D-Net

package eu.dnetlib.data.collector.plugins.sftp;

import java.io.OutputStream;

import java.net.URI;

import java.net.URISyntaxException;

import java.util.*;

import com.jcraft.jsch.*;

import eu.dnetlib.data.collector.rmi.CollectorServiceRuntimeException;

import org.apache.commons.io.output.ByteArrayOutputStream;

import org.apache.commons.lang.StringUtils;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

import org.joda.time.DateTime;

import org.joda.time.format.DateTimeFormat;

import org.joda.time.format.DateTimeFormatter;

/**

 * Created by andrea on 11/01/16.

 */

public class SftpIterator implements Iterator<String> {

    private static final Log log = LogFactory.getLog(SftpIterator.class);

    private static final int MAX_RETRIES = 5;

    private static final int DEFAULT_TIMEOUT = 30000;

    private static final long BACKOFF_MILLIS = 10000;

    private String baseUrl;

    private String sftpURIScheme;

    private String sftpServerAddress;

    private String remoteSftpBasePath;

    private String username;

    private String password;

    private boolean isRecursive;

    private Set<String> extensionsSet;

	private boolean incremental;

    private Session sftpSession;

    private ChannelSftp sftpChannel;

    private Queue<String> queue;

	private DateTime fromDate = null;

	private DateTimeFormatter sftpDateFormatter = DateTimeFormat.forPattern("EEE MMM dd HH:mm:ss 'CET' yyyy");

	private DateTimeFormatter simpleDateTimeFormatter = DateTimeFormat.forPattern("yyyy-MM-dd");

	public SftpIterator(String baseUrl, String username, String password, boolean isRecursive, Set<String> extensionsSet, String fromDate) {

		this.baseUrl = baseUrl;

        this.username = username;

        this.password = password;

        this.isRecursive = isRecursive;

        this.extensionsSet = extensionsSet;

		this.incremental = StringUtils.isNotBlank(fromDate);

		if (incremental) {

			//I expect fromDate in the format 'yyyy-MM-dd'. See class eu.dnetlib.msro.workflows.nodes.collect.FindDateRangeForIncrementalHarvestingJobNode .

			this.fromDate = DateTime.parse(fromDate, simpleDateTimeFormatter);

			log.debug("fromDate string: " + fromDate + " -- parsed: " + this.fromDate.toString());

		}

		try {

            URI sftpServer = new URI(baseUrl);

            this.sftpURIScheme = sftpServer.getScheme();

            this.sftpServerAddress = sftpServer.getHost();

            this.remoteSftpBasePath = sftpServer.getPath();

        } catch (URISyntaxException e) {

            throw new CollectorServiceRuntimeException("Bad syntax in the URL " + baseUrl);

        }

        connectToSftpServer();

        initializeQueue();

    }

    private void connectToSftpServer() {

        JSch jsch = new JSch();

        try {

            JSch.setConfig("StrictHostKeyChecking", "no");

            sftpSession = jsch.getSession(username, sftpServerAddress);

            sftpSession.setPassword(password);

            sftpSession.connect();

            Channel channel = sftpSession.openChannel(sftpURIScheme);

            channel.connect();

            sftpChannel = (ChannelSftp) channel;

	        String pwd = sftpChannel.pwd();

	        log.debug("PWD from server: " + pwd);

	        String fullPath = pwd + remoteSftpBasePath;

	        sftpChannel.cd(fullPath);

	        log.debug("PWD from server 2 after 'cd " + fullPath + "' : " + sftpChannel.pwd());

	        log.info("Connected to SFTP server " + sftpServerAddress);

        } catch (JSchException e) {

            throw new CollectorServiceRuntimeException("Unable to connect to remote SFTP server.", e);

        } catch (SftpException e) {

            throw new CollectorServiceRuntimeException("Unable to access the base remote path on the SFTP server.", e);

        }

    }

    private void disconnectFromSftpServer() {

        sftpChannel.exit();

        sftpSession.disconnect();

    }

    private void initializeQueue() {

        queue = new LinkedList<String>();

	    log.info(String.format("SFTP collector plugin collecting from %s with recursion = %s, incremental = %s with fromDate=%s", remoteSftpBasePath,

			    isRecursive,

			    incremental, fromDate));

	    listDirectoryRecursive(".", "");

    }

    private void listDirectoryRecursive(final String parentDir, final String currentDir) {

        String dirToList = parentDir;

	    if (StringUtils.isNotBlank(currentDir)) {

		    dirToList += "/" + currentDir;

        }

	    log.debug("PARENT DIR: " + parentDir);

	    log.debug("DIR TO LIST: " + dirToList);

	    try {

            Vector<ChannelSftp.LsEntry> ls = sftpChannel.ls(dirToList);

            for (ChannelSftp.LsEntry entry : ls) {

                String currentFileName = entry.getFilename();

                if (currentFileName.equals(".") || currentFileName.equals("..")) {

                    // skip parent directory and directory itself

                    continue;

                }

                SftpATTRS attrs = entry.getAttrs();

                if (attrs.isDir()) {

                    if (isRecursive) {

                        listDirectoryRecursive(dirToList, currentFileName);

                    }

                } else {

                    // test the file for extensions compliance and, just in case, add it to the list.

                    for (String ext : extensionsSet) {

                        if (currentFileName.endsWith(ext)) {

	                        //test if the file has been changed after the last collection date:

	                        if (incremental) {

		                        String mtimeStr = attrs.getMtimeString();

		                        DateTime dt = DateTime.parse(mtimeStr, sftpDateFormatter);

		                        log.debug("Mtime string: " + mtimeStr + " -- parsed: " + dt.toString());

		                        if (dt.isAfter(fromDate)) {

			                        // queue.add(dirToList + "/" + currentFileName);

			                        queue.add(currentFileName);

			                        log.debug(currentFileName + " has changed and must be re-collected");

		                        } else {

			                        if (log.isDebugEnabled()) {

				                        log.debug(currentFileName + " has not changed since last collection");

			                        }

		                        }

	                        } else {

		                        //if it is not incremental, just add it to the queue

		                        //queue.add(dirToList + "/" + currentFileName);

		                        queue.add(currentFileName);

	                        }

                        }

                    }

                }

            }

        } catch (SftpException e) {

            throw new CollectorServiceRuntimeException("Cannot list the sftp remote directory", e);

        }

    }

    @Override

    public boolean hasNext() {

        if (queue.isEmpty()) {

            disconnectFromSftpServer();

            return false;

        } else {

            return true;

        }

    }

    @Override

    public String next() {

        String nextRemotePath = queue.remove();

        int nRepeat = 0;

	    String fullPathFile = nextRemotePath;

	    while (nRepeat < MAX_RETRIES) {

            try {

                OutputStream baos = new ByteArrayOutputStream();

                sftpChannel.get(nextRemotePath, baos);

	            if (log.isDebugEnabled()) {

		            fullPathFile = sftpChannel.pwd() + "/" + nextRemotePath;

		            log.debug(String.format("Collected file from SFTP: %s%s", sftpServerAddress, fullPathFile));

	            }

	            return baos.toString();

            } catch (SftpException e) {

                nRepeat++;

	            log.warn(String.format("An error occurred [%s] for %s%s, retrying.. [retried %s time(s)]", e.getMessage(), sftpServerAddress, fullPathFile,

			            nRepeat));

	            // disconnectFromSftpServer();

                try {

                    Thread.sleep(BACKOFF_MILLIS);

                } catch (InterruptedException e1) {

                    log.error(e1);

                }

            }

        }

	    throw new CollectorServiceRuntimeException(

			    String.format("Impossible to retrieve FTP file %s after %s retries. Aborting FTP collection.", fullPathFile, nRepeat));

    }

    @Override

    public void remove() {

        throw new UnsupportedOperationException();

    }

}