/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch licenses this file to you 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.elasticsearch.search.suggest;

import com.google.common.collect.ImmutableMap;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.util.CharsRefBuilder;
import org.elasticsearch.ElasticsearchException;
import org.elasticsearch.common.component.AbstractComponent;
import org.elasticsearch.common.inject.Inject;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.search.SearchParseElement;
import org.elasticsearch.search.SearchPhase;
import org.elasticsearch.search.internal.SearchContext;
import org.elasticsearch.search.suggest.Suggest.Suggestion;
import org.elasticsearch.search.suggest.Suggest.Suggestion.Entry;
import org.elasticsearch.search.suggest.Suggest.Suggestion.Entry.Option;
import org.elasticsearch.search.suggest.SuggestionSearchContext.SuggestionContext;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

/**
 */
public class SuggestPhase extends AbstractComponent implements SearchPhase {

    private final SuggestParseElement parseElement;

    @Inject
    public SuggestPhase(Settings settings, SuggestParseElement suggestParseElement) {
        super(settings);
        this.parseElement = suggestParseElement;
    }

    @Override
    public Map<String, ? extends SearchParseElement> parseElements() {
        ImmutableMap.Builder<String, SearchParseElement> parseElements = ImmutableMap.builder();
        parseElements.put("suggest", parseElement);
        return parseElements.build();
    }

    public SuggestParseElement parseElement() {
        return parseElement;
    }

    @Override
    public void preProcess(SearchContext context) {
    }

    @Override
    public void execute(SearchContext context) throws ElasticsearchException {
        final SuggestionSearchContext suggest = context.suggest();
        if (suggest == null) {
            return;
        }
        context.queryResult().suggest(execute(suggest, context.searcher()));
    }

    public Suggest execute(SuggestionSearchContext suggest, IndexSearcher searcher) {
        try {
            CharsRefBuilder spare = new CharsRefBuilder();
            final List<Suggestion<? extends Entry<? extends Option>>> suggestions = new ArrayList<>(suggest.suggestions().size());

            for (Map.Entry<String, SuggestionSearchContext.SuggestionContext> entry : suggest.suggestions().entrySet()) {
                SuggestionSearchContext.SuggestionContext suggestion = entry.getValue();
                Suggester<SuggestionContext> suggester = suggestion.getSuggester();
                Suggestion<? extends Entry<? extends Option>> result = suggester.execute(entry.getKey(), suggestion, searcher, spare);
                if (result != null) {
                    assert entry.getKey().equals(result.name);
                    suggestions.add(result);
                }
            }

            return new Suggest(Suggest.Fields.SUGGEST, suggestions);
        } catch (IOException e) {
            throw new ElasticsearchException("I/O exception during suggest phase", e);
        }
    }
}

