/*
 * Copyright 1999-2018 Alibaba Group Holding Ltd.
 *
 * 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.alibaba.nacos.common.utils;

import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;

/**
 * Copy from {@link org.apache.commons.collections}.
 *
 * @author <a href="mailto:liaochuntao@live.com">liaochuntao</a>
 */
public final class CollectionUtils {
    
    /**
     * Constant to avoid repeated object creation.
     */
    private static final Integer INTEGER_ONE = 1;

    private CollectionUtils() {
    }
    
    /**
     * Returns the <code>index</code>-th value in <code>object</code>, throwing
     * <code>IndexOutOfBoundsException</code> if there is no such element or
     * <code>IllegalArgumentException</code> if <code>object</code> is not an
     * instance of one of the supported types.
     *
     * <p>The supported types, and associated semantics are:
     * <ul>
     * <li> Map -- the value returned is the <code>Map.Entry</code> in position
     *      <code>index</code> in the map's <code>entrySet</code> iterator,
     *      if there is such an entry.</li>
     * <li> List -- this method is equivalent to the list's get method.</li>
     * <li> Array -- the <code>index</code>-th array entry is returned,
     *      if there is such an entry; otherwise an <code>IndexOutOfBoundsException</code>
     *      is thrown.</li>
     * <li> Collection -- the value returned is the <code>index</code>-th object
     *      returned by the collection's default iterator, if there is such an element.</li>
     * <li> Iterator or Enumeration -- the value returned is the
     *      <code>index</code>-th object in the Iterator/Enumeration, if there
     *      is such an element.  The Iterator/Enumeration is advanced to
     *      <code>index</code> (or to the end, if <code>index</code> exceeds the
     *      number of entries) as a side effect of this method.</li>
     * </ul>
     *
     * @param object the object to get a value from
     * @param index  the index to get
     * @return the object at the specified index
     * @throws IndexOutOfBoundsException if the index is invalid
     * @throws IllegalArgumentException  if the object type is invalid
     */
    public static Object get(Object object, int index) {
        if (index < 0) {
            throw new IndexOutOfBoundsException("Index cannot be negative: " + index);
        }
        if (object instanceof Map) {
            Map map = (Map) object;
            Iterator iterator = map.entrySet().iterator();
            return get(iterator, index);
        } else if (object instanceof List) {
            return ((List) object).get(index);
        } else if (object instanceof Object[]) {
            return ((Object[]) object)[index];
        } else if (object instanceof Iterator) {
            Iterator it = (Iterator) object;
            while (it.hasNext()) {
                index--;
                if (index == -1) {
                    return it.next();
                } else {
                    it.next();
                }
            }
            throw new IndexOutOfBoundsException("Entry does not exist: " + index);
        } else if (object instanceof Collection) {
            Iterator iterator = ((Collection) object).iterator();
            return get(iterator, index);
        } else if (object instanceof Enumeration) {
            Enumeration it = (Enumeration) object;
            while (it.hasMoreElements()) {
                index--;
                if (index == -1) {
                    return it.nextElement();
                } else {
                    it.nextElement();
                }
            }
            throw new IndexOutOfBoundsException("Entry does not exist: " + index);
        } else if (object == null) {
            throw new IllegalArgumentException("Unsupported object type: null");
        } else {
            try {
                return Array.get(object, index);
            } catch (IllegalArgumentException ex) {
                throw new IllegalArgumentException("Unsupported object type: " + object.getClass().getName());
            }
        }
    }
    
    /**
     * Gets the size of the collection/iterator specified.
     *
     * <p>This method can handles objects as follows
     * <ul>
     * <li>Collection - the collection size
     * <li>Map - the map size
     * <li>Array - the array size
     * <li>Iterator - the number of elements remaining in the iterator
     * <li>Enumeration - the number of elements remaining in the enumeration
     * </ul>
     *
     * @param object the object to get the size of
     * @return the size of the specified collection
     * @throws IllegalArgumentException thrown if object is not recognised or null
     * @since Commons Collections 3.1
     */
    public static int size(Object object) {
        int total = 0;
        if (object instanceof Map) {
            total = ((Map) object).size();
        } else if (object instanceof Collection) {
            total = ((Collection) object).size();
        } else if (object instanceof Object[]) {
            total = ((Object[]) object).length;
        } else if (object instanceof Iterator) {
            Iterator it = (Iterator) object;
            while (it.hasNext()) {
                total++;
                it.next();
            }
        } else if (object instanceof Enumeration) {
            Enumeration it = (Enumeration) object;
            while (it.hasMoreElements()) {
                total++;
                it.nextElement();
            }
        } else if (object == null) {
            throw new IllegalArgumentException("Unsupported object type: null");
        } else {
            try {
                total = Array.getLength(object);
            } catch (IllegalArgumentException ex) {
                throw new IllegalArgumentException("Unsupported object type: " + object.getClass().getName());
            }
        }
        return total;
    }
    
    /**
     * Judge whether object is empty.
     *
     * @param object object
     * @return true if object is empty, otherwise false
     * @throws IllegalArgumentException if object has no length or size
     */
    public static boolean sizeIsEmpty(Object object) {
        if (object instanceof Collection) {
            return ((Collection) object).isEmpty();
        } else if (object instanceof Map) {
            return ((Map) object).isEmpty();
        } else if (object instanceof Object[]) {
            return ((Object[]) object).length == 0;
        } else if (object instanceof Iterator) {
            return ((Iterator) object).hasNext() == false;
        } else if (object instanceof Enumeration) {
            return ((Enumeration) object).hasMoreElements() == false;
        } else if (object == null) {
            throw new IllegalArgumentException("Unsupported object type: null");
        } else {
            try {
                return Array.getLength(object) == 0;
            } catch (IllegalArgumentException ex) {
                throw new IllegalArgumentException("Unsupported object type: " + object.getClass().getName());
            }
        }
    }
    
    /**
     * Whether contain item in collection.
     *
     * @param coll   collection
     * @param target target value
     * @param <T>    General Type
     * @return true if contain, otherwise false
     */
    public static <T> boolean contains(Collection<T> coll, T target) {
        if (isEmpty(coll)) {
            return false;
        }
        return coll.contains(target);
    }
    
    /**
     * Null-safe check if the specified collection is empty.
     *
     * <p>Null returns true.
     *
     * @param coll the collection to check, may be null
     * @return true if empty or null
     * @since Commons Collections 3.2
     */
    public static boolean isEmpty(Collection coll) {
        return (coll == null || coll.isEmpty());
    }
    
    /**
     * Null-safe check if the specified collection is not empty.
     *
     * <p>Null returns false.
     *
     * @param coll the collection to check, may be null
     * @return true if non-null and non-empty
     * @since Commons Collections 3.2
     */
    public static boolean isNotEmpty(Collection coll) {
        return !CollectionUtils.isEmpty(coll);
    }
    
    /**
     * Returns the value to which the specified index , or {@code defaultValue} if this collection contains no value for
     * the index.
     *
     * @param obj          the object to get a value from
     * @param index        the index to get
     * @param defaultValue default value
     * @param <T>          General Type
     * @return the value to which the specified index , or {@code defaultValue} if this collection contains no value for
     * the index.
     */
    public static <T> T getOrDefault(Object obj, int index, T defaultValue) {
        try {
            return (T) get(obj, index);
        } catch (IndexOutOfBoundsException e) {
            return defaultValue;
        }
    }
    
    /**
     * return an arraylist containing all input parameters.
     *
     * @param elements element array
     * @return arraylist containing all input parameters
     * @author zzq
     */
    public static <T> List<T> list(T... elements) {
        if (elements == null) {
            throw new IllegalArgumentException("Expected an array of elements (or empty array) but received a null.");
        }
        ArrayList<T> list = new ArrayList<>(elements.length);
        Collections.addAll(list, elements);
        return list;
    }
    
    /**
     * Return a set containing all input parameters.
     *
     * @param elements elements element array
     * @return set containing all input parameters
     */
    public static <T> Set<T> set(T... elements) {
        if (elements == null) {
            throw new IllegalArgumentException("Expected an array of elements (or empty array) but received a null.");
        } else {
            return new LinkedHashSet<>(Arrays.asList(elements));
        }
    }
    
    /**
     * return the first element, if the iterator contains multiple elements, will throw {@code
     * IllegalArgumentException}.
     *
     * @throws NoSuchElementException   if the iterator is empty
     * @throws IllegalArgumentException if the iterator contains multiple elements. The state of the iterator is
     *                                  unspecified.
     */
    public static <T> T getOnlyElement(Iterable<T> iterable) {
        if (iterable == null) {
            throw new IllegalArgumentException("iterable cannot be null.");
        }
        Iterator<T> iterator = iterable.iterator();
        T first = iterator.next();
        if (!iterator.hasNext()) {
            return first;
        }
        throw new IllegalArgumentException(buildExceptionMessage(iterator, first));
    }
    
    @SuppressWarnings("PMD.UndefineMagicConstantRule")
    private static <T> String buildExceptionMessage(Iterator<T> iterator, T first) {
        StringBuilder msg = new StringBuilder();
        msg.append("expected one element but was: <");
        msg.append(first);
        for (int i = 0; i < 4 && iterator.hasNext(); i++) {
            msg.append(", ");
            msg.append(iterator.next());
        }
        if (iterator.hasNext()) {
            msg.append(", ...");
        }
        msg.append('>');
        return msg.toString();
    }
    
    /**
     * Return {@code true} if the supplied Map is {@code null} or empty. Otherwise, return {@code false}.
     *
     * @param map the Map to check
     * @return whether the given Map is empty
     */
    public static boolean isMapEmpty(Map<?, ?> map) {
        return (map == null || map.isEmpty());
    }
    
    /**
     * Returns a {@link Map} mapping each unique element in the given {@link Collection} to an {@link Integer}
     * representing the number of occurrences of that element in the {@link Collection}.
     *
     * <p>Only those elements present in the collection will appear as keys in the map.
     *
     * @param coll the collection to get the cardinality map for, must not be null
     * @return the populated cardinality map
     */
    public static Map getCardinalityMap(final Collection coll) {
        Map count = new HashMap(coll.size());
        for (Iterator it = coll.iterator(); it.hasNext(); ) {
            Object obj = it.next();
            Integer c = (Integer) (count.get(obj));
            if (c == null) {
                count.put(obj, INTEGER_ONE);
            } else {
                count.put(obj, c + 1);
            }
        }
        return count;
    }
    
    /**
     * Returns <tt>true</tt> iff the given {@link Collection}s contain exactly the same elements with exactly the same
     * cardinalities.
     *
     * <p>That is, iff the cardinality of <i>e</i> in <i>a</i> is equal to the cardinality of <i>e</i> in <i>b</i>, for
     * each element <i>e</i> in <i>a</i> or <i>b</i>.
     *
     * @param a the first collection, must not be null
     * @param b the second collection, must not be null
     * @return <code>true</code> iff the collections contain the same elements with the same cardinalities.
     */
    public static boolean isEqualCollection(final Collection a, final Collection b) {
        if (a.size() != b.size()) {
            return false;
        } else {
            Map mapa = getCardinalityMap(a);
            Map mapb = getCardinalityMap(b);
            if (mapa.size() != mapb.size()) {
                return false;
            } else {
                Iterator it = mapa.keySet().iterator();
                while (it.hasNext()) {
                    Object obj = it.next();
                    if (getFreq(obj, mapa) != getFreq(obj, mapb)) {
                        return false;
                    }
                }
                return true;
            }
        }
    }
    
    private static int getFreq(final Object obj, final Map freqMap) {
        Integer count = (Integer) freqMap.get(obj);
        if (count != null) {
            return count.intValue();
        }
        return 0;
    }
}
