# NumericValidator.java

    /*
     * Copyright (c) 2019, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
     *
     * WSO2 Inc. licenses this file to you 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 org.apache.synapse.commons.json.jsonprocessor.validators;

    import com.google.gson.JsonArray;
    import com.google.gson.JsonObject;
    import com.google.gson.JsonPrimitive;
    import org.apache.synapse.commons.json.jsonprocessor.constants.ValidatorConstants;
    import org.apache.synapse.commons.json.jsonprocessor.exceptions.ParserException;
    import org.apache.synapse.commons.json.jsonprocessor.exceptions.ValidatorException;
    import org.apache.synapse.commons.json.jsonprocessor.utils.DataTypeConverter;
    import org.apache.synapse.commons.json.jsonprocessor.utils.JsonProcessorUtils;

    /**
     * validate numeric instances according to the given schema.
     */
    public class NumericValidator {

        private static final String INTEGER_STRING = "integer";
        private static final String MINIMUM_VALUE = "minimum";
        private static final String MAXIMUM_VALUE = "maximum";
        private static final String EXCLUSIVE_MINIMUM = "exclusiveMinimum";
        private static final String EXCLUSIVE_MAXIMUM = "exclusiveMaximum";
        private static final String MULTIPLE_OF = "multipleOf";

        // use without instantiating.
        private NumericValidator() {

        }

        /**
         * Take JSON schema, number as a string input and validate.
         *
         * @param inputObject JSON schema.
         * @param value       numeric value
         * @return JsonPrimitive contains a number
         * @throws ParserException    Exception occurred in data type conversions.
         * @throws ValidatorException Exception occurred in schema validations.
         */
        public static JsonPrimitive validateNumeric(JsonObject inputObject, String value) throws ParserException,
                ValidatorException {
            Double multipleOf;
            if (value == null) {
                throw new ValidatorException("Expected a number but found null");
            }
            //replacing enclosing quotes
            value = JsonProcessorUtils.replaceEnclosingQuotes(value);
            if (isNumeric(value)) {
                String type = null;
                if (inputObject.has(ValidatorConstants.TYPE_KEY)) {
                    type = JsonProcessorUtils.replaceEnclosingQuotes(
                            inputObject.get(ValidatorConstants.TYPE_KEY).getAsString());
                }
                // handling multiples of condition
                Double doubleValue = DataTypeConverter.convertToDouble(value);
                if (inputObject.has(MULTIPLE_OF)) {
                    multipleOf = DataTypeConverter.convertToDouble(JsonProcessorUtils.replaceEnclosingQuotes(
                            inputObject.get(MULTIPLE_OF).getAsString()));
                    if (doubleValue % multipleOf != 0) {
                        throw new ValidatorException("Number " + value + " is not a multiple of " +
                                "" + multipleOf + ". multipleOf constraint in " + inputObject.toString() + " is violated " +
                                "by the input " + value);
                    }
                }
                // handling maximum and minimum
                if (inputObject.has(MINIMUM_VALUE)) {
                    String minimumString = JsonProcessorUtils.replaceEnclosingQuotes(
                            inputObject.get(MINIMUM_VALUE).getAsString());
                    if (!minimumString.isEmpty() && doubleValue < DataTypeConverter.convertToDouble(minimumString)) {
                        throw new ValidatorException("Number " + value + " is less than the " +
                                "minimum allowed value" + ". minimumValue constraint in " + inputObject.toString() +
                                " is violated by the input " + ": " + value);
                    }
                }
                if (inputObject.has(MAXIMUM_VALUE)) {
                    String maximumString = JsonProcessorUtils.replaceEnclosingQuotes(
                            inputObject.get(MAXIMUM_VALUE).getAsString());
                    if (!maximumString.isEmpty() && doubleValue > DataTypeConverter.convertToDouble(maximumString)) {
                        throw new ValidatorException("Number " + value + " is greater than the " +
                                "maximum allowed value. maximumValue constraint in " + inputObject.toString() +
                                " is violated by the input " + ": " + value);
                    }
                }
                // handling exclusive maximum and minimum
                if (inputObject.has(EXCLUSIVE_MINIMUM)) {
                    String minimumString = JsonProcessorUtils.replaceEnclosingQuotes(
                            inputObject.get(EXCLUSIVE_MINIMUM).getAsString());
                    if (!minimumString.isEmpty() && doubleValue <= DataTypeConverter.convertToDouble(minimumString)) {
                        throw new ValidatorException("Number " + value + " is less than the " +
                                "minimum allowed value. ExclusiveMinimum constraint in " + inputObject.toString() +
                                " is violated by the " + "input : " + value );
                    }
                }
                if (inputObject.has(EXCLUSIVE_MAXIMUM)) {
                    String maximumString = JsonProcessorUtils.replaceEnclosingQuotes(
                            inputObject.get(EXCLUSIVE_MAXIMUM).getAsString());
                    if (!maximumString.isEmpty() && doubleValue >= DataTypeConverter.convertToDouble(maximumString)) {
                        throw new ValidatorException("Number " + value + " is greater than the " +
                                "maximum allowed value. ExclusiveMaximum constraint in " +
                                inputObject.toString() + " is violated by the " + "input : " + value);
                    }
                }
                // Enum validations
                if (inputObject.has(ValidatorConstants.ENUM)) {
                    JsonArray enumElements = inputObject.getAsJsonArray(ValidatorConstants.ENUM);
                    if (enumElements.size() > 0 && !enumElements.contains(new JsonPrimitive(doubleValue))) {
                        throw new ValidatorException("Number \"" + value + "\" not contains any " +
                                "element from the enum. Input " + value + " not contains any value from the enum in " +
                                inputObject.toString());
                    }
                }
                //Const validation
                if (inputObject.has(ValidatorConstants.CONST) && !doubleValue.equals(inputObject.getAsJsonPrimitive
                        (ValidatorConstants.CONST).getAsDouble())) {
                    throw new ValidatorException("Number \"" + value + "\" is not equal to the " +
                            "const value input " + value + " not contains the const defined in " + inputObject.toString());
                }
                // convert to integer of give value is a float
                if (INTEGER_STRING.equals(type)) {
                    return new JsonPrimitive(DataTypeConverter.convertToInt(value));
                } else {
                    // this condition address both type number and empty json schemas
                    return new JsonPrimitive(doubleValue);
                }
            }
            throw new ParserException("\"" + value + "\"" + " is not a number. " +
                    "A number expected in the schema " + inputObject.toString() + " but received " + value);
        }

        /**
         * Check whether a given number is numeric. (alternative :- commons-lang3 isCreatable())
         * @param str input string.
         * @return number or not.
         */
        private static boolean isNumeric(String str) {
            try {
                Double.parseDouble(str);
            } catch (NumberFormatException nfe) {
                return false;
            }
            return true;
        }
    }