<?php
/**
 * @author Andreas Fischer <bantu@owncloud.com>
 * @author Hendrik Leppelsack <hendrik@leppelsack.de>
 * @author Jens-Christian Fischer <jens-christian.fischer@switch.ch>
 * @author Lukas Reschke <lukas@statuscode.ch>
 * @author Morris Jobke <hey@morrisjobke.de>
 * @author Robin Appelman <icewind@owncloud.com>
 * @author Robin McCorkell <robin@mccorkell.me.uk>
 * @author Roeland Jago Douma <rullzer@owncloud.com>
 * @author Thomas Müller <thomas.mueller@tmit.eu>
 * @author Thomas Tanghus <thomas@tanghus.net>
 * @author Vincent Petry <pvince81@owncloud.com>
 *
 * @copyright Copyright (c) 2018, ownCloud GmbH
 * @license AGPL-3.0
 *
 * This code is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License, version 3,
 * along with this program.  If not, see <http://www.gnu.org/licenses/>
 *
 */

namespace OC\Files\Type;

use OCP\Files\IMimeTypeDetector;
use OCP\IURLGenerator;

/**
 * Class Detection
 *
 * Mimetype detection
 *
 * @package OC\Files\Type
 */
class Detection implements IMimeTypeDetector {
	protected $mimetypes = [];
	protected $secureMimeTypes = [];

	protected $mimetypeIcons = [];
	/** @var string[] */
	protected $mimeTypeAlias = [];

	/** @var IURLGenerator */
	private $urlGenerator;

	/** @var string */
	private $customConfigDir;

	/** @var string */
	private $defaultConfigDir;

	/**
	 * @param IURLGenerator $urlGenerator
	 * @param string $customConfigDir
	 * @param string $defaultConfigDir
	 */
	public function __construct(
		IURLGenerator $urlGenerator,
		$customConfigDir,
		$defaultConfigDir
	) {
		$this->urlGenerator = $urlGenerator;
		$this->customConfigDir = $customConfigDir;
		$this->defaultConfigDir = $defaultConfigDir;
	}

	/**
	 * Add an extension -> mimetype mapping
	 *
	 * $mimetype is the assumed correct mime type
	 * The optional $secureMimeType is an alternative to send to send
	 * to avoid potential XSS.
	 *
	 * @param string $extension
	 * @param string $mimetype
	 * @param string|null $secureMimeType
	 */
	public function registerType(
		$extension,
		$mimetype,
		$secureMimeType = null
	) {
		$this->mimetypes[$extension] = [$mimetype, $secureMimeType];
		$this->secureMimeTypes[$mimetype] = $secureMimeType ?: $mimetype;
	}

	/**
	 * Add an array of extension -> mimetype mappings
	 *
	 * The mimetype value is in itself an array where the first index is
	 * the assumed correct mimetype and the second is either a secure alternative
	 * or null if the correct is considered secure.
	 *
	 * @param array $types
	 */
	public function registerTypeArray($types) {
		$this->mimetypes = \array_merge($this->mimetypes, $types);

		// Update the alternative mimetypes to avoid having to look them up each time.
		foreach ($this->mimetypes as $mimeType) {
			$this->secureMimeTypes[$mimeType[0]] = isset($mimeType[1]) ? $mimeType[1]: $mimeType[0];
		}
	}

	/**
	 * Add the mimetype aliases if they are not yet present
	 */
	private function loadAliases() {
		if (!empty($this->mimeTypeAlias)) {
			return;
		}

		$this->mimeTypeAlias = \json_decode(\file_get_contents($this->defaultConfigDir . '/mimetypealiases.dist.json'), true);

		if (\file_exists($this->customConfigDir . '/mimetypealiases.json')) {
			$custom = \json_decode(\file_get_contents($this->customConfigDir . '/mimetypealiases.json'), true);
			$this->mimeTypeAlias = \array_merge($this->mimeTypeAlias, $custom);
		}
	}

	/**
	 * @return string[]
	 */
	public function getAllAliases() {
		$this->loadAliases();
		return $this->mimeTypeAlias;
	}

	/**
	 * Add mimetype mappings if they are not yet present
	 */
	private function loadMappings() {
		if (!empty($this->mimetypes)) {
			return;
		}

		$mimetypeMapping = \json_decode(\file_get_contents($this->defaultConfigDir . '/mimetypemapping.dist.json'), true);

		//Check if need to load custom mappings
		if (\file_exists($this->customConfigDir . '/mimetypemapping.json')) {
			$custom = \json_decode(\file_get_contents($this->customConfigDir . '/mimetypemapping.json'), true);
			$mimetypeMapping = \array_merge($mimetypeMapping, $custom);
		}

		$this->registerTypeArray($mimetypeMapping);
	}

	/**
	 * Detect if the file is a shared object file. We detect this file
	 * with a regex.
	 *
	 * @param string $fileName
	 * @return bool true if file is a shared object else false
	 */
	private function detectSharedObjFileName($fileName) {
		\preg_match("/(.*?)(\.so)([\.]*?.*)/i", $fileName, $match);
		/**
		 * 1. Exactly 4 indexes to match ( check the regex grouping above preg_match )
		 * 2. Check if the filename has '.so'
		 * 3. Check if the filename has extension after '.so', say .so.1. or .so.
		 * That is anything like '.so.*'. This match is made in the 4th index.
		 * No extension after '.so' is considered to be shared object file
		 */
		return (\count($match) === 4) && ($match[2] === '.so')
			&& ($match[3] === '' || ($match[3] !== '' && \strpos($match[3], '.') === 0));
	}

	/**
	 * @return array
	 */
	public function getAllMappings() {
		$this->loadMappings();
		return $this->mimetypes;
	}

	/**
	 * detect mimetype only based on filename, content of file is not used
	 *
	 * @param string $path
	 * @return string
	 */
	public function detectPath($path) {
		$this->loadMappings();

		$fileName = \basename($path);
		# let's eat the first char if it is a .
		$fileName = ltrim($fileName, ".");
		//try to guess the type by the file extension
		if ($this->detectSharedObjFileName($fileName)) {
			$extension = 'so';
		} else {
			$extension = \strtolower(\strrchr($fileName, '.'));
			$extension = \substr($extension, 1); //remove leading .
		}
		return (isset($this->mimetypes[$extension], $this->mimetypes[$extension][0]))
			? $this->mimetypes[$extension][0]
			: 'application/octet-stream';
	}

	/**
	 * detect mimetype based on both filename and content
	 *
	 * @param string $path
	 * @return string
	 */
	public function detect($path) {
		$this->loadMappings();

		if (@\is_dir($path)) {
			// directories are easy
			return "httpd/unix-directory";
		}

		$mimeType = $this->detectPath($path);

		if ($mimeType === 'application/octet-stream' and \function_exists('finfo_open')
			and \function_exists('finfo_file') and $finfo = \finfo_open(FILEINFO_MIME)
		) {
			$info = @\strtolower(\finfo_file($finfo, $path));
			\finfo_close($finfo);
			if ($info) {
				$mimeType = \substr($info, 0, \strpos($info, ';'));
				return empty($mimeType) ? 'application/octet-stream' : $mimeType;
			}
		}
		$isWrapped = (\strpos($path, '://') !== false) and (\substr($path, 0, 7) === 'file://');
		if (!$isWrapped and $mimeType === 'application/octet-stream' && \function_exists("mime_content_type")) {
			// use mime magic extension if available
			$mimeType = \mime_content_type($path);
		}
		if (!$isWrapped and $mimeType === 'application/octet-stream' && \OC_Helper::canExecute("file")) {
			// it looks like we have a 'file' command,
			// lets see if it does have mime support
			$path = \escapeshellarg($path);
			$fp = \popen("file -b --mime-type $path 2>/dev/null", "r");
			$reply = \fgets($fp);
			\pclose($fp);

			//trim the newline
			$mimeType = \trim($reply);

			if (empty($mimeType)) {
				$mimeType = 'application/octet-stream';
			}
		}
		return $mimeType;
	}

	/**
	 * detect mimetype based on the content of a string
	 *
	 * @param string $data
	 * @return string
	 */
	public function detectString($data) {
		if (\function_exists('finfo_open') and \function_exists('finfo_file')) {
			$finfo = \finfo_open(FILEINFO_MIME);
			return \finfo_buffer($finfo, $data);
		} else {
			$tmpFile = \OC::$server->getTempManager()->getTemporaryFile();
			$fh = \fopen($tmpFile, 'wb');
			\fwrite($fh, $data, 8024);
			\fclose($fh);
			$mime = $this->detect($tmpFile);
			unset($tmpFile);
			return $mime;
		}
	}

	/**
	 * Get a secure mimetype that won't expose potential XSS.
	 *
	 * @param string $mimeType
	 * @return string
	 */
	public function getSecureMimeType($mimeType) {
		$this->loadMappings();

		return isset($this->secureMimeTypes[$mimeType])
			? $this->secureMimeTypes[$mimeType]
			: 'application/octet-stream';
	}

	/**
	 * Get path to the icon of a file type
	 * @param string $mimetype the MIME type
	 * @return string the url
	 */
	public function mimeTypeIcon($mimetype) {
		$this->loadAliases();

		while (isset($this->mimeTypeAlias[$mimetype])) {
			$mimetype = $this->mimeTypeAlias[$mimetype];
		}
		if (isset($this->mimetypeIcons[$mimetype])) {
			return $this->mimetypeIcons[$mimetype];
		}

		// Replace slash and backslash with a minus
		$icon = \str_replace('/', '-', $mimetype);
		$icon = \str_replace('\\', '-', $icon);

		// Is it a dir?
		if ($mimetype === 'dir') {
			$this->mimetypeIcons[$mimetype] = $this->urlGenerator->imagePath('core', 'filetypes/folder.svg');
			return $this->mimetypeIcons[$mimetype];
		}
		if ($mimetype === 'dir-shared') {
			$this->mimetypeIcons[$mimetype] = $this->urlGenerator->imagePath('core', 'filetypes/folder-shared.svg');
			return $this->mimetypeIcons[$mimetype];
		}
		if ($mimetype === 'dir-external') {
			$this->mimetypeIcons[$mimetype] = $this->urlGenerator->imagePath('core', 'filetypes/folder-external.svg');
			return $this->mimetypeIcons[$mimetype];
		}

		// Icon exists?
		try {
			$this->mimetypeIcons[$mimetype] = $this->urlGenerator->imagePath('core', 'filetypes/' . $icon . '.svg');
			return $this->mimetypeIcons[$mimetype];
		} catch (\RuntimeException $e) {
			// Specified image not found
		}

		// Try only the first part of the filetype
		$mimePart = \substr($icon, 0, \strpos($icon, '-'));
		try {
			$this->mimetypeIcons[$mimetype] = $this->urlGenerator->imagePath('core', 'filetypes/' . $mimePart . '.svg');
			return $this->mimetypeIcons[$mimetype];
		} catch (\RuntimeException $e) {
			// Image for the first part of the mimetype not found
		}

		$this->mimetypeIcons[$mimetype] = $this->urlGenerator->imagePath('core', 'filetypes/file.svg');
		return $this->mimetypeIcons[$mimetype];
	}
}
