonResource;
 use Illuminate\Routing\Route;
@@ -58,6 +59,7 @@ class OpenApiBuilder
     {
         $this->extensions = [
             new WorkspaceHeaderExtension,
+            new VersionExtension,
             new RateLimitExtension,
             new SunsetExtension,
             new ApiKeyAuthExtension,

src/php/src/Api/Tests/Feature/OpenApiVersionHeadersTest.php

@@ -0,0 +1,43 @@
+<?php
+
+declare(strict_types=1);
+
+use Core\Api\Documentation\OpenApiBuilder;
+use Illuminate\Support\Facades\Config;
+use Illuminate\Support\Facades\Route as RouteFacade;
+
+beforeEach(function () {
+    Config::set('api.headers.include_version', true);
+    Config::set('api.headers.include_deprecation', true);
+    Config::set('api.versioning.deprecated', [1]);
+    Config::set('api.versioning.sunset', [
+        1 => '2025-06-01',
+    ]);
+    Config::set('api-docs.routes.include', ['api/*']);
+    Config::set('api-docs.routes.exclude', []);
+});
+
+it('documents version headers and version-driven deprecation on versioned routes', function () {
+    RouteFacade::prefix('api/v1')
+        ->middleware(['api', 'api.version:1'])
+        ->group(function () {
+            RouteFacade::get('/legacy-status', fn () => response()->json(['ok' => true]));
+        });
+
+    $spec = (new OpenApiBuilder)->build();
+
+    expect($spec['components']['headers']['xapiversion'] ?? null)->not->toBeNull();
+
+    $operation = $spec['paths']['/api/v1/legacy-status']['get'];
+
+    expect($operation['deprecated'] ?? null)->toBeTrue();
+
+    foreach (['200', '400', '500'] as $status) {
+        $headers = $operation['responses'][$status]['headers'] ?? [];
+
+        expect($headers)->toHaveKey('X-API-Version');
+        expect($headers)->toHaveKey('Deprecation');
+        expect($headers)->toHaveKey('Sunset');
+        expect($headers)->toHaveKey('X-API-Warn');
+    }
+});