feat: add a function to download libraries and its test

src/core/index.ts

@@ -1,3 +1,4 @@
 export * as java from "./java";
 export * as version from "./version";
 export * as natives from "./natives";
+export * as libraries from "./libraries";

src/core/libraries.ts

@@ -0,0 +1,20 @@
+import path from "path";
+import { parseRule } from "../utils/rules";
+import { Library, PoolFile, Version } from "../utils/types";
+import { DownloadPool } from "../utils/fetch";
+
+export async function download(destination: string, versionManifest: Version) {
+  // Download libraries
+  const files = versionManifest.libraries.map<PoolFile>((library: Library) => {
+    if (!parseRule(library)) {
+      return {
+        url: library.downloads.artifact.url,
+        path: path.join(destination, library.downloads.artifact.path),
+      };
+    }
+  });
+
+  const dPool = new DownloadPool(files, 5);
+
+  await dPool.run();
+}

src/utils/fetch.ts

@@ -2,6 +2,8 @@ import fs from "fs";
 import { pipeline } from "stream/promises";
 import { PoolFile } from "./types";
 import { Task } from "./task";
+import { ensureDir } from "./fs";
+import path from "path";
 
 export async function fetchJson<T>(url: string): Promise<T> {
   return await (await fetch(url)).json();
@@ -13,6 +15,7 @@ export async function downloadFile(
 ) {
   try {
     if (!file) return;
+    await ensureDir(path.dirname(file.path), true);
     const res = await fetch(file.url, { signal });
 
     if (!res.ok)

tests/libraries.test.ts

@@ -0,0 +1,31 @@
+import { expect, test } from "vitest";
+import * as nlk from "../dist/index.js";
+import path from "path";
+import fs from "fs/promises";
+
+const librariesPath = path.join(import.meta.dirname, "temp/libraries");
+await fs.rm(librariesPath, { recursive: true, force: true });
+await fs.mkdir(librariesPath, { recursive: true });
+
+async function exists(path: string) {
+  try {
+    await fs.access(path, fs.constants.F_OK);
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+test(
+  "download libraries for 1.21.8 correctly",
+  { timeout: 10000 },
+  async () => {
+    const versionManifest = await nlk.core.version.getVersionManifest("1.21.8");
+    await nlk.core.libraries.download(librariesPath, versionManifest);
+
+    expect(
+      await exists(path.join(librariesPath, "com/fasterxml/jackson/core/jackson-core/2.13.4/jackson-core-2.13.4.jar")),
+      "com/fasterxml/jackson/core/jackson-core/2.13.4/jackson-core-2.13.4.jar exists",
+    ).toBe(true);
+  },
+);