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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 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.api.jsonata4java.expressions.utils.NumberUtils;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.node.JsonNodeFactory;
import com.fasterxml.jackson.databind.node.LongNode;

/**
 * http://docs.jsonata.org/numeric-functions.html
 * 
 * Casts the arg parameter to a number using the following casting rules:
 * 
 * - Numbers are unchanged - Strings that contain a sequence of characters that
 * represent a legal JSON number are converted to that number - All other values
 * cause an error to be thrown.
 * 
 * If arg is not specified (i.e. this function is invoked with no arguments),
 * then the context value is used as the value of arg.
 * 
 * Examples
 * 
 * $number("5")==5 ["1", "2", "3", "4", "5"].$number()==[1, 2, 3, 4, 5]
 * 
 */
public class NumberFunction extends FunctionBase implements Function {

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

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

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

		// Make sure that we have the right number of arguments
		if (argCount == 1 || useContext) {
			if (!useContext) {
				argString = FunctionUtils.getValuesListExpression(expressionVisitor, ctx, 0);
			}
			if (argString == null) {
				return null;
			}
			// Check the type of the argument
			if (argString.isObject()) {
				throw new EvaluateRuntimeException(ERR_ARG1BADTYPE);
			} else if (argString.isTextual()) {
				/*
				 * For consistency with the JavaScript implementation of JSONata, we limit the
				 * size of the numbers that we handle to be within the range Double.MAX_VALUE
				 * and -Double.MAX_VALUE. If we did not do this we would need to implement a lot
				 * of extra code to handle BigInteger and BigDecimal. The
				 * NumberUtils::convertNumberToValueNode will check whether the number is within
				 * the valid range and throw a suitable exception if it is not.
				 */
				result = NumberUtils.convertNumberToValueNode(argString.asText());
			} else if (argString.isNumber()) {
				/*
				 * The argument is already a number... and we have already checked whether it is
				 * within the valid range when it was parsed by the
				 * ExpressionVisitor::visitNumber method. Simply return the argument unchanged.
				 */
				result = argString;
			} else if (argString.isArray()) {
				throw new EvaluateRuntimeException(ERR_ARG1BADTYPE);
			} else if (argString.isBoolean()) {
				result = argString.asBoolean() ? new LongNode(1) : new LongNode(0);
			} else {
				// The argument is a neither a number or a string. Throw a
				// suitable exception.
				throw new EvaluateRuntimeException(ERR_ARG1BADTYPE);
			}
		} else {
			throw new EvaluateRuntimeException(argCount == 0 ? ERR_BAD_CONTEXT : ERR_ARG2BADTYPE);
		}
		
		return result;
	}

	@Override
	public int getMaxArgs() {
		return 1;
	}
	@Override
	public int getMinArgs() {
		return 0; // account for context variable
	}

	@Override
	public String getSignature() {
		// accepts a number or string or boolean (or context variable), returns a number
		return "<(nsb)-:n>";
	}
}