/*
 * 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
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * 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.
 */

package org.apache.logging.log4j.smtp.appender;

import java.io.Serializable;

import org.apache.logging.log4j.core.Appender;
import org.apache.logging.log4j.core.Core;
import org.apache.logging.log4j.core.Filter;
import org.apache.logging.log4j.core.Layout;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.appender.AbstractAppender;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.config.DefaultConfiguration;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
import org.apache.logging.log4j.core.config.plugins.PluginConfiguration;
import org.apache.logging.log4j.core.config.plugins.PluginElement;
import org.apache.logging.log4j.core.config.plugins.PluginFactory;
import org.apache.logging.log4j.core.config.plugins.validation.constraints.Required;
import org.apache.logging.log4j.core.config.plugins.validation.constraints.ValidPort;
import org.apache.logging.log4j.core.filter.ThresholdFilter;
import org.apache.logging.log4j.core.layout.HtmlLayout;
import org.apache.logging.log4j.core.util.Booleans;

/**
 * Send an e-mail when a specific logging event occurs, typically on errors or
 * fatal errors.
 *
 * <p>
 * The number of logging events delivered in this e-mail depend on the value of
 * <b>BufferSize</b> option. The <code>SmtpAppender</code> keeps only the last
 * <code>BufferSize</code> logging events in its cyclic buffer. This keeps
 * memory requirements at a reasonable level while still delivering useful
 * application context.
 *
 * By default, an email message will formatted as HTML. This can be modified by
 * setting a layout for the appender.
 *
 * By default, an email message will be sent when an ERROR or higher severity
 * message is appended. This can be modified by setting a filter for the
 * appender.
 */
@Plugin(name = "SMTP", category = Core.CATEGORY_NAME, elementType = Appender.ELEMENT_TYPE, printObject = true)
public final class SmtpAppender extends AbstractAppender {

    private static final int DEFAULT_BUFFER_SIZE = 512;

    /** The SMTP Manager */
    private final SmtpManager manager;

    private SmtpAppender(final String name, final Filter filter, final Layout<? extends Serializable> layout, final SmtpManager manager,
                         final boolean ignoreExceptions) {
        super(name, filter, layout, ignoreExceptions);
        this.manager = manager;
    }

    /**
     * Create a SmtpAppender.
     *
     * @param name
     *            The name of the Appender.
     * @param to
     *            The comma-separated list of recipient email addresses.
     * @param cc
     *            The comma-separated list of CC email addresses.
     * @param bcc
     *            The comma-separated list of BCC email addresses.
     * @param from
     *            The email address of the sender.
     * @param replyTo
     *            The comma-separated list of reply-to email addresses.
     * @param subject The subject of the email message.
     * @param smtpProtocol The SMTP transport protocol (such as "smtps", defaults to "smtp").
     * @param smtpHost
     *            The SMTP hostname to send to.
     * @param smtpPortStr
     *            The SMTP port to send to.
     * @param smtpUsername
     *            The username required to authenticate against the SMTP server.
     * @param smtpPassword
     *            The password required to authenticate against the SMTP server.
     * @param smtpDebug
     *            Enable mail session debuging on STDOUT.
     * @param bufferSizeStr
     *            How many log events should be buffered for inclusion in the
     *            message?
     * @param layout
     *            The layout to use (defaults to HtmlLayout).
     * @param filter
     *            The Filter or null (defaults to ThresholdFilter, level of
     *            ERROR).
     * @param ignore If {@code "true"} (default) exceptions encountered when appending events are logged; otherwise
     *               they are propagated to the caller.
     * @return The SmtpAppender.
     */
    @PluginFactory
    public static SmtpAppender createAppender(
            @PluginConfiguration final Configuration config,
            @PluginAttribute("name") @Required final String name,
            @PluginAttribute("to") final String to,
            @PluginAttribute("cc") final String cc,
            @PluginAttribute("bcc") final String bcc,
            @PluginAttribute("from") final String from,
            @PluginAttribute("replyTo") final String replyTo,
            @PluginAttribute("subject") final String subject,
            @PluginAttribute("smtpProtocol") final String smtpProtocol,
            @PluginAttribute("smtpHost") final String smtpHost,
            @PluginAttribute(value = "smtpPort", defaultString = "0") @ValidPort final String smtpPortStr,
            @PluginAttribute("smtpUsername") final String smtpUsername,
            @PluginAttribute(value = "smtpPassword", sensitive = true) final String smtpPassword,
            @PluginAttribute("smtpDebug") final String smtpDebug,
            @PluginAttribute("bufferSize") final String bufferSizeStr,
            @PluginElement("Layout") Layout<? extends Serializable> layout,
            @PluginElement("Filter") Filter filter,
            @PluginAttribute("ignoreExceptions") final String ignore) {
        if (name == null) {
            LOGGER.error("No name provided for SmtpAppender");
            return null;
        }

        final boolean ignoreExceptions = Booleans.parseBoolean(ignore, true);
        final int smtpPort = AbstractAppender.parseInt(smtpPortStr, 0);
        final boolean isSmtpDebug = Boolean.parseBoolean(smtpDebug);
        final int bufferSize = bufferSizeStr == null ? DEFAULT_BUFFER_SIZE : Integer.parseInt(bufferSizeStr);

        if (layout == null) {
            layout = HtmlLayout.createDefaultLayout();
        }
        if (filter == null) {
            filter = ThresholdFilter.createFilter(null, null, null);
        }
        final Configuration configuration = config != null ? config : new DefaultConfiguration();

        final SmtpManager manager = SmtpManager.getSmtpManager(configuration, to, cc, bcc, from, replyTo, subject, smtpProtocol,
            smtpHost, smtpPort, smtpUsername, smtpPassword, isSmtpDebug, filter.toString(),  bufferSize);
        if (manager == null) {
            return null;
        }

        return new SmtpAppender(name, filter, layout, manager, ignoreExceptions);
    }

    /**
     * Capture all events in CyclicBuffer.
     * @param event The Log event.
     * @return true if the event should be filtered.
     */
    @Override
    public boolean isFiltered(final LogEvent event) {
        final boolean filtered = super.isFiltered(event);
        if (filtered) {
            manager.add(event);
        }
        return filtered;
    }

    /**
     * Perform SmtpAppender specific appending actions, mainly adding the event
     * to a cyclic buffer and checking if the event triggers an e-mail to be
     * sent.
     * @param event The Log event.
     */
    @Override
    public void append(final LogEvent event) {
        manager.sendEvents(getLayout(), event);
    }
}