Restructure code into separate files

packages/safe-chain/src/installation/downloadAgent.js

@@ -0,0 +1,40 @@
+import { createWriteStream } from "fs";
+import { pipeline } from "stream/promises";
+import fetch from "make-fetch-happen";
+
+const ULTIMATE_VERSION = "v0.2.0";
+
+/**
+ * @typedef {"windows"} Platform
+ * @typedef {"amd64" | "arm64"} Architecture
+ */
+
+/**
+ * Builds the download URL for the SafeChain Agent installer.
+ * @param {Platform} platform
+ * @param {Architecture} architecture
+ */
+export function getAgentDownloadUrl(platform, architecture) {
+  const extension = platform === "windows" ? "msi" : "pkg";
+  return `https://github.com/AikidoSec/safechain-internals/releases/download/${ULTIMATE_VERSION}/SafeChainAgent-${platform}-${architecture}.${extension}`;
+}
+
+/**
+ * Downloads a file from a URL to a local path.
+ * @param {string} url
+ * @param {string} destPath
+ */
+export async function downloadFile(url, destPath) {
+  const response = await fetch(url);
+  if (!response.ok) {
+    throw new Error(`Download failed: ${response.statusText}`);
+  }
+  await pipeline(response.body, createWriteStream(destPath));
+}
+
+/**
+ * Returns the current agent version.
+ */
+export function getAgentVersion() {
+  return ULTIMATE_VERSION;
+}