<?php
	/* libraries/captcha.php
	 *
	 * Copyright (C) by Hugo Leisink <hide@address.com>
	 * This file is part of the Banshee PHP framework
	 * http://www.banshee-php.org/
	 */

	class captcha {
		private $code = null;
		private $image = null;
		private $font = "../extra/captcha_font.ttf";

		/* Constructor
		 *
		 * INPUT:  [int image width[, int image height[, int number of characters]]]
		 * OUTPUT: -
		 * ERROR:  -
		 */
		public function __construct($width = 150, $height = 40, $characters = 8) {
			$this->code = "";
			$possible = "23456789bcdfghjkmnpqrstvwxyz";
			$pos_max = strlen($possible) - 1;
			for ($i = 0; $i < $characters; $i++) {
				$this->code .= $possible[mt_rand(0, $pos_max)];
			}

			$font_size = $height * 0.75;
			if (($image = imagecreate($width, $height)) == false) {
				return;
			}

			$background_color = imagecolorallocate($image, 255, 255, 255);
			$this->random_color($red, $green, $blue);
			$dot_color = imagecolorallocate($image, $red, $green, $blue);
			$this->random_color($red, $green, $blue);
			$line_color = imagecolorallocate($image, $red, $green, $blue);
			$this->random_color($red, $green, $blue);
			$text_color = imagecolorallocate($image, $red, $green, $blue);

			for ($i = 0; $i < ($width * $height) / 150; $i++) {
				imageline($image, mt_rand(0, $width), mt_rand(0, $height), mt_rand(0, $width), mt_rand(0, $height), $line_color);
			}

			for ($i = 0; $i < ($width * $height) / 3; $i++) {
				imagefilledellipse($image, mt_rand(0, $width), mt_rand(0, $height), 1, 1, $dot_color);
			}

			if (($textbox = imagettfbbox($font_size, 0, $this->font, $this->code)) == false) {
				return;
			}

			$x = ($width - $textbox[4]) / 2;
			$y = ($height - $textbox[5]) / 2;

			if (imagettftext($image, $font_size, 0, $x + 1, $y + 1, $background_color, $this->font, $this->code) == false) {
				return;
			}
			if (imagettftext($image, $font_size, 0, $x, $y, $text_color, $this->font, $this->code) == false) {
				return;
			}

			$_SESSION["captcha_code"] = $this->code;
			$this->image = $image;
		}

		/* Destructor
		 *
		 * INPUT:  -
		 * OUTPUT: -
		 * ERROR:  -
		 */
		public function __destruct() {
			if ($this->image != false) {
				imagedestroy($this->image);
			}
		}

		/* Magic method get
		 *
		 * INPUT:  string key
		 * OUTPUT: mixed value
		 * ERROR:  null
		 */
		public function __get($key) {
			switch ($key) {
				case "created": return $this->image !== null;
				case "code": return $this->code;
			}

			return null;
		}

		/* Generate random RGB color
		 *
		 * INPUT:  &int red, &int green, &int blue
		 * OUTPUT: -
		 * ERROR:  -
		 */
		private function random_color(&$red, &$green, &$blue) {
			$max = array(255, 128, 40);
			$result = array();

			for ($i = 0; $i < 3; $i++) {
				$skip = mt_rand(0, 2 - $i);
				while ($skip-- > 0) {
					array_push($max, array_shift($max));
				}
				$result[$i] = mt_rand(0, array_shift($max));
			}

			list($red, $green, $blue) = $result;
		}

		/* Send captcha image to client
		 *
		 * INPUT:  -
		 * OUTPUT: true
		 * ERROR:  false
		 */
		public function to_output() {
			if ($this->image === null) {
				return false;
			}

			header("Content-Type: image/png");
			header("Expires: ".gmdate("D, d M Y H:i:s")." GMT");
			header("Last-Modified: ".gmdate("D, d M Y H:i:s")." GMT"); 
			header("Cache-Control: no-store, no-cache, must-revalidate");
			header("Cache-Control: post-check=0, pre-check=0", false);
			header("Pragma: no-cache");

			return imagepng($this->image);
		}
	}
?>