From dd582a1c6041a5c9667d916a44a0269b4649096b Mon Sep 17 00:00:00 2001
From: Jon Tzeng <jon@edge.app>
Date: Mon, 23 Oct 2023 14:55:56 -0700
Subject: [PATCH] fixup! Fix generateExperimentConfigVal

---
 src/experimentConfig.ts | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/src/experimentConfig.ts b/src/experimentConfig.ts
index 3129b4d9a67..a13c39116ae 100644
--- a/src/experimentConfig.ts
+++ b/src/experimentConfig.ts
@@ -24,13 +24,12 @@ const DEFAULT_EXPERIMENT_CONFIG: ExperimentConfig = {
 
 const experimentConfigDisklet = makeReactNativeDisklet()
 
-// The probability (0-1) of a feature config being set to the first value(s):
-// the configuration that differs from the default feature configuration.
+// The probability of an experiment config feature being set for a given key
 const experimentDistribution = {
-  swipeLastUsp: [0.5],
-  createAccountType: [0.5],
+  swipeLastUsp: [50, 50],
+  createAccountType: [50, 50],
   legacyLanding: [0],
-  createAccountText: [0.33, 0.33]
+  createAccountText: [33.33, 33.33, 33.33]
 }
 
 /**
@@ -40,20 +39,27 @@ const experimentDistribution = {
 const generateExperimentConfigVal = <T>(key: keyof typeof experimentDistribution, configVals: T[]): T => {
   const variantProbability = experimentDistribution[key]
 
-  if (variantProbability.length !== configVals.length - 1) {
+  if (variantProbability.length !== configVals.length) {
     console.error(`Misconfigured experimentDistribution for: '${key}'`)
   } else {
+    // Distribute the probability of each config value
+    const totalProbability = variantProbability.reduce((sum, probability) => sum + probability, 0)
+    if (totalProbability > 101 || totalProbability < 99) {
+      console.warn(`Config values for ${key} do not add up to 100% +/- 1%`)
+    }
+    const distributedProbabilities = variantProbability.map(probability => probability / totalProbability)
+
     // Generate a random number between 0 and 1
     const random = Math.random()
 
     // Check which index the random number falls into and return the configVal:
     let lowerBound = 0
-    let upperBound = variantProbability[0]
-    for (let i = 0; i < variantProbability.length; i++) {
+    let upperBound = distributedProbabilities[0]
+    for (let i = 0; i < distributedProbabilities.length; i++) {
       if (random >= lowerBound && random < upperBound) return configVals[i]
 
       lowerBound = upperBound
-      upperBound += variantProbability[i]
+      upperBound += distributedProbabilities[i]
     }
   }