/*******************************************************************************
 * Copyright 2017 The MIT Internet Trust Consortium
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *******************************************************************************/

package org.mitre.openid.connect.config;

import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Locale;
import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.support.AbstractMessageSource;
import org.springframework.core.io.Resource;

import com.google.common.base.Splitter;
import com.google.gson.JsonElement;
import com.google.gson.JsonIOException;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import com.google.gson.JsonSyntaxException;

/**
 * @author jricher
 *
 */
public class JsonMessageSource extends AbstractMessageSource {
        // Logger for this class
        private static final Logger logger = LoggerFactory.getLogger(JsonMessageSource.class);

        private Resource baseDirectory;

        private Locale fallbackLocale = new Locale("en"); // US English is the fallback language

        private Map<Locale, List<JsonObject>> languageMaps = new HashMap<>();

        @Autowired
        private ConfigurationPropertiesBean config;

        @Override
        protected MessageFormat resolveCode(String code, Locale locale) {

                List<JsonObject> langs = getLanguageMap(locale);

                String value = getValue(code, langs);

                if (value == null) {
                        // if we haven't found anything, try the default locale
                        langs = getLanguageMap(fallbackLocale);
                        value = getValue(code, langs);
                }

                if (value == null) {
                        // if it's still null, return null
                        return null;
                } else {
                        // otherwise format the message
                        return new MessageFormat(value, locale);
                }

        }

        /**
         * Get a value from the set of maps, taking the first match in order
         * @param code
         * @param langs
         * @return
         */
        private String getValue(String code, List<JsonObject> langs) {
                if (langs == null || langs.isEmpty()) {
                        // no language maps, nothing to look up
                        return null;
                }

                for (JsonObject lang : langs) {
                        String value = getValue(code, lang);
                        if (value != null) {
                                // short circuit out of here if we find a match, otherwise keep going through the list
                                return value;
                        }
                }

                // if we didn't find anything return null
                return null;
        }

        /**
         * Get a value from a single map
         * @param code
         * @param locale
         * @param lang
         * @return
         */
        private String getValue(String code, JsonObject lang) {

                // if there's no language map, nothing to look up
                if (lang == null) {
                        return null;
                }

                JsonElement e = lang;

                Iterable<String> parts = Splitter.on('.').split(code);
                Iterator<String> it = parts.iterator();

                String value = null;

                while (it.hasNext()) {
                        String p = it.next();
                        if (e.isJsonObject()) {
                                JsonObject o = e.getAsJsonObject();
                                if (o.has(p)) {
                                        e = o.get(p); // found the next level
                                        if (!it.hasNext()) {
                                                // we've reached a leaf, grab it
                                                if (e.isJsonPrimitive()) {
                                                        value = e.getAsString();
                                                }
                                        }
                                } else {
                                        // didn't find it, stop processing
                                        break;
                                }
                        } else {
                                // didn't find it, stop processing
                                break;
                        }
                }


                return value;

        }

        /**
         * @param locale
         * @return
         */
        private List<JsonObject> getLanguageMap(Locale locale) {

                if (!languageMaps.containsKey(locale)) {
                        try {
                                List<JsonObject> set = new ArrayList<>();
                                for (String namespace : config.getLanguageNamespaces()) {
                                        // full locale string, e.g. "en_US"
                                        String filename = locale.getLanguage() + "_" + locale.getCountry() + File.separator + namespace + ".json";

                                        Resource r = getBaseDirectory().createRelative(filename);

                                        if (!r.exists()) {
                                                // fallback to language only
                                                logger.debug("Fallback locale to language only.");
                                                filename = locale.getLanguage() + File.separator + namespace + ".json";
                                                r = getBaseDirectory().createRelative(filename);
                                        }

                                        logger.info("No locale loaded, trying to load from " + r);

                                        JsonParser parser = new JsonParser();
                                        JsonObject obj = (JsonObject) parser.parse(new InputStreamReader(r.getInputStream(), "UTF-8"));

                                        set.add(obj);
                                }
                                languageMaps.put(locale, set);
                        } catch (JsonIOException | JsonSyntaxException | IOException e) {
                                logger.error("Unable to load locale", e);
                        }
                }

                return languageMaps.get(locale);



        }

        /**
         * @return the baseDirectory
         */
        public Resource getBaseDirectory() {
                return baseDirectory;
        }

        /**
         * @param baseDirectory the baseDirectory to set
         */
        public void setBaseDirectory(Resource baseDirectory) {
                this.baseDirectory = baseDirectory;
        }

}