Add a function to get when feeds were last updated

This is an optimization for Fever, which returns this information with
every API call.

lib/Database.php

@@ -10,7 +10,6 @@ use JKingWeb\DrUUID\UUID;
 use JKingWeb\Arsse\Db\Statement;
 use JKingWeb\Arsse\Misc\Query;
 use JKingWeb\Arsse\Context\Context;
-use JKingWeb\Arsse\Context\ExclusionContext;
 use JKingWeb\Arsse\Misc\Date;
 use JKingWeb\Arsse\Misc\ValueInfo;
 
@@ -751,6 +750,8 @@ class Database {
                 arsse_subscriptions.feed as feed,
                 url,favicon,source,folder,pinned,err_count,err_msg,order_type,added,
                 arsse_feeds.updated as updated,
+                arsse_feeds.modified as edited,
+                arsse_subscriptions.modified as modified,
                 topmost.top as top_folder,
                 coalesce(arsse_subscriptions.title, arsse_feeds.title) as title,
                 (articles - marked) as unread
@@ -946,6 +947,23 @@ class Database {
         return (string) $this->db->prepare($q->getQuery(), $q->getTypes())->run($q->getValues())->getValue();
     }
 
+    /** Returns the time at which any of a user's subscriptions (or a specific subscription) was last refreshed, as a DateTimeImmutable object */
+    public function subscriptionRefreshed(string $user, int $id = null) {
+        if (!Arsse::$user->authorize($user, __FUNCTION__)) {
+            throw new User\ExceptionAuthz("notAuthorized", ["action" => __FUNCTION__, "user" => $user]);
+        }
+        $q = new Query("SELECT max(arsse_feeds.updated) from arsse_feeds join arsse_subscriptions on arsse_subscriptions.feed = arsse_feeds.id");
+        $q->setWhere("arsse_subscriptions.owner = ?", "str", $user);
+        if ($id) {
+            $q->setWhere("arsse_subscriptions.id = ?", "int", $id);
+        }
+        $out = $this->db->prepare($q->getQuery(), $q->getTypes())->run($q->getValues())->getValue();
+        if (!$out && $id) {
+            throw new Db\ExceptionInput("subjectMissing", ["action" => __FUNCTION__, "field" => "feed", 'id' => $id]);
+        }
+        return ValueInfo::normalize($out, ValueInfo::T_DATE | ValueInfo::M_NULL, "sql");
+    }
+
     /** Ensures the specified subscription exists and raises an exception otherwise
      * 
      * Returns an associative array containing the id of the subscription and the id of the underlying newsfeed

tests/cases/Database/SeriesSubscription.php

@@ -47,6 +47,7 @@ trait SeriesSubscription {
                     'title'      => "str",
                     'username'   => "str",
                     'password'   => "str",
+                    'updated'    => "datetime",
                     'next_fetch' => "datetime",
                     'favicon'    => "str",
                 ],
@@ -134,9 +135,9 @@ trait SeriesSubscription {
             ],
         ];
         $this->data['arsse_feeds']['rows'] = [
-            [1,"http://example.com/feed1", "Ook", "", "",strtotime("now"),''],
-            [2,"http://example.com/feed2", "eek", "", "",strtotime("now - 1 hour"),'http://example.com/favicon.ico'],
-            [3,"http://example.com/feed3", "Ack", "", "",strtotime("now + 1 hour"),''],
+            [1,"http://example.com/feed1", "Ook", "", "",strtotime("now"),strtotime("now"),''],
+            [2,"http://example.com/feed2", "eek", "", "",strtotime("now - 1 hour"),strtotime("now - 1 hour"),'http://example.com/favicon.ico'],
+            [3,"http://example.com/feed3", "Ack", "", "",strtotime("now + 1 hour"),strtotime("now + 1 hour"),''],
         ];
         // initialize a partial mock of the Database object to later manipulate the feedUpdate method
         Arsse::$db = Phake::partialMock(Database::class, static::$drv);
@@ -491,4 +492,21 @@ trait SeriesSubscription {
         $this->assertException("notAuthorized", "User", "ExceptionAuthz");
         Arsse::$db->subscriptionTagsGet("john.doe@example.com", 1);
     }
+
+    public function testGetRefreshTimeOfASubscription() {
+        $user = "john.doe@example.com";
+        $this->assertTime(strtotime("now + 1 hour"), Arsse::$db->subscriptionRefreshed($user));
+        $this->assertTime(strtotime("now - 1 hour"), Arsse::$db->subscriptionRefreshed($user, 1));
+    }
+
+    public function testGetRefreshTimeOfAMissingSubscription() {
+        $this->assertException("subjectMissing", "Db", "ExceptionInput");
+        $this->assertTime(strtotime("now - 1 hour"), Arsse::$db->subscriptionRefreshed("john.doe@example.com", 2));
+    }
+
+    public function testGetRefreshTimeOfASubscriptionWithoutAuthority() {
+        Phake::when(Arsse::$user)->authorize->thenReturn(false);
+        $this->assertException("notAuthorized", "User", "ExceptionAuthz");
+        $this->assertTime(strtotime("now + 1 hour"), Arsse::$db->subscriptionRefreshed("john.doe@example.com"));
+    }
 }