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Port of jsonata.js to Java to enable rules for JSON content
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/**
 * (c) Copyright 2018, 2019 IBM Corporation
 * 1 New Orchard Road, 
 * Armonk, New York, 10504-1722
 * United States
 * +1 914 499 1900
 * support: Nathaniel Mills [email protected]
 *
 * 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 com.api.jsonata4java.expressions.functions;

import org.antlr.v4.runtime.ParserRuleContext;

import com.api.jsonata4java.expressions.EvaluateRuntimeException;
import com.api.jsonata4java.expressions.ExpressionsVisitor;
import com.api.jsonata4java.expressions.ExpressionsVisitor.SelectorArrayNode;
import com.api.jsonata4java.expressions.generated.MappingExpressionParser.Fct_chainContext;
import com.api.jsonata4java.expressions.generated.MappingExpressionParser.Function_callContext;
import com.api.jsonata4java.expressions.utils.ArrayUtils;
import com.api.jsonata4java.expressions.utils.Constants;
import com.api.jsonata4java.expressions.utils.FunctionUtils;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.JsonNodeFactory;

public class AppendFunction extends FunctionBase implements Function {

	private static final long serialVersionUID = -1826593618672666459L;

	public static String ERR_BAD_CONTEXT = String.format(Constants.ERR_MSG_BAD_CONTEXT, Constants.FUNCTION_APPEND);
	public static String ERR_ARG1BADTYPE = String.format(Constants.ERR_MSG_ARG1_BAD_TYPE, Constants.FUNCTION_APPEND);
	public static String ERR_ARG2BADTYPE = String.format(Constants.ERR_MSG_ARG2_BAD_TYPE, Constants.FUNCTION_APPEND);
	public static String ERR_ARG3BADTYPE = String.format(Constants.ERR_MSG_ARG3_BAD_TYPE, Constants.FUNCTION_APPEND);

	public JsonNode invoke(ExpressionsVisitor expressionVisitor, Function_callContext ctx) {

		SelectorArrayNode result = new SelectorArrayNode(JsonNodeFactory.instance);

		// Retrieve the number of arguments
		JsonNode argArray = JsonNodeFactory.instance.nullNode();
		boolean useContext = FunctionUtils.useContextVariable(this, ctx, getSignature());
		int argCount = getArgumentCount(ctx);
		if (useContext) {
			argArray = FunctionUtils.getContextVariable(expressionVisitor);
			ParserRuleContext prc = ctx.getParent();
			if ((prc != null && prc instanceof Fct_chainContext) || (argArray != null && argArray.isNull() == false)) {
				argCount++;
			} else {
				useContext = false;
			}
		}

		// Make sure that we have the right number of arguments
		if (argCount == 2) {
			if (!useContext) {
				argArray = FunctionUtils.getValuesListExpression(expressionVisitor, ctx, 0);
			}
			JsonNode arg2Array = FunctionUtils.getValuesListExpression(expressionVisitor, ctx, useContext ? 0 : 1);

			ArrayNode a = null;
			if (argArray != null) {
				a = ArrayUtils.ensureArray(argArray);
			} else {
				// TODO: remove this once jsonata is updated
				return arg2Array;
			}
			ArrayNode b = null;
			if (arg2Array != null) {
				b = ArrayUtils.ensureArray(arg2Array);
			} else {
				// TODO: remove this once jsonata is updated
				return argArray;
			}

			if (a != null) {
				result.addAll(a);
			}
			if (b != null) {
				result.addAll(b);
			}

		} else {
			throw new EvaluateRuntimeException(
					argCount == 0 ? ERR_BAD_CONTEXT : argCount == 1 ? ERR_ARG2BADTYPE : ERR_ARG3BADTYPE);
		}

		return result;
	}

	@Override
	public String getSignature() {
		// accepts anything, anything, returns an array
		return "";
	}

	@Override
	public int getMaxArgs() {
		return 2;
	}
	@Override
	public int getMinArgs() {
		return 2;
	}

}