(function() {
 'use strict';

 // Parses versions in URL segments like:
 // "3", "dev", "release/2.7" or "3.6rc2"
 var version_regexs = [
 '(?:\\d)',
 '(?:\\d\\.\\d[\\w\\d\\.]*)',
 '(?:dev)',
 '(?:release/\\d.\\d[\\x\\d\\.]*)'];

 var all_versions = {
 '3.9': 'dev (3.9)',
 '3.8': 'pre (3.8)',
 '3.7': '3.7',
 '3.6': '3.6',
 '3.5': '3.5',
 '2.7': '2.7',
 };

 var all_languages = {
 'en': 'English',
 'fr': 'French',
 'ja': 'Japanese',
 'ko': 'Korean',
 'zh-cn': 'Simplified Chinese',
 };

 function build_version_select(current_version, current_release) {
 var buf = ['<select>'];

 $.each(all_versions, function(version, title) {
 buf.push('<option value="' + version + '"');
 if (version == current_version)
 buf.push(' selected="selected">' + current_release + '</option>');
 else
 buf.push('>' + title + '</option>');
 });

 buf.push('</select>');
 return buf.join('');
 }

 function build_language_select(current_language) {
 var buf = ['<select>'];

 $.each(all_languages, function(language, title) {
 if (language == current_language)
 buf.push('<option value="' + language + '" selected="selected">' +
 all_languages[current_language] + '</option>');
 else
 buf.push('<option value="' + language + '">' + title + '</option>');
 });
 if (!(current_language in all_languages)) {
 // In case we're browsing a language that is not yet in all_languages.
 buf.push('<option value="' + current_language + '" selected="selected">' +
 current_language + '</option>');
 all_languages[current_language] = current_language;
 }
 buf.push('</select>');
 return buf.join('');
 }

 function navigate_to_first_existing(urls) {
 // Navigate to the first existing URL in urls.
 var url = urls.shift();
 if (urls.length == 0) {
 window.location.href = url;
 return;
 }
 $.ajax({
 url: url,
 success: function() {
 window.location.href = url;
 },
 error: function() {
 navigate_to_first_existing(urls);
 }
 });
 }

 function on_version_switch() {
 var selected_version = $(this).children('option:selected').attr('value') + '/';
 var url = window.location.href;
 var current_language = language_segment_from_url(url);
 var current_version = version_segment_in_url(url);
 var new_url = url.replace('.org/' + current_language + current_version,
 '.org/' + current_language + selected_version);
 if (new_url != url) {
 navigate_to_first_existing([
 new_url,
 url.replace('.org/' + current_language + current_version,
 '.org/' + selected_version),
 'https://docs.python.org/' + current_language + selected_version,
 'https://docs.python.org/' + selected_version,
 'https://docs.python.org/'
 ]);
 }
 }

 function on_language_switch() {
 var selected_language = $(this).children('option:selected').attr('value') + '/';
 var url = window.location.href;
 var current_language = language_segment_from_url(url);
 var current_version = version_segment_in_url(url);
 if (selected_language == 'en/') // Special 'default' case for english.
 selected_language = '';
 var new_url = url.replace('.org/' + current_language + current_version,
 '.org/' + selected_language + current_version);
 if (new_url != url) {
 navigate_to_first_existing([
 new_url,
 'https://docs.python.org/'
 ]);
 }
 }

 // Returns the path segment of the language as a string, like 'fr/'
 // or '' if not found.
 function language_segment_from_url(url) {
 var language_regexp = '\.org/([a-z]{2}(?:-[a-z]{2})?/)';
 var match = url.match(language_regexp);
 if (match !== null)
 return match[1];
 return '';
 }

 // Returns the path segment of the version as a string, like '3.6/'
 // or '' if not found.
 function version_segment_in_url(url) {
 var language_segment = '(?:[a-z]{2}(?:-[a-z]{2})?/)';
 var version_segment = '(?:(?:' + version_regexs.join('|') + ')/)';
 var version_regexp = '\\.org/' + language_segment + '?(' + version_segment + ')';
 var match = url.match(version_regexp);
 if (match !== null)
 return match[1];
 return ''
 }

 $(document).ready(function() {
 var release = DOCUMENTATION_OPTIONS.VERSION;
 var language_segment = language_segment_from_url(window.location.href);
 var current_language = language_segment.replace(/\/+$/g, '') || 'en';
 var version = release.substr(0, 3);
 var version_select = build_version_select(version, release);

 $('.version_switcher_placeholder').html(version_select);
 $('.version_switcher_placeholder select').bind('change', on_version_switch);

 var language_select = build_language_select(current_language);

 $('.language_switcher_placeholder').html(language_select);
 $('.language_switcher_placeholder select').bind('change', on_language_switch);
 });
})();