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 <?php
 
 // This script is intended to handle requests for files that do not exist
 // This may occur because:
 // 1) It is a language-free URL and we need to send the user to the most language appropriate version for them
 // 2) The page has moved elsewhere and we need to send them to the appropriate page
 // 3) The request is for a legacy page that existed on the older Mediawiki based setup, in which case we need to once again send them to the most appropriate page
 //
 // SPDX-License-Identifier: MIT
 
 // NOTE: enable supported languages.
 //       English is always enabled. Respect alphabetic order.
 //       Other languages must be listed in locale/ sub-directory from root directory of this git repository.
 //       All changes from this list must be also applied to the docs-digikam-org section from the JSON config file in binary-factory-tooling repository
 //       https://invent.kde.org/sysadmin/binary-factory-tooling/-/blob/master/staticweb/custom-jobs.json
 //       all_langs list in ressources/static/js/version_switch.js file from this repository needs to be also updated.
 
 $supported_languages = array(
     "ca",
     "cs",
     "da",
     "de",
     "en",
     "es",
     "fr",
     "it",
     "ja",
     "ko",
     "lt",
     "nl",
     "sk",
     "sl",
     "sv",
     "ru",
     "tr",
     "pl",
     "pt_BR",
     "pt_PT",
     "uk_UA",
     "zh_CN",
     "zh_TW"
 );
 
 // List of page redirect rules
 // These should always be free of the language code, as this will be automatically added on when formulating the URL to forward the user on to
 $redirect_rules = array(
     // Default front page
     "^$" => "index.html"
 );
 
 //// SETTINGS END
 //// CHANGES SHOULD NOT BE NEEDED TO THE BELOW
 
 // Helper function to determine the most appropriate language for the user
 // Parameters:
 // $request              The web path that the user is trying to reach
 // $browser_languages    The languages accepted by the user browser, in Accept-Language format
 // $supported_languages  Array of languages that we support - in ISO language code format
 function determine_appropriate_language( $request, $browser_languages, $supported_languages )
 {
     // First we start by looking at the request we have received
     // If this contains a language code, then we should be using that as the user has chosen to use that language explicitly
     // We assume that this language is supported
     if( preg_match( '/^([a-z][a-z](_[A-Z][A-Z])?)\//', $request, $result ) ) {
         // Then the user has specified a language - let's use that!
         return $result[1];
     }
 
     // Now that we know that the URL has not specified a language we can move on to looking at Accept-Language
     // First split the list up by the language separator
     $browser_requested_languages = explode( ",", $browser_languages );
 
     // Now go through each browser requested language in turn
     foreach( $browser_requested_languages as $language ) {
         // First as this might have a weighting value on it, we need to rip that off
         // Safest way to do this is just to split again by the appropriate separator for that
         $components = explode(";", $language);
         $language = $components[0];
 
         if( preg_match( '/^zh(-han[ts])?(-[a-z]{2})?$/i', $language, $result, PREG_UNMATCHED_AS_NULL ) ) {
             // Handle Chinese as a special case. Chinese lang tags may carry
             // a `Hant` or `Hans` script subtag, and/or a region subtag.
             // As long as a translation for `zh_HK` isn't available, this
             // matching is sufficient.
             if( strcasecmp($result[1], "-hant") === 0 ) {
                 $language = "zh_TW";
             } else if( strcasecmp($result[1], "-hans") === 0 ) {
                 $language = "zh_CN";
             } else if( strcasecmp($result[2], "-tw") === 0 || strcasecmp($result[2], "-hk") === 0 || strcasecmp($result[2], "-mo") === 0 ) {
                 $language = "zh_TW";
             } else {
                 // Note this also matches `zh` without script or region subtag.
                 $language = "zh_CN";
             }
         } else {
             // Browsers use dashes to seperate language variants
             // But KDE translation systems use underscores for this so ensure we are consistent here
             $language = str_replace("-", "_", $language);
         }
 
         // Is this one of our supported languages?
         if( in_array($language, $supported_languages) ) {
             // Then we have a winner!
             return $language;
         }
     }
 
     // Finally if we found nothing we fallback to English
     return 'en';
 }
 
 // Start - Retrieve the values we need to work with here
 $requested_url = $_SERVER['REQUEST_URI'];
 $requested_languages = $_SERVER["HTTP_ACCEPT_LANGUAGE"];
 
 // Before we can do anything else we need to clean up the URL we have received to remove the leading slash
 $requested_url = substr($requested_url, 1);
 
 // Now determine the language we should be sending the user to
 $language = determine_appropriate_language( $requested_url, $requested_languages, $supported_languages );
 
 // Split out the content part of the URL
 // We will need this for the matching we are about to do above
 if( !preg_match( '/^([a-z][a-z](_[A-Z][A-Z])?\/)?(.*)/', $requested_url, $result ) ) {
     // This shouldn't happen...
     // But in case it does, serve a 404 and bail
     http_response_code(404);
     include("../$language/404.html");
     exit();
 }
 
 // Save our result...
 $requested_page = $result[3];
 
 // First do a local check and see if $language/$requested_page exists..
 // This allows for urls such as https://docs.krita.org/user_manual/getting_started/starting_krita.html to work
 if( file_exists("../$language/$requested_page") ) {
     // Then redirect them there
     header("HTTP/1.1 301 Moved Permanently");
     header("Location: /$language/$requested_page");
     exit();
 }
 
 // Go across all of our redirect rules now and see if we have any matches
 foreach( $redirect_rules as $rule => $replacement ) {
     // Try to match it...
     if( !preg_match( "/$rule/", $requested_page, $result ) ) {
         // Then we need to try another one...
         continue;
     }
 
     // We have a winner!
     // Perform the redirect
     header("HTTP/1.1 301 Moved Permanently"); 
     header("Location: /$language/$replacement"); 
     exit();
 }
 
 // Alas it looks like we have no match :(
 // Send a 404
 http_response_code(404);
 include("../$language/404.html");
 exit();
 
 ?>