feat(withSplit): passable rewrite rules manually

src/make-rewrites.spec.ts

@@ -0,0 +1,68 @@
+import { makeRewrites } from './make-rewrites'
+
+describe('makeRewrites', () => {
+  it('must return inactiveRewiteRule when no challenger', () => {
+    return makeRewrites({ main: '' }, 'top', true, undefined)().then((res) => {
+      expect(res).toEqual({
+        beforeFiles: [{ destination: '/top', source: '/' }]
+      })
+    })
+  })
+  it('must return inactiveRewiteRule when active flag is not true', () => {
+    return makeRewrites(
+      { main: '', challenger: 'https://example.com' },
+      'top',
+      false,
+      undefined
+    )().then((res) => {
+      expect(res).toEqual({
+        beforeFiles: [{ destination: '/top', source: '/' }]
+      })
+    })
+  })
+  it('must return activeRewiteRule when has mappings and active flag is true', () => {
+    return makeRewrites(
+      { main: '', challenger: 'https://example.com' },
+      'top',
+      true,
+      undefined
+    )().then((res) => {
+      expect(res).toEqual({
+        beforeFiles: [
+          {
+            destination: '/top/',
+            has: [{ key: 'next-with-split', type: 'cookie', value: 'main' }],
+            source: '/'
+          },
+          {
+            destination: '/:path*',
+            has: [{ key: 'next-with-split', type: 'cookie', value: 'main' }],
+            source: '/:path*/'
+          },
+          {
+            destination: 'https://example.com/top/',
+            has: [
+              { key: 'next-with-split', type: 'cookie', value: 'challenger' }
+            ],
+            source: '/'
+          },
+          {
+            destination: 'https://example.com/:path*',
+            has: [
+              { key: 'next-with-split', type: 'cookie', value: 'challenger' }
+            ],
+            source: '/:path*/'
+          },
+          {
+            destination: 'https://example.com/:path*',
+            has: [
+              { key: 'next-with-split', type: 'cookie', value: 'challenger' }
+            ],
+            source: '/:path*'
+          },
+          { destination: '/_split-challenge', source: '/:path*/' }
+        ]
+      })
+    })
+  })
+})

src/make-rewrites.ts

@@ -0,0 +1,56 @@
+import { Rewrite, RouteHas } from 'next/dist/lib/load-custom-routes'
+import { mergeRewrites } from './merge-rewrites'
+const rule = (
+  source: string,
+  destination: string,
+  additional = {}
+): Rewrite => ({
+  source,
+  destination,
+  ...additional
+})
+const has = (value: string): RouteHas[] => [
+  {
+    type: 'cookie',
+    key: 'next-with-split',
+    value
+  }
+]
+
+export type Mappings = { [branch: string]: string }
+
+export type Rewrites = {
+  beforeFiles?: Rewrite[]
+  afterFiles?: Rewrite[]
+  fallback?: Rewrite[]
+}
+
+export const makeRewrites =
+  (
+    mappings: Mappings,
+    rootPage: string,
+    active: boolean,
+    originalRewrite: (() => Promise<Rewrites | Rewrite[]>) | undefined
+  ) =>
+  async (): Promise<Rewrites> => {
+    const rewrite = await originalRewrite?.()
+    if (!active || Object.keys(mappings).length < 2)
+      return mergeRewrites(rewrite, {
+        beforeFiles: [rule('/', `/${rootPage}`)]
+      })
+
+    return mergeRewrites(rewrite, {
+      beforeFiles: [
+        ...Object.entries(mappings)
+          .map(([branch, origin]) => [
+            rule('/', `${origin}/${rootPage}/`, { has: has(branch) }),
+            rule('/:path*/', `${origin}/:path*`, { has: has(branch) }),
+            ...(origin
+              ? [rule('/:path*', `${origin}/:path*`, { has: has(branch) })]
+              : [])
+          ])
+          .flat(),
+        rule('/:path*/', '/_split-challenge')
+      ]
+    })
+  }