INSTALLING.md

@@ -43,3 +43,12 @@ Data is stored under the `/src/data` directory, and the default database name is
 ### Date/Time Format
 
 The default format for dates and times look like "May 28, 2023 at 3:15pm". Changing the string there will alter the display on the main page and when reading an item. Any [supported PHP date or time token](https://www.php.net/manual/en/datetime.format.php) is supported.
+
+### Item Purging
+
+Feed Reader Central tries to keep the database tidy by purging items that have been read and are no longer required. There are four variants:
+- `Feed::PURGE_NONE` does no purging (items have a "Delete" button, so they may be deleted manually) 
+- `Feed::PURGE_READ` purges non-bookmarked read items for a feed whenever it is refreshed. This is the most aggressive purging strategy, but it is also the only one that will not purge unread items.
+- `Feed::PURGE_BY_DAYS` purges non-bookmarked items that are older than `PURGE_NUMBER` days old. This is the default value, and `PURGE_NUMBER`'s default value is 30; items will be kept for 30 days, read or unread.
+- `Feed::PURGE_BY_COUNT` purges items to preserve at most `PURGE_NUMBER` non-bookmarked items for each feed.
+ 

src/app-config.php

@@ -1,7 +1,7 @@
 <?php
 
 /** The current Feed Reader Central version */
-const FRC_VERSION = '1.0.0-alpha4';
+const FRC_VERSION = '1.0.0-alpha5';
 
 spl_autoload_register(function ($class) {
     $file = implode(DIRECTORY_SEPARATOR, [__DIR__, 'lib', "$class.php"]);
@@ -15,3 +15,6 @@ spl_autoload_register(function ($class) {
 require 'user-config.php';
 
 Data::ensureDb();
+
+/** @var string The date the world wide web was created */
+const WWW_EPOCH = '1993-04-30T00:00:00+00:00';

src/lib/Data.php

@@ -98,4 +98,14 @@ class Data {
             if (is_null($dbConn)) $db->close();
         }
     }
+
+    /**
+     * Return the last SQLite error message as a result array
+     *
+     * @param SQLite3 $db The database connection on which the error has occurred
+     * @return string[] ['error' => message] for last SQLite error message
+     */
+    public static function error(SQLite3 $db): array {
+        return ['error' => 'SQLite error: ' . $db->lastErrorMsg()];
+    }
 }

src/lib/Feed.php

@@ -1,84 +1,5 @@
 <?php
 
-/**
- * Information for a feed item
- */
-class FeedItem {
-
-    /** @var string The title of the feed item */
-    public string $title = '';
-
-    /** @var string The unique ID for the feed item */
-    public string $guid = '';
-
-    /** @var string The link to the original content */
-    public string $link = '';
-
-    /** @var string When this item was published */
-    public string $publishedOn = '';
-
-    /** @var ?string When this item was last updated */
-    public ?string $updatedOn = null;
-
-    /** @var string The content for the item */
-    public string $content = '';
-
-    /**
-     * Construct a feed item from an Atom feed's `<entry>` tag
-     *
-     * @param DOMNode $node The XML node from which a feed item should be constructed
-     * @return FeedItem A feed item constructed from the given node
-     */
-    public static function fromAtom(DOMNode $node): FeedItem {
-        $guid = Feed::atomValue($node, 'id');
-        $link = '';
-        foreach ($node->getElementsByTagName('link') as $linkElt) {
-            if ($linkElt->hasAttributes()) {
-                $relAttr = $linkElt->attributes->getNamedItem('rel');
-                if ($relAttr && $relAttr->value == 'alternate') {
-                    $link = $linkElt->attributes->getNamedItem('href')->value;
-                    break;
-                }
-            }
-        }
-        if ($link == '' && str_starts_with($guid, 'http')) $link = $guid;
-
-        $item              = new FeedItem();
-        $item->guid        = $guid;
-        $item->title       = Feed::atomValue($node, 'title');
-        $item->link        = $link;
-        $item->publishedOn = Data::formatDate(Feed::atomValue($node, 'published'));
-        $item->updatedOn   = Data::formatDate(Feed::atomValue($node, 'updated'));
-        $item->content     = Feed::atomValue($node, 'content');
-
-        return $item;
-    }
-
-    /**
-     * Construct a feed item from an RSS feed's `<item>` tag
-     *
-     * @param DOMNode $node The XML node from which a feed item should be constructed
-     * @return FeedItem A feed item constructed from the given node
-     */
-    public static function fromRSS(DOMNode $node): FeedItem {
-        $itemGuid = Feed::rssValue($node, 'guid');
-        $updNodes = $node->getElementsByTagNameNS(Feed::ATOM_NS,    'updated');
-        $encNodes = $node->getElementsByTagNameNS(Feed::CONTENT_NS, 'encoded');
-
-        $item              = new FeedItem();
-        $item->guid        = $itemGuid == 'guid not found' ? Feed::rssValue($node, 'link') : $itemGuid;
-        $item->title       = Feed::rssValue($node, 'title');
-        $item->link        = Feed::rssValue($node, 'link');
-        $item->publishedOn = Data::formatDate(Feed::rssValue($node, 'pubDate'));
-        $item->updatedOn   = Data::formatDate($updNodes->length > 0 ? $updNodes->item(0)->textContent : null);
-        $item->content     = $encNodes->length > 0
-            ? $encNodes->item(0)->textContent
-            : Feed::rssValue($node, 'description');
-
-        return $item;
-    }
-}
-
 /**
  * Feed retrieval, parsing, and manipulation
  */
@@ -105,6 +26,22 @@ class Feed {
     /** @var string The XML namespace for XHTML */
     public const string XHTML_NS = 'http://www.w3.org/1999/xhtml';
 
+    /** @var string The user agent for Feed Reader Central's refresh requests */
+    private const string USER_AGENT =
+        'FeedReaderCentral/' . FRC_VERSION . ' +https://bitbadger.solutions/open-source/feed-reader-central';
+
+    /** @var int Do not purge items */
+    public const int PURGE_NONE = 0;
+
+    /** @var int Purge all read items (will not purge unread items) */
+    public const int PURGE_READ = 1;
+
+    /** @var int Purge items older than the specified number of days */
+    public const int PURGE_BY_DAYS = 2;
+
+    /** @var int Purge items in number greater than the specified number of items to keep */
+    public const int PURGE_BY_COUNT = 3;
+
     /**
      * When parsing XML into a DOMDocument, errors are presented as warnings; this creates an exception for them
      *
@@ -114,7 +51,7 @@ class Feed {
      * @throws DOMException If the error is a warning
      */
     private static function xmlParseError(int $errno, string $errstr): bool {
-        if ($errno == E_WARNING && substr_count($errstr, 'DOMDocument::loadXml()') > 0) {
+        if ($errno == E_WARNING && substr_count($errstr, 'DOMDocument::loadXML()') > 0) {
             throw new DOMException($errstr, $errno);
         }
         return false;
@@ -161,15 +98,16 @@ class Feed {
     private static function fromRSS(DOMDocument $xml, string $url): array {
         $channel = $xml->getElementsByTagName('channel')->item(0);
         if (!($channel instanceof DOMElement)) {
-            return ['error' => "Channel element not found ($channel->nodeType)"];
+            $type = $channel?->nodeType ?? -1;
+            return ['error' => "Channel element not found ($type)"];
         }
 
         // The Atom namespace provides a lastBuildDate, which contains the last time an item in the feed was updated; if
         // that is not present, use the pubDate element instead
-        $updatedOn = self::rssValue($channel, 'lastBuildDate');
-        if ($updatedOn == 'lastBuildDate not found') {
-            $updatedOn = self::rssValue($channel, 'pubDate');
-            if ($updatedOn == 'pubDate not found') $updatedOn = null;
+        if (($updatedOn = self::rssValue($channel, 'lastBuildDate')) == 'lastBuildDate not found') {
+            if (($updatedOn = self::rssValue($channel, 'pubDate')) == 'pubDate not found') {
+                $updatedOn = null;
+            }
         }
 
         $feed            = new Feed();
@@ -181,6 +119,17 @@ class Feed {
         return ['ok' => $feed];
     }
 
+    /**
+     * Get an attribute value from a DOM node
+     *
+     * @param DOMNode $node The node with an attribute value to obtain
+     * @param string $name The name of the attribute whose value should be obtained
+     * @return string The attribute value if it exists, an empty string if not
+     */
+    private static function attrValue(DOMNode $node, string $name): string {
+        return ($node->hasAttributes() ? $node->attributes->getNamedItem($name)?->value : null) ?? '';
+
+    }
     /**
      * Get the value of a child element by its tag name for an Atom feed
      *
@@ -196,7 +145,7 @@ class Feed {
         if ($tags->length == 0) return "$tagName not found";
         $tag = $tags->item(0);
         if (!($tag instanceof DOMElement)) return $tag->textContent;
-        if ($tag->hasAttributes() && $tag->attributes->getNamedItem('type') == 'xhtml') {
+        if (self::attrValue($tag, 'type') == 'xhtml') {
             $div = $tag->getElementsByTagNameNS(Feed::XHTML_NS, 'div');
             if ($div->length == 0) return "-- invalid XHTML content --";
             return $div->item(0)->textContent;
@@ -212,9 +161,8 @@ class Feed {
      * @return array|Feed[] ['ok' => feed]
      */
     private static function fromAtom(DOMDocument $xml, string $url): array {
-        $root      = $xml->getElementsByTagNameNS(self::ATOM_NS, 'feed')->item(0);
-        $updatedOn = self::atomValue($root, 'updated');
-        if ($updatedOn == 'pubDate not found') $updatedOn = null;
+        $root = $xml->getElementsByTagNameNS(self::ATOM_NS, 'feed')->item(0);
+        if (($updatedOn = self::atomValue($root, 'updated')) == 'pubDate not found') $updatedOn = null;
 
         $feed            = new Feed();
         $feed->title     = self::atomValue($root, 'title');
@@ -225,6 +173,55 @@ class Feed {
         return ['ok' => $feed];
     }
 
+    /**
+     * Retrieve a document (http/https)
+     *
+     * @param string $url The URL of the document to retrieve
+     * @return array ['content' => document content, 'error' => error message, 'code' => HTTP response code,
+     *      'url' => effective URL]
+     */
+    private static function retrieveDocument(string $url): array {
+        $docReq = curl_init($url);
+        curl_setopt($docReq, CURLOPT_FOLLOWLOCATION, true);
+        curl_setopt($docReq, CURLOPT_RETURNTRANSFER, true);
+        curl_setopt($docReq, CURLOPT_CONNECTTIMEOUT, 5);
+        curl_setopt($docReq, CURLOPT_TIMEOUT,        15);
+        curl_setopt($docReq, CURLOPT_USERAGENT,      self::USER_AGENT);
+
+        $result = [
+            'content' => curl_exec($docReq),
+            'error'   => curl_error($docReq),
+            'code'    => curl_getinfo($docReq, CURLINFO_RESPONSE_CODE),
+            'url'     => curl_getinfo($docReq, CURLINFO_EFFECTIVE_URL)
+        ];
+
+        curl_close($docReq);
+        return $result;
+    }
+
+    /**
+     * Derive a feed URL from an HTML document
+     *
+     * @param string $content The HTML document content from which to derive a feed URL
+     * @return array|string[] ['ok' => feed URL] if successful, ['error' => message] if not
+     */
+    private static function deriveFeedFromHTML(string $content): array {
+        $html = new DOMDocument();
+        $html->loadHTML(substr($content, 0, strpos($content, '</head>') + 7));
+        $headTags = $html->getElementsByTagName('head');
+        if ($headTags->length < 1) return ['error' => 'Cannot find feed at this URL'];
+        $head = $headTags->item(0);
+        foreach ($head->getElementsByTagName('link') as $link) {
+            if (self::attrValue($link, 'rel') == 'alternate') {
+                $type = self::attrValue($link, 'type');
+                if ($type == 'application/rss+xml' || $type == 'application/atom+xml') {
+                    return ['ok' => self::attrValue($link, 'href')];
+                }
+            }
+        }
+        return ['error' => 'Cannot find feed at this URL'];
+    }
+
     /**
      * Retrieve the feed
      *
@@ -232,34 +229,33 @@ class Feed {
      * @return array|Feed[]|string[] ['ok' => feed] if successful, ['error' => message] if not
      */
     public static function retrieveFeed(string $url): array {
-        $feedReq = curl_init($url);
-        curl_setopt($feedReq, CURLOPT_FOLLOWLOCATION, true);
-        curl_setopt($feedReq, CURLOPT_RETURNTRANSFER, true);
-        curl_setopt($feedReq, CURLOPT_CONNECTTIMEOUT, 5);
-        curl_setopt($feedReq, CURLOPT_TIMEOUT,        15);
+        $doc = self::retrieveDocument($url);
 
-        $feedContent = curl_exec($feedReq);
-
-        $result = array();
-        $error  = curl_error($feedReq);
-        $code   = curl_getinfo($feedReq, CURLINFO_RESPONSE_CODE);
-        if ($error) {
-            $result['error'] = $error;
-        } elseif ($code == 200) {
-            $parsed = self::parseFeed($feedContent);
-            if (array_key_exists('error', $parsed)) {
-                $result['error'] = $parsed['error'];
-            } else {
-                $extract = $parsed['ok']->getElementsByTagNameNS(self::ATOM_NS, 'feed')->length > 0
-                    ? self::fromAtom(...) : self::fromRSS(...);
-                $result  = $extract($parsed['ok'], curl_getinfo($feedReq, CURLINFO_EFFECTIVE_URL));
-            }
-        } else {
-            $result['error'] = "Prospective feed URL $url returned HTTP Code $code: $feedContent";
+        if ($doc['error'] != '') return ['error' => $doc['error']];
+        if ($doc['code'] != 200) {
+            return ['error' => "Prospective feed URL $url returned HTTP Code {$doc['code']}: {$doc['content']}"];
         }
 
-        curl_close($feedReq);
-        return $result;
+        $start = strtolower(strlen($doc['content']) >= 9 ? substr($doc['content'], 0, 9) : $doc['content']);
+        if ($start == '<!doctype' || str_starts_with($start, '<html')) {
+            $derivedURL = self::deriveFeedFromHTML($doc['content']);
+            if (array_key_exists('error', $derivedURL)) return ['error' => $derivedURL['error']];
+            $feedURL = $derivedURL['ok'];
+            if (!str_starts_with($feedURL, 'http')) {
+                // Relative URL; feed should be retrieved in the context of the original URL
+                $original = parse_url($url);
+                $port     = array_key_exists('port', $original) ? ":{$original['port']}" : '';
+                $feedURL  = $original['scheme'] . '://' . $original['host'] . $port . $feedURL;
+            }
+            $doc = self::retrieveDocument($feedURL);
+        }
+
+        $parsed = self::parseFeed($doc['content']);
+        if (array_key_exists('error', $parsed)) return ['error' => $parsed['error']];
+
+        $extract = $parsed['ok']->getElementsByTagNameNS(self::ATOM_NS, 'feed')->length > 0
+            ? self::fromAtom(...) : self::fromRSS(...);
+        return $extract($parsed['ok'], $doc['url']);
     }
 
     /**
@@ -268,8 +264,9 @@ class Feed {
      * @param int $itemId The ID of the item to be updated
      * @param FeedItem $item The item to be updated
      * @param SQLite3 $db A database connection to use for the update
+     * @return bool|SQLite3Result The result if the update is successful, false if it failed
      */
-    private static function updateItem(int $itemId, FeedItem $item, SQLite3 $db): void {
+    private static function updateItem(int $itemId, FeedItem $item, SQLite3 $db): bool|SQLite3Result {
         $query = $db->prepare(<<<'SQL'
             UPDATE item
                SET title        = :title,
@@ -284,7 +281,7 @@ class Feed {
         $query->bindValue(':updated',   $item->updatedOn);
         $query->bindValue(':content',   $item->content);
         $query->bindValue(':id',        $itemId);
-        $query->execute();
+        return $query->execute();
     }
 
     /**
@@ -293,8 +290,9 @@ class Feed {
      * @param int $feedId The ID of the feed to which the item should be added
      * @param FeedItem $item The item to be added
      * @param SQLite3 $db A database connection to use for the addition
+     * @return bool|SQLite3Result The result if the update is successful, false if it failed
      */
-    private static function addItem(int $feedId, FeedItem $item, SQLite3 $db): void {
+    private static function addItem(int $feedId, FeedItem $item, SQLite3 $db): bool|SQLite3Result {
         $query = $db->prepare(<<<'SQL'
             INSERT INTO item (
                 feed_id, item_guid, item_link, title, published_on, updated_on, content
@@ -309,7 +307,7 @@ class Feed {
         $query->bindValue(':published', $item->publishedOn);
         $query->bindValue(':updated',   $item->updatedOn);
         $query->bindValue(':content',   $item->content);
-        $query->execute();
+        return $query->execute();
     }
 
     /**
@@ -317,56 +315,90 @@ class Feed {
      *
      * @param int $feedId The ID of the feed to which these items belong
      * @param Feed $feed The extracted Atom or RSS feed items
+     * @param DateTimeInterface $lastChecked When this feed was last checked (only new items will be added)
      * @return array ['ok' => true] if successful, ['error' => message] if not
      */
-    public static function updateItems(int $feedId, Feed $feed, SQLite3 $db): array {
-        try {
-            foreach ($feed->items as $item) {
+    public static function updateItems(int $feedId, Feed $feed, DateTimeInterface $lastChecked, SQLite3 $db): array {
+        $results =
+            array_map(function ($item) use ($db, $feedId) {
                 $existsQuery = $db->prepare(
                     'SELECT id, published_on, updated_on FROM item WHERE feed_id = :feed AND item_guid = :guid');
                 $existsQuery->bindValue(':feed', $feedId);
                 $existsQuery->bindValue(':guid', $item->guid);
-                $exists = $existsQuery->execute();
-                if ($exists) {
-                    $existing = $exists->fetchArray(SQLITE3_ASSOC);
-                    if ($existing) {
+                if ($exists = $existsQuery->execute()) {
+                    if ($existing = $exists->fetchArray(SQLITE3_ASSOC)) {
                         if (   $existing['published_on']       != $item->publishedOn
                             || ($existing['updated_on'] ?? '') != ($item->updatedOn ?? '')) {
-                            self::updateItem($existing['id'], $item, $db);
+                            if (!self::updateItem($existing['id'], $item, $db)) return Data::error($db);
                         }
                     } else {
-                        self::addItem($feedId, $item, $db);
+                        if (!self::addItem($feedId, $item, $db)) return Data::error($db);
                     }
                 } else {
-                    throw new Exception($db->lastErrorMsg());
+                    return Data::error($db);
                 }
+                return ['ok' => true];
+            }, array_filter($feed->items,
+                fn($it) => date_create_immutable($it->updatedOn ?? $it->publishedOn) >= $lastChecked));
+        $errors = array_map(fn($it) => $it['error'], array_filter($results, fn($it) => array_key_exists('error', $it)));
+        return sizeof($errors) > 0 ? ['error' => implode("\n", $errors)] : ['ok' => true];
+    }
+
+    /**
+     * Purge items for a feed
+     *
+     * @param int $feedId The ID of the feed to be purged
+     * @param SQLite3 $db The database connection on which items should be purged
+     * @return array|string[]|true[] ['ok' => true] if purging was successful, ['error' => message] if not
+     */
+    private static function purgeItems(int $feedId, SQLite3 $db): array {
+        if (!array_search(PURGE_TYPE, [self::PURGE_READ, self::PURGE_BY_DAYS, self::PURGE_BY_COUNT])) {
+            return ['error' => 'Unrecognized purge type ' . PURGE_TYPE];
+        }
+
+        try {
+            $sql = match (PURGE_TYPE) {
+                self::PURGE_READ     => 'AND is_read = 1',
+                self::PURGE_BY_DAYS  => 'AND date(coalesce(updated_on, published_on)) < date(:oldest)',
+                self::PURGE_BY_COUNT => 'AND id IN (SELECT id FROM item WHERE feed_id = :feed
+                                         ORDER BY date(coalesce(updated_on, published_on)) DESC
+                                         LIMIT -1 OFFSET :keep)'
+            };
+
+            $purge = $db->prepare("DELETE FROM item WHERE feed_id = :feed AND is_bookmarked = 0 $sql");
+            $purge->bindValue(':feed', $feedId);
+            if (PURGE_TYPE == self::PURGE_BY_DAYS) {
+                $purge->bindValue(':oldest', Data::formatDate('-' . PURGE_NUMBER . ' day'));
+            } elseif (PURGE_TYPE == self::PURGE_BY_COUNT) {
+                $purge->bindValue(':keep', PURGE_NUMBER);
             }
+            return $purge->execute() ? ['ok' => true] : Data::error($db);
         } catch (Exception $ex) {
             return ['error' => $ex->getMessage()];
         }
-        return ['ok', true];
     }
 
     /**
      * Refresh a feed
      *
+     * @param int $feedId The ID of the feed to be refreshed
      * @param string $url The URL of the feed to be refreshed
      * @param SQLite3 $db A database connection to use to refresh the feed
      * @return array|string[]|true[] ['ok' => true] if successful, ['error' => message] if not
      */
-    private static function refreshFeed(string $url, SQLite3 $db): array {
-        $feedQuery = $db->prepare('SELECT id FROM feed WHERE url = :url AND user_id = :user');
-        $feedQuery->bindValue(':url',  $url);
-        $feedQuery->bindValue(':user', $_SESSION[Key::USER_ID]);
-        $feedResult = $feedQuery->execute();
-        $feedId = $feedResult ? $feedResult->fetchArray(SQLITE3_NUM)[0] : -1;
-        if ($feedId < 0) return ['error' => "No feed for URL $url found"];
+    public static function refreshFeed(int $feedId, string $url, SQLite3 $db): array {
+        $feedRetrieval = self::retrieveFeed($url);
+        if (array_key_exists('error', $feedRetrieval)) return $feedRetrieval;
+        $feed = $feedRetrieval['ok'];
 
-        $feedExtract = self::retrieveFeed($url);
-        if (array_key_exists('error', $feedExtract)) return $feedExtract;
+        $lastCheckedQuery = $db->prepare('SELECT checked_on FROM feed where id = :id');
+        $lastCheckedQuery->bindValue(':id', $feedId);
+        if (!($lastCheckedResult = $lastCheckedQuery->execute())) return Data::error($db);
+        if (!($lastChecked = date_create_immutable($lastCheckedResult->fetchArray(SQLITE3_NUM)[0] ?? WWW_EPOCH))) {
+            return ['error' => 'Could not derive date last checked for feed'];
+        }
 
-        $feed = $feedExtract['ok'];
-        $itemUpdate = self::updateItems($feedId, $feed, $db);
+        $itemUpdate = self::updateItems($feedId, $feed, $lastChecked, $db);
         if (array_key_exists('error', $itemUpdate)) return $itemUpdate;
 
         $urlUpdate = $url == $feed->url ? '' : ', url = :url';
@@ -383,9 +415,9 @@ class Feed {
         $feedUpdate->bindValue(':checked', Data::formatDate('now'));
         $feedUpdate->bindValue(':id',      $feedId);
         if ($urlUpdate != '') $feedUpdate->bindValue(':url', $feed->url);
-        $feedUpdate->execute();
+        if (!$feedUpdate->execute()) return Data::error($db);
 
-        return ['ok' => true];
+        return PURGE_TYPE == self::PURGE_NONE ? ['ok' => true] : self::purgeItems($feedId, $db);
     }
 
     /**
@@ -398,22 +430,30 @@ class Feed {
         $feedExtract = self::retrieveFeed($url);
         if (array_key_exists('error', $feedExtract)) return $feedExtract;
 
-        $feed  = $feedExtract['ok'];
+        $feed = $feedExtract['ok'];
+
+        $existsQuery = $db->prepare('SELECT COUNT(*) FROM feed WHERE user_id = :user AND url = :url');
+        $existsQuery->bindValue(':user', $_SESSION[Key::USER_ID]);
+        $existsQuery->bindValue(':url',  $feed->url);
+        if (!($exists = $existsQuery->execute()))    return Data::error($db);
+        if ($exists->fetchArray(SQLITE3_NUM)[0] > 0) return ['error' => "Already subscribed to feed $feed->url"];
+
         $query = $db->prepare(<<<'SQL'
-            INSERT INTO feed (user_id, url, title, updated_on, checked_on)
-            VALUES (:user, :url, :title, :updated, :checked)
+            INSERT INTO feed (
+                user_id, url, title, updated_on, checked_on
+            ) VALUES (
+                :user, :url, :title, :updated, :checked
+            )
             SQL);
         $query->bindValue(':user',    $_SESSION[Key::USER_ID]);
         $query->bindValue(':url',     $feed->url);
         $query->bindValue(':title',   $feed->title);
         $query->bindValue(':updated', $feed->updatedOn);
         $query->bindValue(':checked', Data::formatDate('now'));
-        $result = $query->execute();
+        if (!$query->execute()) return Data::error($db);
 
-        $feedId = $result ? $db->lastInsertRowID() : -1;
-        if ($feedId < 0) return ['error' => $db->lastErrorMsg()];
-
-        $result = self::updateItems($feedId, $feed, $db);
+        $feedId = $db->lastInsertRowID();
+        $result = self::updateItems($feedId, $feed, date_create_immutable(WWW_EPOCH), $db);
         if (array_key_exists('error', $result)) return $result;
 
         return ['ok' => $feedId];
@@ -432,31 +472,46 @@ class Feed {
         $query->bindValue(':url',  $url);
         $query->bindValue(':id',   $existing['id']);
         $query->bindValue(':user', $_SESSION[Key::USER_ID]);
-        $query->execute();
+        if (!$query->execute()) return Data::error($db);
 
-        return self::refreshFeed($url, $db);
+        return self::refreshFeed($existing['id'], $url, $db);
+    }
+
+    /**
+     * Retrieve all feeds, optionally for a specific user
+     *
+     * @param SQLite3 $db The database connection to use to retrieve the feeds
+     * @param int $user The ID of the user whose feeds should be retrieved (optional, defaults to all feeds)
+     * @return array An array of arrays with ['id', 'url', 'email'] keys
+     */
+    public static function retrieveAll(SQLite3 $db, int $user = 0): array {
+        $extraSQL = $user > 0 ? ' WHERE u.id = :user' : '';
+        $query = $db->prepare(
+            "SELECT f.id, f.url, u.email FROM feed f INNER JOIN frc_user u ON u.id = f.user_id$extraSQL");
+        if ($user > 0) $query->bindValue(':user', $user);
+        if (!($result = $query->execute())) return Data::error($db);
+        $feeds = [];
+        while ($feed = $result->fetchArray(SQLITE3_ASSOC)) $feeds[] = $feed;
+        return $feeds;
     }
 
     /**
      * Refresh all feeds
      *
      * @param SQLite3 $db The database connection to use for refreshing feeds
-     * @return array|true[] ['ok => true] if successful, ['error' => message] if not (may have multiple error lines)
+     * @return array|true[]|string[] ['ok' => true] if successful,
+     *      ['error' => message] if not (may have multiple error lines)
      */
     public static function refreshAll(SQLite3 $db): array {
-        $query = $db->prepare('SELECT url FROM feed WHERE user_id = :user');
-        $query->bindValue(':user', $_SESSION[Key::USER_ID]);
-        $result = $query->execute();
-        $url    = $result ? $result->fetchArray(SQLITE3_NUM) : false;
-        if ($url) {
-            $errors = array();
-            while ($url) {
-                $updateResult = self::refreshFeed($url[0], $db);
-                if (array_key_exists('error', $updateResult)) $errors[] = $updateResult['error'];
-                $url = $result->fetchArray(SQLITE3_NUM);
-            }
-            return sizeof($errors) == 0 ? ['ok' => true] : ['error' => implode("\n", $errors)];
-        }
-        return ['error' => $db->lastErrorMsg()];
+        $feeds = self::retrieveAll($db, $_SESSION[Key::USER_ID]);
+        if (array_key_exists('error', $feeds)) return $feeds;
+
+        $errors = [];
+        array_walk($feeds, function ($feed) use ($db, &$errors) {
+            $result = self::refreshFeed($feed['id'], $feed['url'], $db);
+            if (array_key_exists('error', $result)) $errors[] = $result['error'];
+        });
+
+        return sizeof($errors) == 0 ? ['ok' => true] : ['error' => implode("\n", $errors)];
     }
 }

src/lib/FeedItem.php

@@ -0,0 +1,80 @@
+<?php
+
+/**
+ * Information for a feed item
+ */
+class FeedItem {
+
+    /** @var string The title of the feed item */
+    public string $title = '';
+
+    /** @var string The unique ID for the feed item */
+    public string $guid = '';
+
+    /** @var string The link to the original content */
+    public string $link = '';
+
+    /** @var string When this item was published */
+    public string $publishedOn = '';
+
+    /** @var ?string When this item was last updated */
+    public ?string $updatedOn = null;
+
+    /** @var string The content for the item */
+    public string $content = '';
+
+    /**
+     * Construct a feed item from an Atom feed's `<entry>` tag
+     *
+     * @param DOMNode $node The XML node from which a feed item should be constructed
+     * @return FeedItem A feed item constructed from the given node
+     */
+    public static function fromAtom(DOMNode $node): FeedItem {
+        $guid = Feed::atomValue($node, 'id');
+        $link = '';
+        foreach ($node->getElementsByTagName('link') as $linkElt) {
+            if ($linkElt->hasAttributes()) {
+                $relAttr = $linkElt->attributes->getNamedItem('rel');
+                if ($relAttr && $relAttr->value == 'alternate') {
+                    $link = $linkElt->attributes->getNamedItem('href')->value;
+                    break;
+                }
+            }
+        }
+        if ($link == '' && str_starts_with($guid, 'http')) $link = $guid;
+
+        $item              = new FeedItem();
+        $item->guid        = $guid;
+        $item->title       = Feed::atomValue($node, 'title');
+        $item->link        = $link;
+        $item->publishedOn = Data::formatDate(Feed::atomValue($node, 'published'));
+        $item->updatedOn   = Data::formatDate(Feed::atomValue($node, 'updated'));
+        $item->content     = Feed::atomValue($node, 'content');
+
+        return $item;
+    }
+
+    /**
+     * Construct a feed item from an RSS feed's `<item>` tag
+     *
+     * @param DOMNode $node The XML node from which a feed item should be constructed
+     * @return FeedItem A feed item constructed from the given node
+     */
+    public static function fromRSS(DOMNode $node): FeedItem {
+        $itemGuid = Feed::rssValue($node, 'guid');
+        $updNodes = $node->getElementsByTagNameNS(Feed::ATOM_NS,    'updated');
+        $encNodes = $node->getElementsByTagNameNS(Feed::CONTENT_NS, 'encoded');
+
+        $item              = new FeedItem();
+        $item->guid        = $itemGuid == 'guid not found' ? Feed::rssValue($node, 'link') : $itemGuid;
+        $item->title       = Feed::rssValue($node, 'title');
+        $item->link        = Feed::rssValue($node, 'link');
+        $item->publishedOn = Data::formatDate(Feed::rssValue($node, 'pubDate'));
+        $item->updatedOn   = Data::formatDate($updNodes->length > 0 ? $updNodes->item(0)->textContent : null);
+        $item->content     = $encNodes->length > 0
+            ? $encNodes->item(0)->textContent
+            : Feed::rssValue($node, 'description');
+
+        return $item;
+    }
+}

src/public/assets/style.css

@@ -43,6 +43,38 @@ header {
 main {
     padding: 0 .5rem;
 
+    .refresh, .loading {
+        font-style: italic;
+        font-size: .9rem;
+    }
+    .htmx-request .refresh {
+        display: none;
+    }
+
+    .loading {
+        display: none;
+    }
+    .htmx-request .loading {
+        display: inline;
+    }
+
+    .user_messages {
+        display: flex;
+        flex-flow: column;
+        justify-content: center;
+    }
+    .user_message {
+        margin: .25rem auto;
+        border: solid 1px navy;
+        border-radius: .5rem;
+        background-color: rgba(255, 255, 255, .75);
+        padding: .25rem;
+    }
+
+    .user_messages + h1 {
+        margin-top: .25rem;
+    }
+
     .item_heading {
         margin-bottom: 0;
     }
@@ -78,7 +110,7 @@ input[type=url],
 input[type=text],
 input[type=email],
 input[type=password] {
-    width: 50%;
+    width: 40%;
     font-size: 1rem;
     padding: .25rem;
     border-radius: .25rem;

src/public/docs/index.php

@@ -10,6 +10,7 @@ page_head('Documentation'); ?>
     <p><a href=./the-cli>About the CLI</a> provides orientation on Feed Reader Central&rsquo;s command line interface
     <p><a href=./security-modes>Configuring Security Modes</a> describes the three security modes and how to manage each
         of them
+    <p><a href=./refresh-feeds>Refresh Feeds</a> has instructions on how feeds can be refreshed on a schedule
 </article><?php
 page_foot();
 $db->close();

src/public/docs/refresh-feeds.php

@@ -0,0 +1,52 @@
+<?php
+include '../../start.php';
+
+$db = Data::getConnection();
+Security::verifyUser($db, redirectIfAnonymous: false);
+
+page_head('Refresh Feeds | Documentation'); ?>
+<h1>Refresh Feeds</h1>
+<p class=back-link><a href=./>&lang;&lang; Documentation Home</a>
+<article class=docs>
+    <h2>Manual Feed Refresh</h2>
+    <p>Next to the &ldquo;Your Unread Items&rdquo; heading on the main page, there is a link labeled &ldquo;Refresh All
+        Feeds&rdquo;. Clicking this link will reload the main page once the feeds have been refreshed. Depending on the
+        number and size of feeds, this may take a bit of time; each feed is refreshed individually.
+    <h2>Automatic Refreshing</h2>
+    <p>The <code>refresh</code> utility script will perform this refresh from the CLI. As it runs, it will list the
+        feeds as it processes them, and if it encounters any errors, that is noted as well. This process can be
+        automated via <code>cron</code> on Linux or Mac systems. This is most easily implemented by writing a small
+        shell script to provide some environment settings, then telling <code>cron</code> to run that script.
+    <pre class=item_content>
+#!/bin/bash
+exec 1> >(logger -t feed-reader-central) 2>&1
+cd /path/to/frc
+php-cli util/refresh.php all</pre>
+    <p>Save this (<code>frc-refresh.sh</code> might be a good name) and be sure it is executable
+        (<code>chmod +x ./frc-refresh.sh</code>). Before we put it in crontab, though, let&rsquo;s understand what each
+        line does:
+    <ul>
+        <li>Line 1 tells the operating system to use the <code>bash</code> shell.
+        <li>Line 2 directs all output to the system log (<code>/var/log/syslog</code>), labeling each entry with
+            <code>feed-reader-central</code>. This lets you review the output for its runs in a log that is already
+            maintained and rotated by the operating system.
+        <li>Line 3 changes the current directory to the one where Feed Reader Central is installed; modify it for where
+            you have installed it. Since we are setting up for a <a href=./the-cli>CLI execution</a>, this should place
+            us one directory up from <code>/public</code>.
+        <li>Line 4 executes the refresh script.
+    </ul>
+    <p>Finally, we are ready to add this to our crontab. Enter <code>crontab -e</code> to edit the file, then add a row
+        at the bottom that looks like this:
+    <pre class=item_content>
+0 */6 * * *  /path/to/job/frc-refresh.sh</pre>
+    <p>The items before the path specify when it should run. This example will run at the top of the hour every six
+        hours. Crontab schedules can be tricky to create; a full treatment is outside the scope of this documentation.
+        However, <a href=https://crontab.guru/#0_*/6_*_*_* target=_blank rel=noopener title="Crontab.guru">this site</a>
+        lets you put values in each position and it translates that to words; this lets you see if what you put is what
+        you meant.
+    <p>This should not require many resources; the majority of its time will be spent waiting for the websites to return
+        their feeds so it can process them. However, if you want it to yield to everything else happening on the server,
+        add <code>nice -n 1</code> (with a trailing space) before the path to the script.
+</article><?php
+page_foot();
+$db->close();

src/public/index.php

@@ -32,13 +32,17 @@ $query->bindValue(':userId', $_SESSION[Key::USER_ID]);
 $result = $query->execute();
 $item   = $result ? $result->fetchArray(SQLITE3_ASSOC) : false;
 
-page_head('Welcome'); ?>
-<h1>Your Unread Items &nbsp; <a href=/?refresh><small><small><em>(Refresh All Feeds)</em></small></small></a></h1>
+page_head('Your Unread Items'); ?>
+<h1>
+    Your Unread Items &nbsp;
+    <a class=refresh href=/?refresh hx-get=/?refresh hx-indicator="closest h1">(Refresh All Feeds)</a>
+    <span class=loading>Refreshing&hellip;</span>
+</h1>
 <article><?php
 if ($item) {
     while ($item) { ?>
-        <p><a href=/item?id=<?=$item['id']?>><?=strip_tags($item['item_title'])?></a><br>
-            <?=htmlentities($item['feed_title'])?><br><small><em><?=date_time($item['as_of'])?></em></small><?php
+        <p><a href=/item?id=<?=$item['id']?> hx-get=/item?id=<?=$item['id']?>><?=strip_tags($item['item_title'])?></a>
+            <br><?=htmlentities($item['feed_title'])?><br><small><em><?=date_time($item['as_of'])?></em></small><?php
         $item = $result->fetchArray(SQLITE3_ASSOC);
     }
 } else { ?>

src/public/item.php

@@ -30,6 +30,26 @@ if ($_SERVER['REQUEST_METHOD'] == 'POST') {
     frc_redirect('/');
 }
 
+if ($_SERVER['REQUEST_METHOD'] == 'DELETE') {
+    $deleteQuery = $db->prepare(<<<'SQL'
+        DELETE FROM item
+         WHERE id IN (
+                 SELECT item.id
+                   FROM item INNER JOIN feed ON feed.id = item.feed_id
+                  WHERE item.id      = :id
+                    AND feed.user_id = :user)
+        SQL);
+    $deleteQuery->bindValue(':id',   $_GET['id']);
+    $deleteQuery->bindValue(':user', $_SESSION[Key::USER_ID]);
+    if ($deleteQuery->execute()) {
+        add_info('Item deleted');
+    } else {
+        add_error(Data::error($db)['error']);
+    }
+    $db->close();
+    frc_redirect('/');
+}
+
 $query = $db->prepare(<<<'SQL'
     SELECT item.title AS item_title, item.item_link, item.published_on, item.updated_on, item.content,
            feed.title AS feed_title
@@ -61,10 +81,11 @@ page_head(htmlentities("{$item['item_title']} | {$item['feed_title']}")); ?>
 </div>
 <article>
     <div class=item_content><?=str_replace('<a ', '<a target=_blank rel=noopener ', $item['content'])?></div>
-    <form class=action_buttons action=/item method=POST>
+    <form class=action_buttons action=/item method=POST hx-post=/item>
         <input type=hidden name=id value=<?=$_GET['id']?>>
-        <a href="/">Done</a>
+        <a href=/ hx-get="/">Done</a>
         <button type=submit>Keep as New</button>
+        <button type=button hx-delete=/item>Delete</button>
     </form>
 </article><?php
 page_foot();

src/public/user/log-on.php

@@ -18,7 +18,7 @@ $isSingle = SECURITY_MODEL == Security::SINGLE_USER_WITH_PASSWORD;
 page_head('Log On'); ?>
 <h1>Log On</h1>
 <article>
-    <form method=POST action=/user/log-on hx-post=/user/log-on><?php
+    <form method=POST action=/user/log-on><?php
         if (($_GET['returnTo'] ?? '') != '') { ?>
             <input type=hidden name=returnTo value="<?=$_GET['returnTo']?>"><?php
         }

src/start.php

@@ -16,8 +16,8 @@ session_start([
  * @param string $message The message itself
  */
 function add_message(string $level, string $message): void {
-    if (!array_key_exists(Key::USER_MSG, $_REQUEST)) $_REQUEST[Key::USER_MSG] = array();
-    $_REQUEST[Key::USER_MSG][] = ['level' => $level, 'message' => $message];
+    if (!array_key_exists(Key::USER_MSG, $_SESSION)) $_SESSION[Key::USER_MSG] = array();
+    $_SESSION[Key::USER_MSG][] = ['level' => $level, 'message' => $message];
 }
 
 /**
@@ -38,49 +38,75 @@ function add_info(string $message): void {
     add_message('INFO', $message);
 }
 
+/** @var bool $is_htmx True if this request was initiated by htmx, false if not */
+$is_htmx = array_key_exists('HTTP_HX_REQUEST', $_SERVER)
+    && !array_key_exists('HTTP_HX_HISTORY_RESTORE_REQUEST', $_SERVER);
+
 /**
  * Render the page title
  * @param string $title The title of the page being displayed
  */
 function page_head(string $title): void {
+    global $is_htmx;
     $version = match (true) {
         str_ends_with(FRC_VERSION, '.0.0') => substr(FRC_VERSION, 0, strlen(FRC_VERSION) - 4),
         str_ends_with(FRC_VERSION, '.0')   => substr(FRC_VERSION, 0, strlen(FRC_VERSION) - 2),
         default                            => FRC_VERSION
-    } ?>
+    };
+    //if ($is_htmx) header('HX-Push-Url: true');
+    ?>
 <!DOCTYPE html>
 <html lang=en>
 <head>
-    <meta name=viewport content="width=device-width, initial-scale=1">
-    <title><?=$title?> | Feed Reader Central</title>
-    <link href=/assets/style.css rel=stylesheet>
+    <title><?=$title?> | Feed Reader Central</title><?php
+    if (!$is_htmx) { ?>
+        <meta name=viewport content="width=device-width, initial-scale=1">
+        <link href=/assets/style.css rel=stylesheet><?php
+    } ?>
 </head>
-<body>
-<header>
-    <div><a class=title href="/">Feed Reader Central</a><span class=version>v<?=$version?></span></div>
-    <div><?php
-        if (array_key_exists(Key::USER_ID, $_SESSION)) {
-            echo '<a href=/feed?id=new>Add Feed</a> | <a href=/docs/>Docs</a> | <a href=/user/log-off>Log Off</a>';
-            if ($_SESSION[Key::USER_EMAIL] != Security::SINGLE_USER_EMAIL) echo " | {$_SESSION[Key::USER_EMAIL]}";
-        } else {
-            echo '<a href=/user/log-on>Log On</a> | <a href=/docs/>Docs</a>';
-        } ?>
-    </div>
-</header>
-<main hx-target=this><?php
-    foreach ($_REQUEST[Key::USER_MSG] ?? [] as $msg) { ?>
-        <div>
-            <?=$msg['level'] == 'INFO' ? '' : "<strong>{$msg['level']}</strong><br>"?>
-            <?=$msg['message']?>
-        </div><?php
+<body><?php
+    if (!$is_htmx) { ?>
+        <header hx-target=#main hx-push-url=true>
+            <div><a class=title href=/ hx-get="/">Feed Reader Central</a><span class=version>v<?=$version?></span></div>
+            <div><?php
+                if (array_key_exists(Key::USER_ID, $_SESSION)) { ?>
+                    <a href=/feed?id=new hx-get=/feed?id=new>Add Feed</a> |
+                    <a href=/docs/ hx-get=/docs/>Docs</a> |
+                    <a href=/user/log-off hx-get=/user/log-off>Log Off</a><?php
+                    if ($_SESSION[Key::USER_EMAIL] != Security::SINGLE_USER_EMAIL) { ?>
+                        | <?=$_SESSION[Key::USER_EMAIL]?><?php
+                    }
+                } else { ?>
+                    <a href=/user/log-on hx-get=/user/log-on>Log On</a> | <a href=/docs/ hx-get=/docs/>Docs</a><?php
+                } ?>
+            </div>
+        </header>
+        <main id=main hx-target=this hx-push-url=true hx-swap="innerHTML show:window:top"><?php
     }
+        if (sizeof($messages = $_SESSION[Key::USER_MSG] ?? []) > 0) { ?>
+            <div class=user_messages><?php
+                array_walk($messages, function ($msg) { ?>
+                    <div class=user_message>
+                        <?=$msg['level'] == 'INFO' ? '' : "<strong>{$msg['level']}</strong><br>"?>
+                        <?=$msg['message']?>
+                    </div><?php
+                }); ?>
+            </div><?php
+            $_SESSION[Key::USER_MSG] = [];
+        }
 }
 
 /**
  * Render the end of the page
  */
 function page_foot(): void {
-    echo '</main></body></html>';
+    global $is_htmx; ?>
+    </main><?php
+    if (!$is_htmx) { ?>
+        <script src=/assets/htmx.min.js></script><?php
+    } ?>
+</body>
+</html><?php
     session_commit();
 }
 

src/user-config.dist.php

@@ -25,3 +25,17 @@ const DATABASE_NAME = 'frc.db';
  * The default, 'F j, Y \a\t g:ia', equates to "August 17, 2023 at 4:45pm"
  */
 const DATE_TIME_FORMAT = 'F j, Y \a\t g:ia';
+
+/**
+ * How should item purging be done? (Purging never applies to bookmarked items.) Options are:
+ * - Feed::PURGE_NONE - Do not purge items
+ * - Feed::PURGE_READ - Purge all read items whenever purging is run (will not purge unread items)
+ * - Feed::PURGE_BY_DAYS - Purge read and unread items older than a number of days (PURGE_NUMBER below)
+ * - Feed::PURGE_BY_COUNT - Purge read and unread items beyond the number to keep (PURGE_NUMBER below)
+ */
+const PURGE_TYPE = Feed::PURGE_BY_DAYS;
+
+/**
+ * For purge-by-days, how many days of items should be kept; for purge-by-count, how many items should be kept
+ */
+const PURGE_NUMBER = 30;

src/util/refresh.php

@@ -0,0 +1,53 @@
+<?php
+use JetBrains\PhpStorm\NoReturn;
+
+require __DIR__ . '/../cli-start.php';
+
+cli_title('FEED REFRESH');
+
+if ($argc < 2) display_help();
+
+switch ($argv[1]) {
+    case 'all':
+        refresh_all();
+        break;
+    default:
+        printfn('Unrecognized option "%s"', $argv[1]);
+        display_help();
+}
+
+
+/**
+ * Display the options for this utility and exit
+ */
+#[NoReturn]
+function display_help(): void {
+    printfn('Options:');
+    printfn(' - all');
+    printfn('     Refreshes all feeds');
+    exit(0);
+}
+
+function refresh_all(): void {
+    $db = Data::getConnection();
+
+    try {
+        $feeds = Feed::retrieveAll($db);
+        if (array_key_exists('error', $feeds)) {
+            printfn('SQLite error: %s', $feeds['error']);
+            return;
+        }
+        array_walk($feeds, function ($feed) use ($db) {
+            $result = Feed::refreshFeed($feed['id'], $feed['url'], $db);
+            if (array_key_exists('error', $result)) {
+                printfn('ERR (%s) %s', $feed['email'], $feed['url']);
+                printfn('         %s', $result['error']);
+            } else {
+                printfn('OK  (%s) %s', $feed['email'], $feed['url']);
+            }
+        });
+        printfn(PHP_EOL . 'All feeds refreshed');
+    } finally {
+        $db->close();
+    }
+}