/// Copyright (c) 2014, 2016 ControlsFX
/// All rights reserved.
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/// * Redistributions of source code must retain the above copyright
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/// notice, this list of conditions and the following disclaimer in the
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/// names of its contributors may be used to endorse or promote products
/// derived from this software without specific prior written permission.
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package org.jabref.gui.autocompleter;

import java.util.Collection;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import com.google.common.base.Equivalence;
import org.controlsfx.control.textfield.AutoCompletionBinding.ISuggestionRequest;

/// This is a simple implementation of a generic suggestion provider callback.
///
/// @param <T> Type of suggestions
public abstract class SuggestionProvider<T> {

    public final Collection<T> provideSuggestions(ISuggestionRequest request) {
        if (!request.getUserText().isEmpty()) {
            Comparator<T> comparator = getComparator();
            Equivalence<T> equivalence = getEquivalence();
            return getSource().filter(candidate -> isMatch(candidate, request))
                              .map(equivalence::wrap) // Need to do a bit of acrobatic as there is no distinctBy method
                              .distinct()
                              .limit(10)
                              .map(Equivalence.Wrapper::get)
                              .sorted(comparator)
                              .collect(Collectors.toList());
        } else {
            return List.of();
        }
    }

    protected abstract Equivalence<T> getEquivalence();

    public List<T> getPossibleSuggestions() {
        Comparator<T> comparator = getComparator().reversed();
        Equivalence<T> equivalence = getEquivalence();
        return getSource().map(equivalence::wrap) // Need to do a bit of acrobatic as there is no distinctBy method
                          .distinct()
                          .map(Equivalence.Wrapper::get)
                          .sorted(comparator)
                          .collect(Collectors.toList());
    }

    /// Get the comparator to order the suggestions
    protected abstract Comparator<T> getComparator();

    /// Check the given candidate is a match (ie a valid suggestion)
    protected abstract boolean isMatch(T candidate, ISuggestionRequest request);

    public abstract Stream<T> getSource();
}
