<?php
/**
 * TCaptcha class file
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @link http://www.pradosoft.com/
 * @copyright Copyright &copy; 2005-2007 PradoSoft
 * @license http://www.pradosoft.com/license/
 * @version $Id$
 * @package System.Web.UI.WebControls
 */

Prado::using('System.Web.UI.WebControls.TImage');

/**
 * TCaptcha class.
 *
 * TCaptcha displays a CAPTCHA (a token displayed as an image) that can be used
 * to determine if the input is entered by a real user instead of some program.
 *
 * The token (a string consisting of alphanumeric characters) displayed is automatically
 * generated and can be configured in several ways. To specify the length of characters
 * in the token, set {@link setMinTokenLength MinTokenLength} and {@link setMaxTokenLength MaxTokenLength}.
 * To use case-insensitive comparison and generate upper-case-only token, set {@link setCaseSensitive CaseSensitive}
 * to false.
 *
 * Upon postback, user input can be validated by calling {@link validate()}.
 * The {@link TCaptchaValidator} control can also be used to do validation, which provides
 * client-side validation besides the server-side validation.  By default, the token will
 * remain the same during multiple postbacks. A new one can be generated by calling
 * {@link regenerateToken()} manually.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @version $Id$
 * @package System.Web.UI.WebControls
 * @since 3.1.1
 */
class TCaptcha extends TImage
{
	const MIN_TOKEN_LENGTH=4;
	const MAX_TOKEN_LENGTH=40;

	public function onInit($param)
	{
		parent::onInit($param);
		$this->checkRequirements();
	}

	/**
	 * @return integer the minimum length of the token. Defaults to 5.
	 */
	public function getMinTokenLength()
	{
		return $this->getViewState('MinTokenLength',5);
	}

	/**
	 * @param integer the minimum length of the token. It must be between 2 and 40.
	 */
	public function setMinTokenLength($value)
	{
		$length=TPropertyValue::ensureInteger($value);
		if($length>=self::MIN_TOKEN_LENGTH && $length<=self::MAX_TOKEN_LENGTH)
			$this->setViewState('MinTokenLength',$length,5);
		else
			throw new TConfigurationException('captcha_mintokenlength_invalid',self::MIN_TOKEN_LENGTH,self::MAX_TOKEN_LENGTH);
	}

	/**
	 * @return integer the maximum length of the token. Defaults to 8.
	 */
	public function getMaxTokenLength()
	{
		return $this->getViewState('MaxTokenLength',8);
	}

	/**
	 * @param integer the maximum length of the token. It must be between 2 and 40.
	 */
	public function setMaxTokenLength($value)
	{
		$length=TPropertyValue::ensureInteger($value);
		if($length>=self::MIN_TOKEN_LENGTH && $length<=self::MAX_TOKEN_LENGTH)
			$this->setViewState('MaxTokenLength',$length,8);
		else
			throw new TConfigurationException('captcha_maxtokenlength_invalid',self::MIN_TOKEN_LENGTH,self::MAX_TOKEN_LENGTH);
	}

	/**
	 * @return boolean whether the token should be treated as case-sensitive. Defaults to true.
	 */
	public function getCaseSensitive()
	{
		return $this->getViewState('CaseSensitive',true);
	}

	/**
	 * @param boolean whether the token should be treated as case-sensitive. If false, only upper-case letters will appear in the token.
	 */
	public function setCaseSensitive($value)
	{
		$this->setViewState('CaseSensitive',TPropertyValue::ensureBoolean($value),true);
	}

	/**
	 * @return string the public key used for generating the token. A random one will be generated and returned if this is not set.
	 */
	public function getPublicKey()
	{
		if(($publicKey=$this->getViewState('PublicKey',''))==='')
		{
			$publicKey=$this->generateRandomKey();
			$this->setPublicKey($publicKey);
		}
		return $publicKey;
	}

	/**
	 * @param string the public key used for generating the token. A random one will be generated if this is not set.
	 */
	public function setPublicKey($value)
	{
		$this->setViewState('PublicKey',$value,'');
	}

	/**
	 * @return string the token that will be displayed
	 */
	public function getToken()
	{
		return $this->generateToken($this->getPublicKey(),$this->getPrivateKey(),$this->getTokenLength(),$this->getCaseSensitive());
	}

	protected function getTokenLength()
	{
		if(($tokenLength=$this->getViewState('TokenLength'))===null)
		{
			$minLength=$this->getMinTokenLength();
			$maxLength=$this->getMaxTokenLength();
			if($minLength>$maxLength)
				$tokenLength=rand($maxLength,$minLength);
			else if($minLength<$maxLength)
				$tokenLength=rand($minLength,$maxLength);
			else
				$tokenLength=$minLength;
			$this->setViewState('TokenLength',$tokenLength);
		}
		return $tokenLength;
	}

	/**
	 * @return string the private key used for generating the token. This is randomly generated and kept in a file for persistency.
	 */
	public function getPrivateKey()
	{
		$fileName=$this->generatePrivateKeyFile();
		$content=file_get_contents($fileName);
		$matches=array();
		if(preg_match("/privateKey='(.*?)'/ms",$content,$matches)>0)
			return $matches[1];
		else
			throw new TConfigurationException('captcha_private_unknown');
	}

	/**
	 * Validates a user input with the token.
	 * @param string user input
	 * @return boolean if the user input is not the same as the token.
	 */
	public function validate($input)
	{
		return $this->getToken()===($this->getCaseSensitive()?$input:strtoupper($input));
	}

	/**
	 * Regenerates the token to be displayed.
	 * By default, a token, once generated, will remain the same during the following page postbacks.
	 * Calling this method will generate a new token.
	 */
	public function regenerateToken()
	{
		$this->clearViewState('TokenLength');
		$this->setPublicKey('');
		$this->clearViewState('TokenGenerated');
	}

	/**
	 * Configures the image URL that shows the token.
	 * @param mixed event parameter
	 */
	public function onPreRender($param)
	{
		parent::onPreRender($param);
		if(!$this->getViewState('TokenGenerated',false))
		{
			$token=$this->getToken();
			$tokenLength=strlen($token);
			$manager=$this->getApplication()->getAssetManager();
			$manager->publishFilePath($this->getFontFile());
			$url=$manager->publishFilePath($this->getCaptchaScriptFile());
			$url.='?pk='.urlencode($this->getPublicKey());
			$url.='&amp;length='.$tokenLength;
			$url.='&amp;case='.($this->getCaseSensitive()?'1':'0');
			$this->setImageUrl($url);
			$this->generatePrivateKeyFile();

			$this->setViewState('TokenGenerated',true);
		}
	}

	/**
	 * @return string the file path of the PHP script generating the token image
	 */
	protected function getCaptchaScriptFile()
	{
		return dirname(__FILE__).DIRECTORY_SEPARATOR.'assets'.DIRECTORY_SEPARATOR.'captcha.php';
	}

	protected function getFontFile()
	{
		return dirname(__FILE__).DIRECTORY_SEPARATOR.'assets'.DIRECTORY_SEPARATOR.'verase.ttf';
	}

	/**
	 * Generates a file with a randomly generated private key.
	 * @return string the path of the file keeping the private key
	 */
	protected function generatePrivateKeyFile()
	{
		$captchaScript=$this->getCaptchaScriptFile();
		$path=dirname($this->getApplication()->getAssetManager()->getPublishedPath($captchaScript));
		$fileName=$path.DIRECTORY_SEPARATOR.'captcha_key.php';
		if(!is_file($fileName))
		{
			@mkdir($path);
			$key=$this->generateRandomKey();
			$content="<?php
\$privateKey='$key';
?>";
			file_put_contents($fileName,$content);
		}
		return $fileName;
	}

	/**
	 * @return string a randomly generated key
	 */
	protected function generateRandomKey()
	{
		return md5(rand().rand().rand().rand());
	}

	/**
	 * Generates the token.
	 * @param string public key
	 * @param string private key
	 * @param integer the length of the token
	 * @param boolean whether the token is case sensitive
	 * @return string the token generated.
	 */
	protected function generateToken($publicKey,$privateKey,$tokenLength,$caseSensitive)
	{
		$token=substr($this->hash2string(md5($publicKey.$privateKey)).$this->hash2string(md5($privateKey.$publicKey)),0,$tokenLength);
		return $caseSensitive?$token:strtoupper($token);
	}

	/**
	 * Converts a hash string into a string with characters consisting of alphanumeric characters.
	 * @param string the hexadecimal representation of the hash string
	 * @param string the alphabet used to represent the converted string. If empty, it means '234578adefhijmnrtwyABDEFGHIJLMNQRTWY', which excludes those confusing characters.
	 * @return string the converted string
	 */
	protected function hash2string($hex,$alphabet='')
	{
		if(strlen($alphabet)<2)
			$alphabet='234578adefhijmnrtABDEFGHJLMNQRT';
		$hexLength=strlen($hex);
		$base=strlen($alphabet);
		$result='';
		for($i=0;$i<$hexLength;$i+=6)
		{
			$number=hexdec(substr($hex,$i,6));
			while($number)
			{
				$result.=$alphabet[$number%$base];
				$number=floor($number/$base);
			}
		}
		return $result;
	}

	protected function checkRequirements()
	{
		if(!extension_loaded('gd'))
			throw new TConfigurationException('captcha_gd2_required');
		if(!function_exists('imagettftext'))
			throw new TConfigurationException('captcha_imagettftext_required');
		if(!function_exists('imagepng'))
			throw new TConfigurationException('captcha_imagepng_required');
	}
}

?>