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package com.google.refine.browsing.facets;

import java.util.Optional;
import java.util.Set;

import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonSubTypes;
import com.fasterxml.jackson.annotation.JsonSubTypes.Type;
import com.fasterxml.jackson.annotation.JsonTypeInfo;

import com.google.refine.model.Project;

/**
 * Represents the configuration of a facet, as stored in the engine configuration and in the JSON serialization of
 * operations. It does not contain the actual values displayed by the facet.
 * 
 * @author Antonin Delpeuch
 *
 */
@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type")
@JsonSubTypes({
        @Type(value = ListFacet.ListFacetConfig.class, name = "list"),
        @Type(value = RangeFacet.RangeFacetConfig.class, name = "range"),
        @Type(value = TimeRangeFacet.TimeRangeFacetConfig.class, name = "timerange"),
        @Type(value = TextSearchFacet.TextSearchFacetConfig.class, name = "text"),
        @Type(value = ScatterplotFacet.ScatterplotFacetConfig.class, name = "scatterplot") })
public interface FacetConfig {

    /**
     * Instantiates the given facet on a particular project.
     * 
     * @param project
     * @return a computed facet on the given project.
     */
    public Facet apply(Project project);

    /**
     * The facet type as stored in json.
     */
    @JsonIgnore // already included by @JsonTypeInfo
    public String getJsonType();

    /**
     * Checks that this facet is correctly configured (such as that expressions are syntactically correct and that
     * options are not contradictory). This should not be done in the constructor, as it would endanger the
     * deserialization.
     * 
     * @throws IllegalArgumentException
     *             if any parameter is missing or inconsistent
     */
    public default void validate() {
    }

    /**
     * Returns an approximation of the names of the columns this facet depends on. This approximation is designed to be
     * safe: if a set of column names is returned, then the expression does not read any other column than the ones
     * mentioned, regardless of the data it is executed on.
     *
     * @return {@link Optional#empty()} if the columns could not be isolated: in this case, the facet might depend on
     *         all columns in the project. Note that this is different from returning an empty set, which means that the
     *         facet's evaluation does not depend on any column.
     */
    @JsonIgnore
    public default Optional<Set<String>> getColumnDependencies() {
        return Optional.empty();
    }
}
