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 * Licensed to the Apache Software Foundation (ASF) under one   *
 * or more contributor license agreements.  See the NOTICE file *
 * distributed with this work for additional information        *
 * regarding copyright ownership.  The ASF licenses this file   *
 * to you under the Apache License, Version 2.0 (the            *
 * "License"); you may not use this file except in compliance   *
 * with the License.  You may obtain a copy of the License at   *
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 *   http://www.apache.org/licenses/LICENSE-2.0                 *
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 * Unless required by applicable law or agreed to in writing,   *
 * software distributed under the License is distributed on an  *
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
 * KIND, either express or implied.  See the License for the    *
 * specific language governing permissions and limitations      *
 * under the License.                                           *
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package org.apache.james.protocols.pop3.core;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import javax.inject.Inject;

import org.apache.james.metrics.api.MetricFactory;
import org.apache.james.protocols.api.ProtocolSession.State;
import org.apache.james.protocols.api.Request;
import org.apache.james.protocols.api.Response;
import org.apache.james.protocols.api.handler.CommandHandler;
import org.apache.james.protocols.pop3.POP3Response;
import org.apache.james.protocols.pop3.POP3Session;
import org.apache.james.protocols.pop3.mailbox.MessageMetaData;
import org.apache.james.util.MDCBuilder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;

/**
 * Handles STAT command
 */
public class StatCmdHandler implements CommandHandler<POP3Session> {
    private static final Logger LOGGER = LoggerFactory.getLogger(StatCmdHandler.class);
    private static final Collection<String> COMMANDS = ImmutableSet.of("STAT");

    private final MetricFactory metricFactory;

    @Inject
    public StatCmdHandler(MetricFactory metricFactory) {
        this.metricFactory = metricFactory;
    }

    /**
     * Handler method called upon receipt of a STAT command. Returns the number
     * of messages in the mailbox and its aggregate size.
     */
    @Override
    public Response onCommand(POP3Session session, Request request) {
        return metricFactory.decorateSupplierWithTimerMetric("pop3-stat", () ->
            MDCBuilder.withMdc(
                MDCBuilder.create()
                    .addContext(MDCBuilder.ACTION, "STAT")
                    .addContext(MDCConstants.withSession(session)),
                () -> stat(session)));
    }

    private Response stat(POP3Session session) {
        LOGGER.trace("STAT command received");
        if (session.getHandlerState() == POP3Session.TRANSACTION) {

            List<MessageMetaData> uidList = session.getAttachment(POP3Session.UID_LIST, State.Transaction).orElse(ImmutableList.of());
            List<String> deletedUidList = session.getAttachment(POP3Session.DELETED_UID_LIST, State.Transaction).orElse(ImmutableList.of());
            long size = 0;
            int count = 0;
            if (!uidList.isEmpty()) {
                List<MessageMetaData> validResults = new ArrayList<>();
                for (MessageMetaData data : uidList) {
                    if (!deletedUidList.contains(data.getUid())) {
                        size += data.getSize();
                        count++;
                        validResults.add(data);
                    }
                }
            }
            StringBuilder responseBuffer = new StringBuilder(32).append(count).append(" ").append(size);
            return new POP3Response(POP3Response.OK_RESPONSE, responseBuffer.toString());

        } else {
            return POP3Response.ERR;
        }
    }

    @Override
    public Collection<String> getImplCommands() {
        return COMMANDS;
    }

}
