feat(backend): add username-based public profile lookup endpoint

Closes #283

Author: Spagero763

backend/src/users/users.controller.ts

@@ -91,6 +91,21 @@ export class UsersController {
     return this.userService.getMyStats(req.user.id as string);
   }
 
+  @Get('by-username/:username')
+  async getPublicProfileByUsername(
+    @Param('username') username: string,
+  ): Promise<{
+    id: string;
+    username: string | null;
+    xp: number;
+    badgesCount: number;
+    coursesCompleted: number;
+    avatarUrl: string | null;
+    bio: string | null;
+  }> {
+    return this.userService.findByUsername(username);
+  }
+
   @Get(':id/public')
   async getPublicProfile(@Param('id') id: string): Promise<{
     id: string;

backend/src/users/users.service.ts

@@ -6,7 +6,7 @@ import {
   BadRequestException,
 } from '@nestjs/common';
 import { InjectRepository } from '@nestjs/typeorm';
-import { Repository, MoreThan } from 'typeorm';
+import { ILike, Repository, MoreThan } from 'typeorm';
 import * as crypto from 'crypto';
 import * as bcrypt from 'bcrypt';
 import { RegisterDto } from 'src/auth/dto/register.dto';
@@ -302,4 +302,36 @@ export class UserService {
       bio: user.bio ?? null,
     };
   }
+
+  async findByUsername(username: string): Promise<{
+    id: string;
+    username: string | null;
+    xp: number;
+    badgesCount: number;
+    coursesCompleted: number;
+    avatarUrl: string | null;
+    bio: string | null;
+  }> {
+    const user = await this.userRepository.findOne({
+      where: { username: ILike(username) },
+    });
+
+    if (!user) {
+      throw new NotFoundException('User not found');
+    }
+
+    const badgesCount = await this.userBadgeRepository.count({
+      where: { userId: user.id },
+    });
+
+    return {
+      id: user.id,
+      username: user.username ?? user.name ?? null,
+      xp: this.resolveXp(user),
+      badgesCount,
+      coursesCompleted: user.coursesCompleted ?? 0,
+      avatarUrl: user.avatarUrl ?? null,
+      bio: user.bio ?? null,
+    };
+  }
 }