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package io.virtdata.api;

import io.virtdata.core.DataMapperFunctionMapper;
import io.virtdata.core.ResolvedFunction;

import java.util.List;
import java.util.Optional;

/**
 * 
 * A DataMapperLibrary is an independently loadable library of data mapping functions.
 * 
 */
public interface DataMapperLibrary {

    /**
     * Return the name for this data mapper implementation, as it can be used in spec strings, etc.
     *
     * @return Simple lower-case canonical library name
     */
    String getLibraryName();

    /**
     * Find the implementation for and construct an instance of a data mapper function, as described.
     *
     * @param spec A specifier that describes the type and or parameterization of a data mapping function instance.
     * @param   The result type produced by the data mapping function.
     * @return An optional data mapping function instance
     */
    default  Optional> getDataMapper(String spec) {
        if (canParseSpec(spec)) {
            Optional resolvedFunction = resolveFunction(spec);
            return resolvedFunction
                    .map(ResolvedFunction::getFunctionObject)
                    .map(DataMapperFunctionMapper::map);
        }
        return Optional.empty();
    }

    default  Optional> getOptionalDataMapper(String spec, Class clazz) {
        return Optional.ofNullable(getDataMapper(spec, clazz));
    }

    @SuppressWarnings("unchecked")
    default  DataMapper getDataMapper(String spec, Class clazz) {
        if (!canParseSpec(spec)) {
            return null;
        }
        Optional resolvedFunction = resolveFunction(spec);
        if (!resolvedFunction.isPresent()) {
            return null;
        }
        ResolvedFunction rf = resolvedFunction.get();
        DataMapper