/*
 * 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.nifi.processors.email;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import org.apache.commons.lang3.StringUtils;
import org.apache.nifi.annotation.behavior.InputRequirement;
import org.apache.nifi.annotation.behavior.InputRequirement.Requirement;
import org.apache.nifi.annotation.behavior.SideEffectFree;
import org.apache.nifi.annotation.behavior.SupportsBatching;
import org.apache.nifi.annotation.behavior.WritesAttribute;
import org.apache.nifi.annotation.behavior.WritesAttributes;
import org.apache.nifi.annotation.documentation.CapabilityDescription;
import org.apache.nifi.annotation.documentation.Tags;
import org.apache.nifi.components.PropertyDescriptor;
import org.apache.nifi.flowfile.FlowFile;
import org.apache.nifi.flowfile.attributes.CoreAttributes;
import org.apache.nifi.logging.ComponentLog;
import org.apache.nifi.processor.AbstractProcessor;
import org.apache.nifi.processor.ProcessContext;
import org.apache.nifi.processor.ProcessSession;
import org.apache.nifi.processor.Relationship;
import org.apache.nifi.processor.exception.FlowFileHandlingException;
import org.apache.nifi.processor.io.InputStreamCallback;
import org.apache.nifi.processor.io.OutputStreamCallback;
import org.apache.poi.hmef.Attachment;
import org.apache.poi.hmef.HMEFMessage;


@SupportsBatching
@SideEffectFree
@Tags({"split", "email"})
@InputRequirement(Requirement.INPUT_REQUIRED)
@CapabilityDescription("Extract attachments from a mime formatted email file, splitting them into individual flowfiles.")
@WritesAttributes({
        @WritesAttribute(attribute = "filename ", description = "The filename of the attachment"),
        @WritesAttribute(attribute = "email.tnef.attachment.parent.filename ", description = "The filename of the parent FlowFile"),
        @WritesAttribute(attribute = "email.tnef.attachment.parent.uuid", description = "The UUID of the original FlowFile.")})

public class ExtractTNEFAttachments extends AbstractProcessor {
    public static final String ATTACHMENT_ORIGINAL_FILENAME = "email.tnef.attachment.parent.filename";
    public static final String ATTACHMENT_ORIGINAL_UUID = "email.tnef.attachment.parent.uuid";

    public static final Relationship REL_ATTACHMENTS = new Relationship.Builder()
            .name("attachments")
            .description("Each individual attachment will be routed to the attachments relationship")
            .build();
    public static final Relationship REL_ORIGINAL = new Relationship.Builder()
            .name("original")
            .description("Each original flowfile (i.e. before extraction) will be routed to the original relationship")
            .build();
    public static final Relationship REL_FAILURE = new Relationship.Builder()
            .name("failure")
            .description("Each individual flowfile that could not be parsed will be routed to the failure relationship")
            .build();

    private final static Set<Relationship> RELATIONSHIPS;
    private final static List<PropertyDescriptor> DESCRIPTORS;


    static {
        final Set<Relationship> _relationships = new HashSet<>();
        _relationships.add(REL_ATTACHMENTS);
        _relationships.add(REL_ORIGINAL);
        _relationships.add(REL_FAILURE);
        RELATIONSHIPS = Collections.unmodifiableSet(_relationships);

        final List<PropertyDescriptor> _descriptors = new ArrayList<>();
        DESCRIPTORS = Collections.unmodifiableList(_descriptors);
    }

    @Override
    public void onTrigger(final ProcessContext context, final ProcessSession session) {
        final ComponentLog logger = getLogger();
        final FlowFile originalFlowFile = session.get();
        if (originalFlowFile == null) {
            return;
        }
        final List<FlowFile> attachmentsList = new ArrayList<>();
        final List<FlowFile> invalidFlowFilesList = new ArrayList<>();
        final List<FlowFile> originalFlowFilesList = new ArrayList<>();

        session.read(originalFlowFile, new InputStreamCallback() {
            @Override
            public void process(final InputStream rawIn) throws IOException {
                try (final InputStream in = new BufferedInputStream(rawIn)) {
                    Properties props = new Properties();

                    HMEFMessage hmefMessage = null;

                    // This will trigger an exception in case content is not a TNEF.
                    hmefMessage = new HMEFMessage(in);

                    // Add otiginal flowfile (may revert later on in case of errors) //
                    originalFlowFilesList.add(originalFlowFile);

                    if (hmefMessage != null) {
                        // Attachments isn empty, proceeding.
                        if (!hmefMessage.getAttachments().isEmpty()) {
                            final String originalFlowFileName = originalFlowFile.getAttribute(CoreAttributes.FILENAME.key());
                            try {
                                for (final Attachment attachment : hmefMessage.getAttachments()) {
                                    FlowFile split = session.create(originalFlowFile);
                                    final Map<String, String> attributes = new HashMap<>();
                                    if (StringUtils.isNotBlank(attachment.getLongFilename())) {
                                        attributes.put(CoreAttributes.FILENAME.key(), attachment.getFilename());
                                    }

                                    String parentUuid = originalFlowFile.getAttribute(CoreAttributes.UUID.key());
                                    attributes.put(ATTACHMENT_ORIGINAL_UUID, parentUuid);
                                    attributes.put(ATTACHMENT_ORIGINAL_FILENAME, originalFlowFileName);

                                    // TODO: Extract Mime Type (HMEF doesn't seem to be able to get this info.

                                    split = session.append(split, new OutputStreamCallback() {
                                        @Override
                                        public void process(OutputStream out) throws IOException {
                                            out.write(attachment.getContents());
                                        }
                                    });
                                    split = session.putAllAttributes(split, attributes);
                                    attachmentsList.add(split);
                                }
                            } catch (FlowFileHandlingException e) {
                                // Something went wrong
                                // Removing splits that may have been created
                                session.remove(attachmentsList);
                                // Removing the original flow from its list
                                originalFlowFilesList.remove(originalFlowFile);
                                logger.error("Flowfile {} triggered error {} while processing message removing generated FlowFiles from sessions", new Object[]{originalFlowFile, e});
                                invalidFlowFilesList.add(originalFlowFile);
                            }
                        }
                    }
                } catch (Exception e) {
                    // Another error hit...
                    // Removing the original flow from its list
                    originalFlowFilesList.remove(originalFlowFile);
                    logger.error("Could not parse the flowfile {} as an email, treating as failure", new Object[]{originalFlowFile, e});
                    // Message is invalid or triggered an error during parsing
                    invalidFlowFilesList.add(originalFlowFile);
                }
            }
        });

        session.transfer(attachmentsList, REL_ATTACHMENTS);

        // As per above code, originalFlowfile may be routed to invalid or
        // original depending on RFC2822 compliance.
        session.transfer(invalidFlowFilesList, REL_FAILURE);
        session.transfer(originalFlowFilesList, REL_ORIGINAL);

        // check if attachments have been extracted
        if (attachmentsList.size() != 0) {
            if (attachmentsList.size() > 10) {
                // If more than 10, summarise log
                logger.info("Split {} into {} files", new Object[]{originalFlowFile, attachmentsList.size()});
            } else {
                // Otherwise be more verbose and list each individual split
                logger.info("Split {} into {} files: {}", new Object[]{originalFlowFile, attachmentsList.size(), attachmentsList});
            }
        }
     }

    @Override
    public Set<Relationship> getRelationships() {
        return RELATIONSHIPS;
    }

    @Override
    public final List<PropertyDescriptor> getSupportedPropertyDescriptors() {
        return DESCRIPTORS;
    }


}

