<?php
/**
 * @link http://www.yiiframework.com/
 * @copyright Copyright (c) 2008 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */

namespace yii\captcha;

use Yii;
use yii\base\Action;
use yii\base\InvalidConfigException;
use yii\helpers\Url;

/**
 * CaptchaAction renders a CAPTCHA image.
 *
 * CaptchaAction is used together with [[Captcha]] and [[\yii\captcha\CaptchaValidator]]
 * to provide the [CAPTCHA](http://en.wikipedia.org/wiki/Captcha) feature.
 *
 * By configuring the properties of CaptchaAction, you may customize the appearance of
 * the generated CAPTCHA images, such as the font color, the background color, etc.
 *
 * Note that CaptchaAction requires either GD2 extension or ImageMagick PHP extension.
 *
 * Using CAPTCHA involves the following steps:
 *
 * 1. Override [[\yii\web\Controller::actions()]] and register an action of class CaptchaAction with ID 'captcha'
 * 2. In the form model, declare an attribute to store user-entered verification code, and declare the attribute
 *    to be validated by the 'captcha' validator.
 * 3. In the controller view, insert a [[Captcha]] widget in the form.
 *
 * @property string $verifyCode The verification code. This property is read-only.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @since 2.0
 */
class CaptchaAction extends Action
{
	/**
	 * The name of the GET parameter indicating whether the CAPTCHA image should be regenerated.
	 */
	const REFRESH_GET_VAR = 'refresh';
	/**
	 * @var integer how many times should the same CAPTCHA be displayed. Defaults to 3.
	 * A value less than or equal to 0 means the test is unlimited (available since version 1.1.2).
	 */
	public $testLimit = 3;
	/**
	 * @var integer the width of the generated CAPTCHA image. Defaults to 120.
	 */
	public $width = 120;
	/**
	 * @var integer the height of the generated CAPTCHA image. Defaults to 50.
	 */
	public $height = 50;
	/**
	 * @var integer padding around the text. Defaults to 2.
	 */
	public $padding = 2;
	/**
	 * @var integer the background color. For example, 0x55FF00.
	 * Defaults to 0xFFFFFF, meaning white color.
	 */
	public $backColor = 0xFFFFFF;
	/**
	 * @var integer the font color. For example, 0x55FF00. Defaults to 0x2040A0 (blue color).
	 */
	public $foreColor = 0x2040A0;
	/**
	 * @var boolean whether to use transparent background. Defaults to false.
	 */
	public $transparent = false;
	/**
	 * @var integer the minimum length for randomly generated word. Defaults to 6.
	 */
	public $minLength = 6;
	/**
	 * @var integer the maximum length for randomly generated word. Defaults to 7.
	 */
	public $maxLength = 7;
	/**
	 * @var integer the offset between characters. Defaults to -2. You can adjust this property
	 * in order to decrease or increase the readability of the captcha.
	 **/
	public $offset = -2;
	/**
	 * @var string the TrueType font file. This can be either a file path or path alias.
	 */
	public $fontFile = '@yii/captcha/SpicyRice.ttf';
	/**
	 * @var string the fixed verification code. When this property is set,
	 * [[getVerifyCode()]] will always return the value of this property.
	 * This is mainly used in automated tests where we want to be able to reproduce
	 * the same verification code each time we run the tests.
	 * If not set, it means the verification code will be randomly generated.
	 */
	public $fixedVerifyCode;


	/**
	 * Initializes the action.
	 * @throws InvalidConfigException if the font file does not exist.
	 */
	public function init()
	{
		$this->fontFile = Yii::getAlias($this->fontFile);
		if (!is_file($this->fontFile)) {
			throw new InvalidConfigException("The font file does not exist: {$this->fontFile}");
		}
	}

	/**
	 * Runs the action.
	 */
	public function run()
	{
		if (Yii::$app->request->getQueryParam(self::REFRESH_GET_VAR) !== null) {
			// AJAX request for regenerating code
			$code = $this->getVerifyCode(true);
			return json_encode([
				'hash1' => $this->generateValidationHash($code),
				'hash2' => $this->generateValidationHash(strtolower($code)),
				// we add a random 'v' parameter so that FireFox can refresh the image
				// when src attribute of image tag is changed
				'url' => Url::to([$this->id, 'v' => uniqid()]),
			]);
		} else {
			$this->setHttpHeaders();
			return $this->renderImage($this->getVerifyCode());
		}
	}

	/**
	 * Generates a hash code that can be used for client side validation.
	 * @param string $code the CAPTCHA code
	 * @return string a hash code generated from the CAPTCHA code
	 */
	public function generateValidationHash($code)
	{
		for ($h = 0, $i = strlen($code) - 1; $i >= 0; --$i) {
			$h += ord($code[$i]);
		}
		return $h;
	}

	/**
	 * Gets the verification code.
	 * @param boolean $regenerate whether the verification code should be regenerated.
	 * @return string the verification code.
	 */
	public function getVerifyCode($regenerate = false)
	{
		if ($this->fixedVerifyCode !== null) {
			return $this->fixedVerifyCode;
		}

		$session = Yii::$app->getSession();
		$session->open();
		$name = $this->getSessionKey();
		if ($session[$name] === null || $regenerate) {
			$session[$name] = $this->generateVerifyCode();
			$session[$name . 'count'] = 1;
		}
		return $session[$name];
	}

	/**
	 * Validates the input to see if it matches the generated code.
	 * @param string $input user input
	 * @param boolean $caseSensitive whether the comparison should be case-sensitive
	 * @return boolean whether the input is valid
	 */
	public function validate($input, $caseSensitive)
	{
		$code = $this->getVerifyCode();
		$valid = $caseSensitive ? ($input === $code) : strcasecmp($input, $code) === 0;
		$session = Yii::$app->getSession();
		$session->open();
		$name = $this->getSessionKey() . 'count';
		$session[$name] = $session[$name] + 1;
		if ($valid || $session[$name] > $this->testLimit && $this->testLimit > 0) {
			$this->getVerifyCode(true);
		}
		return $valid;
	}

	/**
	 * Generates a new verification code.
	 * @return string the generated verification code
	 */
	protected function generateVerifyCode()
	{
		if ($this->minLength > $this->maxLength) {
			$this->maxLength = $this->minLength;
		}
		if ($this->minLength < 3) {
			$this->minLength = 3;
		}
		if ($this->maxLength > 20) {
			$this->maxLength = 20;
		}
		$length = mt_rand($this->minLength, $this->maxLength);

		$letters = 'bcdfghjklmnpqrstvwxyz';
		$vowels = 'aeiou';
		$code = '';
		for ($i = 0; $i < $length; ++$i) {
			if ($i % 2 && mt_rand(0, 10) > 2 || !($i % 2) && mt_rand(0, 10) > 9) {
				$code .= $vowels[mt_rand(0, 4)];
			} else {
				$code .= $letters[mt_rand(0, 20)];
			}
		}

		return $code;
	}

	/**
	 * Returns the session variable name used to store verification code.
	 * @return string the session variable name
	 */
	protected function getSessionKey()
	{
		return '__captcha/' . $this->getUniqueId();
	}

	/**
	 * Renders the CAPTCHA image.
	 * @param string $code the verification code
	 * @return string image contents
	 */
	protected function renderImage($code)
	{
		if (Captcha::checkRequirements() === 'gd') {
			return $this->renderImageByGD($code);
		} else {
			return $this->renderImageByImagick($code);
		}
	}

	/**
	 * Renders the CAPTCHA image based on the code using GD library.
	 * @param string $code the verification code
	 * @return string image contents
	 */
	protected function renderImageByGD($code)
	{
		$image = imagecreatetruecolor($this->width, $this->height);

		$backColor = imagecolorallocate($image,
			(int)($this->backColor % 0x1000000 / 0x10000),
			(int)($this->backColor % 0x10000 / 0x100),
			$this->backColor % 0x100);
		imagefilledrectangle($image, 0, 0, $this->width, $this->height, $backColor);
		imagecolordeallocate($image, $backColor);

		if ($this->transparent) {
			imagecolortransparent($image, $backColor);
		}

		$foreColor = imagecolorallocate($image,
			(int)($this->foreColor % 0x1000000 / 0x10000),
			(int)($this->foreColor % 0x10000 / 0x100),
			$this->foreColor % 0x100);

		$length = strlen($code);
		$box = imagettfbbox(30, 0, $this->fontFile, $code);
		$w = $box[4] - $box[0] + $this->offset * ($length - 1);
		$h = $box[1] - $box[5];
		$scale = min(($this->width - $this->padding * 2) / $w, ($this->height - $this->padding * 2) / $h);
		$x = 10;
		$y = round($this->height * 27 / 40);
		for ($i = 0; $i < $length; ++$i) {
			$fontSize = (int)(rand(26, 32) * $scale * 0.8);
			$angle = rand(-10, 10);
			$letter = $code[$i];
			$box = imagettftext($image, $fontSize, $angle, $x, $y, $foreColor, $this->fontFile, $letter);
			$x = $box[2] + $this->offset;
		}

		imagecolordeallocate($image, $foreColor);

		ob_start();
		imagepng($image);
		imagedestroy($image);
		return ob_get_clean();
	}

	/**
	 * Renders the CAPTCHA image based on the code using ImageMagick library.
	 * @param string $code the verification code
	 * @return \Imagick image instance. Can be used as string. In this case it will contain image contents.
	 */
	protected function renderImageByImagick($code)
	{
		$backColor = $this->transparent ? new \ImagickPixel('transparent') : new \ImagickPixel('#' . dechex($this->backColor));
		$foreColor = new \ImagickPixel('#' . dechex($this->foreColor));

		$image = new \Imagick();
		$image->newImage($this->width, $this->height, $backColor);

		$draw = new \ImagickDraw();
		$draw->setFont($this->fontFile);
		$draw->setFontSize(30);
		$fontMetrics = $image->queryFontMetrics($draw, $code);

		$length = strlen($code);
		$w = (int)($fontMetrics['textWidth']) - 8 + $this->offset * ($length - 1);
		$h = (int)($fontMetrics['textHeight']) - 8;
		$scale = min(($this->width - $this->padding * 2) / $w, ($this->height - $this->padding * 2) / $h);
		$x = 10;
		$y = round($this->height * 27 / 40);
		for ($i = 0; $i < $length; ++$i) {
			$draw = new \ImagickDraw();
			$draw->setFont($this->fontFile);
			$draw->setFontSize((int)(rand(26, 32) * $scale * 0.8));
			$draw->setFillColor($foreColor);
			$image->annotateImage($draw, $x, $y, rand(-10, 10), $code[$i]);
			$fontMetrics = $image->queryFontMetrics($draw, $code[$i]);
			$x += (int)($fontMetrics['textWidth']) + $this->offset;
		}

		$image->setImageFormat('png');
		return $image;
	}

	/**
	 * Sets the HTTP headers needed by image response.
	 */
	protected function setHttpHeaders()
	{
		Yii::$app->getResponse()->getHeaders()
			->set('Pragma', 'public')
			->set('Expires', '0')
			->set('Cache-Control', 'must-revalidate, post-check=0, pre-check=0')
			->set('Content-Transfer-Encoding', 'binary')
			->set('Content-type', 'image/png');
	}
}
