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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 java.util.Iterator;

import com.api.jsonata4java.expressions.EvaluateRuntimeException;
import com.api.jsonata4java.expressions.ExpressionsVisitor;
import com.api.jsonata4java.expressions.generated.MappingExpressionParser.Function_callContext;
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;
import com.fasterxml.jackson.databind.node.ObjectNode;

/**
 * From http://docs.jsonata.org/object-functions.html
 * 
 * $merge(array)
 * 
 * Returns the merger of the objects in an array of objects. It is an error if
 * the input is not an array of objects.
 * 
 * Example
 * 
 * $merge([{"a":1},{"b":2}])=={"a":1, "b":2}
 * 
 */
public class MergeFunction extends FunctionBase implements Function {

	private static final long serialVersionUID = -99966498930256770L;

	public static String ERR_BAD_CONTEXT = String.format(Constants.ERR_MSG_BAD_CONTEXT, Constants.FUNCTION_MERGE);
	public static String ERR_ARG1BADTYPE = String.format(Constants.ERR_MSG_ARG1_BAD_TYPE, Constants.FUNCTION_MERGE);
	public static String ERR_ARG2BADTYPE = String.format(Constants.ERR_MSG_ARG2_BAD_TYPE, Constants.FUNCTION_MERGE);
	public static String ERR_ARG1_MUST_BE_OBJECT_ARRAY = String.format(Constants.ERR_MSG_ARG1_MUST_BE_ARRAY_OF_OBJECTS,
			Constants.FUNCTION_MERGE);

	public JsonNode invoke(ExpressionsVisitor expressionVisitor, Function_callContext ctx) {
		// Create the variable to return
		ObjectNode result = JsonNodeFactory.instance.objectNode();

		// 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);
			if (argArray != null && argArray.isNull() == false) {
				argCount++;
			} else {
				useContext = false;
			}
		}

		// Make sure that we have the right number of arguments
		if (argCount == 1) {
			if (!useContext) {
				argArray = FunctionUtils.getValuesListExpression(expressionVisitor, ctx, 0);
			}
			String key = null;
			if (argArray == null) {
				return null;
			}
			if (argArray.isArray()) {
				ArrayNode array = (ArrayNode) argArray;
				for (int i = 0; i < array.size(); i++) {
					JsonNode obj = array.get(i);
					if (obj.isObject()) {
						ObjectNode cell = (ObjectNode) obj;
						for (Iterator it = cell.fieldNames(); it.hasNext();) {
							key = it.next();
							result.set(key, cell.get(key));
						}
					} else {
						throw new EvaluateRuntimeException(ERR_ARG1_MUST_BE_OBJECT_ARRAY);
					}
				}
			} else {
				if (argArray.isObject()) {
					result = (ObjectNode) argArray;
				} else {
					/*
					 * The input argument is not an array. Throw a suitable exception
					 */
					throw new EvaluateRuntimeException(ERR_ARG1BADTYPE);
				}
			}
		} else {
			throw new EvaluateRuntimeException(argCount == 0 ? ERR_ARG1BADTYPE : ERR_ARG2BADTYPE);
		}

		return result;
	}

	@Override
	public int getMaxArgs() {
		return 1;
	}
	@Override
	public int getMinArgs() {
		return 1;
	}

	@Override
	public String getSignature() {
		// accepts an array of objects, returns an object
		return ":o>";
	}
}
 















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