json/src/main/java/org/apache/james/json/DTOConverter.java

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package org.apache.james.json;

import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.function.Function;

import com.github.steveash.guavate.Guavate;
import com.google.common.collect.ImmutableSet;

public class DTOConverter<T, U extends DTO> {

    private final Map<String, DTOModule<? extends T, ? extends U>> typeToModule;
    private final Map<Class<? extends T>, DTOModule<? extends T, ? extends U>> domainClassToModule;

    @SafeVarargs
    public static <T, U extends DTO> DTOConverter<T, U> of(DTOModule<? extends T, ? extends U>... modules) {
        return new DTOConverter<>(ImmutableSet.copyOf(modules));
    }

    public DTOConverter(Set<? extends DTOModule<? extends T, ? extends U>> modules) {
        typeToModule = modules.stream()
            .collect(Guavate.toImmutableMap(
                DTOModule::getDomainObjectType,
                Function.identity()));

        domainClassToModule = modules.stream()
            .collect(Guavate.toImmutableMap(
                DTOModule::getDomainObjectClass,
                Function.identity()));
    }

    @SuppressWarnings("unchecked")
    public Optional<U> toDTO(T domainObject) {
        return Optional
            .ofNullable(domainClassToModule.get(domainObject.getClass()))
            .map(module -> (DTOModule<T, U>) module)
            .map(module -> module.toDTO(domainObject));
    }

    @SuppressWarnings("unchecked")
    public Optional<T> toDomainObject(U dto) {
        String type = dto.getType();
        return Optional
            .ofNullable(typeToModule.get(type))
            .map(module -> (DTOModule<T, U>) module)
            .map(DTOModule::getToDomainObjectConverter)
            .map(convert -> convert.convert(dto));
    }
}