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107 lines
3.2 KiB
107 lines
3.2 KiB
const _ = require('lodash'); |
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const logger = require( 'pelias-logger' ).get( 'api' ); |
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/** |
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this middleware is responsible for negotiating HTTP locales for incoming |
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browser requests by reading the querystring param 'lang' or 'Accept-Language' request headers. |
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the preferred language will then be available on the $req object: |
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eg. for '?lang=fr' or 'Accept-Language: fr': |
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``` |
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console.log( req.language ); |
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{ |
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name: 'French', |
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type: 'living', |
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scope: 'individual', |
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iso6393: 'fra', |
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iso6392B: 'fre', |
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iso6392T: 'fra', |
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iso6391: 'fr', |
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defaulted: false |
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} |
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``` |
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for configuration options see: |
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https://github.com/florrain/locale |
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**/ |
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const locale = require('locale'); |
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/** |
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BCP47 language tags can contain three parts: |
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1. A language subtag (en, zh). |
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2. A script subtag (Hant, Latn). |
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3. A region subtag (US, CN). |
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at time of writing we will only be concerned with 1. (the language subtag) with |
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the intention of being compatible with the language standard of whosonfirst data. |
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whosonfirst data is in ISO 639-3 format so we will need to configure the library |
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to support all ISO 639-1 (2 char) codes and convert them to 639-1 (3-char) codes. |
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see: https://github.com/whosonfirst/whosonfirst-names |
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**/ |
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const iso6393 = require('iso-639-3'); |
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// create a dictionary which maps the ISO 639-1 language subtags to a map |
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// of it's represenation in several different standards. |
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const language = {}; |
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iso6393.filter( i => !!i.iso6391 ).forEach( i => language[ i.iso6391 ] = i ); |
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// a pre-processed locale list of language subtags we support (all of them). |
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const allLocales = new locale.Locales( Object.keys( language ) ); |
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// return the middleware |
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module.exports = function middleware( req, res, next ){ |
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// init an object to store clean (sanitized) input parameters if not initialized |
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req.clean = req.clean || {}; |
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// init warnings array if not initialized |
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req.warnings = req.warnings || []; |
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// set defaults |
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var lang = language.en; |
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var locales, best, via = 'default'; |
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// input language via query param |
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if( via === 'default' && req.query && req.query.lang ){ |
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locales = new locale.Locales( req.query.lang ); |
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best = locales.best( allLocales ); |
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if( best.defaulted ){ |
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req.warnings.push( 'invalid language provided via querystring' ); |
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} else { |
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lang = language[ best.language ]; |
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via = 'querystring'; |
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} |
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} |
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// input language via request headers |
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if( via === 'default' && req.headers && req.headers['accept-language'] ){ |
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locales = new locale.Locales( req.headers['accept-language'] ); |
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best = locales.best( allLocales ); |
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if( best.defaulted ){ |
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req.warnings.push( 'invalid language provided via header' ); |
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} else { |
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lang = language[ best.language ]; |
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via = 'header'; |
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} |
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} |
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// set $req.language property |
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req.language = _.clone( lang ); |
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req.language.defaulted = ( via === 'default' ); |
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// set $req.clean property in order to print language info in response header |
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req.clean.lang = { |
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name: req.language.name, |
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iso6391: req.language.iso6391, |
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iso6393: req.language.iso6393, |
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defaulted: req.language.defaulted |
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}; |
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logger.debug( '[lang] \'%s\' via \'%s\'', lang.iso6391, via ); |
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next(); |
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};
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