feat: add extensive test suite

app/(ui)/rubgram/callback/handler.ts

@@ -0,0 +1,107 @@
+type OAuthConfig = {
+  clientId: string;
+  clientSecret: string;
+  redirectUri: string;
+  guildId: string;
+  botToken: string;
+};
+
+type OAuthUser = { id: string; username: string; global_name?: string | null };
+
+type CallbackDependencies = {
+  config: OAuthConfig;
+  fetch: (input: RequestInfo | URL, init?: RequestInit) => Promise<Response>;
+  getState: () => string | undefined;
+  clearState: () => void;
+  setSession: (token: string) => void;
+  saveUser: (user: {
+    uid: string;
+    display: string;
+    username: string;
+  }) => Promise<string>;
+  redirect: (path: string) => Response;
+  logError?: (message: string, error?: unknown) => void;
+};
+
+export function createRubgramCallbackHandler(
+  dependencies: CallbackDependencies,
+) {
+  return async function GET(request: Request): Promise<Response> {
+    const searchParams = new URL(request.url).searchParams;
+    const oauthError = searchParams.has("error");
+    const code = searchParams.get("code");
+    if (!code && !oauthError)
+      return Response.json({ error: "No code provided" }, { status: 400 });
+
+    const expectedState = dependencies.getState();
+    const state = searchParams.get("state");
+    dependencies.clearState();
+    if (!expectedState || !state || state !== expectedState)
+      return Response.json({ error: "Invalid OAuth state" }, { status: 400 });
+    if (oauthError) return dependencies.redirect("/rubgram");
+
+    try {
+      const tokenResponse = await dependencies.fetch(
+        "https://discord.com/api/oauth2/token",
+        {
+          method: "POST",
+          headers: { "Content-Type": "application/x-www-form-urlencoded" },
+          body: new URLSearchParams({
+            client_id: dependencies.config.clientId,
+            client_secret: dependencies.config.clientSecret,
+            grant_type: "authorization_code",
+            code: code!,
+            redirect_uri: dependencies.config.redirectUri,
+          }),
+        },
+      );
+      if (!tokenResponse.ok)
+        throw new Error(`Failed to exchange code: ${tokenResponse.status}`);
+
+      const tokenData = (await tokenResponse.json()) as {
+        access_token?: string;
+      };
+      if (!tokenData.access_token)
+        throw new Error("Discord omitted access token");
+      const accessToken = tokenData.access_token;
+
+      const userResponse = await dependencies.fetch(
+        "https://discord.com/api/users/@me",
+        { headers: { Authorization: `Bearer ${accessToken}` } },
+      );
+      if (!userResponse.ok) throw new Error("Failed to fetch user data");
+      const user = (await userResponse.json()) as OAuthUser;
+
+      const memberResponse = await dependencies.fetch(
+        `https://discord.com/api/users/@me/guilds/${dependencies.config.guildId}/member`,
+        { headers: { Authorization: `Bearer ${accessToken}` } },
+      );
+      if (!memberResponse.ok) {
+        const addResponse = await dependencies.fetch(
+          `https://discord.com/api/guilds/${dependencies.config.guildId}/members/${user.id}`,
+          {
+            method: "PUT",
+            headers: {
+              Authorization: `Bot ${dependencies.config.botToken}`,
+              "Content-Type": "application/json",
+            },
+            body: JSON.stringify({ access_token: accessToken }),
+          },
+        );
+        if (!addResponse.ok)
+          dependencies.logError?.("Failed to add user to guild");
+      }
+
+      const token = await dependencies.saveUser({
+        uid: user.id,
+        display: user.global_name || user.username,
+        username: user.username,
+      });
+      dependencies.setSession(token);
+      return dependencies.redirect("/rubgram");
+    } catch (error) {
+      dependencies.logError?.("Discord OAuth error", error);
+      return Response.json({ error: "Authentication failed" }, { status: 500 });
+    }
+  };
+}