fix: rum instrumentation

assets/scripts/scripts.js

@@ -10,6 +10,69 @@
  * governing permissions and limitations under the License.
  */
 
+/**
+ * log RUM if part of the sample.
+ * @param {string} checkpoint identifies the checkpoint in funnel
+ * @param {Object} data additional data for RUM sample
+ */
+export function sampleRUM(checkpoint, data = {}) {
+  sampleRUM.defer = sampleRUM.defer || [];
+  const defer = (fnname) => {
+    sampleRUM[fnname] = sampleRUM[fnname]
+      || ((...args) => sampleRUM.defer.push({ fnname, args }));
+  };
+  sampleRUM.drain = sampleRUM.drain
+    || ((dfnname, fn) => {
+      sampleRUM[dfnname] = fn;
+      sampleRUM.defer
+        .filter(({ fnname }) => dfnname === fnname)
+        .forEach(({ fnname, args }) => sampleRUM[fnname](...args));
+    });
+  sampleRUM.on = (chkpnt, fn) => { sampleRUM.cases[chkpnt] = fn; };
+  defer('observe');
+  defer('cwv');
+  try {
+    window.hlx = window.hlx || {};
+    if (!window.hlx.rum) {
+      const usp = new URLSearchParams(window.location.search);
+      const weight = (usp.get('rum') === 'on') ? 1 : 100; // with parameter, weight is 1. Defaults to 100.
+      // eslint-disable-next-line no-bitwise
+      const hashCode = (s) => s.split('').reduce((a, b) => (((a << 5) - a) + b.charCodeAt(0)) | 0, 0);
+      const id = `${hashCode(window.location.href)}-${new Date().getTime()}-${Math.random().toString(16).substr(2, 14)}`;
+      const random = Math.random();
+      const isSelected = (random * weight < 1);
+      // eslint-disable-next-line object-curly-newline
+      window.hlx.rum = { weight, id, random, isSelected, sampleRUM };
+    }
+    const { weight, id } = window.hlx.rum;
+    if (window.hlx && window.hlx.rum && window.hlx.rum.isSelected) {
+      const sendPing = (pdata = data) => {
+        // eslint-disable-next-line object-curly-newline, max-len, no-use-before-define
+        const body = JSON.stringify({ weight, id, referer: window.location.href, generation: window.hlx.RUM_GENERATION, checkpoint, ...data });
+        const url = `https://rum.hlx.page/.rum/${weight}`;
+        // eslint-disable-next-line no-unused-expressions
+        navigator.sendBeacon(url, body);
+        // eslint-disable-next-line no-console
+        console.debug(`ping:${checkpoint}`, pdata);
+      };
+      sampleRUM.cases = sampleRUM.cases || {
+        cwv: () => sampleRUM.cwv(data) || true,
+        lazy: () => {
+          // use classic script to avoid CORS issues
+          const script = document.createElement('script');
+          script.src = 'https://rum.hlx.page/.rum/@adobe/helix-rum-enhancer@^1/src/index.js';
+          document.head.appendChild(script);
+          return true;
+        },
+      };
+      sendPing(data);
+      if (sampleRUM.cases[checkpoint]) { sampleRUM.cases[checkpoint](); }
+    }
+  } catch (error) {
+    // something went wrong
+  }
+}
+
 /**
  * Builds an HTML DOM element.
  * @param {string} tag The type of element
@@ -923,4 +986,20 @@ async function decoratePage(doc) {
   }, 3 * 1000);
 }
 
-decoratePage(document);
+function init() {
+  sampleRUM('top');
+
+  window.addEventListener('load', () => sampleRUM('load'));
+
+  window.addEventListener('unhandledrejection', (event) => {
+    sampleRUM('error', { source: event.reason.sourceURL, target: event.reason.line });
+  });
+
+  window.addEventListener('error', (event) => {
+    sampleRUM('error', { source: event.filename, target: event.lineno });
+  });
+
+  decoratePage(document);
+}
+
+init();