feat(media): add in-place media file replacement flow

apps/admin/src/app/media/[id]/page.tsx

@@ -1,10 +1,15 @@
+import {
+  getMediaUploadMaxBytes,
+  isMimeAllowedForMediaType,
+  mediaAssetTypeSchema,
+} from "@cms/content"
 import { deleteMediaAsset, getMediaAssetById, updateMediaAsset } from "@cms/db"
 import { Button } from "@cms/ui/button"
 import Link from "next/link"
 import { redirect } from "next/navigation"
 
 import { AdminShell } from "@/components/admin-shell"
-import { deleteStoredMediaObject } from "@/lib/media/storage"
+import { deleteStoredMediaObject, storeUpload } from "@/lib/media/storage"
 import { requirePermissionForRoute } from "@/lib/route-guards"
 
 export const dynamic = "force-dynamic"
@@ -79,7 +84,10 @@ function readTags(formData: FormData): string[] {
     .filter((item) => item.length > 0)
 }
 
-function redirectWithState(mediaAssetId: string, params: { notice?: string; error?: string }) {
+function redirectWithState(
+  mediaAssetId: string,
+  params: { notice?: string; error?: string },
+): never {
   const query = new URLSearchParams()
 
   if (params.notice) {
@@ -189,6 +197,80 @@ export default async function MediaAssetEditorPage({ params, searchParams }: Pag
     redirect("/media?notice=Media+asset+deleted")
   }
 
+  async function replaceMediaFileAction(formData: FormData) {
+    "use server"
+
+    await requirePermissionForRoute({
+      nextPath: "/media",
+      permission: "media:write",
+      scope: "team",
+    })
+
+    const fileEntry = formData.get("file")
+
+    if (!(fileEntry instanceof File) || fileEntry.size === 0) {
+      redirectWithState(mediaAssetId, { error: "Select a replacement file first." })
+    }
+
+    const parsedType = mediaAssetTypeSchema.safeParse(mediaAsset.type)
+
+    if (!parsedType.success) {
+      redirectWithState(mediaAssetId, { error: "Media type is invalid for replacement." })
+    }
+    const mediaType = parsedType.data
+    const maxBytes = getMediaUploadMaxBytes(mediaType)
+
+    if (fileEntry.size > maxBytes) {
+      redirectWithState(mediaAssetId, {
+        error: `Replacement file is too large for ${mediaType}. Max ${Math.floor(maxBytes / 1024 / 1024)} MB.`,
+      })
+    }
+
+    if (!isMimeAllowedForMediaType(mediaType, fileEntry.type)) {
+      redirectWithState(mediaAssetId, {
+        error: `File type ${fileEntry.type || "unknown"} is not allowed for ${mediaType}.`,
+      })
+    }
+
+    const previousStorageKey = mediaAsset.storageKey
+
+    try {
+      const stored = await storeUpload({
+        file: fileEntry,
+        assetId: mediaAssetId,
+        variant: "original",
+        fileRole: "original",
+      })
+
+      await updateMediaAsset({
+        id: mediaAssetId,
+        storageKey: stored.storageKey,
+        mimeType: fileEntry.type || null,
+        sizeBytes: fileEntry.size,
+        width: null,
+        height: null,
+      })
+
+      if (previousStorageKey && previousStorageKey !== stored.storageKey) {
+        try {
+          await deleteStoredMediaObject(previousStorageKey)
+        } catch {
+          redirectWithState(mediaAssetId, {
+            notice: "Media file replaced, but old file cleanup failed in storage backend.",
+          })
+        }
+      }
+
+      const replacementNotice = stored.fallbackReason
+        ? `Media file replaced. ${stored.fallbackReason}`
+        : `Media file replaced via ${stored.provider}.`
+
+      redirectWithState(mediaAssetId, { notice: replacementNotice })
+    } catch {
+      redirectWithState(mediaAssetId, { error: "Failed to replace media file." })
+    }
+  }
+
   return (
     <AdminShell
       role={role}
@@ -254,6 +336,25 @@ export default async function MediaAssetEditorPage({ params, searchParams }: Pag
         ) : null}
       </section>
 
+      <section className="rounded-xl border border-neutral-200 p-6">
+        <h3 className="text-lg font-medium">Replace File</h3>
+        <p className="mt-1 text-sm text-neutral-600">
+          Upload a new source file for this media asset while keeping the same metadata and asset
+          ID.
+        </p>
+        <form action={replaceMediaFileAction} className="mt-4 flex flex-wrap items-center gap-3">
+          <input
+            name="file"
+            type="file"
+            required
+            className="rounded border border-neutral-300 px-3 py-2 text-sm"
+          />
+          <Button type="submit" variant="secondary">
+            Replace media file
+          </Button>
+        </form>
+      </section>
+
       <section className="rounded-xl border border-neutral-200 p-6">
         <div className="flex flex-wrap items-center justify-between gap-3">
           <div>