Refactor site generation into a modular content pipeline

output.js

@@ -0,0 +1,29 @@
+import { mkdtemp, rename, rm, stat } from 'node:fs/promises'
+import { dirname, join } from 'node:path'
+
+const exists = async (path) => {
+  try {
+    await stat(path)
+    return true
+  } catch (error) {
+    if (error.code === 'ENOENT') return false
+    throw error
+  }
+}
+
+export const createOutput = (destination) => mkdtemp(join(dirname(destination), '.generated-next-'))
+
+export const publishOutput = async (staging, destination) => {
+  const previous = `${staging}-previous`
+  const hadPrevious = await exists(destination)
+  if (hadPrevious) await rename(destination, previous)
+  try {
+    await rename(staging, destination)
+  } catch (error) {
+    if (hadPrevious) await rename(previous, destination)
+    throw error
+  }
+  if (hadPrevious) await rm(previous, { recursive: true })
+}
+
+export const discardOutput = (staging) => rm(staging, { recursive: true, force: true })