mail send 로직 구현

src/main/java/com/example/daemawiki/domain/mail/service/MailSend.java

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+package com.example.daemawiki.domain.mail.service;
+
+import com.example.daemawiki.domain.mail.dto.AuthCodeRequest;
+import com.example.daemawiki.domain.mail.model.AuthCode;
+import com.example.daemawiki.domain.mail.repository.AuthCodeRepository;
+import com.example.daemawiki.domain.mail.repository.AuthMailRepository;
+import jakarta.mail.internet.InternetAddress;
+import jakarta.mail.internet.MimeMessage;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.mail.javamail.JavaMailSender;
+import org.springframework.mail.javamail.MimeMessageHelper;
+import org.springframework.stereotype.Service;
+import reactor.core.publisher.Mono;
+
+import java.util.Random;
+
+@Service
+public class MailSend {
+    private final AuthCodeRepository codeRepository;
+    private final JavaMailSender mailSender;
+
+    public MailSend(AuthCodeRepository authCodeRepository, JavaMailSender javaMailSender) {
+        this.codeRepository = authCodeRepository;
+        this.mailSender = javaMailSender;
+    }
+
+    @Value("${admin.mail}")
+    private static String admin;
+
+    private static final Random rand = new Random();
+
+    public Mono<Void> execute(AuthCodeRequest request) {
+        return sendMail(request.mail())
+                .doOnNext(mailSender::send)
+                .then();
+    }
+
+    private Mono<MimeMessage> sendMail(String to) {
+        String authCode = getRandomCode();
+
+        return Mono.fromCallable(() -> {
+            MimeMessage message = mailSender.createMimeMessage();
+            MimeMessageHelper helper = new MimeMessageHelper(message, true, "UTF-8");
+
+            helper.setTo(to);
+            helper.setSubject("DSM 메일 인증");
+
+            String mail = getMailTemplate(authCode);
+
+            helper.setText(mail);
+            helper.setFrom(new InternetAddress(admin, "DSM-MAIL-AUTH"));
+
+            return message;
+        }).flatMap(message -> codeRepository.save(AuthCode.builder()
+                        .mail(to)
+                        .code(authCode).build())
+                .thenReturn(message));
+    }
+
+    private String getMailTemplate(String key) {
+        return "<div style='margin: 10px; background-color: #f5f5f5; padding: 20px; border-radius: 10px;'>"
+                + "<p style='font-size: 16px; color: #333;'><b><span style='color: #007bff;'>D</span><span style='color: #ffcc00;'>S</span><span style='color: #ff0000;'>M</span></b> 이메일 인증 코드 :</p>"
+                + "<p style='font-size: 24px; font-weight: bold; color: #007bff; letter-spacing: 3px;'>" + key + "</p>"
+                + "<p style='font-size: 14;font-style: italic; color: #999;'>인증 코드는 3시간 동안 유효합니다.</p>"
+                + "</div>";
+    }
+
+    private String getRandomCode() {
+        int num = rand.nextInt(900000) + 100000;
+        return String.valueOf(num);
+    }
+
+}