Added oldestArticle and latestArticle context options

lib/Database.php

@@ -917,7 +917,13 @@ class Database {
             }
             $q->setWhere("exists(select article from arsse_label_members where assigned is 1 and article is arsse_articles.id and label is ?)", "int", $id);
         }
-        // filter based on edition offset
+        // filter based on article or edition offset
+        if ($context->oldestArticle()) {
+            $q->setWhere("arsse_articles.id >= ?", "int", $context->oldestArticle);
+        }
+        if ($context->latestArticle()) {
+            $q->setWhere("arsse_articles.id <= ?", "int", $context->latestArticle);
+        }
         if ($context->oldestEdition()) {
             $q->setWhere("edition >= ?", "int", $context->oldestEdition);
         }

lib/Misc/Context.php

@@ -16,6 +16,8 @@ class Context {
     public $folder;
     public $folderShallow;
     public $subscription;
+    public $oldestArticle;
+    public $latestArticle;
     public $oldestEdition;
     public $latestEdition;
     public $unread = null;
@@ -81,6 +83,14 @@ class Context {
         return $this->act(__FUNCTION__, func_num_args(), $spec);
     }
     
+    public function latestArticle(int $spec = null) {
+        return $this->act(__FUNCTION__, func_num_args(), $spec);
+    }
+    
+    public function oldestArticle(int $spec = null) {
+        return $this->act(__FUNCTION__, func_num_args(), $spec);
+    }
+    
     public function latestEdition(int $spec = null) {
         return $this->act(__FUNCTION__, func_num_args(), $spec);
     }

tests/Misc/TestContext.php

@@ -32,6 +32,8 @@ class TestContext extends Test\AbstractTest {
             'subscription' => 2112,
             'article' => 255,
             'edition' => 65535,
+            'latestArticle' => 47,
+            'oldestArticle' => 1337,
             'latestEdition' => 47,
             'oldestEdition' => 1337,
             'unread' => true,

tests/lib/Database/SeriesArticle.php

@@ -411,6 +411,9 @@ trait SeriesArticle {
         $this->compareIds([19], (new Context)->subscription(5)->latestEdition(19));
         $this->compareIds([20], (new Context)->subscription(5)->oldestEdition(999));
         $this->compareIds([20], (new Context)->subscription(5)->oldestEdition(1001));
+        // get items relative to article ID
+        $this->compareIds([1,2,3], (new Context)->latestArticle(3));
+        $this->compareIds([19,20], (new Context)->oldestArticle(19));
         // get items relative to (feed) modification date
         $exp = [2,4,6,8,20];
         $this->compareIds($exp, (new Context)->modifiedSince("2005-01-01T00:00:00Z"));