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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.time.Instant;

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.JsonNodeFactory;
import com.fasterxml.jackson.databind.node.TextNode;

/**
 * From http://docs.jsonata.org/string-functions.html:
 * 
 * $fromMillis(number)
 * 
 * Convert a number representing milliseconds since the Unix Epoch (1 January,
 * 1970 UTC) to a timestamp string in the ISO 8601 format.
 * 
 * Examples
 * 
 * $fromMillis(1510067557121)=="2017-11-07T15:12:37.121Z"
 * 
 */
public class FromMillisFunction extends FunctionBase implements Function {

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

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

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

		// Make sure that we have the right number of arguments
		if (argCount == 1) {
			if (!useContext) {
				argNumber = FunctionUtils.getValuesListExpression(expressionVisitor, ctx, 0);
			}
			if (argNumber == null) {
				return null;
			}
			if (argNumber.isNumber()) {
				final Long millis = argNumber.asLong();
				Instant instant = Instant.ofEpochMilli(millis);
				result = new TextNode(instant.toString());
			} else {
				throw new EvaluateRuntimeException(ERR_ARG1BADTYPE);
			}
		} else {
			throw new EvaluateRuntimeException(argCount == 0 ? ERR_BAD_CONTEXT : ERR_ARG2BADTYPE);
		}

		return result;
	}

	@Override
	public int getMaxArgs() {
		return 3;
	}
	@Override
	public int getMinArgs() {
		return 0; // account for context variable
	}

	@Override
	public String getSignature() {
		// accepts a number (or context variable), an optional string, another optional
		// string, returns a number
		return "";
	}
}