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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 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.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
 * 
 * $lookup(object,key)
 * 
 * Returns the value corresponding to the key in the supplied object. It is an
 * error if the input is not an object, and if the key is not a String.
 * 
 * Example
 * 
 * $lookup({"a":1,"b":2},"b")==2
 * 
 */
public class LookupFunction extends FunctionBase implements Function {

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

	public JsonNode invoke(ExpressionsVisitor expressionVisitor, Function_callContext ctx) {
		// Create the variable to return
		JsonNode result = null;

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

		// Make sure that we have the right number of arguments
		if (argCount >= 1 && argCount <= 3) {
			if (!useContext) {
				argObject = FunctionUtils.getValuesListExpression(expressionVisitor, ctx, 0);
			}
			if (argObject == null) {
				return null;
			}
			if (argCount == 2) {
				JsonNode keyObj = FunctionUtils.getValuesListExpression(expressionVisitor, ctx,
						useContext ? 0 : 1);
				if (keyObj == null || !keyObj.isTextual()) {
					throw new EvaluateRuntimeException(ERR_ARG2BADTYPE);
				}
				final String key = keyObj.asText();
				SelectorArrayNode array = new SelectorArrayNode(JsonNodeFactory.instance);
				// Check the type of the argument
				if (argObject.isObject()) {
					ObjectNode obj = (ObjectNode) argObject;
					captureKeyValues(obj, key, array);
					if (array.size() != 1) {
						result = array;
					} else {
						// make singleton
						result = array.get(0);
					}
				} else {
					if (argObject.isArray()) {
						findObjects((ArrayNode)argObject, key, array);
						if (array.size() == 0) {
						   result = null;
						} else if (array.size() != 1) {
							result = array;
						} else {
							// make singleton
							result = array.get(0);
						}
					} else {
						/*
						 * The input argument is not an array. Throw a suitable exception
						 */
						throw new EvaluateRuntimeException(ERR_ARG1BADTYPE);
					}
				}
			} else {
				throw new EvaluateRuntimeException(ERR_ARG2BADTYPE);
			}
		} else {
			throw new EvaluateRuntimeException(argCount == 0 ? ERR_BAD_CONTEXT : ERR_ARG3BADTYPE);
		}

		if (result != null && result.isArray() && result.size() == 0) {
			result = null;
		}
		return result;
	}
	
	static void findObjects(ArrayNode array, String key, ArrayNode result) {
		for (int i=0;i";
	}
}