From 48e7b616b849ef2398a06d4f615acd93a7be0dc7 Mon Sep 17 00:00:00 2001
From: DmytroHryshyn <125881252+DmytroHryshyn@users.noreply.github.com>
Date: Wed, 15 Nov 2023 20:06:18 +0200
Subject: [PATCH] chore: [app dir bootstrapping 10] adds ab tests middleware
 (#12045)

## What does this PR do?
 - Adds AB tests middleware that redirects users to the app-dir pages with probability that is defined by env var

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Fixes # (issue)

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## Requirement/Documentation

<!-- Please provide all documents that are important to understand the reason of that PR. -->

This PR requires new env variables:
`APP_ROUTER_EVENT_TYPES_ENABLED`  - boolean that defines if app dir event-types page redirect is enabled
`AB_TEST_BUCKET_PROBABILITY` - number [0, 100] that defines the percentage of users getting redirected to the app dir pages

## Type of change

<!-- Please delete bullets that are not relevant. -->

- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] Chore (refactoring code, technical debt, workflow improvements)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
- [ ] This change requires a documentation update

## How should this be tested?

<!-- Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration. Write details that help to start the tests -->
Does not requires testing, implements middleware as a dead code

## Mandatory Tasks

- [x] Make sure you have self-reviewed the code. A decent size PR without self-review might be rejected.
---
 apps/web/abTest/middlewareFactory.ts | 50 ++++++++++++++++++++++++++++
 apps/web/abTest/utils.ts             |  9 +++++
 packages/lib/constants.ts            |  1 +
 turbo.json                           |  2 ++
 4 files changed, 62 insertions(+)
 create mode 100644 apps/web/abTest/middlewareFactory.ts
 create mode 100644 apps/web/abTest/utils.ts

diff --git a/apps/web/abTest/middlewareFactory.ts b/apps/web/abTest/middlewareFactory.ts
new file mode 100644
index 0000000000..bb2115e47a
--- /dev/null
+++ b/apps/web/abTest/middlewareFactory.ts
@@ -0,0 +1,50 @@
+import { getBucket } from "abTest/utils";
+import type { NextMiddleware, NextRequest } from "next/server";
+import { NextResponse } from "next/server";
+import z from "zod";
+
+const ROUTES: [RegExp, boolean][] = [
+  [/^\/event-types$/, Boolean(process.env.APP_ROUTER_EVENT_TYPES_ENABLED)],
+];
+
+const FUTURE_ROUTES_OVERRIDE_COOKIE_NAME = "x-calcom-future-routes-override";
+const FUTURE_ROUTES_ENABLED_COOKIE_NAME = "x-calcom-future-routes-enabled";
+
+const bucketSchema = z.union([z.literal("legacy"), z.literal("future")]).default("legacy");
+
+export const abTestMiddlewareFactory =
+  (next: (req: NextRequest) => Promise<NextResponse<unknown>>): NextMiddleware =>
+  async (req: NextRequest) => {
+    const response = await next(req);
+
+    const { pathname } = req.nextUrl;
+
+    const override = req.cookies.has(FUTURE_ROUTES_OVERRIDE_COOKIE_NAME);
+
+    const route = ROUTES.find(([regExp]) => regExp.test(pathname)) ?? null;
+
+    const enabled = route !== null ? route[1] || override : false;
+
+    if (pathname.includes("future") || !enabled) {
+      return response;
+    }
+
+    const safeParsedBucket = override
+      ? { success: true as const, data: "future" as const }
+      : bucketSchema.safeParse(req.cookies.get(FUTURE_ROUTES_ENABLED_COOKIE_NAME)?.value);
+
+    if (!safeParsedBucket.success) {
+      // cookie does not exist or it has incorrect value
+
+      const res = NextResponse.next(response);
+      res.cookies.set(FUTURE_ROUTES_ENABLED_COOKIE_NAME, getBucket(), { expires: 1000 * 60 * 30 }); // 30 min in ms
+      return res;
+    }
+
+    const bucketUrlPrefix = safeParsedBucket.data === "future" ? "future" : "";
+
+    const url = req.nextUrl.clone();
+    url.pathname = `${bucketUrlPrefix}${pathname}/`;
+
+    return NextResponse.rewrite(url, response);
+  };
diff --git a/apps/web/abTest/utils.ts b/apps/web/abTest/utils.ts
new file mode 100644
index 0000000000..ed40c9fca9
--- /dev/null
+++ b/apps/web/abTest/utils.ts
@@ -0,0 +1,9 @@
+import { AB_TEST_BUCKET_PROBABILITY } from "@calcom/lib/constants";
+
+const cryptoRandom = () => {
+  return crypto.getRandomValues(new Uint8Array(1))[0] / 0xff;
+};
+
+export const getBucket = () => {
+  return cryptoRandom() * 100 < AB_TEST_BUCKET_PROBABILITY ? "future" : "legacy";
+};
diff --git a/packages/lib/constants.ts b/packages/lib/constants.ts
index 59ac3a80ad..cc5fb76143 100644
--- a/packages/lib/constants.ts
+++ b/packages/lib/constants.ts
@@ -106,3 +106,4 @@ export const APP_CREDENTIAL_SHARING_ENABLED =
 
 export const DEFAULT_LIGHT_BRAND_COLOR = "#292929";
 export const DEFAULT_DARK_BRAND_COLOR = "#fafafa";
+export const AB_TEST_BUCKET_PROBABILITY = Number(process.env.AB_TEST_BUCKET_PROBABILITY ?? "10");
diff --git a/turbo.json b/turbo.json
index 7f1282d0c4..2b171f6723 100644
--- a/turbo.json
+++ b/turbo.json
@@ -194,9 +194,11 @@
   },
   "globalDependencies": ["yarn.lock"],
   "globalEnv": [
+    "AB_TEST_BUCKET_PROBABILITY",
     "ALLOWED_HOSTNAMES",
     "ANALYZE",
     "API_KEY_PREFIX",
+    "APP_ROUTER_EVENT_TYPES_ENABLED",
     "APP_USER_NAME",
     "BASECAMP3_CLIENT_ID",
     "BASECAMP3_CLIENT_SECRET",