feat(auth): add signUpUseCase (test red until DI lands)

packages/auth/src/application/use-cases/sign-up.use-case.ts

@@ -0,0 +1,46 @@
+import { AuthenticationError } from "../../entities/errors";
+import type { Cookie } from "../../entities/cookie";
+import type { Session } from "../../entities/session";
+import type { User } from "../../entities/user";
+import { authContainer } from "../../di/container";
+import { AUTH_SYMBOLS } from "../../di/symbols";
+import type { IUsersRepository } from "../repositories/users-repository.interface";
+import type { IAuthenticationService } from "../services/authentication-service.interface";
+
+export async function signUpUseCase(input: {
+  username: string;
+  password: string;
+}): Promise<{
+  session: Session;
+  cookie: Cookie;
+  user: Pick<User, "id" | "username">;
+}> {
+  const usersRepository = authContainer.get<IUsersRepository>(
+    AUTH_SYMBOLS.IUsersRepository,
+  );
+  const authService = authContainer.get<IAuthenticationService>(
+    AUTH_SYMBOLS.IAuthenticationService,
+  );
+
+  const existingUser = await usersRepository.getUserByUsername(input.username);
+  if (existingUser) {
+    throw new AuthenticationError("Username taken");
+  }
+
+  const passwordHash = await authService.hashPassword(input.password);
+  const userId = authService.generateUserId();
+
+  const newUser = await usersRepository.createUser({
+    id: userId,
+    username: input.username,
+    passwordHash,
+  });
+
+  const { cookie, session } = await authService.createSession(newUser);
+
+  return {
+    cookie,
+    session,
+    user: { id: newUser.id, username: newUser.username },
+  };
+}