templates/blogpost: share on mastodon button

templates/blogpost.html

@@ -47,4 +47,55 @@
 
 <hr />
 
+<!-- The button that should be clicked. -->
+<button onclick="share_on_mastodon()">Share on Mastodon</button>
+<script>
+
+// The actual function. Set this as an onclick function for your "Share on Mastodon" button
+function share_on_mastodon() {
+        // Prefill the form with the user's previously-specified Mastodon instance, if applicable
+        var default_url = localStorage['mastodon_instance']; 
+
+        // If there is no cached instance/domain, then insert a "https://" with no domain at the start of the prompt. 
+        if (!default_url)
+                default_url = "https://"; 
+
+        var instance = prompt("Enter your instance's address: (ex: https://linuxrocks.online)", default_url);
+        if (instance) { 
+                // Handle URL formats
+                if ( !instance.startsWith("https://") && !instance.startsWith("http://") )
+                        instance = "https://" + instance;  
+
+                // Get the current page's URL
+                var url   = window.location.href;
+        
+                // Get the page title from the og:title meta tag, if it exists.
+                var title = document.querySelectorAll('meta[property="og:title"]')[0].getAttribute("content"); 
+        
+                // Otherwise, use the <title> tag as the title
+                if (!title)    var title = document.getElementsByTagName("title")[0].innerHTML;
+        
+                // Handle slash
+                if ( !instance.endsWith("/") )
+                        instance = instance + "/"; 
+
+                // Cache the instance/domain for future requests
+                localStorage['mastodon_instance'] = instance; 
+
+                // Hashtags 
+                var hashtags = "#blogpost";
+
+                // Tagging users, such as offical accounts or the author of the post 
+                var author   = "@cadey@mst3k.interlinked.me"; 
+
+                // Create the Share URL
+                // https://someinstance.tld/share?text=URL%20encoded%20text
+                mastodon_url = instance + "share?text=" + encodeURIComponent(title + "\n\n" + url + "\n\n" + hashtags + " " + author);
+
+                // Open a new window at the share location   
+                window.open(mastodon_url, '_blank');
+        }
+}
+</script>
+
 {{ end }}