<?php
/**
 * CSS Minifier
 *
 * Please report bugs on https://github.com/matthiasmullie/minify/issues
 *
 * @author Matthias Mullie <minify@mullie.eu>
 * @copyright Copyright (c) 2012, Matthias Mullie. All rights reserved
 * @license MIT License
 */

namespace WP_Rocket\Dependencies\Minify;

use WP_Rocket\Dependencies\Minify\Exceptions\FileImportException;
use WP_Rocket\Dependencies\PathConverter\ConverterInterface;
use WP_Rocket\Dependencies\PathConverter\Converter;

/**
 * CSS minifier
 *
 * Please report bugs on https://github.com/matthiasmullie/minify/issues
 *
 * @package Minify
 * @author Matthias Mullie <minify@mullie.eu>
 * @author Tijs Verkoyen <minify@verkoyen.eu>
 * @copyright Copyright (c) 2012, Matthias Mullie. All rights reserved
 * @license MIT License
 */
class CSS extends Minify
{
	/**
	 * @var int maximum inport size in kB
	 */
	protected $maxImportSize = 5;

	/**
	 * @var string[] valid import extensions
	 */
	protected $importExtensions = array(
		'gif' => 'data:image/gif',
		'png' => 'data:image/png',
		'jpe' => 'data:image/jpeg',
		'jpg' => 'data:image/jpeg',
		'jpeg' => 'data:image/jpeg',
		'svg' => 'data:image/svg+xml',
		'woff' => 'data:application/x-font-woff',
		'tif' => 'image/tiff',
		'tiff' => 'image/tiff',
		'xbm' => 'image/x-xbitmap',
	);

	/**
	 * Set the maximum size if files to be imported.
	 *
	 * Files larger than this size (in kB) will not be imported into the CSS.
	 * Importing files into the CSS as data-uri will save you some connections,
	 * but we should only import relatively small decorative images so that our
	 * CSS file doesn't get too bulky.
	 *
	 * @param int $size Size in kB
	 */
	public function setMaxImportSize($size)
	{
		$this->maxImportSize = $size;
	}

	/**
	 * Set the type of extensions to be imported into the CSS (to save network
	 * connections).
	 * Keys of the array should be the file extensions & respective values
	 * should be the data type.
	 *
	 * @param string[] $extensions Array of file extensions
	 */
	public function setImportExtensions(array $extensions)
	{
		$this->importExtensions = $extensions;
	}

	/**
	 * Move any import statements to the top.
	 *
	 * @param string $content Nearly finished CSS content
	 *
	 * @return string
	 */
	protected function moveImportsToTop($content)
	{
		if (preg_match_all('/(;?)(@import (?<url>url\()?(?P<quotes>["\']?).+?(?P=quotes)(?(url)\)));?/', $content, $matches)) {
			// remove from content
			foreach ($matches[0] as $import) {
				$content = str_replace($import, '', $content);
			}

			// add to top
			$content = implode(';', $matches[2]).';'.trim($content, ';');
		}

		return $content;
	}

	/**
	 * Combine CSS from import statements.
	 *
	 * @import's will be loaded and their content merged into the original file,
	 * to save HTTP requests.
	 *
	 * @param string   $source  The file to combine imports for
	 * @param string   $content The CSS content to combine imports for
	 * @param string[] $parents Parent paths, for circular reference checks
	 *
	 * @return string
	 *
	 * @throws FileImportException
	 */
	protected function combineImports($source, $content, $parents)
	{
		$importRegexes = array(
			// @import url(xxx)
			'/
			# import statement
			@import

			# whitespace
			\s+

				# open url()
				url\(

					# (optional) open path enclosure
					(?P<quotes>["\']?)

						# fetch path
						(?P<path>.+?)

					# (optional) close path enclosure
					(?P=quotes)

				# close url()
				\)

				# (optional) trailing whitespace
				\s*

				# (optional) media statement(s)
				(?P<media>[^;]*)

				# (optional) trailing whitespace
				\s*

			# (optional) closing semi-colon
			;?

			/ix',

			// @import 'xxx'
			'/

			# import statement
			@import

			# whitespace
			\s+

				# open path enclosure
				(?P<quotes>["\'])

					# fetch path
					(?P<path>.+?)

				# close path enclosure
				(?P=quotes)

				# (optional) trailing whitespace
				\s*

				# (optional) media statement(s)
				(?P<media>[^;]*)

				# (optional) trailing whitespace
				\s*

			# (optional) closing semi-colon
			;?

			/ix',
		);

		// find all relative imports in css
		$matches = array();
		foreach ($importRegexes as $importRegex) {
			if (preg_match_all($importRegex, $content, $regexMatches, PREG_SET_ORDER)) {
				$matches = array_merge($matches, $regexMatches);
			}
		}

		$search = array();
		$replace = array();

		// loop the matches
		foreach ($matches as $match) {
			// get the path for the file that will be imported
			$importPath = dirname($source).'/'.$match['path'];

			// only replace the import with the content if we can grab the
			// content of the file
			if (!$this->canImportByPath($match['path']) || !$this->canImportFile($importPath)) {
				continue;
			}

			// check if current file was not imported previously in the same
			// import chain.
			if (in_array($importPath, $parents)) {
				throw new FileImportException('Failed to import file "'.$importPath.'": circular reference detected.');
			}

			// grab referenced file & minify it (which may include importing
			// yet other @import statements recursively)
			$minifier = new self($importPath);
			$minifier->setMaxImportSize($this->maxImportSize);
			$minifier->setImportExtensions($this->importExtensions);
			$importContent = $minifier->execute($source, $parents);

			// check if this is only valid for certain media
			if (!empty($match['media'])) {
				$importContent = '@media '.$match['media'].'{'.$importContent.'}';
			}

			// add to replacement array
			$search[] = $match[0];
			$replace[] = $importContent;
		}

		// replace the import statements
		return str_replace($search, $replace, $content);
	}

	/**
	 * Import files into the CSS, base64-ized.
	 *
	 * @url(image.jpg) images will be loaded and their content merged into the
	 * original file, to save HTTP requests.
	 *
	 * @param string $source  The file to import files for
	 * @param string $content The CSS content to import files for
	 *
	 * @return string
	 */
	protected function importFiles($source, $content)
	{
		$regex = '/url\((["\']?)(.+?)\\1\)/i';
		if ($this->importExtensions && preg_match_all($regex, $content, $matches, PREG_SET_ORDER)) {
			$search = array();
			$replace = array();

			// loop the matches
			foreach ($matches as $match) {
				$extension = substr(strrchr($match[2], '.'), 1);
				if ($extension && !array_key_exists($extension, $this->importExtensions)) {
					continue;
				}

				// get the path for the file that will be imported
				$path = $match[2];
				$path = dirname($source).'/'.$path;

				// only replace the import with the content if we're able to get
				// the content of the file, and it's relatively small
				if ($this->canImportFile($path) && $this->canImportBySize($path)) {
					// grab content && base64-ize
					$importContent = $this->load($path);
					$importContent = base64_encode($importContent);

					// build replacement
					$search[] = $match[0];
					$replace[] = 'url('.$this->importExtensions[$extension].';base64,'.$importContent.')';
				}
			}

			// replace the import statements
			$content = str_replace($search, $replace, $content);
		}

		return $content;
	}

	/**
	 * Minify the data.
	 * Perform CSS optimizations.
	 *
	 * @param string[optional] $path    Path to write the data to
	 * @param string[]         $parents Parent paths, for circular reference checks
	 *
	 * @return string The minified data
	 */
	public function execute($path = null, $parents = array())
	{
		$content = '';

		// loop CSS data (raw data and files)
		foreach ($this->data as $source => $css) {
			/*
			 * Let's first take out strings & comments, since we can't just
			 * remove whitespace anywhere. If whitespace occurs inside a string,
			 * we should leave it alone. E.g.:
			 * p { content: "a   test" }
			 */
			$this->extractStrings();
			$this->stripComments();
			$this->extractMath();
			$this->extractCustomProperties();
			$css = $this->replace($css);

			$css = $this->stripWhitespace($css);
			$css = $this->shortenColors($css);
			$css = $this->shortenZeroes($css);
			$css = $this->shortenFontWeights($css);
			$css = $this->stripEmptyTags($css);

			// restore the string we've extracted earlier
			$css = $this->restoreExtractedData($css);

			$source = is_int($source) ? '' : $source;
			$parents = $source ? array_merge($parents, array($source)) : $parents;
			$css = $this->combineImports($source, $css, $parents);
			$css = $this->importFiles($source, $css);

			/*
			 * If we'll save to a new path, we'll have to fix the relative paths
			 * to be relative no longer to the source file, but to the new path.
			 * If we don't write to a file, fall back to same path so no
			 * conversion happens (because we still want it to go through most
			 * of the move code, which also addresses url() & @import syntax...)
			 */
			$converter = $this->getPathConverter($source, $path ?: $source);
			$css = $this->move($converter, $css);

			// combine css
			$content .= $css;
		}

		$content = $this->moveImportsToTop($content);

		return $content;
	}

	/**
	 * Moving a css file should update all relative urls.
	 * Relative references (e.g. ../images/image.gif) in a certain css file,
	 * will have to be updated when a file is being saved at another location
	 * (e.g. ../../images/image.gif, if the new CSS file is 1 folder deeper).
	 *
	 * @param ConverterInterface $converter Relative path converter
	 * @param string             $content   The CSS content to update relative urls for
	 *
	 * @return string
	 */
	protected function move(ConverterInterface $converter, $content)
	{
		/*
		 * Relative path references will usually be enclosed by url(). @import
		 * is an exception, where url() is not necessary around the path (but is
		 * allowed).
		 * This *could* be 1 regular expression, where both regular expressions
		 * in this array are on different sides of a |. But we're using named
		 * patterns in both regexes, the same name on both regexes. This is only
		 * possible with a (?J) modifier, but that only works after a fairly
		 * recent PCRE version. That's why I'm doing 2 separate regular
		 * expressions & combining the matches after executing of both.
		 */
		$relativeRegexes = array(
			// url(xxx)
			'/
			# open url()
			url\(

				\s*

				# open path enclosure
				(?P<quotes>["\'])?

					# fetch path
					(?P<path>.+?)

				# close path enclosure
				(?(quotes)(?P=quotes))

				\s*

			# close url()
			\)

			/ix',

			// @import "xxx"
			'/
			# import statement
			@import

			# whitespace
			\s+

				# we don\'t have to check for @import url(), because the
				# condition above will already catch these

				# open path enclosure
				(?P<quotes>["\'])

					# fetch path
					(?P<path>.+?)

				# close path enclosure
				(?P=quotes)

			/ix',
		);

		// find all relative urls in css
		$matches = array();
		foreach ($relativeRegexes as $relativeRegex) {
			if (preg_match_all($relativeRegex, $content, $regexMatches, PREG_SET_ORDER)) {
				$matches = array_merge($matches, $regexMatches);
			}
		}

		$search = array();
		$replace = array();

		// loop all urls
		foreach ($matches as $match) {
			// determine if it's a url() or an @import match
			$type = (strpos($match[0], '@import') === 0 ? 'import' : 'url');

			$url = $match['path'];
			if ($this->canImportByPath($url)) {
				// attempting to interpret GET-params makes no sense, so let's discard them for awhile
				$params = strrchr($url, '?');
				$url = $params ? substr($url, 0, -strlen($params)) : $url;

				// fix relative url
				$url = $converter->convert($url);

				// now that the path has been converted, re-apply GET-params
				$url .= $params;
			}

			/*
			 * Urls with control characters above 0x7e should be quoted.
			 * According to Mozilla's parser, whitespace is only allowed at the
			 * end of unquoted urls.
			 * Urls with `)` (as could happen with data: uris) should also be
			 * quoted to avoid being confused for the url() closing parentheses.
			 * And urls with a # have also been reported to cause issues.
			 * Urls with quotes inside should also remain escaped.
			 *
			 * @see https://developer.mozilla.org/nl/docs/Web/CSS/url#The_url()_functional_notation
			 * @see https://hg.mozilla.org/mozilla-central/rev/14abca4e7378
			 * @see https://github.com/matthiasmullie/minify/issues/193
			 */
			$url = trim($url);
			if (preg_match('/[\s\)\'"#\x{7f}-\x{9f}]/u', $url)) {
				$url = $match['quotes'] . $url . $match['quotes'];
			}

			// build replacement
			$search[] = $match[0];
			if ($type === 'url') {
				$replace[] = 'url('.$url.')';
			} elseif ($type === 'import') {
				$replace[] = '@import "'.$url.'"';
			}
		}

		// replace urls
		return str_replace($search, $replace, $content);
	}

	/**
	 * Shorthand hex color codes.
	 * #FF0000 -> #F00.
	 *
	 * @param string $content The CSS content to shorten the hex color codes for
	 *
	 * @return string
	 */
	protected function shortenColors($content)
	{
		$content = preg_replace('/(?<=[: ])#([0-9a-z])\\1([0-9a-z])\\2([0-9a-z])\\3(?:([0-9a-z])\\4)?(?=[; }])/i', '#$1$2$3$4', $content);

		// remove alpha channel if it's pointless...
		$content = preg_replace('/(?<=[: ])#([0-9a-z]{6})ff?(?=[; }])/i', '#$1', $content);
		$content = preg_replace('/(?<=[: ])#([0-9a-z]{3})f?(?=[; }])/i', '#$1', $content);

		$colors = array(
			// we can shorten some even more by replacing them with their color name
			'#F0FFFF' => 'azure',
			'#F5F5DC' => 'beige',
			'#A52A2A' => 'brown',
			'#FF7F50' => 'coral',
			'#FFD700' => 'gold',
			'#808080' => 'gray',
			'#008000' => 'green',
			'#4B0082' => 'indigo',
			'#FFFFF0' => 'ivory',
			'#F0E68C' => 'khaki',
			'#FAF0E6' => 'linen',
			'#800000' => 'maroon',
			'#000080' => 'navy',
			'#808000' => 'olive',
			'#CD853F' => 'peru',
			'#FFC0CB' => 'pink',
			'#DDA0DD' => 'plum',
			'#800080' => 'purple',
			'#F00' => 'red',
			'#FA8072' => 'salmon',
			'#A0522D' => 'sienna',
			'#C0C0C0' => 'silver',
			'#FFFAFA' => 'snow',
			'#D2B48C' => 'tan',
			'#FF6347' => 'tomato',
			'#EE82EE' => 'violet',
			'#F5DEB3' => 'wheat',
			// or the other way around
			'WHITE' => '#fff',
			'BLACK' => '#000',
		);

		return preg_replace_callback(
			'/(?<=[: ])('.implode('|', array_keys($colors)).')(?=[; }])/i',
			function ($match) use ($colors) {
				return $colors[strtoupper($match[0])];
			},
			$content
		);
	}

	/**
	 * Shorten CSS font weights.
	 *
	 * @param string $content The CSS content to shorten the font weights for
	 *
	 * @return string
	 */
	protected function shortenFontWeights($content)
	{
		$weights = array(
			'normal' => 400,
			'bold' => 700,
		);

		$callback = function ($match) use ($weights) {
			return $match[1].$weights[$match[2]];
		};

		return preg_replace_callback('/(font-weight\s*:\s*)('.implode('|', array_keys($weights)).')(?=[;}])/', $callback, $content);
	}

	/**
	 * Shorthand 0 values to plain 0, instead of e.g. -0em.
	 *
	 * @param string $content The CSS content to shorten the zero values for
	 *
	 * @return string
	 */
	protected function shortenZeroes($content)
	{
		// we don't want to strip units in `calc()` expressions:
		// `5px - 0px` is valid, but `5px - 0` is not
		// `10px * 0` is valid (equates to 0), and so is `10 * 0px`, but
		// `10 * 0` is invalid
		// we've extracted calcs earlier, so we don't need to worry about this

		// reusable bits of code throughout these regexes:
		// before & after are used to make sure we don't match lose unintended
		// 0-like values (e.g. in #000, or in http://url/1.0)
		// units can be stripped from 0 values, or used to recognize non 0
		// values (where wa may be able to strip a .0 suffix)
		$before = '(?<=[:(, ])';
		$after = '(?=[ ,);}])';
		$units = '(em|ex|%|px|cm|mm|in|pt|pc|ch|rem|vh|vw|vmin|vmax|vm)';

		// strip units after zeroes (0px -> 0)
		// NOTE: it should be safe to remove all units for a 0 value, but in
		// practice, Webkit (especially Safari) seems to stumble over at least
		// 0%, potentially other units as well. Only stripping 'px' for now.
		// @see https://github.com/matthiasmullie/minify/issues/60
		$content = preg_replace('/'.$before.'(-?0*(\.0+)?)(?<=0)px'.$after.'/', '\\1', $content);

		// strip 0-digits (.0 -> 0)
		$content = preg_replace('/'.$before.'\.0+'.$units.'?'.$after.'/', '0\\1', $content);
		// strip trailing 0: 50.10 -> 50.1, 50.10px -> 50.1px
		$content = preg_replace('/'.$before.'(-?[0-9]+\.[0-9]+)0+'.$units.'?'.$after.'/', '\\1\\2', $content);
		// strip trailing 0: 50.00 -> 50, 50.00px -> 50px
		$content = preg_replace('/'.$before.'(-?[0-9]+)\.0+'.$units.'?'.$after.'/', '\\1\\2', $content);
		// strip leading 0: 0.1 -> .1, 01.1 -> 1.1
		$content = preg_replace('/'.$before.'(-?)0+([0-9]*\.[0-9]+)'.$units.'?'.$after.'/', '\\1\\2\\3', $content);

		// strip negative zeroes (-0 -> 0) & truncate zeroes (00 -> 0)
		$content = preg_replace('/'.$before.'-?0+'.$units.'?'.$after.'/', '0\\1', $content);

		// IE doesn't seem to understand a unitless flex-basis value (correct -
		// it goes against the spec), so let's add it in again (make it `%`,
		// which is only 1 char: 0%, 0px, 0 anything, it's all just the same)
		// @see https://developer.mozilla.org/nl/docs/Web/CSS/flex
		$content = preg_replace('/flex:([0-9]+\s[0-9]+\s)0([;\}])/', 'flex:${1}0%${2}', $content);
		$content = preg_replace('/flex-basis:0([;\}])/', 'flex-basis:0%${1}', $content);

		return $content;
	}

	/**
	 * Strip empty tags from source code.
	 *
	 * @param string $content
	 *
	 * @return string
	 */
	protected function stripEmptyTags($content)
	{
		$content = preg_replace('/(?<=^)[^\{\};]+\{\s*\}/', '', $content);
		$content = preg_replace('/(?<=(\}|;))[^\{\};]+\{\s*\}/', '', $content);

		return $content;
	}

	/**
	 * Strip comments from source code.
	 */
	protected function stripComments()
	{
		// PHP only supports $this inside anonymous functions since 5.4
		$minifier = $this;
		$callback = function ($match) use ($minifier) {
			$count = count($minifier->extracted);
			$placeholder = '/*'.$count.'*/';
			$minifier->extracted[$placeholder] = $match[0];

			return $placeholder;
		};
		$this->registerPattern('/\n?\/\*(!|.*?@license|.*?@preserve).*?\*\/\n?/s', $callback);

		$this->registerPattern('/\/\*.*?\*\//s', '');
	}

	/**
	 * Strip whitespace.
	 *
	 * @param string $content The CSS content to strip the whitespace for
	 *
	 * @return string
	 */
	protected function stripWhitespace($content)
	{
		// remove leading & trailing whitespace
		$content = preg_replace('/^\s*/m', '', $content);
		$content = preg_replace('/\s*$/m', '', $content);

		// replace newlines with a single space
		$content = preg_replace('/\s+/', ' ', $content);

		// remove whitespace around meta characters
		// inspired by stackoverflow.com/questions/15195750/minify-compress-css-with-regex
		$content = preg_replace('/\s*([\*$~^|]?+=|[{};,>~]|!important\b)\s*/', '$1', $content);
		$content = preg_replace('/([\[(:>\+])\s+/', '$1', $content);
		$content = preg_replace('/\s+([\]\)>\+])/', '$1', $content);
		$content = preg_replace('/\s+(:)(?![^\}]*\{)/', '$1', $content);

		// whitespace around + and - can only be stripped inside some pseudo-
		// classes, like `:nth-child(3+2n)`
		// not in things like `calc(3px + 2px)`, shorthands like `3px -2px`, or
		// selectors like `div.weird- p`
		$pseudos = array('nth-child', 'nth-last-child', 'nth-last-of-type', 'nth-of-type');
		$content = preg_replace('/:('.implode('|', $pseudos).')\(\s*([+-]?)\s*(.+?)\s*([+-]?)\s*(.*?)\s*\)/', ':$1($2$3$4$5)', $content);

		// remove semicolon/whitespace followed by closing bracket
		$content = str_replace(';}', '}', $content);

		return trim($content);
	}

	/**
	 * Replace all occurrences of functions that may contain math, where
	 * whitespace around operators needs to be preserved (e.g. calc, clamp)
	 */
	protected function extractMath()
	{
		$functions = array('calc', 'clamp', 'min', 'max');
		$pattern = '/\b('. implode('|', $functions) .')(\(.+?)(?=$|;|})/m';

		// PHP only supports $this inside anonymous functions since 5.4
		$minifier = $this;
		$callback = function ($match) use ($minifier, $pattern, &$callback) {
			$function = $match[1];
			$length = strlen($match[2]);
			$expr = '';
			$opened = 0;

			// the regular expression for extracting math has 1 significant problem:
			// it can't determine the correct closing parenthesis...
			// instead, it'll match a larger portion of code to where it's certain that
			// the calc() musts have ended, and we'll figure out which is the correct
			// closing parenthesis here, by counting how many have opened
			for ($i = 0; $i < $length; $i++) {
				$char = $match[2][$i];
				$expr .= $char;
				if ($char === '(') {
					$opened++;
				} elseif ($char === ')' && --$opened === 0) {
					break;
				}
			}

			// now that we've figured out where the calc() starts and ends, extract it
			$count = count($minifier->extracted);
			$placeholder = 'math('.$count.')';
			$minifier->extracted[$placeholder] = $function.'('.trim(substr($expr, 1, -1)).')';

			// and since we've captured more code than required, we may have some leftover
			// calc() in here too - go recursive on the remaining but of code to go figure
			// that out and extract what is needed
			$rest = "";
			$pos  = strpos($match[0], $function.$expr);
			if ($pos !== false) {
				$rest = substr_replace($match[0], '', $pos, strlen($function.$expr));
			}
			$rest = preg_replace_callback($pattern, $callback, $rest);

			return $placeholder.$rest;
		};

		$this->registerPattern($pattern, $callback);
	}

	/**
	 * Replace custom properties, whose values may be used in scenarios where
	 * we wouldn't want them to be minified (e.g. inside calc)
	 */
	protected function extractCustomProperties()
	{
		// PHP only supports $this inside anonymous functions since 5.4
		$minifier = $this;
		$this->registerPattern(
			'/(?<=^|[;}{])\s*(--[^:;{}"\'\s]+)\s*:([^;{}]+)/m',
			function ($match) use ($minifier) {
				$placeholder = '--custom-'. count($minifier->extracted) . ':0';
				$minifier->extracted[$placeholder] = $match[1] .':'. trim($match[2]);
				return $placeholder;

			}
		);
	}

	/**
	 * Check if file is small enough to be imported.
	 *
	 * @param string $path The path to the file
	 *
	 * @return bool
	 */
	protected function canImportBySize($path)
	{
		return ($size = @filesize($path)) && $size <= $this->maxImportSize * 1024;
	}

	/**
	 * Check if file a file can be imported, going by the path.
	 *
	 * @param string $path
	 *
	 * @return bool
	 */
	protected function canImportByPath($path)
	{
		return preg_match('/^(data:|https?:|\\/)/', $path) === 0;
	}

	/**
	 * Return a converter to update relative paths to be relative to the new
	 * destination.
	 *
	 * @param string $source
	 * @param string $target
	 *
	 * @return ConverterInterface
	 */
	protected function getPathConverter($source, $target)
	{
		return new Converter($source, $target);
	}
}
