package com.mailserver.service;

import com.mailserver.domain.Attachment;
import com.mailserver.domain.Contact;
import com.mailserver.domain.Folder;
import com.mailserver.domain.Message;
import com.mailserver.domain.User;
import com.mailserver.dto.AttachmentResponse;
import com.mailserver.dto.MessageResponse;
import com.mailserver.repository.AttachmentRepository;
import com.mailserver.repository.ContactRepository;
import com.mailserver.repository.FolderRepository;
import com.mailserver.repository.MessageRepository;
import com.mailserver.repository.UserRepository;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Sort;
import org.springframework.http.HttpStatus;
import org.springframework.stereotype.Service;
import org.springframework.web.server.ResponseStatusException;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

import java.io.*;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.time.Instant;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;
import java.util.UUID;

@Service
public class MailService {

    private static final Logger log = LoggerFactory.getLogger(MailService.class);

    private final MessageRepository messageRepository;
    private final FolderRepository folderRepository;
    private final UserRepository userRepository;
    private final AttachmentRepository attachmentRepository;
    private final ContactRepository contactRepository;
    private final SpamFilterService spamFilterService;

    @Value("${mailserver.attachments.dir:./attachments}")
    private String attachmentsDir;



    public MailService(MessageRepository messageRepository, FolderRepository folderRepository,
                       UserRepository userRepository, AttachmentRepository attachmentRepository,
                       ContactRepository contactRepository,
                       SpamFilterService spamFilterService) {
        this.messageRepository = messageRepository;
        this.folderRepository = folderRepository;
        this.userRepository = userRepository;
        this.attachmentRepository = attachmentRepository;
        this.contactRepository = contactRepository;
        this.spamFilterService = spamFilterService;
    }

    /** Copy of a message we sent, in the sender's "Sent" folder. */
    public Mono<MessageResponse> saveSent(User fromUser, String to, String subject, String body, boolean html, String messageId) {
        return folderRepository.findByUserIdAndName(fromUser.getId(), "Sent")
                .switchIfEmpty(Mono.error(new IllegalStateException("Sent folder not found")))
                .flatMap(sentFolder -> {
                    Message message = new Message();
                    message.setFolderId(sentFolder.getId());
                    message.setSenderEmail(fromUser.getEmail());
                    message.setSenderName(fromUser.getDisplayName());
                    message.setRecipientEmail(to);
                    message.setSubject(subject);
                    message.setBody(body);
                    message.setHtml(html);
                    message.setRead(true);
                    message.setReceivedAt(Instant.now());
                    message.setMessageId(messageId);
                    message.setMessageSize((long) (subject.length() + body.length()));
                    return messageRepository.save(message);
                })
                .map(this::toResponse);
    }

    public Mono<Void> receiveMessage(String senderEmail, String senderName, String recipientEmail,
                               String subject, String body, boolean isHtml) {
        return receiveMessage(senderEmail, senderName, recipientEmail, subject, body, isHtml, false);
    }

    public Mono<Void> receiveMessage(String senderEmail, String senderName, String recipientEmail,
                               String subject, String body, boolean isHtml, boolean externalSpamFlag) {
        return userRepository.findByEmail(recipientEmail)
                .switchIfEmpty(Mono.error(new IllegalArgumentException("Recipient not found: " + recipientEmail)))
                .flatMap(recipient ->
                    folderRepository.findByUserIdAndName(recipient.getId(), "INBOX")
                        .switchIfEmpty(Mono.error(new IllegalStateException("INBOX not found")))
                        .flatMap(inbox ->
                            spamFilterService.isBlacklisted(recipient.getId(), senderEmail)
                                .flatMap(isBlacklisted -> {
                                    boolean isSpam = isBlacklisted || externalSpamFlag;
                                    Message message = new Message();
                                    message.setFolderId(inbox.getId());
                                    message.setSenderEmail(senderEmail);
                                    message.setSenderName(senderName);
                                    message.setRecipientEmail(recipientEmail);
                                    message.setSubject(subject);
                                    message.setBody(body);
                                    message.setHtml(isHtml);
                                    message.setRead(false);
                                    message.setSpam(isSpam);
                                    message.setReceivedAt(Instant.now());
                                    message.setMessageId(UUID.randomUUID().toString());
                                    message.setMessageSize((long) (subject.length() + body.length()));
                                    return messageRepository.save(message)
                                        .then(folderRepository.save(inbox));
                                })
                        )
                )
                .then();
    }

    public Flux<MessageResponse> getMessages(Long folderId, Long userId, int page, int size) {
        PageRequest pageable = PageRequest.of(page, size, Sort.by(Sort.Direction.DESC, "receivedAt"));
        return ownedFolder(folderId, userId)
                .flatMapMany(folder -> messageRepository.findByFolderId(folder.getId(), pageable))
                .map(this::toResponse);
    }

    public Flux<MessageResponse> searchMessages(Long folderId, Long userId, String keyword, int page, int size) {
        PageRequest pageable = PageRequest.of(page, size, Sort.by(Sort.Direction.DESC, "receivedAt"));
        return ownedFolder(folderId, userId)
                .flatMapMany(folder -> messageRepository.searchInFolder(folder.getId(), keyword, pageable))
                .map(this::toResponse);
    }

    public Flux<MessageResponse> searchMessagesWithFilters(Long folderId, Long userId,
                                                           String subject, String body,
                                                           String sender, String recipient,
                                                           int page, int size) {
        PageRequest pageable = PageRequest.of(page, size, Sort.by(Sort.Direction.DESC, "receivedAt"));
        return ownedFolder(folderId, userId)
                .flatMapMany(folder -> messageRepository.searchWithFilters(folder.getId(), subject, body, sender, recipient, pageable))
                .map(this::toResponse);
    }

    public Mono<MessageResponse> getMessage(Long messageId, Long userId) {
        return ownedMessage(messageId, userId).map(this::toResponse);
    }

    public Mono<Void> markAsRead(Long messageId, Long userId) {
        return ownedMessage(messageId, userId)
                .flatMap(message -> {
                    message.setRead(true);
                    return messageRepository.save(message).then();
                });
    }

    public Mono<Void> deleteMessage(Long messageId, Long userId) {
        return ownedMessage(messageId, userId).flatMap(messageRepository::delete);
    }

    /** The folder, when it belongs to the user; otherwise 404 — never someone else's mail. */
    private Mono<Folder> ownedFolder(Long folderId, Long userId) {
        return folderRepository.findById(folderId)
                .filter(folder -> folder.getUserId().equals(userId))
                .switchIfEmpty(Mono.error(new ResponseStatusException(HttpStatus.NOT_FOUND, "Folder not found")));
    }

    private Mono<Message> ownedMessage(Long messageId, Long userId) {
        return messageRepository.findById(messageId)
                .filterWhen(message -> folderRepository.findById(message.getFolderId())
                        .map(folder -> folder.getUserId().equals(userId))
                        .defaultIfEmpty(false))
                .switchIfEmpty(Mono.error(new ResponseStatusException(HttpStatus.NOT_FOUND, "Message not found")));
    }

    private Mono<Attachment> ownedAttachment(Long attachmentId, Long userId) {
        return attachmentRepository.findById(attachmentId)
                .filterWhen(attachment -> ownedMessage(attachment.getMessageId(), userId).hasElement()
                        .onErrorReturn(false))
                .switchIfEmpty(Mono.error(new ResponseStatusException(HttpStatus.NOT_FOUND, "Attachment not found")));
    }

    private MessageResponse toResponse(Message message) {
        MessageResponse resp = new MessageResponse();
        resp.setId(message.getId());
        resp.setSenderEmail(message.getSenderEmail());
        resp.setSenderName(message.getSenderName());
        resp.setRecipientEmail(message.getRecipientEmail());
        resp.setSubject(message.getSubject());
        resp.setBody(message.getBody());
        resp.setHtml(message.isHtml());
        resp.setRead(message.isRead());
        resp.setFlagged(message.isFlagged());
        resp.setSpam(message.isSpam());
        resp.setMessageSize(message.getMessageSize());
        resp.setReceivedAt(message.getReceivedAt());
        resp.setFolderId(message.getFolderId());
        return resp;
    }

    public Mono<AttachmentResponse> saveAttachmentReactive(Long messageId, Long userId,
                                                     String originalFilename, String contentType,
                                                     long sizeBytes, String filePath) {
        return ownedMessage(messageId, userId)
                .flatMap(message -> {
                    Attachment attachment = new Attachment();
                    attachment.setMessageId(messageId);
                    attachment.setFilename(originalFilename);
                    attachment.setContentType(contentType);
                    attachment.setSizeBytes(sizeBytes);
                    attachment.setFilePath(filePath);
                    return attachmentRepository.save(attachment);
                })
                .map(this::toAttachmentResponse);
    }

    public String getAttachmentsDir() {
        return attachmentsDir;
    }

    /** The attachment record (file path, name, type) — only the owner's. */
    public Mono<Attachment> getAttachment(Long attachmentId, Long userId) {
        return ownedAttachment(attachmentId, userId);
    }

    public Flux<AttachmentResponse> getMessageAttachments(Long messageId, Long userId) {
        return ownedMessage(messageId, userId)
                .flatMapMany(message -> attachmentRepository.findByMessageId(message.getId()))
                .map(this::toAttachmentResponse);
    }

    public Mono<Void> deleteAttachment(Long attachmentId, Long userId) {
        return ownedAttachment(attachmentId, userId)
                .flatMap(attachment -> {
                    try {
                        Files.deleteIfExists(Paths.get(attachment.getFilePath()));
                    } catch (IOException e) {
                        log.warn("Attachment file {} not deleted: {}", attachment.getFilePath(), e.getMessage());
                    }
                    return attachmentRepository.delete(attachment);
                });
    }

    private AttachmentResponse toAttachmentResponse(Attachment attachment) {
        AttachmentResponse resp = new AttachmentResponse();
        resp.setId(attachment.getId());
        resp.setFilename(attachment.getFilename());
        resp.setContentType(attachment.getContentType());
        resp.setSizeBytes(attachment.getSizeBytes());
        return resp;
    }

    // --- Contacts ---

    public Flux<Contact> getContacts(Long userId) {
        return contactRepository.findByUserId(userId);
    }

    public Mono<Contact> addContact(Long userId, String name, String email, String phone, String company) {
        if (email == null || email.trim().isEmpty()) {
            return Mono.error(new IllegalArgumentException("Email is required"));
        }
        Contact contact = new Contact();
        contact.setUserId(userId);
        contact.setName(name != null ? name : "");
        contact.setEmail(email.trim());
        contact.setPhone(phone != null ? phone : "");
        contact.setCompany(company != null ? company : "");
        return contactRepository.save(contact);
    }

    public Mono<Contact> updateContact(Long id, Long userId, String name, String email, String phone, String company) {
        return contactRepository.findById(id)
            .switchIfEmpty(Mono.error(new IllegalArgumentException("Contact not found")))
            .flatMap(contact -> {
                if (!contact.getUserId().equals(userId)) {
                    return Mono.error(new IllegalArgumentException("Not your contact"));
                }
                if (name != null) contact.setName(name);
                if (email != null) contact.setEmail(email.trim());
                if (phone != null) contact.setPhone(phone);
                if (company != null) contact.setCompany(company);
                return contactRepository.save(contact);
            });
    }

    public Mono<Void> deleteContact(Long id, Long userId) {
        return contactRepository.findById(id)
            .switchIfEmpty(Mono.error(new IllegalArgumentException("Contact not found")))
            .flatMap(contact -> {
                if (!contact.getUserId().equals(userId)) {
                    return Mono.error(new IllegalArgumentException("Not your contact"));
                }
                return contactRepository.delete(contact);
            });
    }
}