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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.ExprContext;
import com.api.jsonata4java.expressions.generated.MappingExpressionParser.Function_callContext;
import com.api.jsonata4java.expressions.generated.MappingExpressionParser.Function_declContext;
import com.api.jsonata4java.expressions.utils.BooleanUtils;
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.BooleanNode;
import com.fasterxml.jackson.databind.node.JsonNodeFactory;

/**
 * From http://docs.jsonata.org/boolean-functions.html
 * 
 * $boolean(arg)
 * 
 * Casts the argument to a Boolean using the following rules:
 * 
 * Boolean: unchanged string: empty false string: non-empty true number: 0 false
 * number: non-zero true null: false array: empty false array: contains a member
 * that casts to true true array: all members cast to false false object: empty
 * false object: non-empty true function: (functions are not currently
 * supported) false
 * 
 */
public class BooleanFunction extends FunctionBase implements Function {

	public static String ERR_BAD_CONTEXT = String.format(Constants.ERR_MSG_BAD_CONTEXT, Constants.FUNCTION_BOOLEAN);
	public static String ERR_ARG2BADTYPE = String.format(Constants.ERR_MSG_ARG2_BAD_TYPE, Constants.FUNCTION_BOOLEAN);

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

		// Retrieve the number of arguments
		JsonNode arg = JsonNodeFactory.instance.nullNode();
		boolean useContext = FunctionUtils.useContextVariable(this, ctx, getSignature());
		int argCount = getArgumentCount(ctx);
		if (useContext) {
			arg = FunctionUtils.getContextVariable(expressionVisitor);
			if (arg != null && (arg.isNull() == false || argCount == 0)) {
				argCount++;
			} else {
				useContext = false;
			}
		}

		// Make sure that we have the right number of arguments
		if (argCount == 1) {
			if (!useContext) {
				arg = FunctionUtils.getValuesListExpression(expressionVisitor, ctx, 0);
			}
			if (arg != null) {
				result = BooleanUtils.convertJsonNodeToBoolean(arg) ? BooleanNode.TRUE : BooleanNode.FALSE;
			} else {
				// special test to see if there is a function that exists with this name
				ExprContext exprCtx = ctx.exprValues().exprList().expr(0);
				if (exprCtx instanceof Function_declContext) {
					result = BooleanNode.FALSE;
				} else if (exprCtx != null) {
					String functionName = exprCtx.getText();
					if (expressionVisitor.getDeclaredFunction(functionName) != null) {
						result = BooleanNode.FALSE;
					} else if (expressionVisitor.getJsonataFunction(functionName) != null) {
						result = BooleanNode.FALSE;
					}
				}
			}
		} 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 anything (or context variable), returns a boolean
		return "";
	}
}