로그인 로직 추가

src/main/java/com/example/daemawiki/domain/auth/service/Login.java

@@ -0,0 +1,38 @@
+package com.example.daemawiki.domain.auth.service;
+
+import com.example.daemawiki.domain.auth.dto.LoginRequest;
+import com.example.daemawiki.domain.auth.dto.LoginResponse;
+import com.example.daemawiki.domain.user.repository.UserRepository;
+import com.example.daemawiki.global.exception.PasswordMismatchException;
+import com.example.daemawiki.global.exception.UserNotFoundException;
+import com.example.daemawiki.global.security.Tokenizer;
+import org.springframework.security.crypto.password.PasswordEncoder;
+import org.springframework.stereotype.Service;
+import reactor.core.publisher.Mono;
+
+@Service
+public class Login {
+    private final UserRepository userRepository;
+    private final PasswordEncoder passwordEncoder;
+    private final Tokenizer tokenizer;
+
+    public Login(UserRepository userRepository, PasswordEncoder passwordEncoder, Tokenizer tokenizer) {
+        this.userRepository = userRepository;
+        this.passwordEncoder = passwordEncoder;
+        this.tokenizer = tokenizer;
+    }
+
+    public Mono<LoginResponse> execute(LoginRequest request) {
+        return userRepository.findByEmail(request.email())
+                .switchIfEmpty(Mono.error(UserNotFoundException.EXCEPTION))
+                .flatMap(user -> Mono.just(user)
+                        .filter(u -> passwordEncoder.matches(u.getPassword(), request.password()))
+                        .switchIfEmpty(Mono.error(PasswordMismatchException.EXCEPTION))
+                        .flatMap(u -> tokenizer.createToken(u.getEmail())
+                                .map(token -> LoginResponse.builder()
+                                        .token(token)
+                                        .build())));
+    }
+
+
+}