FEELFunction.java

/*
 * Copyright 2016 Red Hat, Inc. and/or its affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.kie.dmn.feel.runtime;

import org.kie.dmn.feel.lang.EvaluationContext;
import org.kie.dmn.feel.lang.Symbol;

import java.util.Arrays;
import java.util.List;

/**
 * An interface for all FEEL functions, custom or built-in
 */
public interface FEELFunction {

    /**
     * Returns the name of the function
     * @return
     */
    String getName();

    /**
     * Returns the Symbol of the function
     * @return
     */
    Symbol getSymbol();

    /**
     * Returns the parameter names for each supported signature.
     *
     * @return a List of Lists of Strings with the parameter names. For
     *         a function with multiple signatures, each element of the
     *         list returns the names of the parameters of one signature.
     *         E.g.:
     *
     *         the substring function has 2 supported signatures:
     *
     *         substring( string, start position )
     *         substring( string, start position, length )
     *
     *         So this method will return:
     *
     *         { { "string", "start position" },
     *           { "string", "start position", "length" } }
     */
    List<List<String>> getParameterNames();

    /**
     * Invokes the function reflectively based on the parameters
     *
     * @param ctx
     * @param params
     * @return
     */
    Object invokeReflectively(EvaluationContext ctx, Object[] params);

}