We have an alternate link

include/dfrn.php

@@ -284,6 +284,65 @@ class dfrn {
 		return $atom;
 	}
 
+	/**
+	 * @brief Generate an atom entry for a given item id
+	 *
+	 * @param int $item_id The item id
+	 *
+	 * @return string DFRN feed entry
+	 */
+	public static function itemFeed($item_id) {
+		$r = q("SELECT `item`.*, `item`.`id` AS `item_id`,
+			`contact`.`name`, `contact`.`network`, `contact`.`photo`, `contact`.`url`,
+			`contact`.`name-date`, `contact`.`uri-date`, `contact`.`avatar-date`,
+			`contact`.`thumb`, `contact`.`dfrn-id`, `contact`.`self`,
+			`sign`.`signed_text`, `sign`.`signature`, `sign`.`signer`
+			FROM `item`
+			STRAIGHT_JOIN `contact` ON `contact`.`id` = `item`.`contact-id`
+				AND (NOT `contact`.`blocked` OR `contact`.`pending`)
+			LEFT JOIN `sign` ON `sign`.`iid` = `item`.`id`
+			WHERE `item`.`id` = %d AND `item`.`visible` AND NOT `item`.`moderated` AND `item`.`parent` != 0
+			AND `item`.`wall` AND NOT `item`.`private`",
+			intval($item_id)
+		);
+
+		if (!dbm::is_result($r)) {
+			killme();
+		}
+
+		$item = $r[0];
+
+		$r = q("SELECT `contact`.*, `user`.`nickname`, `user`.`timezone`, `user`.`page-flags`, `user`.`account-type`
+			FROM `contact` INNER JOIN `user` ON `user`.`uid` = `contact`.`uid`
+			WHERE `contact`.`self` AND `user`.`uid` = %d LIMIT 1",
+			intval($item['uid'])
+		);
+
+		if (!dbm::is_result($r)) {
+			killme();
+		}
+
+		$owner = $r[0];
+
+		$doc = new DOMDocument('1.0', 'utf-8');
+		$doc->formatOutput = true;
+
+		$alternatelink = $owner['url'];
+
+		$author = "dfrn:owner";
+		//$author = "author";
+
+		$root = self::add_header($doc, $owner, $author, $alternatelink, true);
+
+		$type = 'html';
+
+		$entry = self::entry($doc, $type, $item, $owner, true);
+		$root->appendChild($entry);
+
+		$atom = trim($doc->saveXML());
+		return $atom;
+	}
+
 	/**
 	 * @brief Create XML text for DFRN mails
 	 *

mod/display.php

@@ -11,6 +11,17 @@ function display_init(App $a) {
 	$nick = (($a->argc > 1) ? $a->argv[1] : '');
 	$profiledata = array();
 
+	if ($a->argc == 3) {
+		if (substr($a->argv[2], -5) == '.atom') {
+			require_once('include/dfrn.php');
+			$item_id = substr($a->argv[2], 0, -5);
+			$xml = dfrn::itemFeed($item_id);
+			header("Content-type: application/atom+xml");
+			echo $xml;
+			http_status_exit(($xml) ? 200 : 500);
+		}
+	}
+
 	// If there is only one parameter, then check if this parameter could be a guid
 	if ($a->argc == 2) {
 		$nick = "";
@@ -278,11 +289,17 @@ function display_content(App $a, $update = 0) {
 		return;
 	}
 
-	$alternate = App::get_baseurl().'/display/'.$nick.'/'.$item_id.'.atom';
+	// We are displaying an "alternate" link if that post was public. See issue 2864
+	$items = q("SELECT `id` FROM `item` WHERE `id` = %d AND NOT `private` AND `wall`", intval($item_id));
+	if (dbm::is_result($items)) {
+		$alternate = App::get_baseurl().'/display/'.$nick.'/'.$item_id.'.atom';
+	} else {
+		$alternate = '';
+	}
+
 	$a->page['htmlhead'] .= replace_macros(get_markup_template('display-head.tpl'),
 				array('$alternate' => $alternate));
 
-
 	$groups = array();
 
 	$contact = null;

view/templates/display-head.tpl

@@ -1,4 +1,4 @@
-<link href='{{$alternate}}' rel='alternate' type='application/atom+xml'>
+{{if $alternate}}<link href='{{$alternate}}' rel='alternate' type='application/atom+xml'>{{/if}}
 <script>
 $(document).ready(function() {
 	$(".comment-edit-wrapper textarea").editor_autocomplete(baseurl+"/acl");