feat: auto install middleware

package.json

@@ -5,6 +5,9 @@
   "main": "./build/index.js",
   "module": "./esm/main.js",
   "types": "./esm/main.d.ts",
+  "bin": {
+    "with-next-split": "./build/script.js"
+  },
   "files": [
     "build",
     "esm"

src/script.ts

@@ -0,0 +1,52 @@
+#!/usr/bin/env node
+
+import { statSync, unlinkSync, writeFileSync } from 'node:fs'
+import { resolve } from 'node:path'
+
+const installMiddleware = (pagePath: string) => {
+  writeFileSync(
+    resolve(__dirname, '../..', pagePath, '_middleware.js'),
+    scriptText
+  )
+}
+
+const removeMiddleware = (pagePath: string) => {
+  ;['js', 'ts'].forEach((ext) => {
+    const path = resolve(__dirname, '../..', pagePath, `_middleware.${ext}`)
+    if (
+      statSync(path, {
+        throwIfNoEntry: false
+      })
+    ) {
+      unlinkSync(path)
+    }
+  })
+}
+
+const scriptText = `// NOTE: in this location, this file does nothing
+// scripts/split.mjs will copy this file to /pages/_middleware.js at
+// install/deploy if process.env.NEXT_SPLIT_ACTIVE == 1
+export { middleware } from 'next-with-split'
+`
+
+const main = () => {
+  const command = process.argv[2]
+  const pagesPath = process.argv[3]
+
+  switch (command) {
+    case 'remove':
+      console.info(
+        `split traffic disabled, removing middleware from ${pagesPath}`
+      )
+      removeMiddleware(pagesPath)
+      break
+    case 'install':
+      console.info(
+        `split traffic enabled, installing middleware to ${pagesPath}`
+      )
+      installMiddleware(pagesPath)
+      break
+  }
+}
+
+main()