Nicer 404 message when a snapshot version is invalid

Also respond 200 if visiting the root of a valid snapshot version.

Author: xuhdev

gen_caddy.ts

@@ -20,7 +20,7 @@
 
 import snapshotVersions from "./snapshot_versions.json" with { type: "json" };
 
-const snapVersionsRegexp = snapshotVersions.join("|");
+const snapshotVersionsRegexp = snapshotVersions.join("|");
 
 const caddyfile = `
 {
@@ -30,14 +30,41 @@ const caddyfile = `
 {$HOST_ADDRESS:localhost} {
 	redir / https://delpa.org permanent
 
-	respond /health-check "OK"
-
-	@snapshot path_regexp ^/snapshot/(${snapVersionsRegexp})/(.*)$
-	redir @snapshot https://raw.githubusercontent.com/delpa-org/melpa-snapshot-{re.1}/refs/heads/master/packages/{re.2} permanent
+  respond /health-check "OK" {
+    close
+  }
 
 	respond "404 Not Found" 404 {
 		close
 	}
+
+  route /snapshot/* {
+    @valid-snapshot-root path_regexp ^/snapshot/(${snapshotVersionsRegexp})/*$
+    respond @valid-snapshot-root 200 {
+      body "{re.1} is a valid snapshot version."
+      close
+    }
+    @valid-snapshot path_regexp ^/snapshot/(${snapshotVersionsRegexp})/(.*)$
+    redir @valid-snapshot https://raw.githubusercontent.com/delpa-org/melpa-snapshot-{re.1}/refs/heads/master/packages/{re.2} permanent
+
+    @invalid-snapshot path_regexp ^/snapshot/([^/]+).*$
+    respond @invalid-snapshot 404 {
+
+      body "404 Not Found. Invalid snapshot version: {re.1}
+
+Currently this server thinks the following snapshots are valid:
+
+${snapshotVersions
+  .toSorted()
+  .reverse()
+  .map((v) => `- ${v}`)
+  .join("\n")}
+
+For more information, please visit the Delpa homepage: https://delpa.org"
+
+      close
+    }
+  }
 }
 `;
 

index.test.ts

@@ -39,10 +39,13 @@ test("/health-check returns 200 with OK", async () => {
 describe("/snapshot", () => {
   const snapshotFirstPathComp = "snapshot" as const;
   for (const [name, path] of [
-    ["valid with a one-level subdir", "2024-01-01/a"],
-    ["valid with a one-level subdir with a trailing slash", "2024-01-01/a/"],
-    ["valid with a two-level subdir", "2024-01-01/a/b"],
-    ["valid with a two-level subdir with a trailing slash", "2024-01-01/a/b/"],
+    ["valid with a one-level subdir", "2024-01-01/a/b"],
+    ["valid with a one-level subdir with a trailing slash", "2024-02-02/a/b/"],
+    ["valid with a two-level subdir", "2024-01-01/a/b/c"],
+    [
+      "valid with a two-level subdir with a trailing slash",
+      "2024-03-03/a/b/c/",
+    ],
   ] as const) {
     test(`Redirect with valid URL under /shapshot: ${name}`, async () => {
       const response = await fetch(
@@ -55,14 +58,33 @@ describe("/snapshot", () => {
       expect(response.status).toBe(301);
       expect(response.headers.get("location")).toBe(
         delpaGitHubRawBaseUrl +
-          "/melpa-snapshot-2024-01-01/refs/heads/master/packages/" +
+          `/melpa-snapshot-${path.split("/")[0]}/refs/heads/master/packages/` +
           path.slice(
             path.indexOf("/") + 1, // Remove the top-level folder in path
           ),
       );
     });
   }
 
+  for (const [name, path] of [
+    ["without a trailing slash", "2024-01-01"],
+    ["with a trailing slash", "2024-02-02/"],
+  ] as const) {
+    test(`Report OK with valid snapshot version at a root dir of /shapshot: ${name}`, async () => {
+      const response = await fetch(
+        `${hostAddress}/${snapshotFirstPathComp}/${path}`,
+        {
+          redirect: "manual",
+        },
+      );
+
+      expect(response.status).toBe(200);
+      const responseText = await response.text();
+      expect(responseText).toContain("valid snapshot version");
+      expect(responseText).toContain(path.split("/")[0]);
+    });
+  }
+
   for (const [name, path] of [
     ["non-existing snapshot", "2025-01-01"],
     ["non-existing partially-matched snapshot", "2024-01"],
@@ -89,7 +111,11 @@ describe("/snapshot", () => {
 
       expect(response.status).toBe(404);
       expect(response.headers.get("content-type")).toContain("text/plain");
-      expect(await response.text()).toBe("404 Not Found");
+      const responseText = await response.text();
+      expect(responseText).toContain("404 Not Found");
+      expect(responseText).toContain(
+        `Invalid snapshot version: ${path.split("/")[0]}`,
+      );
     });
   }
 });

prod.test.ts

@@ -60,6 +60,20 @@ describe("/snapshot", () => {
     );
   });
 
+  test("Report OK with valid snapshot version at a root dir of /shapshot", async () => {
+    const response = await fetch(
+      `${hostAddress}/${snapshotFirstPathComp}/2025-01-02`,
+      {
+        redirect: "manual",
+      },
+    );
+
+    expect(response.status).toBe(200);
+    const responseText = await response.text();
+    expect(responseText).toContain("valid snapshot version");
+    expect(responseText).toContain("2025-01-02");
+  });
+
   test("Return 404 with invalid URL under /shapshot", async () => {
     const response = await fetch(
       `${hostAddress}/${snapshotFirstPathComp}/non-existing`,