<?php
/**
 * SPDX-FileCopyrightText: 2016 Nextcloud GmbH and Nextcloud contributors
 * SPDX-FileCopyrightText: 2016 ownCloud, Inc.
 * SPDX-License-Identifier: AGPL-3.0-only
 */
namespace OC;

use bantu\IniGetWrapper\IniGetWrapper;

/**
 * Helper class for large files on 32-bit platforms.
 */
class LargeFileHelper {
	/**
	 * pow(2, 53) as a base-10 string.
	 * @var string
	 */
	public const POW_2_53 = '9007199254740992';

	/**
	 * pow(2, 53) - 1 as a base-10 string.
	 * @var string
	 */
	public const POW_2_53_MINUS_1 = '9007199254740991';

	/**
	 * @brief Checks whether our assumptions hold on the PHP platform we are on.
	 *
	 * @throws \RuntimeException if our assumptions do not hold on the current
	 *                           PHP platform.
	 */
	public function __construct() {
		$pow_2_53 = (float)self::POW_2_53_MINUS_1 + 1.0;
		if ($this->formatUnsignedInteger($pow_2_53) !== self::POW_2_53) {
			throw new \RuntimeException(
				'This class assumes floats to be double precision or "better".'
			);
		}
	}

	/**
	 * @brief Formats a signed integer or float as an unsigned integer base-10
	 *        string. Passed strings will be checked for being base-10.
	 *
	 * @param int|float|string $number Number containing unsigned integer data
	 *
	 * @throws \UnexpectedValueException if $number is not a float, not an int
	 *                                   and not a base-10 string.
	 *
	 * @return string Unsigned integer base-10 string
	 */
	public function formatUnsignedInteger(int|float|string $number): string {
		if (is_float($number)) {
			// Undo the effect of the php.ini setting 'precision'.
			return number_format($number, 0, '', '');
		} elseif (is_string($number) && ctype_digit($number)) {
			return $number;
		} elseif (is_int($number)) {
			// Interpret signed integer as unsigned integer.
			return sprintf('%u', $number);
		} else {
			throw new \UnexpectedValueException(
				'Expected int, float or base-10 string'
			);
		}
	}

	/**
	 * @brief Tries to get the size of a file via various workarounds that
	 *        even work for large files on 32-bit platforms.
	 *
	 * @param string $filename Path to the file.
	 *
	 * @return int|float Number of bytes as number (float or int)
	 */
	public function getFileSize(string $filename): int|float {
		$fileSize = $this->getFileSizeViaCurl($filename);
		if (!is_null($fileSize)) {
			return $fileSize;
		}
		$fileSize = $this->getFileSizeViaExec($filename);
		if (!is_null($fileSize)) {
			return $fileSize;
		}
		return $this->getFileSizeNative($filename);
	}

	/**
	 * @brief Tries to get the size of a file via a CURL HEAD request.
	 *
	 * @param string $fileName Path to the file.
	 *
	 * @return null|int|float Number of bytes as number (float or int) or
	 *                        null on failure.
	 */
	public function getFileSizeViaCurl(string $fileName): null|int|float {
		if (\OC::$server->get(IniGetWrapper::class)->getString('open_basedir') === '') {
			$encodedFileName = rawurlencode($fileName);
			$ch = curl_init("file:///$encodedFileName");
			curl_setopt($ch, CURLOPT_NOBODY, true);
			curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
			curl_setopt($ch, CURLOPT_HEADER, true);
			$data = curl_exec($ch);
			curl_close($ch);
			if ($data !== false) {
				$matches = [];
				preg_match('/Content-Length: (\d+)/', $data, $matches);
				if (isset($matches[1])) {
					return 0 + $matches[1];
				}
			}
		}
		return null;
	}

	/**
	 * @brief Tries to get the size of a file via an exec() call.
	 *
	 * @param string $filename Path to the file.
	 *
	 * @return null|int|float Number of bytes as number (float or int) or
	 *                        null on failure.
	 */
	public function getFileSizeViaExec(string $filename): null|int|float {
		if (\OCP\Util::isFunctionEnabled('exec')) {
			$os = strtolower(php_uname('s'));
			$arg = escapeshellarg($filename);
			$result = null;
			if (str_contains($os, 'linux')) {
				$result = $this->exec("stat -c %s $arg");
			} elseif (str_contains($os, 'bsd') || str_contains($os, 'darwin')) {
				$result = $this->exec("stat -f %z $arg");
			}
			return $result;
		}
		return null;
	}

	/**
	 * @brief Gets the size of a file via a filesize() call and converts
	 *        negative signed int to positive float. As the result of filesize()
	 *        will wrap around after a file size of 2^32 bytes = 4 GiB, this
	 *        should only be used as a last resort.
	 *
	 * @param string $filename Path to the file.
	 *
	 * @return int|float Number of bytes as number (float or int).
	 */
	public function getFileSizeNative(string $filename): int|float {
		$result = filesize($filename);
		if ($result < 0) {
			// For file sizes between 2 GiB and 4 GiB, filesize() will return a
			// negative int, as the PHP data type int is signed. Interpret the
			// returned int as an unsigned integer and put it into a float.
			return (float) sprintf('%u', $result);
		}
		return $result;
	}

	/**
	 * Returns the current mtime for $fullPath
	 */
	public function getFileMtime(string $fullPath): int {
		try {
			$result = filemtime($fullPath) ?: -1;
		} catch (\Exception $e) {
			$result = - 1;
		}
		if ($result < 0) {
			if (\OCP\Util::isFunctionEnabled('exec')) {
				$os = strtolower(php_uname('s'));
				if (str_contains($os, 'linux')) {
					return (int)($this->exec('stat -c %Y ' . escapeshellarg($fullPath)) ?? -1);
				}
			}
		}
		return $result;
	}

	protected function exec(string $cmd): null|int|float {
		$result = trim(exec($cmd));
		return ctype_digit($result) ? 0 + $result : null;
	}
}