<?php

/**
 * Builtin functions
 * @see https://lesscss.org/functions/
 */
class Less_Functions {

	public $env;
	public $currentFileInfo;

	function __construct( $env, array $currentFileInfo = null ) {
		$this->env = $env;
		$this->currentFileInfo = $currentFileInfo;
	}

	/**
	 * @param string $op
	 * @param float $a
	 * @param float $b
	 */
	public static function operate( $op, $a, $b ) {
		switch ( $op ) {
			case '+':
				return $a + $b;
			case '-':
				return $a - $b;
			case '*':
				return $a * $b;
			case '/':
				return $a / $b;
		}
	}

	public static function clamp( $val, $max = 1 ) {
		return min( max( $val, 0 ), $max );
	}

	public static function fround( $value ) {
		if ( $value === 0 ) {
			return $value;
		}

		if ( Less_Parser::$options['numPrecision'] ) {
			$p = pow( 10, Less_Parser::$options['numPrecision'] );
			return round( $value * $p ) / $p;
		}
		return $value;
	}

	public static function number( $n ) {
		if ( $n instanceof Less_Tree_Dimension ) {
			return floatval( $n->unit->is( '%' ) ? $n->value / 100 : $n->value );
		} elseif ( is_numeric( $n ) ) {
			return $n;
		} else {
			throw new Less_Exception_Compiler( "color functions take numbers as parameters" );
		}
	}

	public static function scaled( $n, $size = 255 ) {
		if ( $n instanceof Less_Tree_Dimension && $n->unit->is( '%' ) ) {
			return (float)$n->value * $size / 100;
		} else {
			return self::number( $n );
		}
	}

	public function rgb( $r = null, $g = null, $b = null ) {
		if ( $r === null || $g === null || $b === null ) {
			throw new Less_Exception_Compiler( "rgb expects three parameters" );
		}
		return $this->rgba( $r, $g, $b, 1.0 );
	}

	public function rgba( $r = null, $g = null, $b = null, $a = null ) {
		$rgb = [ $r, $g, $b ];
		$rgb = array_map( [ 'Less_Functions','scaled' ], $rgb );

		$a = self::number( $a );
		return new Less_Tree_Color( $rgb, $a );
	}

	public function hsl( $h, $s, $l ) {
		return $this->hsla( $h, $s, $l, 1.0 );
	}

	public function hsla( $h, $s, $l, $a ) {
		$h = fmod( self::number( $h ), 360 ) / 360; // Classic % operator will change float to int
		$s = self::clamp( self::number( $s ) );
		$l = self::clamp( self::number( $l ) );
		$a = self::clamp( self::number( $a ) );

		$m2 = $l <= 0.5 ? $l * ( $s + 1 ) : $l + $s - $l * $s;

		$m1 = $l * 2 - $m2;

		return $this->rgba(
			self::hsla_hue( $h + 1 / 3, $m1, $m2 ) * 255,
			self::hsla_hue( $h, $m1, $m2 ) * 255,
			self::hsla_hue( $h - 1 / 3, $m1, $m2 ) * 255,
			$a
		);
	}

	/**
	 * @param float $h
	 * @param float $m1
	 * @param float $m2
	 */
	public function hsla_hue( $h, $m1, $m2 ) {
		$h = $h < 0 ? $h + 1 : ( $h > 1 ? $h - 1 : $h );
		if ( $h * 6 < 1 ) {
			return $m1 + ( $m2 - $m1 ) * $h * 6;
		} elseif ( $h * 2 < 1 ) {
			return $m2;
		} elseif ( $h * 3 < 2 ) {
			return $m1 + ( $m2 - $m1 ) * ( 2 / 3 - $h ) * 6;
		} else {
			return $m1;
		}
	}

	public function hsv( $h, $s, $v ) {
		return $this->hsva( $h, $s, $v, 1.0 );
	}

	/**
	 * @param Less_Tree|float $h
	 * @param Less_Tree|float $s
	 * @param Less_Tree|float $v
	 * @param float $a
	 */
	public function hsva( $h, $s, $v, $a ) {
		$h = ( ( self::number( $h ) % 360 ) / 360 ) * 360;
		$s = self::number( $s );
		$v = self::number( $v );
		$a = self::number( $a );

		$i = floor( (int)( $h / 60 ) % 6 );
		$f = ( $h / 60 ) - $i;

		$vs = [
			$v,
			$v * ( 1 - $s ),
			$v * ( 1 - $f * $s ),
			$v * ( 1 - ( 1 - $f ) * $s )
		];

		$perm = [
			[ 0, 3, 1 ],
			[ 2, 0, 1 ],
			[ 1, 0, 3 ],
			[ 1, 2, 0 ],
			[ 3, 1, 0 ],
			[ 0, 1, 2 ]
		];

		return $this->rgba(
			$vs[$perm[$i][0]] * 255,
			$vs[$perm[$i][1]] * 255,
			$vs[$perm[$i][2]] * 255,
			$a
		);
	}

	public function hue( $color = null ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to hue must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		$c = $color->toHSL();
		return new Less_Tree_Dimension( Less_Parser::round( $c['h'] ) );
	}

	public function saturation( $color = null ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to saturation must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		$c = $color->toHSL();
		return new Less_Tree_Dimension( Less_Parser::round( $c['s'] * 100 ), '%' );
	}

	public function lightness( $color = null ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to lightness must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		$c = $color->toHSL();
		return new Less_Tree_Dimension( Less_Parser::round( $c['l'] * 100 ), '%' );
	}

	public function hsvhue( $color = null ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to hsvhue must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		$hsv = $color->toHSV();
		return new Less_Tree_Dimension( Less_Parser::round( $hsv['h'] ) );
	}

	public function hsvsaturation( $color = null ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to hsvsaturation must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		$hsv = $color->toHSV();
		return new Less_Tree_Dimension( Less_Parser::round( $hsv['s'] * 100 ), '%' );
	}

	public function hsvvalue( $color = null ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to hsvvalue must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		$hsv = $color->toHSV();
		return new Less_Tree_Dimension( Less_Parser::round( $hsv['v'] * 100 ), '%' );
	}

	public function red( $color = null ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to red must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		return new Less_Tree_Dimension( $color->rgb[0] );
	}

	public function green( $color = null ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to green must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		return new Less_Tree_Dimension( $color->rgb[1] );
	}

	public function blue( $color = null ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to blue must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		return new Less_Tree_Dimension( $color->rgb[2] );
	}

	public function alpha( $color = null ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to alpha must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		$c = $color->toHSL();
		return new Less_Tree_Dimension( $c['a'] );
	}

	public function luma( $color = null ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to luma must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		return new Less_Tree_Dimension( Less_Parser::round( $color->luma() * $color->alpha * 100 ), '%' );
	}

	public function luminance( $color = null ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to luminance must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		$luminance =
			( 0.2126 * $color->rgb[0] / 255 )
		  + ( 0.7152 * $color->rgb[1] / 255 )
		  + ( 0.0722 * $color->rgb[2] / 255 );

		return new Less_Tree_Dimension( Less_Parser::round( $luminance * $color->alpha * 100 ), '%' );
	}

	public function saturate( $color = null, $amount = null ) {
		// filter: saturate(3.2);
		// should be kept as is, so check for color
		if ( $color instanceof Less_Tree_Dimension ) {
			return null;
		}

		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to saturate must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$amount instanceof Less_Tree_Dimension ) {
			throw new Less_Exception_Compiler( 'The second argument to saturate must be a percentage' . ( $amount instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		$hsl = $color->toHSL();

		$hsl['s'] += $amount->value / 100;
		$hsl['s'] = self::clamp( $hsl['s'] );

		return $this->hsla( $hsl['h'], $hsl['s'], $hsl['l'], $hsl['a'] );
	}

	/**
	 * @param Less_Tree_Color|null $color
	 * @param Less_Tree_Dimension|null $amount
	 */
	public function desaturate( $color = null, $amount = null ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to desaturate must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$amount instanceof Less_Tree_Dimension ) {
			throw new Less_Exception_Compiler( 'The second argument to desaturate must be a percentage' . ( $amount instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		$hsl = $color->toHSL();
		$hsl['s'] -= $amount->value / 100;
		$hsl['s'] = self::clamp( $hsl['s'] );

		return $this->hsla( $hsl['h'], $hsl['s'], $hsl['l'], $hsl['a'] );
	}

	public function lighten( $color = null, $amount = null ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to lighten must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$amount instanceof Less_Tree_Dimension ) {
			throw new Less_Exception_Compiler( 'The second argument to lighten must be a percentage' . ( $amount instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		$hsl = $color->toHSL();

		$hsl['l'] += $amount->value / 100;
		$hsl['l'] = self::clamp( $hsl['l'] );

		return $this->hsla( $hsl['h'], $hsl['s'], $hsl['l'], $hsl['a'] );
	}

	public function darken( $color = null, $amount = null ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to darken must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$amount instanceof Less_Tree_Dimension ) {
			throw new Less_Exception_Compiler( 'The second argument to darken must be a percentage' . ( $amount instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		$hsl = $color->toHSL();
		$hsl['l'] -= $amount->value / 100;
		$hsl['l'] = self::clamp( $hsl['l'] );

		return $this->hsla( $hsl['h'], $hsl['s'], $hsl['l'], $hsl['a'] );
	}

	public function fadein( $color = null, $amount = null ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to fadein must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$amount instanceof Less_Tree_Dimension ) {
			throw new Less_Exception_Compiler( 'The second argument to fadein must be a percentage' . ( $amount instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		$hsl = $color->toHSL();
		$hsl['a'] += $amount->value / 100;
		$hsl['a'] = self::clamp( $hsl['a'] );
		return $this->hsla( $hsl['h'], $hsl['s'], $hsl['l'], $hsl['a'] );
	}

	public function fadeout( $color = null, $amount = null ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to fadeout must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$amount instanceof Less_Tree_Dimension ) {
			throw new Less_Exception_Compiler( 'The second argument to fadeout must be a percentage' . ( $amount instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		$hsl = $color->toHSL();
		$hsl['a'] -= $amount->value / 100;
		$hsl['a'] = self::clamp( $hsl['a'] );
		return $this->hsla( $hsl['h'], $hsl['s'], $hsl['l'], $hsl['a'] );
	}

	public function fade( $color = null, $amount = null ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to fade must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$amount instanceof Less_Tree_Dimension ) {
			throw new Less_Exception_Compiler( 'The second argument to fade must be a percentage' . ( $amount instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		$hsl = $color->toHSL();

		$hsl['a'] = $amount->value / 100;
		$hsl['a'] = self::clamp( $hsl['a'] );
		return $this->hsla( $hsl['h'], $hsl['s'], $hsl['l'], $hsl['a'] );
	}

	public function spin( $color = null, $amount = null ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to spin must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$amount instanceof Less_Tree_Dimension ) {
			throw new Less_Exception_Compiler( 'The second argument to spin must be a number' . ( $amount instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		$hsl = $color->toHSL();
		$hue = fmod( $hsl['h'] + $amount->value, 360 );

		$hsl['h'] = $hue < 0 ? 360 + $hue : $hue;

		return $this->hsla( $hsl['h'], $hsl['s'], $hsl['l'], $hsl['a'] );
	}

	//
	// Copyright (c) 2006-2009 Hampton Catlin, Nathan Weizenbaum, and Chris Eppstein
	// https://sass-lang.com/
	//

	/**
	 * @param Less_Tree|null $color1
	 * @param Less_Tree|null $color2
	 * @param Less_Tree|null $weight
	 */
	public function mix( $color1 = null, $color2 = null, $weight = null ) {
		if ( !$color1 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to mix must be a color' . ( $color1 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$color2 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The second argument to mix must be a color' . ( $color2 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$weight ) {
			$weight = new Less_Tree_Dimension( '50', '%' );
		}
		if ( !$weight instanceof Less_Tree_Dimension ) {
			throw new Less_Exception_Compiler( 'The third argument to contrast must be a percentage' . ( $weight instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		$p = $weight->value / 100.0;
		$w = $p * 2 - 1;
		$hsl1 = $color1->toHSL();
		$hsl2 = $color2->toHSL();
		$a = $hsl1['a'] - $hsl2['a'];

		$w1 = ( ( ( ( $w * $a ) == -1 ) ? $w : ( $w + $a ) / ( 1 + $w * $a ) ) + 1 ) / 2;
		$w2 = 1 - $w1;

		$rgb = [
			$color1->rgb[0] * $w1 + $color2->rgb[0] * $w2,
			$color1->rgb[1] * $w1 + $color2->rgb[1] * $w2,
			$color1->rgb[2] * $w1 + $color2->rgb[2] * $w2
		];

		$alpha = $color1->alpha * $p + $color2->alpha * ( 1 - $p );

		return new Less_Tree_Color( $rgb, $alpha );
	}

	public function greyscale( $color ) {
		return $this->desaturate( $color, new Less_Tree_Dimension( 100, '%' ) );
	}

	public function contrast( $color, $dark = null, $light = null, $threshold = null ) {
		// filter: contrast(3.2);
		// should be kept as is, so check for color
		if ( !$color instanceof Less_Tree_Color ) {
			return null;
		}
		if ( !$light ) {
			$light = $this->rgba( 255, 255, 255, 1.0 );
		}
		if ( !$dark ) {
			$dark = $this->rgba( 0, 0, 0, 1.0 );
		}

		if ( !$dark instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The second argument to contrast must be a color' . ( $dark instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$light instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The third argument to contrast must be a color' . ( $light instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		// Figure out which is actually light and dark!
		if ( $dark->luma() > $light->luma() ) {
			$t = $light;
			$light = $dark;
			$dark = $t;
		}
		if ( !$threshold ) {
			$threshold = 0.43;
		} else {
			$threshold = self::number( $threshold );
		}

		if ( $color->luma() < $threshold ) {
			return $light;
		} else {
			return $dark;
		}
	}

	public function e( $str ) {
		if ( is_string( $str ) ) {
			return new Less_Tree_Anonymous( $str );
		}
		return new Less_Tree_Anonymous( $str instanceof Less_Tree_JavaScript ? $str->expression : $str->value );
	}

	public function escape( $str ) {
		$revert = [ '%21' => '!', '%2A' => '*', '%27' => "'",'%3F' => '?','%26' => '&','%2C' => ',','%2F' => '/','%40' => '@','%2B' => '+','%24' => '$' ];

		return new Less_Tree_Anonymous( strtr( rawurlencode( $str->value ), $revert ) );
	}

	/**
	 * todo: This function will need some additional work to make it work the same as less.js
	 *
	 */
	public function replace( $string, $pattern, $replacement, $flags = null ) {
		$result = $string->value;

		$expr = '/' . str_replace( '/', '\\/', $pattern->value ) . '/';
		if ( $flags && $flags->value ) {
			$expr .= self::replace_flags( $flags->value );
		}

		$result = preg_replace( $expr, $replacement->value, $result );

		if ( property_exists( $string, 'quote' ) ) {
			return new Less_Tree_Quoted( $string->quote, $result, $string->escaped );
		}
		return new Less_Tree_Quoted( '', $result );
	}

	public static function replace_flags( $flags ) {
		$flags = str_split( $flags, 1 );
		$new_flags = '';

		foreach ( $flags as $flag ) {
			switch ( $flag ) {
				case 'e':
				case 'g':
					break;

				default:
				$new_flags .= $flag;
					break;
			}
		}

		return $new_flags;
	}

	public function _percent() {
		$string = func_get_arg( 0 );

		$args = func_get_args();
		array_shift( $args );
		$result = $string->value;

		foreach ( $args as $arg ) {
			if ( preg_match( '/%[sda]/i', $result, $token ) ) {
				$token = $token[0];
				$value = stristr( $token, 's' ) ? $arg->value : $arg->toCSS();
				$value = preg_match( '/[A-Z]$/', $token ) ? urlencode( $value ) : $value;
				$result = preg_replace( '/%[sda]/i', $value, $result, 1 );
			}
		}
		$result = str_replace( '%%', '%', $result );

		return new Less_Tree_Quoted( $string->quote, $result, $string->escaped );
	}

	public function unit( $val, $unit = null ) {
		if ( !( $val instanceof Less_Tree_Dimension ) ) {
			throw new Less_Exception_Compiler( 'The first argument to unit must be a number' . ( $val instanceof Less_Tree_Operation ? '. Have you forgotten parenthesis?' : '.' ) );
		}

		if ( $unit ) {
			if ( $unit instanceof Less_Tree_Keyword ) {
				$unit = $unit->value;
			} else {
				$unit = $unit->toCSS();
			}
		} else {
			$unit = "";
		}
		return new Less_Tree_Dimension( $val->value, $unit );
	}

	public function convert( $val, $unit ) {
		return $val->convertTo( $unit->value );
	}

	public function round( $n, $f = false ) {
		$fraction = 0;
		if ( $f !== false ) {
			$fraction = $f->value;
		}

		return $this->_math( 'Less_Parser::round', null, $n, $fraction );
	}

	public function pi() {
		return new Less_Tree_Dimension( M_PI );
	}

	public function mod( $a, $b ) {
		return new Less_Tree_Dimension( $a->value % $b->value, $a->unit );
	}

	public function pow( $x, $y ) {
		if ( is_numeric( $x ) && is_numeric( $y ) ) {
			$x = new Less_Tree_Dimension( $x );
			$y = new Less_Tree_Dimension( $y );
		} elseif ( !( $x instanceof Less_Tree_Dimension ) || !( $y instanceof Less_Tree_Dimension ) ) {
			throw new Less_Exception_Compiler( 'Arguments must be numbers' );
		}

		return new Less_Tree_Dimension( pow( $x->value, $y->value ), $x->unit );
	}

	// var mathFunctions = [{name:"ce ...
	public function ceil( $n ) {
		return $this->_math( 'ceil', null, $n );
	}

	public function floor( $n ) {
	return $this->_math( 'floor', null, $n );
	}

	public function sqrt( $n ) {
		return $this->_math( 'sqrt', null, $n );
	}

	public function abs( $n ) {
		return $this->_math( 'abs', null, $n );
	}

	public function tan( $n ) {
		return $this->_math( 'tan', '', $n );
	}

	public function sin( $n ) {
		return $this->_math( 'sin', '', $n );
	}

	public function cos( $n ) {
		return $this->_math( 'cos', '', $n );
	}

	public function atan( $n ) {
		return $this->_math( 'atan', 'rad', $n );
	}

	public function asin( $n ) {
		return $this->_math( 'asin', 'rad', $n );
	}

	public function acos( $n ) {
		return $this->_math( 'acos', 'rad', $n );
	}

	private function _math() {
		$args = func_get_args();
		$fn = array_shift( $args );
		$unit = array_shift( $args );

		if ( $args[0] instanceof Less_Tree_Dimension ) {

			if ( $unit === null ) {
				$unit = $args[0]->unit;
			} else {
				$args[0] = $args[0]->unify();
			}
			$args[0] = (float)$args[0]->value;
			return new Less_Tree_Dimension( call_user_func_array( $fn, $args ), $unit );
		} elseif ( is_numeric( $args[0] ) ) {
			return call_user_func_array( $fn, $args );
		} else {
			throw new Less_Exception_Compiler( "math functions take numbers as parameters" );
		}
	}

	/**
	 * @param bool $isMin
	 * @param array<Less_Tree> $args
	 */
	private function _minmax( $isMin, $args ) {
		$arg_count = count( $args );

		if ( $arg_count < 1 ) {
			throw new Less_Exception_Compiler( 'one or more arguments required' );
		}

		$j = null;
		$unitClone = null;
		$unitStatic = null;

		// elems only contains original argument values.
		$order = [];
		// key is the unit.toString() for unified tree.Dimension values,
		// value is the index into the order array.
		$values = [];

		for ( $i = 0; $i < $arg_count; $i++ ) {
			$current = $args[$i];
			if ( !( $current instanceof Less_Tree_Dimension ) ) {
				// @phan-suppress-next-line PhanUndeclaredProperty Checked Less_Tree->value
				if ( property_exists( $args[$i], 'value' ) && is_array( $args[$i]->value ) ) {
					// @phan-suppress-next-line PhanUndeclaredProperty Checked Less_Tree->value
					$args[] = $args[$i]->value;
				}
				continue;
			}
			// PhanTypeInvalidDimOffset -- False positive, safe after continue or non-first iterations
			'@phan-var non-empty-list<Less_Tree_Dimension> $order';

			if ( $current->unit->toString() === '' && !$unitClone ) {
				$temp = new Less_Tree_Dimension( $current->value, $unitClone );
				$currentUnified = $temp->unify();
			} else {
				$currentUnified = $current->unify();
			}

			if ( $currentUnified->unit->toString() === "" && !$unitStatic ) {
				$unit = $unitStatic;
			} else {
				$unit = $currentUnified->unit->toString();
			}

			if ( $unit !== '' && !$unitStatic || $unit !== '' && $order[0]->unify()->unit->toString() === "" ) {
				$unitStatic = $unit;
			}

			if ( $unit != '' && !$unitClone ) {
				$unitClone = $current->unit->toString();
			}

			if ( isset( $values[''] ) && $unit !== '' && $unit === $unitStatic ) {
				$j = $values[''];
			} elseif ( isset( $values[$unit] ) ) {
				$j = $values[$unit];
			} else {

				if ( $unitStatic && $unit !== $unitStatic ) {
					throw new Less_Exception_Compiler( 'incompatible types' );
				}
				$values[$unit] = count( $order );
				$order[] = $current;
				continue;
			}

			if ( $order[$j]->unit->toString() === "" && $unitClone ) {
				$temp = new Less_Tree_Dimension( $order[$j]->value, $unitClone );
				$referenceUnified = $temp->unify();
			} else {
				$referenceUnified = $order[$j]->unify();
			}
			if ( ( $isMin && $currentUnified->value < $referenceUnified->value ) || ( !$isMin && $currentUnified->value > $referenceUnified->value ) ) {
				$order[$j] = $current;
			}
		}

		if ( count( $order ) == 1 ) {
			return $order[0];
		}
		$args = [];
		foreach ( $order as $a ) {
			$args[] = $a->toCSS();
		}
		return new Less_Tree_Anonymous( ( $isMin ? 'min(' : 'max(' ) . implode( Less_Environment::$_outputMap[','], $args ) . ')' );
	}

	public function min() {
		$args = func_get_args();
		return $this->_minmax( true, $args );
	}

	public function max() {
		$args = func_get_args();
		return $this->_minmax( false, $args );
	}

	public function getunit( $n ) {
		return new Less_Tree_Anonymous( $n->unit );
	}

	public function argb( $color ) {
		if ( !$color instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to argb must be a color' . ( $color instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		return new Less_Tree_Anonymous( $color->toARGB() );
	}

	public function percentage( $n ) {
		return new Less_Tree_Dimension( $n->value * 100, '%' );
	}

	public function color( $n ) {
		if ( $n instanceof Less_Tree_Quoted ) {
			$colorCandidate = $n->value;
			$returnColor = Less_Tree_Color::fromKeyword( $colorCandidate );
			if ( $returnColor ) {
				return $returnColor;
			}
			if ( preg_match( '/^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})/', $colorCandidate ) ) {
				return new Less_Tree_Color( substr( $colorCandidate, 1 ) );
			}
			throw new Less_Exception_Compiler( "argument must be a color keyword or 3/6 digit hex e.g. #FFF" );
		} else {
			throw new Less_Exception_Compiler( "argument must be a string" );
		}
	}

	public function iscolor( $n ) {
		return $this->_isa( $n, 'Less_Tree_Color' );
	}

	public function isnumber( $n ) {
		return $this->_isa( $n, 'Less_Tree_Dimension' );
	}

	public function isstring( $n ) {
		return $this->_isa( $n, 'Less_Tree_Quoted' );
	}

	public function iskeyword( $n ) {
		return $this->_isa( $n, 'Less_Tree_Keyword' );
	}

	public function isurl( $n ) {
		return $this->_isa( $n, 'Less_Tree_Url' );
	}

	public function ispixel( $n ) {
		return $this->isunit( $n, 'px' );
	}

	public function ispercentage( $n ) {
		return $this->isunit( $n, '%' );
	}

	public function isem( $n ) {
		return $this->isunit( $n, 'em' );
	}

	/**
	 * @param Less_Tree $n
	 * @param Less_Tree|string $unit
	 */
	public function isunit( $n, $unit ) {
		if ( is_object( $unit ) && property_exists( $unit, 'value' ) ) {
			// @phan-suppress-next-line PhanUndeclaredProperty Checked Less_Tree->value
			$unit = $unit->value;
		}

		return ( $n instanceof Less_Tree_Dimension ) && $n->unit->is( $unit ) ? new Less_Tree_Keyword( 'true' ) : new Less_Tree_Keyword( 'false' );
	}

	/**
	 * @param Less_Tree $n
	 * @param string $type
	 */
	private function _isa( $n, $type ) {
		return is_a( $n, $type ) ? new Less_Tree_Keyword( 'true' ) : new Less_Tree_Keyword( 'false' );
	}

	public function tint( $color, $amount = null ) {
		return $this->mix( $this->rgb( 255, 255, 255 ), $color, $amount );
	}

	public function shade( $color, $amount = null ) {
		return $this->mix( $this->rgb( 0, 0, 0 ), $color, $amount );
	}

	public function extract( $values, $index ) {
		$index = (int)$index->value - 1; // (1-based index)
		// handle non-array values as an array of length 1
		// return 'undefined' if index is invalid
		if ( property_exists( $values, 'value' ) && is_array( $values->value ) ) {
			if ( isset( $values->value[$index] ) ) {
				return $values->value[$index];
			}
			return null;

		} elseif ( (int)$index === 0 ) {
			return $values;
		}

		return null;
	}

	public function length( $values ) {
		$n = ( property_exists( $values, 'value' ) && is_array( $values->value ) ) ? count( $values->value ) : 1;
		return new Less_Tree_Dimension( $n );
	}

	public function datauri( $mimetypeNode, $filePathNode = null ) {
		$filePath = ( $filePathNode ? $filePathNode->value : null );
		$mimetype = $mimetypeNode->value;

		$args = 2;
		if ( !$filePath ) {
			$filePath = $mimetype;
			$args = 1;
		}

		$filePath = str_replace( '\\', '/', $filePath );
		if ( Less_Environment::isPathRelative( $filePath ) ) {
			$currentFileInfo = $this->currentFileInfo;
			'@phan-var array $currentFileInfo';
			if ( Less_Parser::$options['relativeUrls'] ) {
				$temp = $currentFileInfo['currentDirectory'];
			} else {
				$temp = $currentFileInfo['entryPath'];
			}

			if ( !empty( $temp ) ) {
				$filePath = Less_Environment::normalizePath( rtrim( $temp, '/' ) . '/' . $filePath );
			}

		}

		// detect the mimetype if not given
		if ( $args < 2 ) {

			/* incomplete
			$mime = require('mime');
			mimetype = mime.lookup(path);

			// use base 64 unless it's an ASCII or UTF-8 format
			var charset = mime.charsets.lookup(mimetype);
			useBase64 = ['US-ASCII', 'UTF-8'].indexOf(charset) < 0;
			if (useBase64) mimetype += ';base64';
			*/

			$mimetype = Less_Mime::lookup( $filePath );

			$charset = Less_Mime::charsets_lookup( $mimetype );
			$useBase64 = !in_array( $charset, [ 'US-ASCII', 'UTF-8' ] );
			if ( $useBase64 ) { $mimetype .= ';base64';
			}

		} else {
			$useBase64 = preg_match( '/;base64$/', $mimetype );
		}

		if ( file_exists( $filePath ) ) {
			$buf = @file_get_contents( $filePath );
		} else {
			$buf = false;
		}

		// IE8 cannot handle a data-uri larger than 32KB. If this is exceeded
		// and the --ieCompat flag is enabled, return a normal url() instead.
		$DATA_URI_MAX_KB = 32;
		$fileSizeInKB = round( strlen( $buf ) / 1024 );
		if ( $fileSizeInKB >= $DATA_URI_MAX_KB ) {
			$url = new Less_Tree_Url( ( $filePathNode ?: $mimetypeNode ), $this->currentFileInfo );
			return $url->compile( $this->env );
		}

		if ( $buf ) {
			$buf = $useBase64 ? base64_encode( $buf ) : rawurlencode( $buf );
			$filePath = '"data:' . $mimetype . ',' . $buf . '"';
		}

		return new Less_Tree_Url( new Less_Tree_Anonymous( $filePath ) );
	}

	// svg-gradient
	public function svggradient( $direction ) {
		$throw_message = 'svg-gradient expects direction, start_color [start_position], [color position,]..., end_color [end_position]';
		$arguments = func_get_args();

		if ( count( $arguments ) < 3 ) {
			throw new Less_Exception_Compiler( $throw_message );
		}

		$stops = array_slice( $arguments, 1 );
		$gradientType = 'linear';
		$rectangleDimension = 'x="0" y="0" width="1" height="1"';
		$useBase64 = true;
		$directionValue = $direction->toCSS();

		switch ( $directionValue ) {
			case "to bottom":
				$gradientDirectionSvg = 'x1="0%" y1="0%" x2="0%" y2="100%"';
				break;
			case "to right":
				$gradientDirectionSvg = 'x1="0%" y1="0%" x2="100%" y2="0%"';
				break;
			case "to bottom right":
				$gradientDirectionSvg = 'x1="0%" y1="0%" x2="100%" y2="100%"';
				break;
			case "to top right":
				$gradientDirectionSvg = 'x1="0%" y1="100%" x2="100%" y2="0%"';
				break;
			case "ellipse":
			case "ellipse at center":
				$gradientType = "radial";
				$gradientDirectionSvg = 'cx="50%" cy="50%" r="75%"';
				$rectangleDimension = 'x="-50" y="-50" width="101" height="101"';
				break;
			default:
				throw new Less_Exception_Compiler( "svg-gradient direction must be 'to bottom', 'to right', 'to bottom right', 'to top right' or 'ellipse at center'" );
		}

		$returner = '<?xml version="1.0" ?>' .
			'<svg xmlns="http://www.w3.org/2000/svg" version="1.1" width="100%" height="100%" viewBox="0 0 1 1" preserveAspectRatio="none">' .
			'<' . $gradientType . 'Gradient id="gradient" gradientUnits="userSpaceOnUse" ' . $gradientDirectionSvg . '>';

		for ( $i = 0; $i < count( $stops ); $i++ ) {
			if ( is_object( $stops[$i] ) && property_exists( $stops[$i], 'value' ) ) {
				$color = $stops[$i]->value[0];
				$position = $stops[$i]->value[1];
			} else {
				$color = $stops[$i];
				$position = null;
			}

			if ( !( $color instanceof Less_Tree_Color ) || ( !( ( $i === 0 || $i + 1 === count( $stops ) ) && $position === null ) && !( $position instanceof Less_Tree_Dimension ) ) ) {
				throw new Less_Exception_Compiler( $throw_message );
			}
			if ( $position ) {
				$positionValue = $position->toCSS();
			} elseif ( $i === 0 ) {
				$positionValue = '0%';
			} else {
				$positionValue = '100%';
			}
			$alpha = $color->alpha;
			$returner .= '<stop offset="' . $positionValue . '" stop-color="' . $color->toRGB() . '"' . ( $alpha < 1 ? ' stop-opacity="' . $alpha . '"' : '' ) . '/>';
		}

		$returner .= '</' . $gradientType . 'Gradient><rect ' . $rectangleDimension . ' fill="url(#gradient)" /></svg>';

		if ( $useBase64 ) {
			$returner = "'data:image/svg+xml;base64," . base64_encode( $returner ) . "'";
		} else {
			$returner = "'data:image/svg+xml," . $returner . "'";
		}

		return new Less_Tree_Url( new Less_Tree_Anonymous( $returner ) );
	}

	/**
	 * Php version of javascript's `encodeURIComponent` function
	 *
	 * @param string $string The string to encode
	 * @return string The encoded string
	 */
	public static function encodeURIComponent( $string ) {
		$revert = [ '%21' => '!', '%2A' => '*', '%27' => "'", '%28' => '(', '%29' => ')' ];
		return strtr( rawurlencode( $string ), $revert );
	}

	// Color Blending
	// ref: https://www.w3.org/TR/compositing-1/
	public function colorBlend( $mode, $color1, $color2 ) {
		// backdrop
		$ab = $color1->alpha;
		// source
		$as = $color2->alpha;
		$result = [];

		$ar = $as + $ab * ( 1 - $as );
		for ( $i = 0; $i < 3; $i++ ) {
			$cb = $color1->rgb[$i] / 255;
			$cs = $color2->rgb[$i] / 255;
			$cr = call_user_func( $mode, $cb, $cs );
			if ( $ar ) {
				$cr = ( $as * $cs + $ab * ( $cb - $as * ( $cb + $cs - $cr ) ) ) / $ar;
			}
			$result[$i] = $cr * 255;
		}

		return new Less_Tree_Color( $result, $ar );
	}

	public function multiply( $color1 = null, $color2 = null ) {
		if ( !$color1 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to multiply must be a color' . ( $color1 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$color2 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The second argument to multiply must be a color' . ( $color2 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		return $this->colorBlend( [ $this,'colorBlendMultiply' ],  $color1, $color2 );
	}

	private function colorBlendMultiply( $cb, $cs ) {
		return $cb * $cs;
	}

	public function screen( $color1 = null, $color2 = null ) {
		if ( !$color1 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to screen must be a color' . ( $color1 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$color2 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The second argument to screen must be a color' . ( $color2 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		return $this->colorBlend( [ $this,'colorBlendScreen' ],  $color1, $color2 );
	}

	private function colorBlendScreen( $cb, $cs ) {
		return $cb + $cs - $cb * $cs;
	}

	public function overlay( $color1 = null, $color2 = null ) {
		if ( !$color1 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to overlay must be a color' . ( $color1 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$color2 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The second argument to overlay must be a color' . ( $color2 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		return $this->colorBlend( [ $this,'colorBlendOverlay' ],  $color1, $color2 );
	}

	private function colorBlendOverlay( $cb, $cs ) {
		$cb *= 2;
		return ( $cb <= 1 )
			? $this->colorBlendMultiply( $cb, $cs )
			: $this->colorBlendScreen( $cb - 1, $cs );
	}

	public function softlight( $color1 = null, $color2 = null ) {
		if ( !$color1 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to softlight must be a color' . ( $color1 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$color2 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The second argument to softlight must be a color' . ( $color2 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		return $this->colorBlend( [ $this,'colorBlendSoftlight' ],  $color1, $color2 );
	}

	private function colorBlendSoftlight( $cb, $cs ) {
		$d = 1;
		$e = $cb;
		if ( $cs > 0.5 ) {
			$e = 1;
			$d = ( $cb > 0.25 ) ? sqrt( $cb )
				: ( ( 16 * $cb - 12 ) * $cb + 4 ) * $cb;
		}
		return $cb - ( 1 - 2 * $cs ) * $e * ( $d - $cb );
	}

	public function hardlight( $color1 = null, $color2 = null ) {
		if ( !$color1 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to hardlight must be a color' . ( $color1 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$color2 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The second argument to hardlight must be a color' . ( $color2 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		return $this->colorBlend( [ $this,'colorBlendHardlight' ],  $color1, $color2 );
	}

	private function colorBlendHardlight( $cb, $cs ) {
		return $this->colorBlendOverlay( $cs, $cb );
	}

	public function difference( $color1 = null, $color2 = null ) {
		if ( !$color1 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to difference must be a color' . ( $color1 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$color2 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The second argument to difference must be a color' . ( $color2 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		return $this->colorBlend( [ $this,'colorBlendDifference' ],  $color1, $color2 );
	}

	private function colorBlendDifference( $cb, $cs ) {
		return abs( $cb - $cs );
	}

	public function exclusion( $color1 = null, $color2 = null ) {
		if ( !$color1 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to exclusion must be a color' . ( $color1 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$color2 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The second argument to exclusion must be a color' . ( $color2 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		return $this->colorBlend( [ $this,'colorBlendExclusion' ],  $color1, $color2 );
	}

	private function colorBlendExclusion( $cb, $cs ) {
		return $cb + $cs - 2 * $cb * $cs;
	}

	public function average( $color1 = null, $color2 = null ) {
		if ( !$color1 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to average must be a color' . ( $color1 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$color2 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The second argument to average must be a color' . ( $color2 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		return $this->colorBlend( [ $this,'colorBlendAverage' ],  $color1, $color2 );
	}

	// non-w3c functions:
	public function colorBlendAverage( $cb, $cs ) {
		return ( $cb + $cs ) / 2;
	}

	public function negation( $color1 = null, $color2 = null ) {
		if ( !$color1 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The first argument to negation must be a color' . ( $color1 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}
		if ( !$color2 instanceof Less_Tree_Color ) {
			throw new Less_Exception_Compiler( 'The second argument to negation must be a color' . ( $color2 instanceof Less_Tree_Expression ? ' (did you forgot commas?)' : '' ) );
		}

		return $this->colorBlend( [ $this,'colorBlendNegation' ],  $color1, $color2 );
	}

	public function colorBlendNegation( $cb, $cs ) {
		return 1 - abs( $cb + $cs - 1 );
	}

	// ~ End of Color Blending

}
