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package angry1980.audio.dao;

import com.google.common.collect.ImmutableList;

import java.util.Collection;
import java.util.Objects;
import java.util.Optional;
import java.util.stream.Collectors;

public interface DAO {

    default Optional get(long  id){
        return Optional.ofNullable(tryToGet(id));
    }

    //to support java versions less then 8
    T tryToGet(long id);

    //todo: use paging
    default Collection getAllOrEmpty(){
        return getAll().orElseGet(ImmutableList::of);
    }

    default Optional> getAll(){
        return Optional.ofNullable(tryToGetAll());
    }

    //to support java versions less then 8
    Collection tryToGetAll();

    default Optional create(T entity){
        return Optional.of(tryToCreate(entity));
    }

    default Optional> createAll(Collection entities){
        return Optional.ofNullable(entities)
                .map(this::tryToCreateAll);
    }

    //to support java versions less then 8
    default Collection tryToCreateAll(Collection entities){
        return entities.stream()
                .map(this::tryToCreate)
                .filter(Objects::nonNull)
                .collect(Collectors.toList());
    }

    //to support java versions less then 8
    T tryToCreate(T entity);

}