feat(ab-test): add selectABTest addon for split test selection and persistence

lib/addons/prototypes/ab-test.js

@@ -0,0 +1,78 @@
+/* eslint-disable no-param-reassign */
+
+// Fills missing trafficPercentage values by distributing remaining % evenly across
+// tests that don't specify one.
+export function calculateTrafficPercentages(abTests) {
+  const allocated = abTests
+    .filter((t) => t.trafficPercentage !== undefined)
+    .reduce((sum, t) => sum + t.trafficPercentage, 0);
+  const without = abTests.filter((t) => t.trafficPercentage === undefined);
+  if (without.length > 0) {
+    const even = (100 - allocated) / without.length;
+    without.forEach((t) => {
+      t.trafficPercentage = even;
+    });
+  }
+  return abTests;
+}
+
+// Weighted random bucket selection across tests with assigned trafficPercentage values.
+// Mirrors determineABTest in lib/edge/targeting.ts.
+export function determineABTest(abTests) {
+  if (!abTests || !abTests.length) return null;
+  const total = abTests.reduce((s, t) => s + t.trafficPercentage, 0);
+  if (total > 100) return null;
+  const bucket = Math.floor(Math.random() * 100);
+  let cumulative = 0;
+  for (const test of abTests) {
+    cumulative += test.trafficPercentage;
+    if (bucket < cumulative) return test;
+  }
+  return null;
+}
+
+// Select an A/B test, applying sessionStorage forced-include/exclude overrides before
+// falling back to weighted random selection. Persists the result to OPTABLE_SPLIT_TEST.
+//
+// Override keys (value "1" or "true" to activate):
+//   optableInclude<ID>  — force this test
+//   optableResolve<ID>  — force this test (alias)
+//   optableExclude<ID>  — exclude this test from random selection
+//   optableInclude<ID>=false/"0" — also excludes this test
+export function selectABTest(abTests) {
+  if (!abTests || !abTests.length) return null;
+
+  const tests = calculateTrafficPercentages([...abTests]);
+  const trueVals = ["1", "true"];
+  const falseVals = ["0", "false"];
+
+  // Forced inclusion wins — first matching test is selected immediately.
+  for (const test of tests) {
+    const key = test.id.toUpperCase();
+    const forced =
+      trueVals.includes(sessionStorage.getItem(`optableInclude${key}`)) ||
+      trueVals.includes(sessionStorage.getItem(`optableResolve${key}`));
+    if (forced) {
+      const selected = { ...test, trafficPercentage: 100 };
+      sessionStorage.setItem("OPTABLE_SPLIT_TEST", JSON.stringify(selected));
+      return selected;
+    }
+  }
+
+  // Filter out excluded tests before random selection.
+  const eligible = tests.filter((test) => {
+    const key = test.id.toUpperCase();
+    return (
+      !trueVals.includes(sessionStorage.getItem(`optableExclude${key}`)) &&
+      !falseVals.includes(sessionStorage.getItem(`optableInclude${key}`))
+    );
+  });
+
+  const selected = determineABTest(eligible.length ? eligible : tests);
+  if (selected) {
+    const pinned = { ...selected, trafficPercentage: 100 };
+    sessionStorage.setItem("OPTABLE_SPLIT_TEST", JSON.stringify(pinned));
+    return pinned;
+  }
+  return null;
+}

lib/addons/prototypes/analytics.js

@@ -19,6 +19,8 @@ class OptablePrebidAnalytics {
     this.optableInstance = optableInstance;
     this.isInitialized = true;
 
+    this.selectedTest = config.selectedTest ?? null;
+
     // Store auction data
     this.auctions = {};
     this.maxAuctionDataSize = 20;
@@ -57,6 +59,8 @@ class OptablePrebidAnalytics {
   }
 
   setHooks(pbjs) {
+    this.optableProvider = pbjs?.getConfig?.()?.realTimeData?.dataProviders?.find((p) => p.name === "optable") ?? null;
+
     this.log("Processing missed auctionEnd");
     pbjs.getEvents().forEach((event) => {
       if (event.eventType === "auctionEnd") {
@@ -279,6 +283,8 @@ class OptablePrebidAnalytics {
         tenant: this.config.tenant,
         optableWrapperVersion: SDK_WRAPPER_VERSION, // eslint-disable-line no-undef
         prebidjsVersion: this.prebidInstance?.version || "unknown",
+        optableProvider: this.optableProvider ?? null,
+        selectedABTest: this.selectedTest?.id ?? null,
         sessionDepth: sessionStorage?.optableSessionDepth || 1,
         pageAuctionsCount: window.optable?.pageAuctionsCount || 1,
       };