1 files changed, 84 insertions, 0 deletions
diff --git a/static/js/update.ts b/static/js/update.ts
new file mode 100644
index 0000000..df29f49
--- /dev/null
+++ b/static/js/update.ts
@@ -0,0 +1,84 @@
+(function () {
+
+  const cookiesDisabled = !navigator.cookieEnabled;
+
+  if (cookiesDisabled) {
+    document.cookie = "disabled";
+    document.cookie.indexOf("disabled");
+    return console.warn("WARNING: Update check disabled due to cookie restrictions");
+  }
+
+  function fetch(url, method, callback) {
+    const http = new XMLHttpRequest();
+    http.onreadystatechange = function () {
+      if (http.readyState === 4 && http.status === 200) {
+        if (callback) callback(http);
+      }
+    };
+    http.open(method, url);
+    http.setRequestHeader("Pragma", "no-cache");
+    http.setRequestHeader("Cache-Control", "no-cache");
+    http.send();
+    return http;
+  }
+
+  const state = "on";
+  const key = "config.update";
+
+  let stamps = {};
+
+  if (!sessionStorage[key + ".urls"]) sessionStorage[key + ".urls"] = JSON.stringify(stamps);
+
+  function update() {
+    const url = self.location.href.split("#")[0].split("?")[0];
+
+    const indicator = document.querySelector("a[data-update]");
+    if (indicator === null || indicator.dataset.update === "refresh") return;
+    const anchor = indicator.cloneNode();
+
+    fetch(url, "HEAD", function (request) {
+      const local = document.querySelector('meta[name="last-modified"]').content || document.lastModified;
+      const remote = request.getResponseHeader("last-modified") || '';
+      const modified = Date.parse(remote || local) > Date.parse(local);
+      const drift = Date.parse(remote || local) - Date.parse(local);
+
+      if (drift < 10000) return;
+
+      function reset() {
+        indicator.href = anchor.href;
+        indicator.setAttribute("id", anchor.id);
+        indicator.dataset.update = anchor.dataset.update;
+      }
+
+      stamps = JSON.parse(sessionStorage[key + ".urls"]);
+      if (stamps[url] === remote) return;
+      stamps[url] = remote;
+      sessionStorage[key + ".urls"] = JSON.stringify(stamps);
+
+      if (remote && modified) {
+        fetch(url, "GET", function () {
+          indicator.href = url.replace(/^https:/, "http:");
+          indicator.removeAttribute("id");
+          indicator.dataset.update = "refresh";
+          console.log("INFO: R: " + remote);
+          console.log("INFO: L: " + local);
+          console.log("INFO: D: " + drift);
+          console.log("INFO: M: " + modified);
+        });
+      }
+    });
+  }
+
+  let scrolled;
+  let delay = 1000;
+  let delayed = 0;
+
+  self.addEventListener("scroll", function () {
+    if (scrolled) clearTimeout(scrolled);
+    scrolled = setTimeout(function () { update(); delay = delay + delayed; delayed = delay - delayed; }, delay);
+  });
+
+  ["focus", "load", "URLChangedCustomEvent"].forEach(function (event) {
+    self.addEventListener(event, function () { update(); });
+  });
+})();