Initial Nest.js backend

backend/src/auth/auth.guard.ts

@@ -0,0 +1,39 @@
+import {
+  CanActivate,
+  ExecutionContext,
+  Injectable,
+  UnauthorizedException,
+} from '@nestjs/common';
+import { JwtService } from '@nestjs/jwt';
+import { JWT_SECRET } from '../consts';
+import { AuthUser } from './auth.service';
+
+@Injectable()
+export class AuthGuard implements CanActivate {
+  constructor(private jwtService: JwtService) {}
+
+  async canActivate(context: ExecutionContext): Promise<boolean> {
+    const request = context.switchToHttp().getRequest();
+    const token = this.extractTokenFromHeader(request);
+    if (!token) {
+      throw new UnauthorizedException();
+    }
+    try {
+      const payload = await this.jwtService.verifyAsync(token, {
+        secret: JWT_SECRET,
+      });
+      // 💡 We're assigning the payload to the request object here
+      // so that we can access it in our route handlers
+      request['user'] = payload as AuthUser;
+    } catch {
+      throw new UnauthorizedException();
+    }
+    return true;
+  }
+
+  private extractTokenFromHeader(request: Request): string | undefined {
+    const [type, token] =
+      (request.headers as any).authorization?.split(' ') ?? [];
+    return type === 'Bearer' ? token : undefined;
+  }
+}