<?php

namespace Util;

/**
 * Classe dedicata all'interpretazione dei file XML.
 *
 * @since 2.4.3
 */
class XML
{
    /**
     * Interpreta i contentuti di una stringa in formato XML.
     *
     * @param string $string
     *
     * @return array
     */
    public static function read($string)
    {
        $content = static::stripP7MData($string);
        $content = static::sanitizeXML($content);

        $xml = simplexml_load_string($content, 'SimpleXMLElement', LIBXML_NOCDATA);
        $result = json_decode(json_encode($xml), true);

        return $result;
    }

    /**
     * Interpreta i contenuti di un file XML.
     *
     * @param string $path
     *
     * @return array
     */
    public static function readFile($path)
    {
        return static::read(file_get_contents($path));
    }

    /**
     * Removes the PKCS#7 header and the signature info footer from a digitally-signed .xml.p7m file using CAdES format.
     *
     * TODO: controllare il funzionamento con gli allegati.
     *
     * @param string $string File content
     * @return string An arguably-valid XML string with the .p7m header and footer stripped away.
     *
     * @source https://www.ryadel.com/php-estrarre-contenuto-file-xml-p7m-cades-fattura-elettronica-pa/
     */
    protected static function stripP7MData($string)
    {
        // skip everything before the XML content
        $string = substr($string, strpos($string, '<?xml '));

        // skip everything after the XML content
        preg_match_all('/<\/.+?>/', $string, $matches, PREG_OFFSET_CAPTURE);
        $lastMatch = end($matches[0]);

        $result = substr($string, 0, $lastMatch[1] + strlen($lastMatch[0]) + 1);

        return static::sanitizeXML($result);
    }

    /**
     * Removes invalid characters from a UTF-8 XML string
     *
     * @param string a XML string potentially containing invalid characters
     * @return string
     *
     * @source https://www.ryadel.com/php-eliminare-caratteri-non-validi-file-stringa-xml-utf8-utf-8/
     */
    protected static function sanitizeXML($string)
    {
        if (!empty($string)) {
            $regex = '/(
            [\xC0-\xC1] # Invalid UTF-8 Bytes
            | [\xF5-\xFF] # Invalid UTF-8 Bytes
            | \xE0[\x80-\x9F] # Overlong encoding of prior code point
            | \xF0[\x80-\x8F] # Overlong encoding of prior code point
            | [\xC2-\xDF](?![\x80-\xBF]) # Invalid UTF-8 Sequence Start
            | [\xE0-\xEF](?![\x80-\xBF]{2}) # Invalid UTF-8 Sequence Start
            | [\xF0-\xF4](?![\x80-\xBF]{3}) # Invalid UTF-8 Sequence Start
            | (?<=[\x0-\x7F\xF5-\xFF])[\x80-\xBF] # Invalid UTF-8 Sequence Middle
            | (?<![\xC2-\xDF]|[\xE0-\xEF]|[\xE0-\xEF][\x80-\xBF]|[\xF0-\xF4]|[\xF0-\xF4][\x80-\xBF]|[\xF0-\xF4][\x80-\xBF]{2})[\x80-\xBF] # Overlong Sequence
            | (?<=[\xE0-\xEF])[\x80-\xBF](?![\x80-\xBF]) # Short 3 byte sequence
            | (?<=[\xF0-\xF4])[\x80-\xBF](?![\x80-\xBF]{2}) # Short 4 byte sequence
            | (?<=[\xF0-\xF4][\x80-\xBF])[\x80-\xBF](?![\x80-\xBF]) # Short 4 byte sequence (2)
        )/x';
            $string = preg_replace($regex, '', $string);

            $result = "";
            $current;
            $length = strlen($string);
            for ($i=0; $i < $length; $i++) {
                $current = ord($string{$i});
                if (($current == 0x9) ||
                ($current == 0xA) ||
                ($current == 0xD) ||
                (($current >= 0x20) && ($current <= 0xD7FF)) ||
                (($current >= 0xE000) && ($current <= 0xFFFD)) ||
                (($current >= 0x10000) && ($current <= 0x10FFFF))) {
                    $result .= chr($current);
                } else {
                    $ret;    // use this to strip invalid character(s)
                // $ret .= " ";    // use this to replace them with spaces
                }
            }
            $string = $result;
        }
        return $string;
    }
}