feat(api): add global error handler with typed error classes

- Add AppError base class, ValidationError (400), NotFoundError (404)
- Add central error middleware in app.ts
- Remove inline safeParse error handling from controllers
- Replace plain Error throws with NotFoundError in gameService

apps/api/src/controllers/gameController.ts

@@ -1,32 +1,42 @@
-import type { Request, Response } from "express";
+import type { Request, Response, NextFunction } from "express";
 import { GameRequestSchema, AnswerSubmissionSchema } from "@glossa/shared";
 import { createGameSession, evaluateAnswer } from "../services/gameService.js";
+import { ValidationError } from "../errors/AppError.js";
 
-export const createGame = async (req: Request, res: Response) => {
-  const gameSettings = GameRequestSchema.safeParse(req.body);
+export const createGame = async (
+  req: Request,
+  res: Response,
+  next: NextFunction,
+) => {
+  try {
+    const gameSettings = GameRequestSchema.safeParse(req.body);
 
-  // TODO: remove when global error handler is implemented
-  if (!gameSettings.success) {
-    res.status(400).json({ success: false });
-    return;
+    if (!gameSettings.success) {
+      throw new ValidationError(gameSettings.error.message);
+    }
+
+    const gameQuestions = await createGameSession(gameSettings.data);
+    res.json({ success: true, data: gameQuestions });
+  } catch (error) {
+    next(error);
   }
-
-  const gameQuestions = await createGameSession(gameSettings.data);
-
-  res.json({ success: true, data: gameQuestions });
 };
 
-export const submitAnswer = async (req: Request, res: Response) => {
-  const submission = AnswerSubmissionSchema.safeParse(req.body);
-  // TODO: remove when global error handler is implemented
-  if (!submission.success) {
-    res.status(400).json({ success: false });
-    return;
-  }
+export const submitAnswer = async (
+  req: Request,
+  res: Response,
+  next: NextFunction,
+) => {
   try {
+    const submission = AnswerSubmissionSchema.safeParse(req.body);
+
+    if (!submission.success) {
+      throw new ValidationError(submission.error.message);
+    }
+
     const result = await evaluateAnswer(submission.data);
     res.json({ success: true, data: result });
   } catch (error) {
-    res.status(404).json({ success: false });
+    next(error);
   }
 };