/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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 backtype.storm;
import java.util.Map;

import java.util.Map;

/**
 * Provides functionality for validating configuration fields.
 */
public class ConfigValidation {

    /**
     * Declares methods for validating configuration values.
     */
    public static interface FieldValidator {
        /**
         * Validates the given field.
         * @param name the name of the field.
         * @param field The field to be validated.
         * @throws IllegalArgumentException if the field fails validation.
         */
        public void validateField(String name, Object field) throws IllegalArgumentException;
    }
    
    /**
     * Declares a method for validating configuration values that is nestable.
     */
    public static abstract class NestableFieldValidator implements FieldValidator {
        @Override
        public void validateField(String name, Object field) throws IllegalArgumentException {
            validateField(null, name, field);
        }
        
        /**
         * Validates the given field.
         * @param pd describes the parent wrapping this validator.
         * @param name the name of the field.
         * @param field The field to be validated.
         * @throws IllegalArgumentException if the field fails validation.
         */
        public abstract void validateField(String pd, String name, Object field) throws IllegalArgumentException;
    }

    /**
     * Returns a new NestableFieldValidator for a given class.
     * @param cls the Class the field should be a type of
     * @param nullAllowed whether or not a value of null is valid
     * @return a NestableFieldValidator for that class
     */
    public static NestableFieldValidator fv(final Class cls, final boolean nullAllowed) {
        return new NestableFieldValidator() {
            @Override
            public void validateField(String pd, String name, Object field)
                    throws IllegalArgumentException {
                if (nullAllowed && field == null) {
                    return;
                }
                if (! cls.isInstance(field)) {
                    throw new IllegalArgumentException(
                        pd + name + " must be a " + cls.getName() + ". ("+field+")");
                }
            }
        };
    }
    
    /**
     * Returns a new NestableFieldValidator for a List of the given Class.
     * @param cls the Class of elements composing the list
     * @param nullAllowed whether or not a value of null is valid
     * @return a NestableFieldValidator for a list of the given class
     */
    public static NestableFieldValidator listFv(Class cls, boolean nullAllowed) {
      return listFv(fv(cls, false), nullAllowed);
    }
    
    /**
     * Returns a new NestableFieldValidator for a List where each item is validated by validator.
     * @param validator used to validate each item in the list
     * @param nullAllowed whether or not a value of null is valid
     * @return a NestableFieldValidator for a list with each item validated by a different validator.
     */
    public static NestableFieldValidator listFv(final NestableFieldValidator validator, 
            final boolean nullAllowed) {
        return new NestableFieldValidator() {
            @Override
            public void validateField(String pd, String name, Object field)
                    throws IllegalArgumentException {
                if (nullAllowed && field == null) {
                    return;
                }
                if (field instanceof Iterable) {
                    for (Object e : (Iterable)field) {
                        validator.validateField(pd + "Each element of the list ", name, e);
                    }
                    return;
                }
                throw new IllegalArgumentException(
                        "Field " + name + " must be an Iterable but was " +
                        ((field == null) ? "null" :  ("a " + field.getClass())));
            }
        };
    }

    /**
     * Returns a new NestableFieldValidator for a Map of key to val.
     * @param key the Class of keys in the map
     * @param val the Class of values in the map
     * @param nullAllowed whether or not a value of null is valid
     * @return a NestableFieldValidator for a Map of key to val
     */
    public static NestableFieldValidator mapFv(Class key, Class val, 
            boolean nullAllowed) {
        return mapFv(fv(key, false), fv(val, false), nullAllowed);
    }
 
    /**
     * Returns a new NestableFieldValidator for a Map.
     * @param key a validator for the keys in the map
     * @param val a validator for the values in the map
     * @param nullAllowed whether or not a value of null is valid
     * @return a NestableFieldValidator for a Map
     */   
    public static NestableFieldValidator mapFv(final NestableFieldValidator key, 
            final NestableFieldValidator val, final boolean nullAllowed) {
        return new NestableFieldValidator() {
            @SuppressWarnings("unchecked")
            @Override
            public void validateField(String pd, String name, Object field)
                    throws IllegalArgumentException {
                if (nullAllowed && field == null) {
                    return;
                }
                if (field instanceof Map) {
                    for (Map.Entry<Object, Object> entry: ((Map<Object, Object>)field).entrySet()) {
                      key.validateField("Each key of the map ", name, entry.getKey());
                      val.validateField("Each value in the map ", name, entry.getValue());
                    }
                    return;
                }
                throw new IllegalArgumentException(
                        "Field " + name + " must be a Map");
            }
        };
    }
    
    /**
     * Validates a list of Numbers.
     */
    public static Object NumbersValidator = listFv(Number.class, true);

    /**
     * Validates a list of Strings.
     */
    public static Object StringsValidator = listFv(String.class, true);
    
    /**
     * Validates a map of Strings to Numbers.
     */
    public static Object MapOfStringToNumberValidator = mapFv(String.class, Number.class, true);

    /**
     * Validates is a list of Maps.
     */
    public static Object MapsValidator = listFv(Map.class, true);

    /**
     * Validates a power of 2.
     */
    public static Object PowerOf2Validator = new FieldValidator() {
        @Override
        public void validateField(String name, Object o) throws IllegalArgumentException {
            if (o == null) {
                // A null value is acceptable.
                return;
            }
            final long i;
            if (o instanceof Number &&
                    (i = ((Number)o).longValue()) == ((Number)o).doubleValue())
            {
                // Test whether the integer is a power of 2.
                if (i > 0 && (i & (i-1)) == 0) {
                    return;
                }
            }
            throw new IllegalArgumentException("Field " + name + " must be a power of 2.");
        }
    };

    /**
     * Validates a positive integer.
     */
    public static Object PositiveIntegerValidator = new FieldValidator() {
        @Override
        public void validateField(String name, Object o) throws IllegalArgumentException {
            if (o == null) {
                // A null value is acceptable.
                return;
            }
            final long i;
            if (o instanceof Number &&
                    (i = ((Number)o).longValue()) == ((Number)o).doubleValue())
            {
                if (i > 0) {
                    return;
                }
            }
            throw new IllegalArgumentException("Field " + name + " must be a positive integer.");
        }
    };

    /**
     * Validates Kryo Registration
     */
    public static Object KryoRegValidator = new FieldValidator() {
        @Override
        public void validateField(String name, Object o) throws IllegalArgumentException {
            if (o == null) {
                // A null value is acceptable.
                return;
            }
            if (o instanceof Iterable) {
                for (Object e : (Iterable)o) {
                    if (e instanceof Map) {
                        for (Map.Entry<Object,Object> entry: ((Map<Object,Object>)e).entrySet()) {
                            if (!(entry.getKey() instanceof String) ||
                                !(entry.getValue() instanceof String)) {
                                throw new IllegalArgumentException(
                                    "Each element of the list " + name + " must be a String or a Map of Strings");
                            }
                        }
                    } else if (!(e instanceof String)) {
                        throw new IllegalArgumentException(
                                "Each element of the list " + name + " must be a String or a Map of Strings");
                    }
                }
                return;
            }
            throw new IllegalArgumentException(
                    "Field " + name + " must be an Iterable containing only Strings or Maps of Strings");
        }
    };

    /**
     * Validates a String or a list of Strings
     */
    public static Object StringOrStringListValidator = new FieldValidator() {

        private FieldValidator fv = listFv(String.class, false);

        @Override
        public void validateField(String name, Object o) throws IllegalArgumentException {
            if (o == null || o instanceof String) {
                // A null value or a String value is acceptable
                return;
            }
            this.fv.validateField(name, o);
        }
    };
}