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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.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.JsonNodeFactory;

/**
 * From http://docs.jsonata.org/aggregation-functions.html
 * 
 * $min(array)
 * 
 * Returns the minimum number in an array of numbers. It is an error if the
 * input array contains an item which isn’t a number.
 * 
 * Example
 * 
 * $min([5,1,3,7,4])==1
 * 
 */
public class MinFunction extends FunctionBase implements Function {

	public static String ERR_BAD_CONTEXT = String.format(Constants.ERR_MSG_BAD_CONTEXT, Constants.FUNCTION_MIN);
	public static String ERR_ARG1BADTYPE = String.format(Constants.ERR_MSG_ARG1_BAD_TYPE, Constants.FUNCTION_MIN);
	public static String ERR_ARG2BADTYPE = String.format(Constants.ERR_MSG_ARG2_BAD_TYPE, Constants.FUNCTION_MIN);
	public static final String ERR_ARG_TYPE = String.format(Constants.ERR_MSG_ARG1_MUST_BE_ARRAY_OF_NUMBER,
			Constants.FUNCTION_MIN);

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

		// Retrieve the number of arguments
		JsonNode argArray = JsonNodeFactory.instance.nullNode();
		boolean useContext = FunctionUtils.useContextVariable(ctx, getSignature());
		int argCount = getArgumentCount(ctx);
		if (useContext) {
			argArray = FunctionUtils.getContextVariable(expressionVisitor);
			argCount++;
		}

		// Make sure that we have the right number of arguments
		if (argCount == 1) {
			if (!useContext) {
				argArray = FunctionUtils.getValuesListExpression(expressionVisitor, ctx, 0);
			}
			if (argArray != null) {
				if (argArray.isArray()) {
					// Convert the input node to an ArrayNode and make check that the
					// array is not empty
					ArrayNode items = (ArrayNode) argArray;
					if (items.size() > 0) {
						JsonNode min = null;
						for (JsonNode item : items) {
							if (item.isNumber()) {
								// Check whether the current item is less than the
								// current min
								if (min == null || item.asDouble() < min.asDouble()) {
									min = item;
								}
							} else {
								/*
								 * The input array contains an item that is not a number. Throw a suitable
								 * exception
								 */
								throw new EvaluateRuntimeException(ERR_ARG_TYPE);
							}
						} // FOR

						// Return the node that represents the minimum value
						result = min;
					} else {
						/*
						 * The input array is empty. Throw a suitable exception
						 */
						throw new EvaluateRuntimeException(ERR_ARG_TYPE);
					}
				} else {
					/*
					 * The input argument is not an array. Throw a suitable exception
					 */
					throw new EvaluateRuntimeException(ERR_ARG_TYPE);
				}
			}
		} else {
			throw new EvaluateRuntimeException(argCount == 0 ? ERR_ARG1BADTYPE : ERR_ARG2BADTYPE);
		}

		return result;
	}

	@Override
	public String getSignature() {
		// accepts an array of numbers, returns a number
		return ":n>";
	}
}