<?php
/**
 * The SlideshowPluginSecurity class contains functions for sanitizing in- and output.
 *
 * @author Stefan Boonstra
 * @since 2.1.16
 * @updated 2.1.16
 */
class SlideshowPluginSecurity {

	/**
	 * @since 2.1.16
	 * @var array List of allowed element tags
	 */
	private static $allowedElements = array(
		'b' => array('endTag' => true, 'attributes' => 'default'),
		'br' => array('endTag' => false),
		'div' => array('endTag' => true, 'attributes' => 'default'),
		'h1' => array('endTag' => true, 'attributes' => 'default'),
		'h2' => array('endTag' => true, 'attributes' => 'default'),
		'h3' => array('endTag' => true, 'attributes' => 'default'),
		'h4' => array('endTag' => true, 'attributes' => 'default'),
		'h5' => array('endTag' => true, 'attributes' => 'default'),
		'h6' => array('endTag' => true, 'attributes' => 'default'),
		'i' => array('endTag' => true, 'attributes' => 'default'),
		'li' => array('endTag' => true, 'attributes' => 'default'),
		'ol' => array('endTag' => true, 'attributes' => 'default'),
		'p' => array('endTag' => true, 'attributes' => 'default'),
		'span' => array('endTag' => true, 'attributes' => 'default'),
		'strong' => array('endTag' => true, 'attributes' => 'default'),
		'sub' => array('endTag' => true, 'attributes' => 'default'),
		'sup' => array('endTag' => true, 'attributes' => 'default'),
		'table' => array('endTag' => true, 'attributes' => 'default'),
		'tbody' => array('endTag' => true, 'attributes' => 'default'),
		'td' => array('endTag' => true, 'attributes' => 'default'),
		'tfoot' => array('endTag' => true, 'attributes' => 'default'),
		'th' => array('endTag' => true, 'attributes' => 'default'),
		'thead' => array('endTag' => true, 'attributes' => 'default'),
		'tr' => array('endTag' => true, 'attributes' => 'default'),
		'ul' => array('endTag' => true, 'attributes' => 'default')
	);

	/**
	 * @since 2.1.16
	 * @var array List of attributes allowed in the tags
	 */
	private static $defaultAllowedAttributes = array(
		'class',
		'id',
		'style'
	);

	/**
	 * Similar to the htmlspecialchars($text) function, except this function
	 * allows the exceptions defined in this class.
	 *
	 * @since 2.1.16
	 * @updated 2.1.16
	 */
	static function htmlspecialchars_allow_exceptions($text){
		$text = htmlspecialchars(htmlspecialchars_decode($text));

		$allowedElements = self::$allowedElements;

		// Loop through allowed elements decoding their HTML special chars and allowed attributes.
		if(is_array($allowedElements) && count($allowedElements) > 0){
			foreach($allowedElements as $element => $attributes){

				$position = 0;

				while(($position = stripos($text, $element, $position)) !== false){ // While element tags found

					$openingTag = '<';
					$encodedOpeningTag = htmlspecialchars($openingTag);

					if(substr($text, $position - strlen($encodedOpeningTag), strlen($encodedOpeningTag)) == $encodedOpeningTag){ // Check if an opening tag '<' can be found before the tag name

						// Replace encoded opening tag
						$text = substr_replace($text, '<', $position - strlen($encodedOpeningTag), strlen($encodedOpeningTag));
						$position -= strlen($encodedOpeningTag) - strlen($openingTag);

						// Get the position of the first element closing tag
						$closingTag = '>';
						$encodedClosingTag = htmlspecialchars($closingTag);
						$closingTagPosition = stripos($text, $encodedClosingTag, $position);

						// Replace encoded closing tag
						if($closingTagPosition !== false)
							$text = substr_replace($text, '>', $closingTagPosition, strlen($encodedClosingTag));

						$elementAttributes = null;
						if(isset($attributes['attributes']) && is_array($attributes['attributes']))
							$elementAttributes = $attributes['attributes'];
						elseif(isset($attributes['attributes']) && $attributes['attributes'] == 'default')
							$elementAttributes = self::$defaultAllowedAttributes;
						else
							continue;

						if(!is_array($elementAttributes))
							continue;

						$tagText = substr($text, $position, $closingTagPosition - $position);

						// Decode allowed attributes
						foreach($elementAttributes as $attribute){

							$attributeOpener = $attribute . '=' . htmlspecialchars('"');

							$attributePosition = 0;
							if(($attributePosition = stripos($tagText, $attributeOpener, $attributePosition)) !== false){ // Attribute was found

								$attributeClosingPosition = 0;
								if(($attributeClosingPosition = stripos($tagText, htmlspecialchars('"'), $attributePosition + strlen($attributeOpener))) === false) // If no closing position of attribute was found, skip.
									continue;

								// Open the attribute
								$tagText = str_ireplace($attributeOpener, $attribute . '="', $tagText);

								// Close the attribute
								$attributeClosingPosition -= strlen($attributeOpener) - strlen($attribute . '="');
								$tagText = substr_replace($tagText, '"', $attributeClosingPosition, strlen(htmlspecialchars('"')));
							}

						}

						// Put the attributes of the tag back in place
						$text = substr_replace($text, $tagText, $position, $closingTagPosition - $position);
					}

					$position++;
				}

				// Decode closing tags
				if(isset($attributes['endTag']) && $attributes['endTag'])
					$text = str_ireplace(htmlspecialchars('</' . $element . '>'), '</' . $element . '>', $text);
			}
		}

		return $text;
	}
}