Expose etag through JSON responses for child elements

Signed-off-by: Julius Härtl <jus@bitgrid.net>

lib/Controller/BoardApiController.php

@@ -24,6 +24,7 @@
 
 namespace OCA\Deck\Controller;
 
+use OCA\Deck\Db\Board;
 use OCA\Deck\StatusException;
 use OCP\AppFramework\ApiController;
 use OCP\AppFramework\Http;
@@ -72,7 +73,11 @@ class BoardApiController extends ApiController {
 			}
 			$boards = $this->boardService->findAll($date->getTimestamp(), $details);
 		}
-		return new DataResponse($boards, HTTP::STATUS_OK);
+		$response = new DataResponse($boards, HTTP::STATUS_OK);
+		$response->setETag(md5(json_encode(array_map(function (Board $board) {
+			return $board->getId() . '-' . $board->getETag();
+		}, $boards))));
+		return $response;
 	}
 
 	/**

lib/Db/Label.php

@@ -36,4 +36,8 @@ class Label extends RelationalEntity {
 		$this->addType('cardId', 'integer');
 		$this->addType('lastModified', 'integer');
 	}
+
+	public function getETag() {
+		return md5((string)$this->getLastModified());
+	}
 }

lib/Db/RelationalEntity.php

@@ -80,6 +80,9 @@ class RelationalEntity extends Entity implements \JsonSerializable {
 				$json[$property] = $value;
 			}
 		}
+		if ($reflection->hasMethod('getETag')) {
+			$json['ETag'] = $this->getETag();
+		}
 		return $json;
 	}