/*
 * Axelor Business Solutions
 *
 * Copyright (C) 2018 Axelor (<http://axelor.com>).
 *
 * This program is free software: you can redistribute it and/or  modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package com.axelor.apps.base.service;

import static com.axelor.common.StringUtils.isBlank;

import java.io.UnsupportedEncodingException;
import java.lang.invoke.MethodHandles;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import javax.inject.Singleton;
import javax.mail.internet.InternetAddress;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.axelor.apps.base.db.Partner;
import com.axelor.apps.base.db.repo.PartnerRepository;
import com.axelor.apps.message.service.MailServiceMessageImpl;
import com.axelor.auth.db.User;
import com.axelor.auth.db.repo.UserRepository;
import com.axelor.db.Model;
import com.axelor.db.Query;
import com.axelor.exception.service.TraceBackService;
import com.axelor.inject.Beans;
import com.axelor.mail.db.MailAddress;
import com.axelor.mail.db.MailFollower;
import com.axelor.mail.db.MailMessage;
import com.axelor.mail.db.repo.MailFollowerRepository;
import com.google.common.base.Joiner;
import com.google.common.base.Predicates;
import com.google.common.base.Strings;
import com.google.common.collect.Sets;

@Singleton
public class MailServiceBaseImpl extends MailServiceMessageImpl {
	private final Logger log = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());

	@Override
	public Model resolve(String email) {
		final UserRepository users = Beans.get(UserRepository.class);
		final User user = users.all().filter("self.partner.emailAddress.address = ?1", email).fetchOne();
		if (user != null) {
			return user;
		}
		final PartnerRepository partners = Beans.get(PartnerRepository.class);
		final Partner partner = partners.all().filter("self.emailAddress.address = ?1", email).fetchOne();
		if (partner != null) {
			return partner;
		}
		return super.resolve(email);
	}

	@Override
	public List<InternetAddress> findEmails(String matching, List<String> selected, int maxResult) {

		// Users
		List<String> selectedWithoutNull = new ArrayList<String>(selected);
		for (int i = 0; i < selected.size(); i++) {
			if (Strings.isNullOrEmpty(selected.get(i)))
				selectedWithoutNull.remove(i);
		}

		final List<String> where = new ArrayList<>();
		final Map<String, Object> params = new HashMap<>();

		where.add("((self.partner is not null AND self.partner.emailAddress is not null) OR (self.email is not null))");

		if (!isBlank(matching)) {
			where.add("(LOWER(self.partner.emailAddress.address) like LOWER(:email) OR LOWER(self.partner.fullName) like LOWER(:email) OR LOWER(self.email) like LOWER(:email) OR LOWER(self.name) like LOWER(:email))");
			params.put("email", "%" + matching + "%");
		}
		if (selectedWithoutNull != null && !selectedWithoutNull.isEmpty()) {
			where.add("self.partner.emailAddress.address not in (:selected)");
			params.put("selected", selectedWithoutNull);
		}

		final String filter = Joiner.on(" AND ").join(where);
		final Query<User> query = Query.of(User.class);

		if (!isBlank(filter)) {
			query.filter(filter);
			query.bind(params);
		}

		final List<InternetAddress> addresses = new ArrayList<>();
		for (User user : query.fetch(maxResult)) {
			try {
				if (user.getPartner().getEmailAddress() != null && !Strings.isNullOrEmpty(user.getPartner().getEmailAddress().getAddress())) {
					final InternetAddress item = new InternetAddress(user.getPartner().getEmailAddress().getAddress(), user.getFullName());
					addresses.add(item);
					selectedWithoutNull.add(user.getPartner().getEmailAddress().getAddress());
				} else if (!Strings.isNullOrEmpty(user.getEmail())) {
					final InternetAddress item = new InternetAddress(user.getEmail(), user.getFullName());
					addresses.add(item);
					selectedWithoutNull.add(user.getEmail());
				}

			} catch (UnsupportedEncodingException e) {
				TraceBackService.trace(e);
			}
		}

		// Partners

		final List<String> where2 = new ArrayList<>();
		final Map<String, Object> params2 = new HashMap<>();

		where2.add("self.emailAddress is not null");

		if (!isBlank(matching)) {
			where2.add("(LOWER(self.emailAddress.address) like LOWER(:email) OR LOWER(self.fullName) like LOWER(:email))");
			params2.put("email", "%" + matching + "%");
		}
		if (selectedWithoutNull != null && !selectedWithoutNull.isEmpty()) {
			where2.add("self.emailAddress.address not in (:selected)");
			params2.put("selected", selectedWithoutNull);
		}

		final String filter2 = Joiner.on(" AND ").join(where2);
		final Query<Partner> query2 = Query.of(Partner.class);

		if (!isBlank(filter2)) {
			query2.filter(filter2);
			query2.bind(params2);
		}

		for (Partner partner : query2.fetch(maxResult)) {
			try {
				if (partner.getEmailAddress() != null && !Strings.isNullOrEmpty(partner.getEmailAddress().getAddress())) {
					final InternetAddress item = new InternetAddress(partner.getEmailAddress().getAddress(), partner.getFullName());
					addresses.add(item);
				}
			} catch (UnsupportedEncodingException e) {
				TraceBackService.trace(e);
			}
		}

		return addresses;
	}

	@Override
	protected Set<String> recipients(MailMessage message, Model entity) {
		final Set<String> recipients = new LinkedHashSet<>();
		final MailFollowerRepository followers = Beans.get(MailFollowerRepository.class);
		String entityName = entity.getClass().getName();
		PartnerRepository partnerRepo = Beans.get(PartnerRepository.class);

		if (message.getRecipients() != null) {
			for (MailAddress address : message.getRecipients()) {
				recipients.add(address.getAddress());
			}
		}

		for (MailFollower follower : followers.findAll(message)) {
			if (follower.getArchived()) {
				continue;
			}
			User user = follower.getUser();
			if (user != null) {
				if (!(user.getReceiveEmails() && user.getFollowedModelSet().stream().anyMatch(x -> x.getFullName().equals(entityName)))) {
					continue;
				} else {
					Partner partner = partnerRepo.findByUser(user);
					recipients.add(partner.getEmailAddress().getAddress());
				}
			} else {

				if (follower.getEmail() != null) {
					recipients.add(follower.getEmail().getAddress());
				} else {
					log.info("No email address found for follower : " + follower);

				}
			}
		}
		return Sets.filter(recipients, Predicates.notNull());
	}

}

@@ -3891,32 +3891,61 @@
 ser.getPartner()
+ != null && user.getPartner()
 .getEmailAddress

Fix npe.