1 files changed, 139 insertions, 0 deletions
diff --git a/packages/create-turbo/src/utils/examples.ts b/packages/create-turbo/src/utils/examples.ts
new file mode 100644
index 0000000..b7c4812
--- /dev/null
+++ b/packages/create-turbo/src/utils/examples.ts
@@ -0,0 +1,139 @@
+import got from "got";
+import tar from "tar";
+import { Stream } from "stream";
+import { promisify } from "util";
+import { join } from "path";
+import { tmpdir } from "os";
+import { createWriteStream, promises as fs } from "fs";
+
+const pipeline = promisify(Stream.pipeline);
+
+export type RepoInfo = {
+  username: string;
+  name: string;
+  branch: string;
+  filePath: string;
+};
+
+export async function isUrlOk(url: string): Promise<boolean> {
+  try {
+    const res = await got.head(url);
+    return res.statusCode === 200;
+  } catch (err) {
+    return false;
+  }
+}
+
+export async function getRepoInfo(
+  url: URL,
+  examplePath?: string
+): Promise<RepoInfo | undefined> {
+  const [, username, name, tree, sourceBranch, ...file] =
+    url.pathname.split("/");
+  const filePath = examplePath
+    ? examplePath.replace(/^\//, "")
+    : file.join("/");
+
+  if (
+    // Support repos whose entire purpose is to be a Turborepo example, e.g.
+    // https://github.com/:username/:my-cool-turborepo-example-repo-name.
+    tree === undefined ||
+    // Support GitHub URL that ends with a trailing slash, e.g.
+    // https://github.com/:username/:my-cool-turborepo-example-repo-name/
+    // In this case "t" will be an empty string while the turbo part "_branch" will be undefined
+    (tree === "" && sourceBranch === undefined)
+  ) {
+    try {
+      const infoResponse = await got(
+        `https://api.github.com/repos/${username}/${name}`
+      );
+      const info = JSON.parse(infoResponse.body);
+      return { username, name, branch: info["default_branch"], filePath };
+    } catch (err) {
+      return;
+    }
+  }
+
+  // If examplePath is available, the branch name takes the entire path
+  const branch = examplePath
+    ? `${sourceBranch}/${file.join("/")}`.replace(
+        new RegExp(`/${filePath}|/$`),
+        ""
+      )
+    : sourceBranch;
+
+  if (username && name && branch && tree === "tree") {
+    return { username, name, branch, filePath };
+  }
+}
+
+export function hasRepo({
+  username,
+  name,
+  branch,
+  filePath,
+}: RepoInfo): Promise<boolean> {
+  const contentsUrl = `https://api.github.com/repos/${username}/${name}/contents`;
+  const packagePath = `${filePath ? `/${filePath}` : ""}/package.json`;
+
+  return isUrlOk(contentsUrl + packagePath + `?ref=${branch}`);
+}
+
+export function existsInRepo(nameOrUrl: string): Promise<boolean> {
+  try {
+    const url = new URL(nameOrUrl);
+    return isUrlOk(url.href);
+  } catch {
+    return isUrlOk(
+      `https://api.github.com/repos/vercel/turbo/contents/examples/${encodeURIComponent(
+        nameOrUrl
+      )}`
+    );
+  }
+}
+
+async function downloadTar(url: string, name: string) {
+  const tempFile = join(tmpdir(), `${name}.temp-${Date.now()}`);
+  await pipeline(got.stream(url), createWriteStream(tempFile));
+  return tempFile;
+}
+
+export async function downloadAndExtractRepo(
+  root: string,
+  { username, name, branch, filePath }: RepoInfo
+) {
+  const tempFile = await downloadTar(
+    `https://codeload.github.com/${username}/${name}/tar.gz/${branch}`,
+    `turbo-ct-example`
+  );
+
+  await tar.x({
+    file: tempFile,
+    cwd: root,
+    strip: filePath ? filePath.split("/").length + 1 : 1,
+    filter: (p: string) =>
+      p.startsWith(
+        `${name}-${branch.replace(/\//g, "-")}${
+          filePath ? `/${filePath}/` : "/"
+        }`
+      ),
+  });
+
+  await fs.unlink(tempFile);
+}
+
+export async function downloadAndExtractExample(root: string, name: string) {
+  const tempFile = await downloadTar(
+    `https://codeload.github.com/vercel/turbo/tar.gz/main`,
+    `turbo-ct-example`
+  );
+
+  await tar.x({
+    file: tempFile,
+    cwd: root,
+    strip: 2 + name.split("/").length,
+    filter: (p: string) => p.includes(`turbo-main/examples/${name}/`),
+  });
+
+  await fs.unlink(tempFile);
+}