using System;
using System.Collections;
using System.Collections.Generic;

namespace Lucene.Net.Support
{
    /*
     * 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.
     */

    /// <summary>
    /// Represents a strongly typed list of objects that can be accessed by index.
    /// Provides methods to manipulate lists. Also provides functionality
    /// to compare lists against each other through an implementations of
    /// <see cref="IEquatable{T}"/>, or to wrap an existing list to use
    /// the same comparison logic as this one while not affecting any of its
    /// other functionality.
    /// </summary>
    /// <typeparam name="T">The type of elements in the list.</typeparam>
#if FEATURE_SERIALIZABLE
    [Serializable]
#endif
    public class EquatableList<T> : IList<T>, IEquatable<IList<T>>
#if !NETSTANDARD
        , ICloneable
#endif
    {
        private readonly IList<T> list;

        /// <summary>Initializes a new instance of the
        /// <see cref="EquatableList{T}"/> class that is empty and has the
        /// default initial capacity.</summary>
        public EquatableList()
        {
            list = new List<T>();
        }

        /// <summary>
        /// Initializes a new instance of <see cref="EquatableList{T}"/>.
        /// <para/>
        /// If the <paramref name="wrap"/> parameter is <c>true</c>, the
        /// <paramref name="collection"/> is used as is without doing
        /// a copy operation. Otherwise, the collection is copied 
        /// (which is the same operation as the 
        /// <see cref="EquatableList{T}.EquatableList(IEnumerable{T})"/> overload). 
        /// <para/>
        /// The internal <paramref name="collection"/> is used for
        /// all operations except for <see cref="Equals()"/>, <see cref="GetHashCode()"/>,
        /// and <see cref="ToString()"/>, which are all based on deep analysis
        /// of this collection and any nested collections.
        /// </summary>
        /// <param name="collection">The collection that will either be wrapped or copied 
        /// depending on the value of <paramref name="wrap"/>.</param>
        /// <param name="wrap"><c>true</c> to wrap an existing <see cref="IList{T}"/> without copying,
        /// or <c>false</c> to copy the collection into a new <see cref="List{T}"/>.</param>
        public EquatableList(IList<T> collection, bool wrap)
        {
            if (collection == null)
                throw new ArgumentNullException("collection");

            if (wrap)
            {
                this.list = collection;
            }
            else
            {
                this.list = new List<T>(collection);
            }
        }

        /// <summary>
        /// Initializes a new 
        /// instance of the <see cref="EquatableList{T}"/>
        /// class that contains elements copied from the specified collection and has
        /// sufficient capacity to accommodate the number of elements copied. 
        /// <param name="collection">The collection whose elements are copied to the new list.</param>
        public EquatableList(IEnumerable<T> collection)
        {
            list = new List<T>(collection);
        }

        /// <summary>Initializes a new instance of the <see cref="EquatableList{T}"/>
        /// class that is empty and has the specified initial capacity.</summary>
        /// <param name="capacity">The number of elements that the new list can initially store.</param>
        public EquatableList(int capacity)
        {
            list = new List<T>(capacity);
        }

        #region IList<T> members

        /// <summary>
        /// Gets or sets the element at the specified index.
        /// </summary>
        /// <param name="index">The zero-based index of the element to get or set.</param>
        public virtual T this[int index]
        {
            get { return list[index]; }
            set { list[index] = value; }
        }

        /// <summary>
        /// Gets the number of elements contained in the <see cref="EquatableList{T}"/>.
        /// </summary>
        public virtual int Count
        {
            get { return list.Count; }
        }

        /// <summary>
        /// Gets a value indicating whether the <see cref="EquatableList{T}"/> is read-only.
        /// </summary>
        public virtual bool IsReadOnly
        {
            get { return list.IsReadOnly; }
        }

        /// <summary>
        /// Adds an object to the end of the <see cref="EquatableList{T}"/>.
        /// </summary>
        /// <param name="item">The object to be added to the end of the <see cref="EquatableList{T}"/>. The value can be <c>null</c> for reference types.</param>
        public virtual void Add(T item)
        {
            list.Add(item);
        }

        /// <summary>
        /// Removes all items from the <see cref="EquatableList{T}"/>.
        /// </summary>
        public virtual void Clear()
        {
            list.Clear();
        }

        /// <summary>
        /// Determines whether the <see cref="EquatableList{T}"/> contains a specific value.
        /// </summary>
        /// <param name="item">The object to locate in the <see cref="EquatableList{T}"/>.</param>
        /// <returns><c>true</c> if the Object is found in the <see cref="EquatableList{T}"/>; otherwise, <c>false</c>.</returns>
        public virtual bool Contains(T item)
        {
            return list.Contains(item);
        }

        /// <summary>
        /// Copies the entire <see cref="EquatableList{T}"/> to a compatible one-dimensional array, 
        /// starting at the specified index of the target array.
        /// </summary>
        /// <param name="array">The one-dimensional <see cref="Array"/> that is the 
        /// destination of the elements copied from <see cref="EquatableList{T}"/>. 
        /// The Array must have zero-based indexing.</param>
        /// <param name="arrayIndex">The zero-based index in <paramref name="array"/> at which copying begins.</param>
        public virtual void CopyTo(T[] array, int arrayIndex)
        {
            list.CopyTo(array, arrayIndex);
        }

        /// <summary>
        /// Returns an enumerator that iterates through the <see cref="EquatableList{T}"/>.
        /// </summary>
        /// <returns>An <see cref="IEnumerator{T}"/> for the <see cref="EquatableList{T}"/>.</returns>
        public virtual IEnumerator<T> GetEnumerator()
        {
            return list.GetEnumerator();
        }

        /// <summary>
        /// Determines the index of a specific <paramref name="item"/> in the <see cref="EquatableList{T}"/>.
        /// </summary>
        /// <param name="item">The object to locate in the <see cref="EquatableList{T}"/>.</param>
        /// <returns>The index of <paramref name="item"/> if found in the list; otherwise, -1.</returns>
        public virtual int IndexOf(T item)
        {
            return list.IndexOf(item);
        }

        /// <summary>
        /// Inserts an item to the <see cref="EquatableList{T}"/> at the specified index.
        /// </summary>
        /// <param name="index">The zero-based index at which <paramref name="item"/> should be inserted.</param>
        /// <param name="item">The object to insert into the <see cref="EquatableList{T}"/>.</param>
        public virtual void Insert(int index, T item)
        {
            list.Insert(index, item);
        }

        /// <summary>
        /// Removes the first occurrence of a specific object from the <see cref="EquatableList{T}"/>.
        /// </summary>
        /// <param name="item">The object to remove from the <see cref="EquatableList{T}"/>.</param>
        /// <returns><c>true</c> if <paramref name="item"/> was successfully removed from the 
        /// <see cref="EquatableList{T}"/>; otherwise, <c>false</c>. This method also returns 
        /// <c>false</c> if item is not found in the original <see cref="EquatableList{T}"/>.</returns>
        public virtual bool Remove(T item)
        {
            return list.Remove(item);
        }

        /// <summary>
        /// Removes the <see cref="EquatableList{T}"/> item at the specified index.
        /// </summary>
        /// <param name="index">The zero-based index of the item to remove.</param>
        public virtual void RemoveAt(int index)
        {
            list.RemoveAt(index);
        }

        /// <summary>
        /// Returns an enumerator that iterates through the <see cref="EquatableList{T}"/>.
        /// </summary>
        /// <returns>An <see cref="IEnumerator"/> for the <see cref="EquatableList{T}"/>.</returns>
        IEnumerator IEnumerable.GetEnumerator()
        {
            return list.GetEnumerator();
        }

        #endregion

        #region Operator overrides

        // TODO: When diverging from Java version of Lucene, can uncomment these to adhere to best practices when overriding the Equals method and implementing IEquatable<T>.
        ///// <summary>Overload of the == operator, it compares a
        ///// <see cref="EquatableList{T}"/> to an <see cref="IEnumerable{T}"/>
        ///// implementation.</summary>
        ///// <param name="x">The <see cref="EquatableList{T}"/> to compare
        ///// against <paramref name="y"/>.</param>
        ///// <param name="y">The <see cref="IEnumerable{T}"/> to compare
        ///// against <paramref name="x"/>.</param>
        ///// <returns>True if the instances are equal, false otherwise.</returns>
        //public static bool operator ==(EquatableList<T> x, System.Collections.Generic.IEnumerable<T> y)
        //{
        //    // Call Equals.
        //    return Equals(x, y);
        //}

        ///// <summary>Overload of the == operator, it compares a
        ///// <see cref="EquatableList{T}"/> to an <see cref="IEnumerable{T}"/>
        ///// implementation.</summary>
        ///// <param name="y">The <see cref="EquatableList{T}"/> to compare
        ///// against <paramref name="x"/>.</param>
        ///// <param name="x">The <see cref="IEnumerable{T}"/> to compare
        ///// against <paramref name="y"/>.</param>
        ///// <returns>True if the instances are equal, false otherwise.</returns>
        //public static bool operator ==(System.Collections.Generic.IEnumerable<T> x, EquatableList<T> y)
        //{
        //    // Call equals.
        //    return Equals(x, y);
        //}

        ///// <summary>Overload of the != operator, it compares a
        ///// <see cref="EquatableList{T}"/> to an <see cref="IEnumerable{T}"/>
        ///// implementation.</summary>
        ///// <param name="x">The <see cref="EquatableList{T}"/> to compare
        ///// against <paramref name="y"/>.</param>
        ///// <param name="y">The <see cref="IEnumerable{T}"/> to compare
        ///// against <paramref name="x"/>.</param>
        ///// <returns>True if the instances are not equal, false otherwise.</returns>
        //public static bool operator !=(EquatableList<T> x, System.Collections.Generic.IEnumerable<T> y)
        //{
        //    // Return the negative of the equals operation.
        //    return !(x == y);
        //}

        ///// <summary>Overload of the != operator, it compares a
        ///// <see cref="EquatableList{T}"/> to an <see cref="IEnumerable{T}"/>
        ///// implementation.</summary>
        ///// <param name="y">The <see cref="EquatableList{T}"/> to compare
        ///// against <paramref name="x"/>.</param>
        ///// <param name="x">The <see cref="IEnumerable{T}"/> to compare
        ///// against <paramref name="y"/>.</param>
        ///// <returns>True if the instances are not equal, false otherwise.</returns>
        //public static bool operator !=(System.Collections.Generic.IEnumerable<T> x, EquatableList<T> y)
        //{
        //    // Return the negative of the equals operation.
        //    return !(x == y);
        //}

        #endregion

        #region IEquatable<T> members

        /// <summary>
        /// Compares this sequence to another <see cref="IList{T}"/>
        /// implementation, returning <c>true</c> if they are equal, <c>false</c> otherwise.
        /// <para/>
        /// The comparison takes into consideration any values in this collection and values
        /// of any nested collections, but does not take into consideration the data type.
        /// Therefore, <see cref="EquatableList{T}"/> can equal any <see cref="IList{T}"/>
        /// with the exact same values in the same order.
        /// </summary>
        /// <param name="other">The other <see cref="IList{T}"/> implementation
        /// to compare against.</param>
        /// <returns><c>true</c> if the sequence in <paramref name="other"/>
        /// is the same as this one.</returns>
        public virtual bool Equals(IList<T> other)
        {
            return Collections.Equals(this, other);
        }

        #endregion

        #region IClonable members

        /// <summary>Clones the <see cref="EquatableList{T}"/>.</summary>
        /// <remarks>This is a shallow clone.</remarks>
        /// <returns>A new shallow clone of this
        /// <see cref="EquatableList{T}"/>.</returns>
        public virtual object Clone()
        {
            // Just create a new one, passing this to the constructor.
            return new EquatableList<T>(this);
        }

        #endregion

        #region Object overrides

        /// <summary>
        /// If the object passed implements <see cref="IList{T}"/>,
        /// compares this sequence to <paramref name="other"/>, returning <c>true</c> if they 
        /// are equal, <c>false</c> otherwise.
        /// <para/>
        /// The comparison takes into consideration any values in this collection and values
        /// of any nested collections, but does not take into consideration the data type.
        /// Therefore, <see cref="EquatableList{T}"/> can equal any <see cref="IList{T}"/>
        /// with the exact same values in the same order.
        /// </summary>
        /// <param name="obj">The other object
        /// to compare against.</param>
        /// <returns><c>true</c> if the sequence in <paramref name="other"/>
        /// is the same as this one.</returns>
        public override bool Equals(object obj)
        {
            if (!(obj is IList<T>))
            {
                return false;
            }
            return this.Equals(obj as IList<T>);
        }

        /// <summary>
        /// Returns the hash code value for this list.
        /// <para/>
        /// The hash code determination takes into consideration any values in
        /// this collection and values of any nested collections, but does not
        /// take into consideration the data type. Therefore, the hash codes will
        /// be exactly the same for this <see cref="EquatableList{T}"/> and another
        /// <see cref="IList{T}"/> (including arrays) with the same values in the
        /// same order.
        /// </summary>
        /// <returns>the hash code value for this list</returns>
        public override int GetHashCode()
        {
            return Collections.GetHashCode(this);
        }

        /// <summary>
        /// Returns a string representation of this collection (and any nested collections). 
        /// The string representation consists of a list of the collection's elements in 
        /// the order they are returned by its enumerator, enclosed in square brackets 
        /// ("[]"). Adjacent elements are separated by the characters ", " (comma and space).
        /// </summary>
        /// <returns>a string representation of this collection</returns>
        public override string ToString()
        {
            return Collections.ToString(this);
        }

        #endregion  
    }
}