package ru.soune.nocopy.service.mail;

import jakarta.mail.MessagingException;
import jakarta.mail.internet.MimeMessage;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.core.io.ClassPathResource;
import org.springframework.mail.javamail.JavaMailSender;
import org.springframework.mail.javamail.MimeMessageHelper;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import ru.soune.nocopy.entity.user.AuthToken;
import ru.soune.nocopy.entity.user.EmailVerificationToken;
import ru.soune.nocopy.entity.user.User;
import ru.soune.nocopy.repository.EmailVerificationTokenRepository;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.security.SecureRandom;
import java.time.LocalDateTime;

@Service
@RequiredArgsConstructor
@Slf4j
public class EmailService {

    private final JavaMailSender mailSender;

    private final EmailVerificationTokenRepository emailVerificationTokenRepository;

    @Value("${app.email.verification.standart-subject}")
    private String standartSubject;

    @Value("${app.email.verification.standart-address-from}")
    private String standartAdressFrom;

    @Value("${app.email.verification.user}")
    private String user;

    public void sendVerificationEmail(User user, String code) throws MessagingException, IOException {
        MimeMessage message = mailSender.createMimeMessage();
        MimeMessageHelper helper = new MimeMessageHelper(message, true, "UTF-8");

        helper.setFrom(standartAdressFrom);
        helper.setTo(user.getEmail());
        helper.setSubject(standartSubject);

        String htmlContent = loadAndProcessTemplate(user.getFullName(), code);
        helper.setText(htmlContent, true);

        mailSender.send(message);

        log.info("Email sent to: {}", user.getEmail());
    }

    @Transactional
    public EmailVerificationToken createEmailVerificationToken(AuthToken authToken) {
        EmailVerificationToken emailToken = new EmailVerificationToken();
        emailToken.setUser(authToken.getUser());
        emailToken.setToken(generateVerificationCode());
        emailToken.setCreatedAt(LocalDateTime.now());

        return emailVerificationTokenRepository.save(emailToken);
    }

    private String generateVerificationCode() {
        SecureRandom random = new SecureRandom();
        int code = 100000 + random.nextInt(900000);

        return String.valueOf(code);
    }

    private String loadAndProcessTemplate(String username, String code) throws IOException {
        ClassPathResource resource = new ClassPathResource("templates/email-verification.html");
        String template = new String(resource.getInputStream().readAllBytes(), StandardCharsets.UTF_8);
        String safeUsername = escapeHtml(username != null ? username : user);
        String safeCode = escapeHtml(code);

        return template
                .replace("{{username}}", safeUsername)
                .replace("{{code}}", safeCode);
    }

    private String escapeHtml(String text) {
        if (text == null) return "";
        return text
                .replace("&", "&")
                .replace("<", "&lt;")
                .replace(">", "&gt;")
                .replace("\"", "&quot;")
                .replace("'", "&#39;");
    }
}