package se.bilhalsning.service;

import java.time.Instant;
import java.util.Optional;
import lombok.RequiredArgsConstructor;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import se.bilhalsning.entity.EmailChangeToken;
import se.bilhalsning.entity.User;
import se.bilhalsning.exception.EmailChangeTokenInvalidException;
import se.bilhalsning.repository.EmailChangeTokenRepository;

@Service
@RequiredArgsConstructor
public class EmailChangeService {

    private static final long TOKEN_TTL_HOURS = 24;

    private final UserService userService;
    private final EmailChangeTokenRepository tokenRepository;
    private final EmailService emailService;
    private final PasswordResetService passwordResetService;

    @Value("${app.public-base-url:http://localhost:3000}")
    private String publicBaseUrl;

    @Value("${app.email-change.expose-token:false}")
    private boolean exposeToken;

    @Transactional
    public Optional<String> requestChange(String currentEmail, String password, String newEmail) {
        User user = userService.authenticate(currentEmail, password);
        userService.validateEmailAvailableForChange(user, newEmail);

        String normalizedEmail = newEmail.toLowerCase().trim();
        tokenRepository.deleteUnusedByUserId(user.getId());

        String rawToken = passwordResetService.generateRawToken();
        EmailChangeToken entity = new EmailChangeToken();
        entity.setUser(user);
        entity.setNewEmail(normalizedEmail);
        entity.setTokenHash(PasswordResetService.hashToken(rawToken));
        entity.setExpiresAt(Instant.now().plusSeconds(TOKEN_TTL_HOURS * 3600));
        tokenRepository.save(entity);

        String confirmUrl = publicBaseUrl.replaceAll("/$", "")
                + "/bekrafta-epost?token="
                + rawToken;
        emailService.sendEmailChangeConfirmation(normalizedEmail, confirmUrl);

        return exposeToken ? Optional.of(rawToken) : Optional.empty();
    }

    @Transactional
    public User confirmChange(String rawToken, String password) {
        EmailChangeToken token = tokenRepository
                .findByTokenHashAndUsedAtIsNull(PasswordResetService.hashToken(rawToken))
                .filter(t -> t.getExpiresAt().isAfter(Instant.now()))
                .orElseThrow(EmailChangeTokenInvalidException::new);

        User user = token.getUser();
        userService.authenticate(user.getEmail(), password);
        User updated = userService.applyEmailChange(user, token.getNewEmail());
        token.setUsedAt(Instant.now());
        tokenRepository.deleteUnusedByUserId(user.getId());
        tokenRepository.save(token);
        return updated;
    }
}