<?php
class css_shadow {
	/** Create a point */
	public static function xy($x, $y) {
		return array('x'=>$x, 'y'=>$y);
	}
	
	/** Draw a "line" of shadows between two points */
	public static function draw_line($p1, $p2, $steps, $color) {
		$x1 = $p1['x'];
		$y1 = $p1['y'];
		$x2 = $p2['x'];
		$y2 = $p2['y'];
	
		$xstep = ($x2-$x1)/($steps-1);
		$ystep = ($y2-$y1)/($steps-1);
	
		$x = $x1;
		$y = $y1;
		$str = '';
		for ($i=0; $i<$steps; $i++) {
			$str.= sprintf ("\t%fem %fem %s,\n", $x, $y, $color);
			$x+=$xstep;
			$y+=$ystep;
		}
		return $str;
	}

	/** Connect the dots */
	public static function draw_multiline($points, $steps, $color) {
		$str = '';
		foreach ($points as $point) {
			if (isset($prev_point)) {
				$str.= self::draw_line($prev_point, $point, $steps, $color);
			}
			$prev_point = $point;
		}
		return $str;
	}
	
	public static function points_border($args) {
		$left = $right = $top = $bottom = $xoffset = $yoffset = 0;
		if (isset($args['width'])) {
			$left = $right = $top = $bottom = $args['width'];
		}
		if (isset($args['x'])) {
			$left = $right = $args['x'];
		}
		if (isset($args['y'])) {
			$top = $bottom = $args['y'];
		}
		if (isset($args['left'])) {
			$left = $args['left'];
		}
		if (isset($args['right'])) {
			$right = $args['right'];
		}
		if (isset($args['top'])) {
			$top = $args['top'];
		}
		if (isset($args['bottom'])) {
			$bottom = $args['bottom'];
		}
		if (isset($args['xoffset'])) {
			$xoffset = $args['xoffset'];
		}
		if (isset($args['yoffset'])) {
			$yoffset = $args['yoffset'];
		}
		$p = array('tl'=>self::xy($xoffset-$left , $yoffset-$top   ),
		           'tr'=>self::xy($xoffset+$right, $yoffset-$top   ),
		           'bl'=>self::xy($xoffset-$left , $yoffset+$bottom),
		           'br'=>self::xy($xoffset+$right, $yoffset+$bottom));
		return $p;
	}
	public static function points_border_drop($args) {
		$xoffset = $yoffset = $xdrop = $ydrop = 0;
		if (isset($args['xoffset'])) {
			$xoffset = $args['xoffset'];
		}
		if (isset($args['yoffset'])) {
			$yoffset = $args['yoffset'];
		}
		if (isset($args['drop'])) {
			$xdrop = $ydrop = $args['drop'];
		}
		if (isset($args['xdrop'])) {
			$xdrop = $args['xdrop'];
		}
		if (isset($args['ydrop'])) {
			$ydrop = $args['ydrop'];
		}
		
		$base = self::points_border($args);
		if ($xdrop==$ydrop && $xdrop==0) { return $base; }
		$args['xoffset'] = $xoffset+$xdrop;
		$args['yoffset'] = $yoffset+$ydrop;
		$drop = self::points_border($args);

		$right   = ($xdrop > 0);
		$bottom  = ($ydrop > 0);

		/* 0|1
		 * -+-
		 * 2|3
		 */
		$q = 0;
		if ($right) $q+=1;
		if ($bottom) $q+=2;
		
		switch ($q) {
		case 0: // top-left (or bottom-right)
			// clockwise, start in top-left
			$ret = array($drop['tl'],
			             $drop['tr'],
			             $base['tr'],
			             $base['br'],
			             $base['bl'],
			             $drop['bl'],
			             $drop['tl']);
			return $ret;
		case 1: // top-right (or bottom-left)
			// clockwise, start in top-right
			$ret = array($drop['tr'],
			             $drop['br'],
			             $base['br'],
			             $base['bl'],
			             $base['tl'],
			             $drop['tl'],
			             $drop['tr']);
			return $ret;
		case 2: /* TODO */ break;
		case 3: // top-left (or bottom-right)
			// clockwise, start in top-left
			$ret = array($base['tl'],
			             $base['tr'],
			             $drop['tr'],
			             $drop['br'],
			             $drop['bl'],
			             $base['bl'],
			             $base['tl']);
			return $ret;
		}
	}
	public static function draw_border($args) {
		$steps = 0; $color = '#000000';
		if (isset($args['steps'])) { $steps = $args['steps']; }
		if (isset($args['color'])) { $color = $args['color']; }
		return self::draw_multiline(self::points_border_drop($args), $steps, $color);
	}
}