From fcbca58853d33f6d79091383fb3fd552f4ceeabf Mon Sep 17 00:00:00 2001
From: ryan <ryan@1a063a9b-81f0-0310-95a4-ce76da25c4cd>
Date: Tue, 9 Mar 2010 19:36:38 +0000
Subject: [PATCH] wp_get_shortlink() and pluggable shortlink generation. fixes
 #10640

git-svn-id: http://svn.automattic.com/wordpress/trunk@13635 1a063a9b-81f0-0310-95a4-ce76da25c4cd
---
 wp-admin/edit-form-advanced.php |  4 ++
 wp-includes/default-filters.php |  2 +
 wp-includes/link-template.php   | 79 +++++++++++++++++++++++++++++++++
 3 files changed, 85 insertions(+)

diff --git a/wp-admin/edit-form-advanced.php b/wp-admin/edit-form-advanced.php
index cdec03a0c5..7d539ba615 100644
--- a/wp-admin/edit-form-advanced.php
+++ b/wp-admin/edit-form-advanced.php
@@ -192,6 +192,10 @@ $side_meta_boxes = do_meta_boxes($post_type, 'side', $post);
 <div class="inside">
 <?php
 $sample_permalink_html = get_sample_permalink_html($post->ID);
+$shortlink = wp_get_shortlink($post->ID, 'post');
+if ( !empty($shortlink) )
+    $sample_permalink_html .= '<input id="shortlink" type="hidden" value="' . esc_attr($shortlink) . '" /><a href="#" class="button" onclick="prompt(&#39;URL:&#39;, jQuery(\'#shortlink\').val()); return false;">' . __('Get Shortlink') . '</a>';
+
 if ( !( 'pending' == $post->post_status && !current_user_can( $post_type_object->publish_cap ) ) ) { ?>
 	<div id="edit-slug-box">
 <?php
diff --git a/wp-includes/default-filters.php b/wp-includes/default-filters.php
index ff76912dae..61447475bc 100644
--- a/wp-includes/default-filters.php
+++ b/wp-includes/default-filters.php
@@ -191,6 +191,8 @@ add_action( 'wp_head',             'wp_print_head_scripts',         9     );
 add_action( 'wp_head',             'wp_generator'                         );
 add_action( 'wp_head',             'rel_canonical'                        );
 add_action( 'wp_footer',           'wp_print_footer_scripts'              );
+add_action( 'wp_head',             'wp_shortlink_wp_head'                 );
+add_action( 'wp',                  'wp_shortlink_header'                  );
 
 // Feed Generator Tags
 foreach ( array( 'rss2_head', 'commentsrss2_head', 'rss_head', 'rdf_header', 'atom_head', 'comments_atom_head', 'opml_head', 'app_head' ) as $action ) {
diff --git a/wp-includes/link-template.php b/wp-includes/link-template.php
index 3f2e4ea459..5aab248c32 100644
--- a/wp-includes/link-template.php
+++ b/wp-includes/link-template.php
@@ -2050,4 +2050,83 @@ function wp_ajaxurl() {
 	add_action('wp_head', '_wp_ajaxurl', 1);
 }
 
+/**
+ * Return a shortlink for a post, page, attachment, or blog.
+ *
+ * Shortlinks are not supported by default. A plugin is required to get shortlink support.
+ * This function exists to provide a shortlink tag that all themes and plugins can target.  A plugin must hook in to
+ * provide the actual shortlinks.  Plugins can short circuit this function via the pre_get_shortlink filter or filter the output
+ * via the get_shortlink filter.
+ *
+ * @since 3.0.0.
+ * 
+ * @param int $id A post or blog id.  Default is 0, which means the current post or blog.
+ * @param string $contex Whether the id is a 'blog' id, 'post' id, or 'media' id.  If 'post', the post_type of the post is consulted.  If 'query', the current query is consulted to determine the id and context. Default is 'post'.
+ * @param bool $allow_slugs Whether to allow post slugs in the shortlink. It is up to the plugin how and whether to honor this.
+ * @return string A shortlink or an empty string if no shortlink exists for the requested resource or if shortlinks are not enabled.
+ */
+function wp_get_shortlink($id = 0, $context = 'post', $allow_slugs = true) {
+	// Allow plugins to short-circuit this function.
+	$shortlink = apply_filters('pre_get_shortlink', false, $id, $context, $allow_slugs);
+	if ( false !== $shortlink )
+		return $shortlink;
+
+	global $wp_query;
+	$post_id = 0;
+	if ( 'query' == $context && is_single() )
+		$post_id = $wp_query->get_queried_object_id();
+	elseif ( 'post' == $context )
+		$post_id = $id;
+
+	$shortlink = '';
+
+	// Return p= link for posts.
+	if ( !empty($post_id) ) {
+		$post = get_post($post_id);
+		if ( isset($post->post_type) && 'post' == $post->post_type )
+			$shortlink = home_url('?p=' . $post->ID);
+	}
+
+	return apply_filters('get_shortlink', $shortlink, $id, $context, $allow_slugs);
+}
+
+/**
+ *  Inject rel=sortlink into head if a shortlink is defined for the current page.
+ *
+ *  Attached to the wp_head action.
+ *
+ * @since 3.0.0
+ *
+ * @uses wp_get_shortlink()
+ */
+function wp_shortlink_wp_head() {
+	$shortlink = wp_get_shortlink(0, 'query');
+
+	if ( empty($shortlink) )
+		return;
+
+	echo '<link rel="shortlink" href="' . $shortlink . '" />';
+}
+
+/**
+ * Send a Link: rel=shortlink header if a shortlink is defined for the current page.
+ *
+ * Attached to the wp action.
+ *
+ * @since 3.0.0
+ *
+ * @uses wp_get_shortlink()
+ */
+function wp_shortlink_header() {
+    if ( headers_sent() )
+		return;
+
+	$shortlink = wp_get_shortlink(0, 'query');
+
+	if ( empty($shortlink) )
+		return;
+
+	header('Link: <' . $shortlink . '>; rel=shortlink');
+}
+
 ?>