feat(sync): check which Side a metafile should be downloaded on before downloading it

packages/sync/src/sync.ts

@@ -4,6 +4,8 @@ import {
   type Metafile,
   type PackwizIndex,
   HashFormat,
+  Side,
+  isValidSide,
   doHashesMatch,
 } from "@packwizjs/parser";
 import { write } from "bun";
@@ -62,16 +64,19 @@ function formatBytes(bytes: number, decimals: number = 2) {
 /**
  * Iterates over the files in a Packwiz index and downloads them concurrently.
  * @param index The Packwiz index to iterate over.
+ * @param side The side to download files for (e.g., "client", "server", or "both").
  * @param concurrencyLimit The maximum number of concurrent downloads.
  * @returns A promise that resolves when all files have been downloaded.
  */
 export async function iteratePackwizIndex(
   index: PackwizIndex,
+  side: Side,
   concurrencyLimit: number = 5,
 ) {
   let currentIndex = 0;
   let activeDownloads = 0;
   const totalFiles = index.files.length;
+  side = side.toLowerCase() as Side;
 
   return new Promise<void>((resolve, reject) => {
     function downloadNextFile() {
@@ -96,11 +101,28 @@ export async function iteratePackwizIndex(
 
             if (file.metafile) {
               const metafile = await file.parse();
+
+              if (!metafile.side || !isValidSide(metafile.side)) {
+                throw new Error(
+                  `Metafile ${metafile.filename} has invalid Side: ${metafile.side}`,
+                );
+              }
+
+              if (metafile.side !== Side.Both && metafile.side !== side) {
+                // Don't throw an error here, this is normal behavior!
+                console.log(
+                  `Skipping metafile ${metafile.filename} due to side mismatch: '${metafile.side}' (Wanted '${side}' or '${Side.Both}')`,
+                );
+                return;
+              }
+
               hash = metafile.provider.hash;
               hashFormat = metafile.provider.hashFormat;
               url = metafile.provider.url;
               saveLocation = getSaveLocation(file, index, metafile);
             } else {
+              // we don't check non-metafiles' Side because packwiz doesn't store metadata for whether or not to download them on client / server
+              // so instead, always download them on both sides (assume Side.Both)
               const diff = index.location.diff(file.file);
               hash = file.hash;
               hashFormat = file.hashFormat;