Introduce pluggable email and image upload

src/main/java/com/openisle/controller/AuthController.java

@@ -1,7 +1,7 @@
 package com.openisle.controller;
 
 import com.openisle.model.User;
-import com.openisle.service.EmailService;
+import com.openisle.service.EmailSender;
 import com.openisle.service.JwtService;
 import com.openisle.service.UserService;
 import lombok.Data;
@@ -42,7 +42,7 @@ curl -X POST http://localhost:8080/api/auth/login \
 public class AuthController {
     private final UserService userService;
     private final JwtService jwtService;
-    private final EmailService emailService;
+    private final EmailSender emailService;
 
     @PostMapping("/register")
     public ResponseEntity<?> register(@RequestBody RegisterRequest req) {

src/main/java/com/openisle/controller/UserController.java

@@ -0,0 +1,53 @@
+package com.openisle.controller;
+
+import com.openisle.model.User;
+import com.openisle.service.ImageUploader;
+import com.openisle.service.UserService;
+import lombok.Data;
+import lombok.RequiredArgsConstructor;
+import org.springframework.http.ResponseEntity;
+import org.springframework.security.core.Authentication;
+import org.springframework.web.bind.annotation.*;
+import org.springframework.web.multipart.MultipartFile;
+
+import java.io.IOException;
+import java.util.Map;
+
+@RestController
+@RequestMapping("/api/users")
+@RequiredArgsConstructor
+public class UserController {
+    private final UserService userService;
+    private final ImageUploader imageUploader;
+
+    @GetMapping("/me")
+    public ResponseEntity<UserDto> me(Authentication auth) {
+        User user = userService.findByUsername(auth.getName()).orElseThrow();
+        return ResponseEntity.ok(toDto(user));
+    }
+
+    @PostMapping("/me/avatar")
+    public ResponseEntity<?> uploadAvatar(@RequestParam("file") MultipartFile file,
+                                          Authentication auth) throws IOException {
+        String url = imageUploader.upload(file.getBytes(), file.getOriginalFilename());
+        userService.updateAvatar(auth.getName(), url);
+        return ResponseEntity.ok(Map.of("url", url));
+    }
+
+    private UserDto toDto(User user) {
+        UserDto dto = new UserDto();
+        dto.setId(user.getId());
+        dto.setUsername(user.getUsername());
+        dto.setEmail(user.getEmail());
+        dto.setAvatar(user.getAvatar());
+        return dto;
+    }
+
+    @Data
+    private static class UserDto {
+        private Long id;
+        private String username;
+        private String email;
+        private String avatar;
+    }
+}

src/main/java/com/openisle/model/User.java

@@ -35,6 +35,8 @@ public class User {
 
     private String verificationCode;
 
+    private String avatar;
+
     @Enumerated(EnumType.STRING)
     @Column(nullable = false)
     private Role role = Role.USER;

src/main/java/com/openisle/service/CosImageUploader.java

@@ -0,0 +1,24 @@
+package com.openisle.service;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Service;
+
+/**
+ * ImageUploader implementation using Tencent Cloud COS.
+ * For simplicity this demo just returns a URL composed of the base URL and file name.
+ */
+@Service
+public class CosImageUploader extends ImageUploader {
+
+    private final String baseUrl;
+
+    public CosImageUploader(@Value("${cos.base-url:https://example.com}") String baseUrl) {
+        this.baseUrl = baseUrl;
+    }
+
+    @Override
+    public String upload(byte[] data, String filename) {
+        // In a real implementation you would call COS SDK here
+        return baseUrl + "/" + filename;
+    }
+}

src/main/java/com/openisle/service/EmailSender.java

@@ -0,0 +1,14 @@
+package com.openisle.service;
+
+/**
+ * Abstract email sender used to deliver emails.
+ */
+public abstract class EmailSender {
+    /**
+     * Send an email to a recipient.
+     * @param to recipient email address
+     * @param subject email subject
+     * @param text email body
+     */
+    public abstract void sendEmail(String to, String subject, String text);
+}

src/main/java/com/openisle/service/ImageUploader.java

@@ -0,0 +1,14 @@
+package com.openisle.service;
+
+/**
+ * Abstract service for uploading images.
+ */
+public abstract class ImageUploader {
+    /**
+     * Upload an image and return its accessible URL.
+     * @param data image binary data
+     * @param filename name of the file
+     * @return accessible URL of the uploaded file
+     */
+    public abstract String upload(byte[] data, String filename);
+}

src/main/java/com/openisle/service/ResendEmailSender.java

@@ -12,13 +12,14 @@ import java.util.HashMap;
 import java.util.Map;
 
 @Service
-public class EmailService {
+public class ResendEmailSender extends EmailSender {
 
     @Value("${resend.api.key}")
     private String apiKey;
 
     private final RestTemplate restTemplate = new RestTemplate();
 
+    @Override
     public void sendEmail(String to, String subject, String text) {
         String url = "https://api.resend.com/emails"; // hypothetical endpoint
 

src/main/java/com/openisle/service/UserService.java

@@ -78,4 +78,15 @@ public class UserService {
                 .filter(User::isVerified)
                 .filter(user -> passwordEncoder.matches(password, user.getPassword()));
     }
+
+    public Optional<User> findByUsername(String username) {
+        return userRepository.findByUsername(username);
+    }
+
+    public User updateAvatar(String username, String avatarUrl) {
+        User user = userRepository.findByUsername(username)
+                .orElseThrow(() -> new IllegalArgumentException("User not found"));
+        user.setAvatar(avatarUrl);
+        return userRepository.save(user);
+    }
 }