// dependencies:
// https://mvnrepository.com/artifact/tv.cntt/scaposer
// compile group: 'tv.cntt', name: 'scaposer_2.12', version: '1.11.0'
package internationalization;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import scala.collection.Seq;
import scala.util.Either;
import scaposer.ParseFailure;
import scaposer.Parser$;
import scaposer.Translation;
import java.io.File;
import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.*;

public final class I18n {

    private static final Logger LOG = LoggerFactory.getLogger(I18n.class);

    /**
     * The current language to translate to.
     */
    private static Locale _currentLocale = Locale.ENGLISH;

    private static Map<Locale, scaposer.I18n> _dictionaries = new HashMap<>();

    /**
     * Selects the current language as the default language to translate to.
     * @param locale target language
     */
    public static void select(Locale locale){
        _currentLocale = locale;
    }

    public static String t(String singular){
        if(_dictionaries.containsKey(_currentLocale)){
            return _dictionaries.get(_currentLocale).t(singular);
        }
        return singular; // fallback
    }

    public static String tc(String ctx, String singular){
        if(_dictionaries.containsKey(_currentLocale)){
            return _dictionaries.get(_currentLocale).tc(ctx, singular);
        }
        return singular; // fallback
    }

    public static String tn(String singular, String plural, Long n) {
        if(_dictionaries.containsKey(_currentLocale)){
            return _dictionaries.get(_currentLocale).tn(singular, plural, n);
        }
        return  (n != 1) ? plural : singular; // fallback
    }

    public static String tcn(String ctx, String singular, String plural, Long n){
        if(_dictionaries.containsKey(_currentLocale)){
            return _dictionaries.get(_currentLocale).tcn(ctx, singular, plural, n);
        }
        return  (n != 1) ? plural : singular; // fallback
    }

    public static Locale localeFromFileName(String fileName){
        String[] ns = fileName.split("\\.");
        return Locale.forLanguageTag(ns[0]);
    }

    /**
     * Loads all *.po files from the given <code>path</code>.
     * <p>
     * The files should follow this naming convention:
     * <br>
     * <code>*language_code*.*name*.po</code>
     * <nr
     * *name* is optional
     * <br>
     * example: <code>de.myComponent.po</code> & <code>de.myOtherComponent.po</code> & <code>de.po</code>
     * </p>
     * @param path the path to search for language files for
     */
    public static void init(String path){
        File dir = new File(path);
        if(!dir.isDirectory()){
            throw new IllegalArgumentException("Path needs to point to a directory.");
        }
        String[] fileNames = dir.list((dir1, name) -> name.endsWith(".po"));
        if(fileNames == null || fileNames.length == 0){
            LOG.warn("No translation files (*.po) found.");
            return;
        }
        initPoFiles(path, fileNames);
    }

    private static void initPoFiles(String path, String[] fileNames){
        _dictionaries.clear();
        for(String name: fileNames){
            try {
                Locale loc = localeFromFileName(name);
                scaposer.I18n i18n = readPoFile(path + File.separator + name);
                if(_dictionaries.containsKey(loc)){
                    // if a dictionary already exists, combine them
                    _dictionaries.put(loc, _dictionaries.get(loc).$plus$plus(i18n));
                } else {
                    _dictionaries.put(loc, i18n);
                }
            } catch (IOException e) {
                LOG.error("Error while reading translation file: " + path);
            } catch (PoParseFailure poParseFailure) {
                LOG.error("Error while parsing translation file: " + path + "; Error: " + poParseFailure.getMessage());
            }
        }
    }

    private static scaposer.I18n readPoFile(String pathToFile) throws IOException, PoParseFailure {
        byte[] encoded = Files.readAllBytes(Paths.get(pathToFile));
        String fileContent = new String(encoded, Charset.forName("UTF-8"));
        return parsePoFile(fileContent);
    }

    private static scaposer.I18n parsePoFile(String fileContent) throws PoParseFailure  {
        final Either<ParseFailure, Seq<Translation>> parseFailureSeqEither = Parser$.MODULE$.parse(fileContent);
        if(parseFailureSeqEither.isRight()){
            Seq<Translation> translationSeq = parseFailureSeqEither.right().get();
            return scaposer.I18n.apply(translationSeq);
        }else {
            throw new PoParseFailure (parseFailureSeqEither.left().toString());
        }
    }

    private static class PoParseFailure extends Exception {
        PoParseFailure (String message) {
            super(message);
        }
    }
}