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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.generated.MappingExpressionParser.Var_recallContext;
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.JsonNodeFactory;
import com.fasterxml.jackson.databind.node.TextNode;

/**
 * From http://docs.jsonata.org/string-functions.html:
 * 
 * $string(arg)
 * 
 * Casts the arg parameter to a string using the following casting rules
 * 
 * Strings are unchanged Functions are converted to an empty string Numeric
 * infinity and NaN throw an error because they cannot be represented as a JSON
 * number All other values are converted to a JSON string using the
 * JSON.stringify function 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
 * 
 * $string(5)=="5" [1..5].$string()==["1", "2", "3", "4", "5"]
 * $string([1..5])=="[1,2,3,4,5]"
 */
public class StringFunction extends FunctionBase implements Function {

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

	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);
			// $string only reads context if no parameters are passed and can print NullNodes
			if (arg != null && argCount == 0) {
				argCount++;
			} else {
				useContext = false;
			}
		}

		// Make sure that we have the right number of arguments
		if (argCount >= 1 && argCount <= 2) {
			if (!useContext) {
				/**
				 * need to peek at the expression context since Function_callContext evaluates
				 * to ""
				 */
				ExprContext exprCtx = ctx.exprValues().exprList().expr(0);
				arg = FunctionUtils.getValuesListExpression(expressionVisitor, ctx, 0);
				if (arg == null) {
					if (exprCtx instanceof Function_callContext || exprCtx instanceof Function_declContext) {
						arg = new TextNode("");
					}
					if (exprCtx instanceof Var_recallContext) {
						String varName = ((Var_recallContext)exprCtx).VAR_ID().getText();
						DeclaredFunction declFct = expressionVisitor.getDeclaredFunction(varName);
						if (declFct != null) {
							arg = new TextNode("");
						} else {
							Function fct = expressionVisitor.getJsonataFunction(varName);
							if (fct != null) {
								arg = new TextNode("");
							} else {
								arg = null;
							}
						}
					}
				}
			}
			if (arg == null || (arg.isNull() && useContext)) {
				return null;
			}
			boolean prettify = false;
			if (argCount == 2) {
				JsonNode arg2 = FunctionUtils.getValuesListExpression(expressionVisitor, ctx, useContext ? 0 : 1);
				if (arg2 != null && arg2.isBoolean()) {
					prettify = BooleanUtils.convertJsonNodeToBoolean(arg2);
				} else {
					throw new EvaluateRuntimeException(ERR_ARG2BADTYPE);
				}
			}
			String asString = ExpressionsVisitor.castString(arg, prettify);
			if (asString == null) {
				result = null;
			} else {
				result = new TextNode(asString);
			}
		} else {
			throw new EvaluateRuntimeException(argCount == 0 ? ERR_BAD_CONTEXT : ERR_ARG2BADTYPE);
		}
		return result;
	}

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

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

	@Override
	public String getSignature() {
		// accepts any value or context, returns a string
		return "";
	}
}