<?php

/**
 * @package KantPHP
 * @author  Zhenqiang Zhang <zhenqiang.zhang@hotmail.com>
 * @copyright (c) KantPHP Studio, All rights reserved.
 * @license http://www.opensource.org/licenses/BSD-3-Clause  The BSD 3-Clause License
 */
namespace Kant\Captcha;

use Kant\Kant;
use Kant\Action\Action;
use Kant\Exception\InvalidConfigException;
use Kant\Helper\Url;
use Kant\Http\Response;

/**
 * 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 [[\Kant\Controller\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 = '@kant/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;

    /**
     *
     * @var string the rendering library to use. Currently supported only 'gd' and 'imagick'.
     *      If not set, library will be determined automatically.
     * @since 2.0.7
     */
    public $imageLibrary;

    /**
     * Initializes the action.
     * 
     * @throws InvalidConfigException if the font file does not exist.
     */
    public function init()
    {
        $this->fontFile = Kant::getAlias($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 (Kant::$app->request->get(self::REFRESH_GET_VAR)) {
            // AJAX request for regenerating code
            $code = $this->getVerifyCode(true);
            Kant::$app->response->format = Response::FORMAT_JSON;
            return [
                '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("", [
                    'v' => uniqid()
                ])
            ];
        } else {
            $this->setHttpHeaders();
            Kant::$app->response->format = Response::FORMAT_RAW;
            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;
        }
        
        $session = Kant::$app->getSession();
        $name = $this->getSessionKey();
        if ($session->get($name) == null || $regenerate) {
            $session->put($name, $this->generateVerifyCode());
            $session->put($name . 'count', 1);
            $session->save();
        }
        
        return $session->get($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;
        $session = Kant::$app->getSession();
        $name = $this->getSessionKey() . 'count';
        $session->put($name, $session->get($name) + 1);
        $session->save();
        if ($valid || $session->get($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 $code
     *            the verification code
     * @return string image contents
     * @throws InvalidConfigException if imageLibrary is not supported
     */
    protected function renderImage($code)
    {
        if (isset($this->imageLibrary)) {
            $imageLibrary = $this->imageLibrary;
        } else {
            $imageLibrary = Captcha::checkRequirements();
        }
        if ($imageLibrary === 'gd') {
            return $this->renderImageByGD($code);
        } elseif ($imageLibrary === 'imagick') {
            return $this->renderImageByImagick($code);
        } else {
            throw new InvalidConfigException("Defined library '{$imageLibrary}' is not supported");
        }
    }

    /**
     * Renders the CAPTCHA image based on the code using GD library.
     * 
     * @param string $code
     *            the verification code
     * @return string image contents in PNG format.
     */
    protected function renderImageByGD($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 - 1, $this->height - 1, $backColor);
        imagecolordeallocate($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 $code
     *            the verification code
     * @return string image contents in PNG format.
     */
    protected function renderImageByImagick($code)
    {
        $backColor = $this->transparent ? new \ImagickPixel('transparent') : new \ImagickPixel('#' . str_pad(dechex($this->backColor), 6, 0, STR_PAD_LEFT));
        $foreColor = new \ImagickPixel('#' . str_pad(dechex($this->foreColor), 6, 0, STR_PAD_LEFT));
        
        $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->getImageBlob();
    }

    /**
     * Sets the HTTP headers needed by image response.
     */
    protected function setHttpHeaders()
    {
        Kant::$app->response->headers->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');
    }
}
