game version re-ordering

server/internal/downloads/README.md

@@ -1,8 +0,0 @@
-# Drop Download System
-Drop downloads come in two types:
-
-## Public (not quite) HTTPS downloads endpoints
-These use public HTTPS certificate, and while are authenticated, are 'public' in the sense that they aren't P2P; anyone can connect to them
-
-## Private mTLS P2P endpoints
-Drop clients use P2P mTLS aided by the P2P co-ordinator to transfer chunks between themselves. 

server/internal/downloads/manifest.ts

@@ -0,0 +1,52 @@
+export type DropChunk = {
+  permissions: number;
+  ids: string[];
+  checksums: string[];
+  lengths: string[];
+};
+
+export type DropManifest = {
+  [key: string]: DropChunk;
+};
+
+export type DropManifestMetadata = {
+  manifest: DropManifest;
+  versionName: string;
+};
+
+export type DropGeneratedManifest = DropManifest & {
+  [key: string]: { versionName: string };
+};
+
+class ManifestGenerator {
+  static generateManifest(
+    rootManifest: DropManifestMetadata,
+    ...overlays: DropManifestMetadata[]
+  ): DropGeneratedManifest {
+    if (overlays.length == 0) {
+      return Object.fromEntries(
+        Object.entries(rootManifest.manifest).map(([key, value]) => [
+          key,
+          Object.assign({}, value, { versionName: rootManifest.versionName }),
+        ])
+      );
+    }
+
+    // Recurse in verse order through versions, skipping files that already exist.
+    const versions = [...overlays.reverse(), rootManifest];
+    const manifest: DropGeneratedManifest = {};
+    for (const version of versions) {
+      for (const [filename, chunk] of Object.entries(version.manifest)) {
+        if (manifest[filename]) continue;
+        manifest[filename] = Object.assign({}, chunk, {
+          versionName: version.versionName,
+        });
+      }
+    }
+
+    return manifest;
+  }
+}
+
+export const manifestGenerator = new ManifestGenerator();
+export default manifestGenerator;