<?php
/**
 * Transfer files from FTP using PHP functions. This class also
 * implements a retry mechanism (you can set either a finite or
 * infinite number of attempts).
 *
 * Copyright (C) 2016 - by Alexandru Rusu
 * @author Alexandru Rusu <arusu@bfproject.ro>
 * @license MIT License
 */
class FtpRetryTransferHelper {

	/** @var string */
	private $hostname = "";
	/** @var integer */
	private $hostport = 21;
	/** @var string */
	private $username = "";
	/** @var string */
	private $password = "";

	/** @var integer */
	private $timeout = 30;
	/** @var integer */
	private $maxRetry = 3;
	/** @var integer */
	private $crtRetry = 0;

	/** @var resource */
	private $connection = NULL;
	/** @var NULL|string */
	private $lstError = NULL;

	/**
	 * Class constructor
	 *
	 * @param string $host     Remote FTP server hostname
	 * @param string $user     Remote FTP server user
	 * @param string $pass     Remote FTP server password
	 * @param string $port     Remote FTP server port
	 * @param string $timeout  Connection timeout
	 * @param string $maxRetry Max number of retries (use null or 0 for unlimited)
	 */
    public function __construct($host, $user, $pass, $port = NULL, $timeout = NULL, $maxRetry = NULL) {

		$this->hostname = $host;
		$this->username = $user;
		$this->password = $pass;

		if (!empty($port) && !empty(intval($port))) $this->hostport = $port;
		if (!empty($timeput) && !empty(intval($timeout))) $this->timeout = $timeout;
		if (!empty($maxRetry) && !empty(intval($maxRetry))) $this->maxRetry = $maxRetry;

		// Connect to host
		$this->connection = ftp_connect($this->hostname, $this->hostport, $this->timeout);
		if (!$this->connection)
			throw new Exception("Cannot connect to FTP host.");

		// Login to the user account
		if (!ftp_login($this->connection, $this->username, $this->password))
			thrown new Exception("Cannot authenticate to FTP host.");

		// Set passive mode for transfer
		@ftp_pasv($this->connection, TRUE);
	}

	/**
	 * Class destructor
	 */
	public function __destruct() {
		// Make sure to close the connection
		ftp_close($this->connection);
	}

	/**
	 * Transfer a file from FTP
	 *
	 * @param string $remotePath   Remote FTP host path of the file to be transfered
	 * @param string $localPath    Local path where the file should be saved
	 * @param const  $transferMode (optional) Transfer mode, can be FTP_BINARY or FTP_ASCII
	 *
	 * @return bool Result of the operation
	 */
	public function downloadFile($remotePath, $localPath, $transferMode = FTP_BINARY) {
		$transfered     = FALSE;
		$this->lstError = NULL;
		$this->crtRetry = 0;
		while (!$transfered && !empty($this->lstError) && (empty($this->maxRetry) || $this->crtRetry < $this->maxRetry)) {
			++$this->crtRetry;
			$transfered = $this->_resumeDownload($remotePath, $localPath, $transferMode);
		}
		return $transfered;
	}

	/**
	 * Get last error
	 *
	 * @return mixed Last transfer error or FALSE if transfer was successful
	 */
	public function getLastError() {
		return empty($this->lstError) ? FALSE : $this->lstError;
	}

	/**
	 * Internal method to start or resume a download
	 *
	 * @param string $remotePath   Remote FTP host path of the file to be transfered
	 * @param string $localPath    Local path where the file should be saved
	 * @param const  $transferMode (optional) Transfer mode, can be FTP_BINARY or FTP_ASCII
	 *
	 * @return bool Result of the operation
	 */
	private function _resumeDownload($remotePath, $localPath, $transferMode = FTP_BINARY) {
		$transfered     = FALSE;
		$this->lstError = NULL;
		try {
			$resumePosition = file_exists($localPath) ? filesize($localPath) : 0;
			$transfered     = ftp_get($this->connection, $localPath, $remotePath, $transferMode, $resumePosition);
			if (!$transfered) {
				$this->lstError = "Failed transfering file on retry " . ($this->crtRetry + 1) . " of " . $this->maxRetry;
			}
		} catch (Exception $exp) {
			$transfered     = FALSE;
			$this->lstError = $exp->getMessage();
		}
		return $transfered;
	}
}

/* EOF */