1 files changed, 40 insertions, 0 deletions
diff --git a/static/js/update.ts b/static/js/update.ts
new file mode 100644
index 0000000..2b96751
--- /dev/null
+++ b/static/js/update.ts
@@ -0,0 +1,40 @@
+(function () {
+  function check(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;
+  }
+
+  function update() {
+    const url = self.location.href.split("#")[0].split("?")[0];
+    check(url, "HEAD", function (request) {
+      const local = document.querySelector('meta[name="last-modified"]').content;
+      const remote = request.getResponseHeader("last-modified") || local;
+      const modified = Date.parse(document.lastModified) !== Date.parse(remote);
+      const drift = Date.parse(remote) - Date.parse(local);
+
+      if (modified) {
+        const indicator = document.querySelector("a[data-update]");
+        check(url, "GET");
+        indicator.href = url;
+        indicator.removeAttribute("id");
+        indicator.dataset.update = "refresh";
+        self.removeEventListener("blur", update);
+        console.log("R: " + remote);
+        console.log("L: " + local);
+        console.log("D: " + drift);
+        console.log("M: " + modified);
+      }
+    });
+  }
+
+  self.addEventListener("blur", update);
+})();