//******************************
// Written by Peter Golde
// Copyright (c) 2004-2005, Wintellect
//
// Use and restribution of this code is subject to the license agreement 
// contained in the file "License.txt" accompanying this file.
//******************************

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

namespace Wintellect.PowerCollections
{
    /// <summary>
    /// CollectionBase is a base class that can be used to more easily implement the
    /// generic ICollection&lt;T&gt; and non-generic ICollection interfaces.
    /// </summary>
    /// <remarks>
    /// <para>To use CollectionBase as a base class, the derived class must override
    /// the Count, GetEnumerator, Add, Clear, and Remove methods. </para>
    /// <para>ICollection&lt;T&gt;.Contains need not be implemented by the
    /// derived class, but it should be strongly considered, because the CollectionBase implementation
    /// may not be very efficient.</para>
    /// </remarks>
    /// <typeparam name="T">The item type of the collection.</typeparam>
    [Serializable]
    [DebuggerDisplay("{DebuggerDisplayString()}")]
    public abstract class CollectionBase<T> : ICollection<T>, ICollection
    {
        /// <summary>
        /// Creates a new CollectionBase. 
        /// </summary>
        protected CollectionBase()
        {
        }

        /// <summary>
        /// Shows the string representation of the collection. The string representation contains
        /// a list of the items in the collection. Contained collections (except string) are expanded
        /// recursively.
        /// </summary>
        /// <returns>The string representation of the collection.</returns>
        public override string ToString()
        {
            return Algorithms.ToString(this);
        }


        #region ICollection<T> Members

        /// <summary>
        /// Must be overridden to allow adding items to this collection.
        /// </summary>
        /// <remarks><p>This method is not abstract, although derived classes should always
        /// override it. It is not abstract because some derived classes may wish to reimplement
        /// Add with a different return type (typically bool). In C#, this can be accomplished
        /// with code like the following:</p>
        /// <code>
        ///     public class MyCollection&lt;T&gt;: CollectionBase&lt;T&gt;, ICollection&lt;T&gt;
        ///     {
        ///         public new bool Add(T item) {
        ///             /* Add the item */
        ///         }
        ///  
        ///         void ICollection&lt;T&gt;.Add(T item) {
        ///             Add(item);
        ///         }
        ///     }
        /// </code>
        /// </remarks>
        /// <param name="item">Item to be added to the collection.</param>
        /// <exception cref="NotImplementedException">Always throws this exception to indicated
        /// that the method must be overridden or re-implemented in the derived class.</exception>
        public virtual void Add(T item)
        {
            throw new NotImplementedException(Strings.MustOverrideOrReimplement);
        }


        /// <summary>
        /// Must be overridden to allow clearing this collection.
        /// </summary>
        public abstract void Clear();

        /// <summary>
        /// Must be overridden to allow removing items from this collection.
        /// </summary>
        /// <returns>True if <paramref name="item"/> existed in the collection and
        /// was removed. False if <paramref name="item"/> did not exist in the collection.</returns>
        public abstract bool Remove(T item);

        /// <summary>
        /// Determines if the collection contains a particular item. This default implementation
        /// iterates all of the items in the collection via GetEnumerator, testing each item
        /// against <paramref name="item"/> using IComparable&lt;T&gt;.Equals or
        /// Object.Equals.
        /// </summary>
        /// <remarks>You should strongly consider overriding this method to provide
        /// a more efficient implementation, or if the default equality comparison
        /// is inappropriate.</remarks>
        /// <param name="item">The item to check for in the collection.</param>
        /// <returns>True if the collection contains <paramref name="item"/>, false otherwise.</returns>
        public virtual bool Contains(T item)
        {
            IEqualityComparer<T> equalityComparer = EqualityComparer<T>.Default;
            foreach (T i in this) {
                if (equalityComparer.Equals(i, item))
                    return true;
            }
            return false;
        }

        /// <summary>
        /// Copies all the items in the collection into an array. Implemented by
        /// using the enumerator returned from GetEnumerator to get all the items
        /// and copy them to the provided array.
        /// </summary>
        /// <param name="array">Array to copy to.</param>
        /// <param name="arrayIndex">Starting index in <paramref name="array"/> to copy to.</param>
        public virtual void CopyTo(T[] array, int arrayIndex)
        {
            int count = this.Count;

            if (count == 0)
                return;

            if (array == null)
                throw new ArgumentNullException("array");
            if (count < 0)
                throw new ArgumentOutOfRangeException("count", count, Strings.ArgMustNotBeNegative);
            if (arrayIndex < 0)
                throw new ArgumentOutOfRangeException("arrayIndex", arrayIndex, Strings.ArgMustNotBeNegative);
            if (arrayIndex >= array.Length || count > array.Length - arrayIndex)
                throw new ArgumentException("arrayIndex", Strings.ArrayTooSmall);

            int index = arrayIndex, i = 0;
            foreach (T item in (ICollection<T>)this) {
                if (i >= count)
                    break;

                array[index] = item;
                ++index;
                ++i;
            }
        }

        /// <summary>
        /// Creates an array of the correct size, and copies all the items in the 
        /// collection into the array, by calling CopyTo.
        /// </summary>
        /// <returns>An array containing all the elements in the collection, in order.</returns>
        public virtual T[] ToArray()
        {
            int count = this.Count;

            T[] array = new T[count];
            CopyTo(array, 0);
            return array;
        }

        /// <summary>
        /// Must be overridden to provide the number of items in the collection.
        /// </summary>
        /// <value>The number of items in the collection.</value>
        public abstract int Count { get; }

        /// <summary>
        /// Indicates whether the collection is read-only. Always returns false.
        /// </summary>
        /// <value>Always returns false.</value>
        bool ICollection<T>.IsReadOnly
        {
            get { return false; }
        }

        /// <summary>
        /// Provides a read-only view of this collection. The returned ICollection&lt;T&gt; provides
        /// a view of the collection that prevents modifications to the collection. Use the method to provide
        /// access to the collection without allowing changes. Since the returned object is just a view,
        /// changes to the collection will be reflected in the view.
        /// </summary>
        /// <returns>An ICollection&lt;T&gt; that provides read-only access to the collection.</returns>
        public virtual ICollection<T> AsReadOnly()
        {
            return Algorithms.ReadOnly<T>(this);
        }

        #endregion

        #region Delegate operations

        /// <summary>
        /// Determines if the collection contains any item that satisfies the condition
        /// defined by <paramref name="predicate"/>.
        /// </summary>
        /// <param name="predicate">A delegate that defines the condition to check for.</param>
        /// <returns>True if the collection contains one or more items that satisfy the condition
        /// defined by <paramref name="predicate"/>. False if the collection does not contain
        /// an item that satisfies <paramref name="predicate"/>.</returns>
        public virtual bool Exists(Predicate<T> predicate)
        {
            if (predicate == null)
                throw new ArgumentNullException("predicate");

            return Algorithms.Exists(this, predicate);
        }

        /// <summary>
        /// Determines if all of the items in the collection satisfy the condition
        /// defined by <paramref name="predicate"/>.
        /// </summary>
        /// <param name="predicate">A delegate that defines the condition to check for.</param>
        /// <returns>True if all of the items in the collection satisfy the condition
        /// defined by <paramref name="predicate"/>, or if the collection is empty. False if one or more items
        /// in the collection do not satisfy <paramref name="predicate"/>.</returns>
        public virtual bool TrueForAll(Predicate<T> predicate)
        {
            if (predicate == null)
                throw new ArgumentNullException("predicate");

            return Algorithms.TrueForAll(this, predicate);
        }

        /// <summary>
        /// Counts the number of items in the collection that satisfy the condition
        /// defined by <paramref name="predicate"/>.
        /// </summary>
        /// <param name="predicate">A delegate that defines the condition to check for.</param>
        /// <returns>The number of items in the collection that satisfy <paramref name="predicate"/>.</returns>
        public virtual int CountWhere(Predicate<T> predicate)
        {
            if (predicate == null)
                throw new ArgumentNullException("predicate");

            return Algorithms.CountWhere(this, predicate);
        }

        /// <summary>
        /// Enumerates the items in the collection that satisfy the condition defined
        /// by <paramref name="predicate"/>.
        /// </summary>
        /// <param name="predicate">A delegate that defines the condition to check for.</param>
        /// <returns>An IEnumerable&lt;T&gt; that enumerates the items that satisfy the condition.</returns>
        public virtual IEnumerable<T> FindAll(Predicate<T> predicate)
        {
            if (predicate == null)
                throw new ArgumentNullException("predicate");

            return Algorithms.FindWhere(this, predicate);
        }

        /// <summary>
        /// Removes all the items in the collection that satisfy the condition
        /// defined by <paramref name="predicate"/>.
        /// </summary>
        /// <param name="predicate">A delegate that defines the condition to check for.</param>
        /// <returns>Returns a collection of the items that were removed, in sorted order.</returns>
        public virtual ICollection<T> RemoveAll(Predicate<T> predicate)
        {
            if (predicate == null)
                throw new ArgumentNullException("predicate");

            return Algorithms.RemoveWhere(this, predicate);
        }

        /// <summary>
        /// Performs the specified action on each item in this collection.
        /// </summary>
        /// <param name="action">An Action delegate which is invoked for each item in this collection.</param>
        public virtual void ForEach(Action<T> action)
        {
            if (action == null)
                throw new ArgumentNullException("action");

            Algorithms.ForEach(this, action);
        }

        /// <summary>
        /// Convert this collection of items by applying a delegate to each item in the collection. The resulting enumeration
        /// contains the result of applying <paramref name="converter"/> to each item in this collection, in
        /// order.
        /// </summary>
        /// <typeparam name="TOutput">The type each item is being converted to.</typeparam>
        /// <param name="converter">A delegate to the method to call, passing each item in this collection.</param>
        /// <returns>An IEnumerable&lt;TOutput^gt; that enumerates the resulting collection from applying <paramref name="converter"/> to each item in this collection in
        /// order.</returns>
        /// <exception cref="ArgumentNullException"><paramref name="converter"/> is null.</exception>
        public virtual IEnumerable<TOutput> ConvertAll<TOutput>(Converter<T, TOutput> converter)
        {
            if (converter == null)
                throw new ArgumentNullException("converter");

            return Algorithms.Convert(this, converter);
        }

        #endregion

        #region IEnumerable<T> Members

        /// <summary>
        /// Must be overridden to enumerate all the members of the collection.
        /// </summary>
        /// <returns>A generic IEnumerator&lt;T&gt; that can be used
        /// to enumerate all the items in the collection.</returns>
        public abstract IEnumerator<T> GetEnumerator();

        #endregion

        #region ICollection Members

        /// <summary>
        /// Copies all the items in the collection into an array. Implemented by
        /// using the enumerator returned from GetEnumerator to get all the items
        /// and copy them to the provided array.
        /// </summary>
        /// <param name="array">Array to copy to.</param>
        /// <param name="index">Starting index in <paramref name="array"/> to copy to.</param>
        void ICollection.CopyTo(Array array, int index)
        {
            int count = this.Count;

            if (count == 0)
                return;

            if (array == null)
                throw new ArgumentNullException("array");
            if (index < 0)
                throw new ArgumentOutOfRangeException("index", index, Strings.ArgMustNotBeNegative);
            if (index >= array.Length || count > array.Length - index)
                throw new ArgumentException("index", Strings.ArrayTooSmall);

            int i = 0;
            foreach (object o in (ICollection)this) {
                if (i >= count)
                    break;

                array.SetValue(o, index);
                ++index;
                ++i;
            }
        }

        /// <summary>
        /// Indicates whether the collection is synchronized.
        /// </summary>
        /// <value>Always returns false, indicating that the collection is not synchronized.</value>
        bool ICollection.IsSynchronized
        {
            get { return false; }
        }

        /// <summary>
        /// Indicates the synchronization object for this collection.
        /// </summary>
        /// <value>Always returns this.</value>
        object ICollection.SyncRoot
        {
            get { return this; }
        }

        #endregion

        #region IEnumerable Members

        /// <summary>
        /// Provides an IEnumerator that can be used to iterate all the members of the
        /// collection. This implementation uses the IEnumerator&lt;T&gt; that was overridden
        /// by the derived classes to enumerate the members of the collection.
        /// </summary>
        /// <returns>An IEnumerator that can be used to iterate the collection.</returns>
        IEnumerator IEnumerable.GetEnumerator()
        {
            foreach (T item in this) {
                yield return item;
            }
        }

        #endregion

        /// <summary>
        /// Display the contents of the collection in the debugger. This is intentionally private, it is called
        /// only from the debugger due to the presence of the DebuggerDisplay attribute. It is similar
        /// format to ToString(), but is limited to 250-300 characters or so, so as not to overload the debugger.
        /// </summary>
        /// <returns>The string representation of the items in the collection, similar in format to ToString().</returns>
        internal string DebuggerDisplayString()
        {
            const int MAXLENGTH = 250;

            System.Text.StringBuilder builder = new System.Text.StringBuilder();

            builder.Append('{');

            // Call ToString on each item and put it in.
            bool firstItem = true;
            foreach (T item in this) {
                if (builder.Length >= MAXLENGTH) {
                    builder.Append(",...");
                    break;
                }

                if (!firstItem)
                    builder.Append(',');

                if (item == null)
                    builder.Append("null");
                else
                    builder.Append(item.ToString());

                firstItem = false;
            }

            builder.Append('}');
            return builder.ToString();
        }

    }
}