From 2ac9b262576c0f2765341b6335a34364cd8903f4 Mon Sep 17 00:00:00 2001
From: Bruno Windels <brunow@matrix.org>
Date: Mon, 15 Oct 2018 16:40:51 +0200
Subject: [PATCH] phased rollout expired function

---
 src/PhasedRollOut.js | 62 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 src/PhasedRollOut.js

diff --git a/src/PhasedRollOut.js b/src/PhasedRollOut.js
new file mode 100644
index 0000000000..db91f8ab76
--- /dev/null
+++ b/src/PhasedRollOut.js
@@ -0,0 +1,62 @@
+/*
+Copyright 2015, 2016 OpenMarket Ltd
+Copyright 2017 Vector Creations Ltd
+Copyright 2018 New Vector Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import SdkConfig from './SdkConfig';
+
+function hashCode(str) {
+  var hash = 0, i, chr;
+  if (str.length === 0) return hash;
+  for (i = 0; i < str.length; i++) {
+    chr   = str.charCodeAt(i);
+    hash  = ((hash << 5) - hash) + chr;
+    hash |= 0;
+  }
+  return Math.abs(hash);
+}
+
+export function phasedRollOutExpiredForUser(username, feature, now, rollOutConfig = SdkConfig.get().phasedRollOut) {
+    if (!rollOutConfig) {
+        console.log(`no phased rollout configuration, so enabling ${feature}`);
+        return true;
+    }
+    const featureConfig = rollOutConfig[feature];
+    if (!featureConfig) {
+        console.log(`${feature} doesn't have phased rollout configured, so enabling`);
+        return true;
+    }
+    if (!Number.isFinite(featureConfig.offset) || !Number.isFinite(featureConfig.period)) {
+        console.error(`phased rollout of ${feature} is misconfigured, offset and/or period are not numbers, so disabling`, featureConfig);
+        return false;
+    }
+
+    const hash = hashCode(username);
+    //ms -> min, enable users at minute granularity
+    const bucketRatio = 1000 * 60;
+    const bucketCount = featureConfig.period / bucketRatio;
+    const userBucket = hash % bucketCount;
+    const userMs = userBucket * bucketRatio;
+    const enableAt = featureConfig.offset + userMs;
+    const result = now >= enableAt;
+    const bucketStr = `(bucket ${userBucket}/${bucketCount})`;
+    if (result) {
+        console.log(`${feature} enabled for ${username} ${bucketStr}`)
+    } else {
+        console.log(`${feature} will be enabled for ${username} in ${Math.ceil((enableAt - now)/1000)}s ${bucketStr}`);
+    }
+    return result;
+}