V.1

app/lib/hosted.ts

@@ -0,0 +1,70 @@
+/**
+ * Dumps the site ships with.
+ *
+ * These are never fetched on load. A prebaked dump is tens of megabytes, and
+ * most visitors arrive with their own file or with one already in IndexedDB;
+ * spending their bandwidth on a speculative download would be rude. The
+ * manifest is a few hundred bytes and is all we read until someone asks for
+ * a dump by name.
+ */
+
+export interface HostedDump {
+  /** Stable id, independent of the file name. Recorded on the cached copy so
+   *  a downloaded dump can be struck from the offer list. */
+  id: string
+  /** Path under the site root. */
+  file: string
+  title: string
+  note?: string
+  /** Bytes on the wire, for the "how big is this" question. Optional. */
+  bytes?: number
+  /** 'pdx' is a prebaked column bundle; 'text' is a raw UE4SS dump. */
+  format?: 'text' | 'pdx'
+}
+
+const MANIFEST = '/dumps.json'
+
+export async function listHosted(): Promise<HostedDump[]> {
+  const res = await fetch(MANIFEST, { cache: 'no-cache' })
+  if (!res.ok) return []
+  const body = await res.json()
+  return Array.isArray(body) ? body : (body.dumps ?? [])
+}
+
+/**
+ * Fetch with byte progress. `Content-Length` is absent under chunked transfer
+ * encoding, which nginx will use for these once gzip is on, so the caller has
+ * to tolerate a null fraction rather than a bogus one.
+ */
+export async function download(
+  d: HostedDump,
+  onProgress?: (fraction: number | null, received: number) => void,
+): Promise<ArrayBuffer> {
+  const res = await fetch(d.file)
+  if (!res.ok) throw new Error(`Could not fetch ${d.file} (${res.status})`)
+
+  const declared = Number(res.headers.get('content-length')) || d.bytes || 0
+  if (!res.body) return res.arrayBuffer()
+
+  const reader = res.body.getReader()
+  const chunks: Uint8Array[] = []
+  let received = 0
+  for (;;) {
+    const { done, value } = await reader.read()
+    if (done) break
+    chunks.push(value)
+    received += value.length
+    onProgress?.(declared ? Math.min(1, received / declared) : null, received)
+  }
+
+  const out = new Uint8Array(received)
+  let at = 0
+  for (const c of chunks) {
+    out.set(c, at)
+    at += c.length
+  }
+  return out.buffer
+}
+
+/** File name to record on the cached copy, so titles read like a real file. */
+export const fileNameOf = (d: HostedDump) => d.file.split('/').pop() || d.id