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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 java.util.StringJoiner;

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.TextNode;

/**
 * From http://docs.jsonata.org/string-functions.html:
 * 
 * $join(array[, separator])
 * 
 * Joins an array of component strings into a single concatenated string with
 * each component string separated by the optional separator parameter.
 * 
 * It is an error if the input array contains an item which isn’t a string.
 * 
 * If separator is not specified, then it is assumed to be the empty string,
 * i.e. no separator between the component strings. It is an error if separator
 * is not a string.
 * 
 * Examples
 * 
 * $join(['a','b','c'])=="abc" $split("too much, punctuation. hard; to read",
 * /[ ,.;]+/, 3) ~> $join(', ')=="too, much, punctuation"
 * 
 */
public class JoinFunction extends FunctionBase implements Function {

	public static String ERR_BAD_CONTEXT = String.format(Constants.ERR_MSG_BAD_CONTEXT, Constants.FUNCTION_JOIN);
	public static String ERR_ARG2BADTYPE = String.format(Constants.ERR_MSG_ARG2_BAD_TYPE, Constants.FUNCTION_JOIN);
	public static String ERR_ARG3BADTYPE = String.format(Constants.ERR_MSG_ARG3_BAD_TYPE, Constants.FUNCTION_JOIN);
	public static String ERR_MSG_ARG1_ARR_STR = String.format(Constants.ERR_MSG_ARG1_ARR_STR, Constants.FUNCTION_JOIN);

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

		// Retrieve the number of arguments
		JsonNode argArray = null;
		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 || argCount == 2) {
			if (!useContext) {
				argArray = FunctionUtils.getValuesListExpression(expressionVisitor, ctx, 0);
			}
			if (argArray == null) {
				return null;
			}
			if (!argArray.isArray()) {
			   if (!argArray.isTextual()) {
			      throw new EvaluateRuntimeException(ERR_MSG_ARG1_ARR_STR);
			   }
			   ArrayNode newArray = JsonNodeFactory.instance.arrayNode();
			   newArray.add(argArray);
			   argArray = newArray;
			}

			// Read the separator argument, if present
			String separator = "";
			if (argCount == 2) {
				final JsonNode argSeparator = FunctionUtils.getValuesListExpression(expressionVisitor, ctx,
						useContext ? 0 : 1);
				if (argSeparator != null) {
					if (argSeparator.isTextual()) {
						separator = argSeparator.textValue();
					} else {
						throw new EvaluateRuntimeException(ERR_ARG2BADTYPE);
					}
				}
			}

			// Join the elements of the array argument
			StringJoiner stringJoiner = new StringJoiner(separator);
			Iterator elements = ((ArrayNode) argArray).elements();
			while (elements.hasNext()) {
				JsonNode element = elements.next();
				if (element.isTextual()) {
					stringJoiner.add(element.asText());
				} else if (element.isArray()){
				   for (Iteratorit = ((ArrayNode)element).iterator();it.hasNext();) {
				      stringJoiner.add(it.next().textValue());
				   }
				} else {
					throw new EvaluateRuntimeException(ERR_MSG_ARG1_ARR_STR);
				}
			} // WHILE

			// Create the result from the joined string
			result = new TextNode(stringJoiner.toString());
		} else {
			if (argCount != 0 && argArray == null) {
				return null;
			}
			throw new EvaluateRuntimeException(
					argCount == 0 ? ERR_BAD_CONTEXT : argCount == 1 ? ERR_MSG_ARG1_ARR_STR : ERR_ARG3BADTYPE);
		}

		return result;
	}

	@Override
	public int getMaxArgs() {
		return 2;
	}
	@Override
	public int getMinArgs() {
		return 0; // account for context variable
	}

	@Override
	public String getSignature() {
		// accepts an array of strings, an optional string, returns a string
		return "s?:s>";
	}
}