Implement part of adaptive update interval; improves #51

Implements part of algorithm used when a feed has not been updated; this is much simpler than when a feed has been modified

lib/Database.php

@@ -517,10 +517,9 @@ class Database {
         try {
             if(is_null($articleID)) {
                 $articleID = $this->db->prepare(
-                    'INSERT INTO arsse_articles(feed,url,title,author,published,edited,guid,content,url_title_hash,url_content_hash,title_content_hash) values(?,?,?,?,?,?,?,?,?,?,?)',
-                    'int', 'str', 'str', 'str', 'datetime', 'datetime', 'str', 'str', 'str', 'str', 'str'
+                    'INSERT INTO arsse_articles(url,title,author,published,edited,guid,content,url_title_hash,url_content_hash,title_content_hash,feed) values(?,?,?,?,?,?,?,?,?,?,?)',
+                    'str', 'str', 'str', 'datetime', 'datetime', 'str', 'str', 'str', 'str', 'str', 'int'
                 )->run(
-                    $feedID,
                     $article->url,
                     $article->title,
                     $article->author,
@@ -530,7 +529,8 @@ class Database {
                     $article->content,
                     $article->urlTitleHash,
                     $article->urlContentHash,
-                    $article->titleContentHash
+                    $article->titleContentHash,
+                    $feedID
                 )->lastId();
             } else {
                 $this->db->prepare(
@@ -553,7 +553,7 @@ class Database {
             // If the article has categories add them into the categories database.
             $this->db->prepare('DELETE FROM arsse_categories WHERE article is ?', 'int')->run($articleID);
             $this->categoriesAdd($articleID, $article);
-            // increease the article edition ID
+            // add a new article edition ID
             $this->db->prepare('INSERT INTO arse_editions(article) values(?)', 'int')->run($articleID);
         } catch(\Throwable $e) {
             $this->db->rollback();

lib/Feed.php

@@ -12,6 +12,8 @@ class Feed {
     public $parser;
     public $reader;
     public $resource;
+    public $modified = false;
+    public $lastModified = null;
     public $newItems = [];
     public $changedItems = [];
 
@@ -23,6 +25,11 @@ class Feed {
 
             $this->reader = new Reader($config);
             $this->resource = $this->reader->download($url, $lastModified, $etag, $username, $password);
+            $lastMod = $this->resource->getLastModified();
+            if(strlen($lastMod)) {
+                $this->$lastModified = \DateTime::createFromFormat("!D, d M Y H:i:s e", $lastMod);
+            }
+            $this->modified = $this->resource->isModified();
         } catch (PicoFeedException $e) {
             throw new Feed\Exception($url, $e);
         }
@@ -218,4 +225,29 @@ class Feed {
         }
         return true;
     }
+
+    public function nextFetch(): \DateTime {
+        if(!$this->modified) {
+            $now = time();
+            $diff = $now - $this->lastModified->getTimestamp();
+            if($diff < (30 * 60)) { // less than 30 minutes
+                $offset = "15 minutes";
+            } else if($diff < (60 * 60)) { // less than an hour
+                $offset = "30 minutes";
+            } else if($diff < (3 * 60 * 60)) { // less than three hours
+                $offset = "1 hour";
+            } else if($diff > (36 * 60 * 60)) { // more than 36 hours
+                $offset = "1 day";
+            } else {
+                $offset = "3 hours";
+            }
+            $t = new \DateTime();
+            $t->setTimestamp($now);
+            $t->modify("+".$offset);
+            return $t;
+        } else {
+            // FIXME: implement algorithm to use when a feed has been updated
+            return new \DateTime("now + 3 hours");
+        }
+    }
 }