quash: query parameters for just, has, and do, and some general simplification

www/public/js/params.js

@@ -0,0 +1,45 @@
+!function() {
+  var p = new URLSearchParams(location.search);
+
+  var just = p.get('just');
+  if (just && /^[a-z0-9-]+$/.test(just)) {
+    document.documentElement.dataset.just = just;
+    var css = 'section[data-section]:not([data-section="' + just + '"]){display:none}'
+      + ' section[data-section="' + just + '"] .section-label{pointer-events:none;text-decoration:none;color:inherit}';
+    document.head.appendChild(Object.assign(document.createElement('style'), { textContent: css }));
+  }
+
+  var act = p.get('do');
+  var urls = window.__urls;
+  if (urls && urls.length) {
+    if (act === 'random') {
+      var url = urls[Math.floor(Math.random() * urls.length)];
+      location.replace(url.startsWith('http') ? url : location.origin + url);
+    }
+    if (act === 'newest') {
+      location.replace(urls[0].startsWith('http') ? urls[0] : location.origin + urls[0]);
+    }
+  }
+  if (act === 'admin') {
+    location.replace('/admin');
+  }
+
+  var has = p.get('has');
+  if (has) {
+    document.documentElement.dataset.has = has;
+    has = has.toLowerCase();
+    document.addEventListener('DOMContentLoaded', function() {
+      document.querySelectorAll('section[data-section] pre').forEach(function(pre) {
+        var lines = pre.innerHTML.split('\n');
+        pre.innerHTML = lines.filter(function(line) {
+          return !line.trim() || line.toLowerCase().indexOf(has) !== -1;
+        }).join('\n');
+      });
+      document.querySelectorAll('.guestbook-entry').forEach(function(entry) {
+        if (entry.textContent.toLowerCase().indexOf(has) === -1) {
+          entry.style.display = 'none';
+        }
+      });
+    });
+  }
+}();