<?php
/**
 * Part of the Joomla Framework Filesystem Package
 *
 * @copyright  Copyright (C) 2005 - 2021 Open Source Matters, Inc. All rights reserved.
 * @license    GNU General Public License version 2 or later; see LICENSE
 */

namespace Joomla\Filesystem;

/**
 * A Unified Diff Format Patcher class
 *
 * @link   http://sourceforge.net/projects/phppatcher/ This has been derived from the PhpPatcher version 0.1.1 written by Giuseppe Mazzotta
 * @since  1.0
 */
class Patcher
{
	/**
	 * Regular expression for searching source files
	 *
	 * @var    string
	 * @since  1.0
	 */
	const SRC_FILE = '/^---\\s+(\\S+)\s+\\d{1,4}-\\d{1,2}-\\d{1,2}\\s+\\d{1,2}:\\d{1,2}:\\d{1,2}(\\.\\d+)?\\s+(\+|-)\\d{4}/A';

	/**
	 * Regular expression for searching destination files
	 *
	 * @var    string
	 * @since  1.0
	 */
	const DST_FILE = '/^\\+\\+\\+\\s+(\\S+)\s+\\d{1,4}-\\d{1,2}-\\d{1,2}\\s+\\d{1,2}:\\d{1,2}:\\d{1,2}(\\.\\d+)?\\s+(\+|-)\\d{4}/A';

	/**
	 * Regular expression for searching hunks of differences
	 *
	 * @var    string
	 * @since  1.0
	 */
	const HUNK = '/@@ -(\\d+)(,(\\d+))?\\s+\\+(\\d+)(,(\\d+))?\\s+@@($)/A';

	/**
	 * Regular expression for splitting lines
	 *
	 * @var    string
	 * @since  1.0
	 */
	const SPLIT = '/(\r\n)|(\r)|(\n)/';

	/**
	 * Source files
	 *
	 * @var    array
	 * @since  1.0
	 */
	protected $sources = [];

	/**
	 * Destination files
	 *
	 * @var    array
	 * @since  1.0
	 */
	protected $destinations = [];

	/**
	 * Removal files
	 *
	 * @var    array
	 * @since  1.0
	 */
	protected $removals = [];

	/**
	 * Patches
	 *
	 * @var    array
	 * @since  1.0
	 */
	protected $patches = [];

	/**
	 * Singleton instance of this class
	 *
	 * @var    Patcher
	 * @since  1.0
	 */
	protected static $instance;

	/**
	 * Constructor
	 *
	 * The constructor is protected to force the use of Patcher::getInstance()
	 *
	 * @since   1.0
	 */
	protected function __construct()
	{
	}

	/**
	 * Method to get a patcher
	 *
	 * @return  Patcher  an instance of the patcher
	 *
	 * @since   1.0
	 */
	public static function getInstance()
	{
		if (!isset(static::$instance))
		{
			static::$instance = new static;
		}

		return static::$instance;
	}

	/**
	 * Reset the pacher
	 *
	 * @return  Patcher  This object for chaining
	 *
	 * @since   1.0
	 */
	public function reset()
	{
		$this->sources      = [];
		$this->destinations = [];
		$this->removals     = [];
		$this->patches      = [];

		return $this;
	}

	/**
	 * Apply the patches
	 *
	 * @return  integer  The number of files patched
	 *
	 * @since   1.0
	 * @throws  \RuntimeException
	 */
	public function apply()
	{
		foreach ($this->patches as $patch)
		{
			// Separate the input into lines
			$lines = self::splitLines($patch['udiff']);

			// Loop for each header
			while (self::findHeader($lines, $src, $dst))
			{
				$done = false;

				if ($patch['strip'] === null)
				{
					$src = $patch['root'] . preg_replace('#^([^/]*/)*#', '', $src);
					$dst = $patch['root'] . preg_replace('#^([^/]*/)*#', '', $dst);
				}
				else
				{
					$src = $patch['root'] . preg_replace('#^([^/]*/){' . (int) $patch['strip'] . '}#', '', $src);
					$dst = $patch['root'] . preg_replace('#^([^/]*/){' . (int) $patch['strip'] . '}#', '', $dst);
				}

				// Loop for each hunk of differences
				while (self::findHunk($lines, $srcLine, $srcSize, $dstLine, $dstSize))
				{
					$done = true;

					// Apply the hunk of differences
					$this->applyHunk($lines, $src, $dst, $srcLine, $srcSize, $dstLine, $dstSize);
				}

				// If no modifications were found, throw an exception
				if (!$done)
				{
					throw new \RuntimeException('Invalid Diff');
				}
			}
		}

		// Initialize the counter
		$done = 0;

		// Patch each destination file
		foreach ($this->destinations as $file => $content)
		{
			$content = implode("\n", $content);

			if (File::write($file, $content))
			{
				if (isset($this->sources[$file]))
				{
					$this->sources[$file] = $content;
				}

				$done++;
			}
		}

		// Remove each removed file
		foreach ($this->removals as $file)
		{
			if (File::delete($file))
			{
				if (isset($this->sources[$file]))
				{
					unset($this->sources[$file]);
				}

				$done++;
			}
		}

		// Clear the destinations cache
		$this->destinations = [];

		// Clear the removals
		$this->removals = [];

		// Clear the patches
		$this->patches = [];

		return $done;
	}

	/**
	 * Add a unified diff file to the patcher
	 *
	 * @param   string   $filename  Path to the unified diff file
	 * @param   string   $root      The files root path
	 * @param   integer  $strip     The number of '/' to strip
	 *
	 * @return	Patcher  $this for chaining
	 *
	 * @since   1.0
	 */
	public function addFile($filename, $root, $strip = 0)
	{
		return $this->add(file_get_contents($filename), $root, $strip);
	}

	/**
	 * Add a unified diff string to the patcher
	 *
	 * @param   string   $udiff  Unified diff input string
	 * @param   string   $root   The files root path
	 * @param   integer  $strip  The number of '/' to strip
	 *
	 * @return	Patcher  $this for chaining
	 *
	 * @since   1.0
	 */
	public function add($udiff, $root, $strip = 0)
	{
		$this->patches[] = [
			'udiff' => $udiff,
			'root'  => isset($root) ? rtrim($root, \DIRECTORY_SEPARATOR) . \DIRECTORY_SEPARATOR : '',
			'strip' => $strip,
		];

		return $this;
	}

	/**
	 * Separate CR or CRLF lines
	 *
	 * @param   string  $data  Input string
	 *
	 * @return  array  The lines of the input destination file
	 *
	 * @since   1.0
	 */
	protected static function splitLines($data)
	{
		return preg_split(self::SPLIT, $data);
	}

	/**
	 * Find the diff header
	 *
	 * The internal array pointer of $lines is on the next line after the finding
	 *
	 * @param   array   $lines  The udiff array of lines
	 * @param   string  $src    The source file
	 * @param   string  $dst    The destination file
	 *
	 * @return  boolean  TRUE in case of success, FALSE in case of failure
	 *
	 * @since   1.0
	 * @throws  \RuntimeException
	 */
	protected static function findHeader(&$lines, &$src, &$dst)
	{
		// Get the current line
		$line = current($lines);

		// Search for the header
		while ($line !== false && !preg_match(self::SRC_FILE, $line, $m))
		{
			$line = next($lines);
		}

		if ($line === false)
		{
			// No header found, return false
			return false;
		}

		// Set the source file
		$src = $m[1];

		// Advance to the next line
		$line = next($lines);

		if ($line === false)
		{
			throw new \RuntimeException('Unexpected EOF');
		}

		// Search the destination file
		if (!preg_match(self::DST_FILE, $line, $m))
		{
			throw new \RuntimeException('Invalid Diff file');
		}

		// Set the destination file
		$dst = $m[1];

		// Advance to the next line
		if (next($lines) === false)
		{
			throw new \RuntimeException('Unexpected EOF');
		}

		return true;
	}

	/**
	 * Find the next hunk of difference
	 *
	 * The internal array pointer of $lines is on the next line after the finding
	 *
	 * @param   array   $lines    The udiff array of lines
	 * @param   string  $srcLine  The beginning of the patch for the source file
	 * @param   string  $srcSize  The size of the patch for the source file
	 * @param   string  $dstLine  The beginning of the patch for the destination file
	 * @param   string  $dstSize  The size of the patch for the destination file
	 *
	 * @return  boolean  TRUE in case of success, false in case of failure
	 *
	 * @since   1.0
	 * @throws  \RuntimeException
	 */
	protected static function findHunk(&$lines, &$srcLine, &$srcSize, &$dstLine, &$dstSize)
	{
		$line = current($lines);

		if (preg_match(self::HUNK, $line, $m))
		{
			$srcLine = (int) $m[1];

			if ($m[3] === '')
			{
				$srcSize = 1;
			}
			else
			{
				$srcSize = (int) $m[3];
			}

			$dstLine = (int) $m[4];

			if ($m[6] === '')
			{
				$dstSize = 1;
			}
			else
			{
				$dstSize = (int) $m[6];
			}

			if (next($lines) === false)
			{
				throw new \RuntimeException('Unexpected EOF');
			}

			return true;
		}

		return false;
	}

	/**
	 * Apply the patch
	 *
	 * @param   array   $lines    The udiff array of lines
	 * @param   string  $src      The source file
	 * @param   string  $dst      The destination file
	 * @param   string  $srcLine  The beginning of the patch for the source file
	 * @param   string  $srcSize  The size of the patch for the source file
	 * @param   string  $dstLine  The beginning of the patch for the destination file
	 * @param   string  $dstSize  The size of the patch for the destination file
	 *
	 * @return  void
	 *
	 * @since   1.0
	 * @throws  \RuntimeException
	 */
	protected function applyHunk(&$lines, $src, $dst, $srcLine, $srcSize, $dstLine, $dstSize)
	{
		$srcLine--;
		$dstLine--;
		$line = current($lines);

		// Source lines (old file)
		$source = [];

		// New lines (new file)
		$destin  = [];
		$srcLeft = $srcSize;
		$dstLeft = $dstSize;

		do
		{
			if (!isset($line[0]))
			{
				$source[] = '';
				$destin[] = '';
				$srcLeft--;
				$dstLeft--;
			}
			elseif ($line[0] == '-')
			{
				if ($srcLeft == 0)
				{
					throw new \RuntimeException('Unexpected remove line at line ' . key($lines));
				}

				$source[] = substr($line, 1);
				$srcLeft--;
			}
			elseif ($line[0] == '+')
			{
				if ($dstLeft == 0)
				{
					throw new \RuntimeException('Unexpected add line at line ' . key($lines));
				}

				$destin[] = substr($line, 1);
				$dstLeft--;
			}
			elseif ($line != '\\ No newline at end of file')
			{
				$line     = substr($line, 1);
				$source[] = $line;
				$destin[] = $line;
				$srcLeft--;
				$dstLeft--;
			}

			if ($srcLeft == 0 && $dstLeft == 0)
			{
				// Now apply the patch, finally!
				if ($srcSize > 0)
				{
					$srcLines = & $this->getSource($src);

					if (!isset($srcLines))
					{
						throw new \RuntimeException(
							'Unexisting source file: ' . Path::removeRoot($src)
						);
					}
				}

				if ($dstSize > 0)
				{
					if ($srcSize > 0)
					{
						$dstLines  = & $this->getDestination($dst, $src);
						$srcBottom = $srcLine + \count($source);

						for ($l = $srcLine; $l < $srcBottom; $l++)
						{
							if ($srcLines[$l] != $source[$l - $srcLine])
							{
								throw new \RuntimeException(
									sprintf(
										'Failed source verification of file %1$s at line %2$s',
										Path::removeRoot($src),
										$l
									)
								);
							}
						}

						array_splice($dstLines, $dstLine, \count($source), $destin);
					}
					else
					{
						$this->destinations[$dst] = $destin;
					}
				}
				else
				{
					$this->removals[] = $src;
				}

				next($lines);

				return;
			}

			$line = next($lines);
		}
		while ($line !== false);

		throw new \RuntimeException('Unexpected EOF');
	}

	/**
	 * Get the lines of a source file
	 *
	 * @param   string  $src  The path of a file
	 *
	 * @return  array  The lines of the source file
	 *
	 * @since   1.0
	 */
	protected function &getSource($src)
	{
		if (!isset($this->sources[$src]))
		{
			if (is_readable($src))
			{
				$this->sources[$src] = self::splitLines(file_get_contents($src));
			}
			else
			{
				$this->sources[$src] = null;
			}
		}

		return $this->sources[$src];
	}

	/**
	 * Get the lines of a destination file
	 *
	 * @param   string  $dst  The path of a destination file
	 * @param   string  $src  The path of a source file
	 *
	 * @return  array  The lines of the destination file
	 *
	 * @since   1.0
	 */
	protected function &getDestination($dst, $src)
	{
		if (!isset($this->destinations[$dst]))
		{
			$this->destinations[$dst] = $this->getSource($src);
		}

		return $this->destinations[$dst];
	}
}