/lib/Function.php

<?php
/**
 *
 * Custom CSS functions
 *
 */

class CssCrush_Function {

	// Regex pattern for finding custom functions
	public static $functionPatt;

	// Cache for function names
	public static $functionList;

	public static function init () {
		// Set the custom function regex pattern
		self::$functionList = self::getFunctions();
		self::$functionPatt = '!(^|[^a-z0-9_-])(' . implode( '|', self::$functionList ) . ')?\(!i';
	}

	public static function getFunctions () {

		// Fetch custom function names
		// Include subtraction operator
		$fn_methods = array( '-' );
		$all_methods = get_class_methods( __CLASS__ );
		foreach ( $all_methods as &$_method ) {
			$prefix = 'css_fn__';
			if ( ( $pos = strpos( $_method, $prefix ) ) === 0 ) {
				$fn_methods[] = str_replace( '_', '-', substr( $_method, strlen( $prefix ) ) );
			}
		}
		return $fn_methods;
	}

	public static function parseAndExecuteValue ( $str ) {

		$patt = self::$functionPatt;

		// No bracketed expressions, early return
		if ( false === strpos( $str, '(' ) ) {
			return $str;
		}

		// No custom functions, early return
		if ( !preg_match( $patt, $str ) ) {
			return $str;
		}

		// Need a space inside the front function paren for the following match_all to be reliable
		$str = preg_replace( '!\(([^\s])!', '( $1', $str, -1, $spacing_count );

		// Find custom function matches
		$match_count = preg_match_all( $patt, $str, $m, PREG_OFFSET_CAPTURE | PREG_SET_ORDER  );

		// Step through the matches from last to first
		while ( $match = array_pop( $m ) ) {

			$offset = $match[0][1];
			$before_char = $match[1][0];
			$before_char_len = strlen( $before_char );

			// No function name default to math expression
			// Store the raw function name match
			$raw_fn_name = isset( $match[2] ) ? $match[2][0] : '';
			$fn_name = $raw_fn_name ? $raw_fn_name : 'math';
			if ( '-' === $fn_name ) {
				$fn_name = 'math';
			}

			// Loop throught the string
			$first_paren_offset = strpos( $str, '(', $offset );
			$paren_score = 0;

			for ( $index = $first_paren_offset; $index < strlen( $str ); $index++ ) {
				$char = $str[ $index ];
				if ( '(' === $char ) {
					$paren_score++;
				}
				elseif ( ')' === $char ) {
					$paren_score--;
				}

				if ( 0 === $paren_score ) {
					// Get the function inards
					$content_start = $offset + strlen( $before_char ) + strlen( $raw_fn_name ) + 1;
					$content_finish = $index;
					$content = substr( $str, $content_start, $content_finish - $content_start );
					$content = trim( $content );

					// Calculate offsets
					$func_start = $offset + strlen( $before_char );
					$func_end = $index + 1;

					// Workaround the minus
					$minus_before = '-' === $raw_fn_name ? '-' : '';

					$result = '';
					if ( in_array( $fn_name, self::$functionList ) ) {
						$fn_name_clean = str_replace( '-', '_', $fn_name );
						$result = call_user_func( array( 'self', "css_fn__$fn_name_clean" ), $content );
					}

					// Join together the result
					$str = substr( $str, 0, $func_start ) . $minus_before . $result . substr( $str, $func_end );
					break;
				}
			}
		} // while

		// Restore the whitespace
		if ( $spacing_count ) {
			$str = str_replace( '( ', '(', $str );
		}

		return $str;
	}


	############
	#  Helpers

	protected static function parseMathArgs ( $input ) {
		// Split on comma, trim, and remove empties
		$args = array_filter( array_map( 'trim', explode( ',', $input ) ) );

		// Pass anything non-numeric through math
		foreach ( $args as &$arg ) {
			if ( !preg_match( '!^-?[\.0-9]+$!', $arg ) ) {
				$arg = self::css_fn__math( $arg );
			}
		}
		return $args;
	}

	protected static function parseArgs ( $input, $allowSpaceDelim = false ) {
		$args = CssCrush::splitDelimList( $input, 
				( $allowSpaceDelim ? '\s*[,\s]\s*' : ',' ), 
				true, true );
		return array_map( 'trim', $args->list );
	}

	protected static function colorAdjust ( $color, array $adjustments ) {

		$fn_matched = preg_match( '!^(#|rgba?|hsla?)!', $color, $m );
		$keywords = CssCrush_Color::getKeywords();

		// Support for Hex, RGB, RGBa and keywords
		// HSL and HSLa are passed over
		if ( $fn_matched or array_key_exists( $color, $keywords ) ) {

			$alpha = 1;
			$rgb = null;

			// Get an RGB array from the color argument
			if ( $fn_matched ) {
				switch ( $m[1] ) {
					case '#':
						$rgb = CssCrush_Color::hexToRgb( $color );
						break;

					case 'rgb':
					case 'rgba':
					case 'hsl':
					case 'hsla':
						$function = $m[1];
						$alpha_channel = 4 === strlen( $function ) ? true : false;
						$vals = substr( $color, strlen( $function ) + 1 );  // Trim function name and start paren
						$vals = substr( $vals, 0, strlen( $vals ) - 1 );    // Trim end paren
						$vals = array_map( 'trim', explode( ',', $vals ) ); // Explode to array of arguments
						if ( $alpha_channel ) {
							$alpha = array_pop( $vals );
						}
						if ( 0 === strpos( $function, 'rgb' ) ) {
							$rgb = CssCrush_Color::normalizeCssRgb( $vals );
						}
						else {
							$rgb = CssCrush_Color::cssHslToRgb( $vals );
						}
						break;
				}
			}
			else {
				$rgb = $keywords[ $color ];
			}

			$hsl = CssCrush_Color::rgbToHsl( $rgb );

			// Normalize adjustment parameters to floating point numbers
			// then calculate the new HSL value
			$index = 0;
			foreach ( $adjustments as $val ) {
				// Normalize argument
				$_val = $val ? trim( str_replace( '%', '', $val ) ) : 0;
				
				// Reduce value to float
				$_val /= 100;
				
				// Adjust alpha component if necessary
				if ( 3 === $index ) {
					if ( 0 != $val ) {
						$alpha = max( 0, min( 1, $alpha + $_val ) );
					}
				}
				// Adjust HSL component value if necessary
				else {
					if ( 0 != $val ) {
						$hsl[ $index ] = max( 0, min( 1, $hsl[ $index ] + $_val ) );
					}
				}
				$index++;
			}
			
			// Finally convert new HSL value to RGB
			$rgb = CssCrush_Color::hslToRgb( $hsl );

			// Return as hex if there is no modified alpha channel
			// Otherwise return RGBA string
			if ( 1 === $alpha ) {
				return CssCrush_Color::rgbToHex( $rgb );
			}
			$rgb[] = $alpha;
			return 'rgba(' . implode( ',', $rgb ) . ')';
		}
		else {
			return $color;
		}
	}


	############

	public static function css_fn__math ( $input ) {
		// Whitelist allowed characters
		$input = preg_replace( '![^\.0-9\*\/\+\-\(\)]!', '', $input );
		$result = 0;
		try {
			$result = eval( "return $input;" );
		}
		catch ( Exception $e ) {};
		return round( $result, 10 );
	}

	public static function css_fn__percent ( $input ) {

		$args = self::parseMathArgs( $input );

		// Use precision argument if it exists, default to 7
		$precision = isset( $args[2] ) ? $args[2] : 7;

		$result = 0;
		if ( count( $args ) > 1 ) {
			// Arbitary high precision division
			$div = (string) bcdiv( $args[0], $args[1], 25 );
			// Set precision percentage value
			$result = (string) bcmul( $div, '100', $precision );
			// Trim unnecessary zeros and decimals
			$result = trim( $result, '0' );
			$result = rtrim( $result, '.' );
		}
		return $result . '%';
	}

	// Percent function alias
	public static function css_fn__pc ( $input ) {
		return self::css_fn_percent( $input );
	}

	public static function css_fn__data_uri ( $input ) {

		// Normalize, since argument might be a string token
		if ( strpos( $input, '___s' ) === 0 ) {
			$string_labels = array_keys( CssCrush::$storage->tokens->strings );
			$string_values = array_values( CssCrush::$storage->tokens->strings );
			$input = trim( str_replace( $string_labels, $string_values, $input ), '\'"`' );
		}

		// Default return value
		$result = "url($input)";

		// No attempt to process absolute urls
		if (
			strpos( $input, 'http://' ) === 0 or
			strpos( $input, 'https://' ) === 0
		) {
			return $result;
		}

		// Get system file path
		if ( strpos( $input, '/' ) === 0 ) {
			$file = CssCrush::$config->docRoot . $input;
		}
		else {
			$baseDir = CssCrush::$config->baseDir;
			$file = "$baseDir/$input";
		}

		// File not found
		if ( !file_exists( $file ) ) {
			return $result;
		}

		$file_ext = pathinfo( $file, PATHINFO_EXTENSION );

		// Only allow certain extensions
		$allowed_file_extensions = array(
			'woff' => 'font/woff;charset=utf-8',
			'ttf'  => 'font/truetype;charset=utf-8',
			'svg'  => 'image/svg+xml',
			'svgz' => 'image/svg+xml',
			'gif'  => 'image/gif',
			'jpeg' => 'image/jpg',
			'jpg'  => 'image/jpg',
			'png'  => 'image/png',
		);
		if ( !array_key_exists( $file_ext, $allowed_file_extensions ) ) {
			return $result;
		}

		$mime_type = $allowed_file_extensions[ $file_ext ];
		$base64 = base64_encode( file_get_contents( $file ) );
		$data_uri = "data:{$mime_type};base64,$base64";
		if ( strlen( $data_uri ) > 32000 ) {
			// Too big for IE
		}
		return "url($data_uri)";
	}

	public static function css_fn__h_adjust ( $input ) {
		@list( $color, $h ) = self::parseArgs( $input, true );
		return self::colorAdjust( $color, array( $h, 0, 0, 0 ) );
	}

	public static function css_fn__s_adjust ( $input ) {
		@list( $color, $s ) = self::parseArgs( $input, true );
		return self::colorAdjust( $color, array( 0, $s, 0, 0 ) );
	}

	public static function css_fn__l_adjust ( $input ) {
		@list( $color, $l ) = self::parseArgs( $input, true );
		return self::colorAdjust( $color, array( 0, 0, $l, 0 ) );
	}
	
	public static function css_fn__a_adjust ( $input ) {
		@list( $color, $a ) = self::parseArgs( $input, true );
		return self::colorAdjust( $color, array( 0, 0, 0, $a ) );
	}

}