From fd55bdf9a8874ebf5ee6590656f5d0669cc25133 Mon Sep 17 00:00:00 2001
From: Dennis Lassiter <dennis@lassiter.de>
Date: Fri, 8 Feb 2019 21:48:52 -0500
Subject: [PATCH] Allow params "limit" and "page" in REST-API PR #25, code
 author Dennis Lassiter, many thanks !

---
 application/applicationextension.inc.php | 10 ++++++++--
 core/restservices.class.inc.php          | 21 ++++++++++++++++++++-
 2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/application/applicationextension.inc.php b/application/applicationextension.inc.php
index 030ab6f5e..90aeb4f8e 100644
--- a/application/applicationextension.inc.php
+++ b/application/applicationextension.inc.php
@@ -825,6 +825,10 @@ class RestResult
 	 * Result: the requested operation cannot be performed because it can cause data (integrity) loss 
 	 */
 	const UNSAFE = 12;
+	/**
+	 * Result: the request page number is not valid. It must be an integer greater than 0
+	 */
+	const INVALID_PAGE = 13;
 	/**
 	 * Result: the operation could not be performed, see the message for troubleshooting
 	 */
@@ -1091,10 +1095,12 @@ class RestUtils
 	 * 	 
 	 * @param string $sClass Name of the class
 	 * @param mixed $key Either search criteria (substructure), or an object or an OQL string.
+     * @param int $limit The limit of results to return
+     * @param int $offset The offset of results to return
 	 * @return DBObjectSet The search result set
 	 * @throws Exception If the input structure is not valid
 	 */
-	public static function GetObjectSetFromKey($sClass, $key)
+	public static function GetObjectSetFromKey($sClass, $key, $limit = 0, $offset = 0)
 	{
 		if (is_object($key))
 		{
@@ -1128,7 +1134,7 @@ class RestUtils
 		{
 			throw new Exception("Wrong format for key");
 		}
-		$oObjectSet = new DBObjectSet($oSearch);
+		$oObjectSet = new DBObjectSet($oSearch, array(), array(), null, $limit, $offset);
 		return $oObjectSet;
 	}
 
diff --git a/core/restservices.class.inc.php b/core/restservices.class.inc.php
index 916dd5f72..38852b7fe 100644
--- a/core/restservices.class.inc.php
+++ b/core/restservices.class.inc.php
@@ -436,8 +436,10 @@ class CoreServices implements iRestServiceProvider
 			$key = RestUtils::GetMandatoryParam($aParams, 'key');
 			$aShowFields = RestUtils::GetFieldList($sClass, $aParams, 'output_fields');
 			$bExtendedOutput = (RestUtils::GetOptionalParam($aParams, 'output_fields', '*') == '*+');
+			$limit = (int) RestUtils::GetOptionalParam($aParams, 'limit', 0);
+			$page = (int) RestUtils::GetOptionalParam($aParams, 'page', 1);
 
-			$oObjectSet = RestUtils::GetObjectSetFromKey($sClass, $key);
+			$oObjectSet = RestUtils::GetObjectSetFromKey($sClass, $key, $limit, self::getOffsetFromLimitAndPage($limit, $page));
 			$sTargetClass = $oObjectSet->GetFilter()->GetClass();
 	
 			if (UserRights::IsActionAllowed($sTargetClass, UR_ACTION_READ) != UR_ALLOWED_YES)
@@ -450,6 +452,11 @@ class CoreServices implements iRestServiceProvider
 				$oResult->code = RestResult::UNAUTHORIZED;
 				$oResult->message = "The current user does not have enough permissions for exporting data of class $sTargetClass";
 			}
+			elseif ($page < 1)
+            {
+			    $oResult->code = RestResult::INVALID_PAGE;
+			    $oResult->message = "The request page number is not valid. It must be an integer greater than 0";
+            }
 			else
 			{
 				while ($oObject = $oObjectSet->Fetch())
@@ -774,4 +781,16 @@ class CoreServices implements iRestServiceProvider
 			$oResult->message = $sRes;
 		}
 	}
+
+    /**
+     * Returns the Offset for a given page number
+     *
+     * @param int $limit
+     * @param int $page
+     * @return int
+     */
+	protected static function getOffsetFromLimitAndPage($limit, $page)
+    {
+        return $limit * max(0, $page - 1);
+    }
 }