refactor: move access guards logic into reusable functions (#4535)

* refactor: move access guards logic into reusable functions

* Update src/common/access.js

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Alexandr <qwerty541zxc@gmail.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

src/common/access.js

@@ -0,0 +1,61 @@
+// @ts-check
+
+import { renderError } from "./utils.js";
+import { blacklist } from "./blacklist.js";
+import { whitelist, gistWhitelist } from "./envs.js";
+
+const NOT_WHITELISTED_USERNAME_MESSAGE = "This username is not whitelisted";
+const NOT_WHITELISTED_GIST_MESSAGE = "This gist ID is not whitelisted";
+const BLACKLISTED_MESSAGE = "This username is blacklisted";
+
+/**
+ * Guards access using whitelist/blacklist.
+ *
+ * @param {Object} args The parameters object.
+ * @param {Object} args.res The response object.
+ * @param {string} args.id Resource identifier (username or gist id).
+ * @param {"username"|"gist"|"wakatime"} args.type The type of identifier.
+ * @param {{ title_color?: string, text_color?: string, bg_color?: string, border_color?: string, theme?: string }} args.colors Color options for the error card.
+ * @returns {{ isPassed: boolean, result?: any }} The result object indicating success or failure.
+ */
+const guardAccess = ({ res, id, type, colors }) => {
+  if (!["username", "gist", "wakatime"].includes(type)) {
+    throw new Error(
+      'Invalid type. Expected "username", "gist", or "wakatime".',
+    );
+  }
+
+  const currentWhitelist = type === "gist" ? gistWhitelist : whitelist;
+  const notWhitelistedMsg =
+    type === "gist"
+      ? NOT_WHITELISTED_GIST_MESSAGE
+      : NOT_WHITELISTED_USERNAME_MESSAGE;
+
+  if (Array.isArray(currentWhitelist) && !currentWhitelist.includes(id)) {
+    const result = res.send(
+      renderError(notWhitelistedMsg, "Please deploy your own instance", {
+        ...colors,
+        show_repo_link: false,
+      }),
+    );
+    return { isPassed: false, result };
+  }
+
+  if (
+    type === "username" &&
+    currentWhitelist === undefined &&
+    blacklist.includes(id)
+  ) {
+    const result = res.send(
+      renderError(BLACKLISTED_MESSAGE, "Please deploy your own instance", {
+        ...colors,
+        show_repo_link: false,
+      }),
+    );
+    return { isPassed: false, result };
+  }
+
+  return { isPassed: true };
+};
+
+export { guardAccess };