using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;

namespace Indy.IL2CPU {
    public class ReadOnlyDictionary<K, V> : IDictionary<K, V> {
        private readonly IDictionary<K, V> mBackend;

        public ReadOnlyDictionary(IDictionary<K, V> aBackend) {
            mBackend = aBackend;
        }

        /// <summary>
        /// Returns an enumerator that iterates through the collection.
        /// </summary>
        /// <returns>
        /// A <see cref="T:System.Collections.Generic.IEnumerator`1" /> that can be used to iterate through the collection.
        /// </returns>
        /// <filterpriority>1</filterpriority>
        public IEnumerator<KeyValuePair<K, V>> GetEnumerator() {
            return mBackend.GetEnumerator();
        }

        /// <summary>
        /// Returns an enumerator that iterates through a collection.
        /// </summary>
        /// <returns>
        /// An <see cref="T:System.Collections.IEnumerator" /> object that can be used to iterate through the collection.
        /// </returns>
        /// <filterpriority>2</filterpriority>
        IEnumerator IEnumerable.GetEnumerator() {
            return mBackend.GetEnumerator();
        }

        /// <summary>
        /// Adds an item to the <see cref="T:System.Collections.Generic.ICollection`1" />.
        /// </summary>
        /// <param name="item">The object to add to the <see cref="T:System.Collections.Generic.ICollection`1" />.</param>
        /// <exception cref="T:System.NotSupportedException">The <see cref="T:System.Collections.Generic.ICollection`1" /> is read-only.</exception>
        public void Add(KeyValuePair<K, V> item) {
            throw new InvalidOperationException("Cannot add to a read-only Dictionary!");
        }

        /// <summary>
        /// Removes all items from the <see cref="T:System.Collections.Generic.ICollection`1" />.
        /// </summary>
        /// <exception cref="T:System.NotSupportedException">The <see cref="T:System.Collections.Generic.ICollection`1" /> is read-only. </exception>
        public void Clear() {
            throw new InvalidOperationException("Cannot clear a read-only Dictionary");
        }

        /// <summary>
        /// Determines whether the <see cref="T:System.Collections.Generic.ICollection`1" /> contains a specific value.
        /// </summary>
        /// <returns>
        /// true if <paramref name="item" /> is found in the <see cref="T:System.Collections.Generic.ICollection`1" />; otherwise, false.
        /// </returns>
        /// <param name="item">The object to locate in the <see cref="T:System.Collections.Generic.ICollection`1" />.</param>
        public bool Contains(KeyValuePair<K, V> item) {
            return mBackend.Contains(item);
        }

        /// <summary>
        /// Copies the elements of the <see cref="T:System.Collections.Generic.ICollection`1" /> to an <see cref="T:System.Array" />, starting at a particular <see cref="T:System.Array" /> index.
        /// </summary>
        /// <param name="array">The one-dimensional <see cref="T:System.Array" /> that is the destination of the elements copied from <see cref="T:System.Collections.Generic.ICollection`1" />. The <see cref="T:System.Array" /> must have zero-based indexing.</param>
        /// <param name="arrayIndex">The zero-based index in <paramref name="array" /> at which copying begins.</param>
        /// <exception cref="T:System.ArgumentNullException"><paramref name="array" /> is null.</exception>
        /// <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="arrayIndex" /> is less than 0.</exception>
        /// <exception cref="T:System.ArgumentException"><paramref name="array" /> is multidimensional.-or-<paramref name="arrayIndex" /> is equal to or greater than the length of <paramref name="array" />.-or-The number of elements in the source <see cref="T:System.Collections.Generic.ICollection`1" /> is greater than the available space from <paramref name="arrayIndex" /> to the end of the destination <paramref name="array" />.-or-Type <paramref name="T" /> cannot be cast automatically to the type of the destination <paramref name="array" />.</exception>
        public void CopyTo(KeyValuePair<K, V>[] array,
                           int arrayIndex) {
            mBackend.CopyTo(array,
                            arrayIndex);
        }

        /// <summary>
        /// Removes the first occurrence of a specific object from the <see cref="T:System.Collections.Generic.ICollection`1" />.
        /// </summary>
        /// <returns>
        /// true if <paramref name="item" /> was successfully removed from the <see cref="T:System.Collections.Generic.ICollection`1" />; otherwise, false. This method also returns false if <paramref name="item" /> is not found in the original <see cref="T:System.Collections.Generic.ICollection`1" />.
        /// </returns>
        /// <param name="item">The object to remove from the <see cref="T:System.Collections.Generic.ICollection`1" />.</param>
        /// <exception cref="T:System.NotSupportedException">The <see cref="T:System.Collections.Generic.ICollection`1" /> is read-only.</exception>
        public bool Remove(KeyValuePair<K, V> item) {
         throw new InvalidOperationException("Cannot remove from a read-only Dictionary");
        }

        /// <summary>
        /// Gets the number of elements contained in the <see cref="T:System.Collections.Generic.ICollection`1" />.
        /// </summary>
        /// <returns>
        /// The number of elements contained in the <see cref="T:System.Collections.Generic.ICollection`1" />.
        /// </returns>
        public int Count {
            get {
                return mBackend.Count;
            }
        }

        /// <summary>
        /// Gets a value indicating whether the <see cref="T:System.Collections.Generic.ICollection`1" /> is read-only.
        /// </summary>
        /// <returns>
        /// true if the <see cref="T:System.Collections.Generic.ICollection`1" /> is read-only; otherwise, false.
        /// </returns>
        public bool IsReadOnly {
            get {
                return true;
            }
        }

        /// <summary>
        /// Determines whether the <see cref="T:System.Collections.Generic.IDictionary`2" /> contains an element with the specified key.
        /// </summary>
        /// <returns>
        /// true if the <see cref="T:System.Collections.Generic.IDictionary`2" /> contains an element with the key; otherwise, false.
        /// </returns>
        /// <param name="key">The key to locate in the <see cref="T:System.Collections.Generic.IDictionary`2" />.</param>
        /// <exception cref="T:System.ArgumentNullException"><paramref name="key" /> is null.</exception>
        public bool ContainsKey(K key) {
            return mBackend.ContainsKey(key);
        }

        /// <summary>
        /// Adds an element with the provided key and value to the <see cref="T:System.Collections.Generic.IDictionary`2" />.
        /// </summary>
        /// <param name="key">The object to use as the key of the element to add.</param>
        /// <param name="value">The object to use as the value of the element to add.</param>
        /// <exception cref="T:System.ArgumentNullException"><paramref name="key" /> is null.</exception>
        /// <exception cref="T:System.ArgumentException">An element with the same key already exists in the <see cref="T:System.Collections.Generic.IDictionary`2" />.</exception>
        /// <exception cref="T:System.NotSupportedException">The <see cref="T:System.Collections.Generic.IDictionary`2" /> is read-only.</exception>
        public void Add(K key,
                        V value) {
            throw new InvalidOperationException("Cannot add to a read-only Dictionary");
        }

        /// <summary>
        /// Removes the element with the specified key from the <see cref="T:System.Collections.Generic.IDictionary`2" />.
        /// </summary>
        /// <returns>
        /// true if the element is successfully removed; otherwise, false.  This method also returns false if <paramref name="key" /> was not found in the original <see cref="T:System.Collections.Generic.IDictionary`2" />.
        /// </returns>
        /// <param name="key">The key of the element to remove.</param>
        /// <exception cref="T:System.ArgumentNullException"><paramref name="key" /> is null.</exception>
        /// <exception cref="T:System.NotSupportedException">The <see cref="T:System.Collections.Generic.IDictionary`2" /> is read-only.</exception>
        public bool Remove(K key) {
        throw new InvalidOperationException("Cannot remove from a read-only Dictionary");
        }

        /// <summary>
        /// Gets the value associated with the specified key.
        /// </summary>
        /// <returns>
        /// true if the object that implements <see cref="T:System.Collections.Generic.IDictionary`2" /> contains an element with the specified key; otherwise, false.
        /// </returns>
        /// <param name="key">The key whose value to get.</param>
        /// <param name="value">When this method returns, the value associated with the specified key, if the key is found; otherwise, the default value for the type of the <paramref name="value" /> parameter. This parameter is passed uninitialized.</param>
        /// <exception cref="T:System.ArgumentNullException"><paramref name="key" /> is null.</exception>
        public bool TryGetValue(K key,
                                out V value) {
            return mBackend.TryGetValue(key,
                                        out value);
        }

        /// <summary>
        /// Gets or sets the element with the specified key.
        /// </summary>
        /// <returns>
        /// The element with the specified key.
        /// </returns>
        /// <param name="key">The key of the element to get or set.</param>
        /// <exception cref="T:System.ArgumentNullException"><paramref name="key" /> is null.</exception>
        /// <exception cref="T:System.Collections.Generic.KeyNotFoundException">The property is retrieved and <paramref name="key" /> is not found.</exception>
        /// <exception cref="T:System.NotSupportedException">The property is set and the <see cref="T:System.Collections.Generic.IDictionary`2" /> is read-only.</exception>
        public V this[K key] {
            get {
                return mBackend[key];
            }
            set {
                throw new InvalidOperationException("Cannot change elements in a read-only Dictionary");
            }
        }

        /// <summary>
        /// Gets an <see cref="T:System.Collections.Generic.ICollection`1" /> containing the keys of the <see cref="T:System.Collections.Generic.IDictionary`2" />.
        /// </summary>
        /// <returns>
        /// An <see cref="T:System.Collections.Generic.ICollection`1" /> containing the keys of the object that implements <see cref="T:System.Collections.Generic.IDictionary`2" />.
        /// </returns>
        public ICollection<K> Keys {
            get {
                return mBackend.Keys;
            }
        }

        /// <summary>
        /// Gets an <see cref="T:System.Collections.Generic.ICollection`1" /> containing the values in the <see cref="T:System.Collections.Generic.IDictionary`2" />.
        /// </summary>
        /// <returns>
        /// An <see cref="T:System.Collections.Generic.ICollection`1" /> containing the values in the object that implements <see cref="T:System.Collections.Generic.IDictionary`2" />.
        /// </returns>
        public ICollection<V> Values {
            get {
                return mBackend.Values;
            }
        }
    }
}