Implement correct ETag support

Signed-off-by: Joas Schilling <coding@schilljs.com>

docs/ocs-endpoint-v2.md

@@ -4,6 +4,7 @@
 
 * :new: Support for icons was added with capability-entry `icons`
 * :new: Support for [Rich Object Strings](https://github.com/nextcloud/server/issues/1706) was added with capability-entry `rich-strings`
+* :new: ETag/If-None-Match are now evaluated and respond with `304 Not Modified` and empty body when unchanged.
 
 ## Checking the capabilities of the server
 
@@ -93,7 +94,12 @@ The user needs to be identified/logged in by the server. Then you can just run a
 }
 ```
 
-**Note:** If the HTTP status code is `204` (No content), you can slow down the polling to once per hour. This status code means that there is no app that can generate notifications.
+### Response codes
+
+Status | Explanation
+---|---
+`204 No Content` | please slow down the polling to once per hour, since there are no apps that can generate notifications
+`304 Not Modified` | The provided `If-None-Match` matches the ETag, response body is empty
 
 ### Specification
 

lib/Controller/EndpointController.php

@@ -99,12 +99,9 @@ class EndpointController extends OCSController {
 		}
 
 		$etag = $this->generateEtag($notificationIds);
-		/**
-		 * Not documented yet, check with clients
-		if ($this->request->getHeader('ETag') === $etag) {
-			return new DataResponse($data, Http::STATUS_NOT_MODIFIED);
+		if ($apiVersion !== 'v1' && $this->request->getHeader('If-None-Match') === $etag) {
+			return new DataResponse([], Http::STATUS_NOT_MODIFIED);
 		}
-		 */
 
 		return new DataResponse($data, Http::STATUS_OK, ['ETag' => $etag]);
 	}

tests/Integration/features/bootstrap/FeatureContext.php

@@ -93,15 +93,22 @@ class FeatureContext implements Context, SnippetAcceptingContext {
 	public function gettingNotifications($api, $etag) {
 		$headers = [];
 		if ($etag === ' with different etag') {
-			$headers['ETag'] = md5($this->lastEtag);
+			$headers['If-None-Match'] = substr($this->lastEtag, 0, 16);
 		} else if ($etag === ' with matching etag') {
-			$headers['ETag'] = $this->lastEtag;
+			$headers['If-None-Match'] = $this->lastEtag;
 		}
 
 		$this->sendingToWith('GET', '/apps/notifications/api/' . $api . '/notifications?format=json', null, $headers);
 		$this->lastEtag = $this->response->getHeader('ETag');
 	}
 
+	/**
+	 * @Then /^response body is empty$/
+	 */
+	public function checkResponseBodyIsEmpty() {
+		PHPUnit_Framework_Assert::assertSame('', $this->response->getBody()->getContents());
+	}
+
 	/**
 	 * @Then /^list of notifications has (\d+) entries$/
 	 *

tests/Integration/features/statuscodes-v1.feature

@@ -41,5 +41,7 @@ Feature: statuscodes
     Then status code is 200
     And list of notifications has 3 entries
     When getting notifications on v1 with matching etag
-    Then status code is 200
     # Then status code is 304 - Disabled because it's not listed in the API specs
+    Then status code is 200
+    # And response body is empty - Disabled because it's not listed in the API specs
+    And list of notifications has 3 entries

tests/Integration/features/statuscodes-v2.feature

@@ -41,5 +41,5 @@ Feature: statuscodes
     Then status code is 200
     And list of notifications has 3 entries
     When getting notifications on v2 with matching etag
-    Then status code is 200
-    # Then status code is 304 - Disabled because it's not listed in the API specs
+    Then status code is 304
+    And response body is empty

tests/Integration/run.sh

@@ -18,7 +18,7 @@ ${ROOT_DIR}/occ app:list | grep notifications
 ${ROOT_DIR}/occ app:list | grep provisioning_api
 
 export TEST_SERVER_URL="http://localhost:8080/"
-${APP_INTEGRATION_DIR}/vendor/bin/behat -f junit -f pretty
+${APP_INTEGRATION_DIR}/vendor/bin/behat -f junit -f pretty $1 $2
 RESULT=$?
 
 kill $PHPPID