3 files changed, 50 insertions, 2 deletions
diff --git a/cgithub/src/index.ts b/cgithub/src/index.ts
index 59c98ee..eb3a0ee 100644
--- a/cgithub/src/index.ts
+++ b/cgithub/src/index.ts
@@ -14,6 +14,7 @@ import {
   getGitHubRepo,
   getGitHubTree,
   GitHubHTTPError,
+  RedirectError,
 } from "./scraper.ts";
 
 const __dirname = path.dirname(url.fileURLToPath(import.meta.url));
@@ -32,7 +33,9 @@ async function tryRender<T extends object>(c: Context, template: string, promise
   try {
     data = await promise;
   } catch (e) {
-    if (e instanceof GitHubHTTPError) {
+    if (e instanceof RedirectError) {
+      return c.redirect(e.location);
+    } else if (e instanceof GitHubHTTPError) {
       c.status(e.status as StatusCode);
       const message = `GitHub responded with HTTP ${e.status} ${e.message}`;
       return c.html(await eta.renderAsync("error.eta", { title: e.message, message }));
diff --git a/cgithub/src/scraper.test.ts b/cgithub/src/scraper.test.ts
index 4432231..c20a5ff 100644
--- a/cgithub/src/scraper.test.ts
+++ b/cgithub/src/scraper.test.ts
@@ -9,6 +9,7 @@ import {
   getGitHubRepo,
   getGitHubTree,
   GitHubHTTPError,
+  RedirectError,
 } from "./scraper.ts";
 
 describe("GitHub scraper", () => {
@@ -245,5 +246,30 @@ describe("GitHub scraper", () => {
         return true;
       });
     });
+
+    it("should redirect when fetching a directory as a blob", async () => {
+      await assert.rejects(
+        getGitHubBlob("badlogic", "pi-mono", "main", "packages/agent"),
+        (err) => {
+          assert(err instanceof RedirectError, "error should be a RedirectError");
+          assert.strictEqual(err.location, "/badlogic/pi-mono/tree/main/packages/agent");
+          return true;
+        },
+      );
+    });
+
+    it("should redirect when fetching a file as a tree", async () => {
+      await assert.rejects(
+        getGitHubTree("badlogic", "pi-mono", "main", "packages/agent/package.json"),
+        (err) => {
+          assert(err instanceof RedirectError, "error should be a RedirectError");
+          assert.strictEqual(
+            err.location,
+            "/badlogic/pi-mono/blob/main/packages/agent/package.json",
+          );
+          return true;
+        },
+      );
+    });
   });
 });
diff --git a/cgithub/src/scraper.ts b/cgithub/src/scraper.ts
index 2dcd1d0..04a685b 100644
--- a/cgithub/src/scraper.ts
+++ b/cgithub/src/scraper.ts
@@ -13,6 +13,16 @@ export class GitHubHTTPError extends Error {
   }
 }
 
+export class RedirectError extends Error {
+  location: string;
+
+  constructor(location: string) {
+    super(`Redirect to ${location}`);
+    this.name = "RedirectError";
+    this.location = location;
+  }
+}
+
 interface TreeItem {
   contentType: "directory" | "file";
   name: string;
@@ -286,7 +296,16 @@ async function fetchGitHubPage(path: string): Promise<string> {
     Accept: "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8",
     "Accept-Language": "en-US,en;q=0.5",
   };
-  const response = await fetch(`https://github.com/${path}`, { headers });
+  const response = await fetch(`https://github.com/${path}`, { headers, redirect: "manual" });
+  if (response.status === 301 || response.status === 302) {
+    const location = response.headers.get("location");
+    if (location) {
+      const url = new URL(location);
+      if (url.hostname === "github.com") {
+        throw new RedirectError(url.pathname);
+      }
+    }
+  }
   if (!response.ok) throw new GitHubHTTPError(response.status, response.statusText);
   return response.text();
 }