#region Apache License 2.0
/*
Nuclex .NET Framework
Copyright (C) 2002-2024 Markus Ewald / Nuclex Development Labs

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.
*/
#endregion // Apache License 2.0

using System;
using System.Collections.Generic;
using System.Collections;
using System.Runtime.Serialization;

namespace Nuclex.Support.Collections {

  /// <summary>Wraps a dictionary and prevents users from modifying it</summary>
  /// <typeparam name="KeyType">Type of the keys used in the dictionary</typeparam>
  /// <typeparam name="ValueType">Type of the values used in the dictionary</typeparam>
#if !NO_SERIALIZATION
  [Serializable]
#endif
  public class ReadOnlyDictionary<KeyType, ValueType> :
#if !NO_SERIALIZATION
    ISerializable,
    IDeserializationCallback,
#endif
    IDictionary,
    IDictionary<KeyType, ValueType> {

#if !NO_SERIALIZATION

    #region class SerializedDictionary

    /// <summary>
    ///   Dictionary wrapped used to reconstruct a serialized read only dictionary
    /// </summary>
    private class SerializedDictionary : Dictionary<KeyType, ValueType> {

      /// <summary>
      ///   Initializes a new instance of the System.WeakReference class, using deserialized
      ///   data from the specified serialization and stream objects.
      /// </summary>
      /// <param name="info">
      ///   An object that holds all the data needed to serialize or deserialize the
      ///   current System.WeakReference object.
      /// </param>
      /// <param name="context">
      ///   (Reserved) Describes the source and destination of the serialized stream
      ///   specified by info.
      /// </param>
      /// <exception cref="System.ArgumentNullException">
      ///   The info parameter is null.
      /// </exception>
      public SerializedDictionary(SerializationInfo info, StreamingContext context) :
        base(info, context) { }

    }

    #endregion // class SerializedDictionary

    /// <summary>
    ///   Initializes a new instance of the System.WeakReference class, using deserialized
    ///   data from the specified serialization and stream objects.
    /// </summary>
    /// <param name="info">
    ///   An object that holds all the data needed to serialize or deserialize the
    ///   current System.WeakReference object.
    /// </param>
    /// <param name="context">
    ///   (Reserved) Describes the source and destination of the serialized stream
    ///   specified by info.
    /// </param>
    /// <exception cref="System.ArgumentNullException">
    ///   The info parameter is null.
    /// </exception>
    protected ReadOnlyDictionary(SerializationInfo info, StreamingContext context) :
      this(new SerializedDictionary(info, context)) { }

#endif // !NO_SERIALIZATION

    /// <summary>Initializes a new read-only dictionary wrapper</summary>
    /// <param name="dictionary">Dictionary that will be wrapped</param>
    public ReadOnlyDictionary(IDictionary<KeyType, ValueType> dictionary) {
      this.typedDictionary = dictionary;
      this.objectDictionary = (this.typedDictionary as IDictionary);
    }

    /// <summary>Whether the directory is write-protected</summary>
    public bool IsReadOnly {
      get { return true; }
    }

    /// <summary>
    ///   Determines whether the specified KeyValuePair is contained in the Dictionary
    /// </summary>
    /// <param name="item">KeyValuePair that will be checked for</param>
    /// <returns>True if the provided KeyValuePair was contained in the Dictionary</returns>
    public bool Contains(KeyValuePair<KeyType, ValueType> item) {
      return this.typedDictionary.Contains(item);
    }

    /// <summary>Determines whether the Dictionary contains the specified key</summary>
    /// <param name="key">Key that will be checked for</param>
    /// <returns>
    ///   True if an entry with the specified key was contained in the Dictionary
    /// </returns>
    public bool ContainsKey(KeyType key) {
      return this.typedDictionary.ContainsKey(key);
    }

    /// <summary>Copies the contents of the Dictionary into an array</summary>
    /// <param name="array">Array the Dictionary will be copied into</param>
    /// <param name="arrayIndex">
    ///   Starting index at which to begin filling the destination array
    /// </param>
    public void CopyTo(KeyValuePair<KeyType, ValueType>[] array, int arrayIndex) {
      this.typedDictionary.CopyTo(array, arrayIndex);
    }

    /// <summary>Number of elements contained in the Dictionary</summary>
    public int Count {
      get { return this.typedDictionary.Count; }
    }

    /// <summary>Creates a new enumerator for the Dictionary</summary>
    /// <returns>The new Dictionary enumerator</returns>
    public IEnumerator<KeyValuePair<KeyType, ValueType>> GetEnumerator() {
      return this.typedDictionary.GetEnumerator();
    }

    /// <summary>Collection of all keys contained in the Dictionary</summary>
    public ICollection<KeyType> Keys {
      get {
        if(this.readonlyKeyCollection == null) {
          this.readonlyKeyCollection = new ReadOnlyCollection<KeyType>(
            this.typedDictionary.Keys
          );
        }

        return this.readonlyKeyCollection;
      }
    }

    /// <summary>Collection of all values contained in the Dictionary</summary>
    public ICollection<ValueType> Values {
      get {
        if(this.readonlyValueCollection == null) {
          this.readonlyValueCollection = new ReadOnlyCollection<ValueType>(
            this.typedDictionary.Values
          );
        }

        return this.readonlyValueCollection;
      }
    }

    /// <summary>
    ///   Attempts to retrieve the item with the specified key from the Dictionary
    /// </summary>
    /// <param name="key">Key of the item to attempt to retrieve</param>
    /// <param name="value">
    ///   Output parameter that will receive the key upon successful completion
    /// </param>
    /// <returns>
    ///   True if the item was found and has been placed in the output parameter
    /// </returns>
    public bool TryGetValue(KeyType key, out ValueType value) {
      return this.typedDictionary.TryGetValue(key, out value);
    }

    /// <summary>Accesses an item in the Dictionary by its key</summary>
    /// <param name="key">Key of the item that will be accessed</param>
    public ValueType this[KeyType key] {
      get { return this.typedDictionary[key]; }
    }

    #region IDictionary<,> implementation

    /// <summary>Inserts an item into the Dictionary</summary>
    /// <param name="key">Key under which to add the new item</param>
    /// <param name="value">Item that will be added to the Dictionary</param>
    void IDictionary<KeyType, ValueType>.Add(KeyType key, ValueType value) {
      throw new NotSupportedException(
        "Adding items is not supported by the read-only Dictionary"
      );
    }

    /// <summary>Removes the item with the specified key from the Dictionary</summary>
    /// <param name="key">Key of the elementes that will be removed</param>
    /// <returns>True if an item with the specified key was found and removed</returns>
    bool IDictionary<KeyType, ValueType>.Remove(KeyType key) {
      throw new NotSupportedException(
        "Removing items is not supported by the read-only Dictionary"
      );
    }

    /// <summary>Accesses an item in the Dictionary by its key</summary>
    /// <param name="key">Key of the item that will be accessed</param>
    ValueType IDictionary<KeyType, ValueType>.this[KeyType key] {
      get { return this.typedDictionary[key]; }
      set {
        throw new NotSupportedException(
          "Assigning items is not supported in a read-only Dictionary"
        );
      }
    }

    #endregion

    #region IEnumerable implementation

    /// <summary>Returns a new object enumerator for the Dictionary</summary>
    /// <returns>The new object enumerator</returns>
    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() {
      return (this.typedDictionary as IEnumerable).GetEnumerator();
    }

    #endregion

    #region IDictionary implementation

    /// <summary>Removes all items from the Dictionary</summary>
    void IDictionary.Clear() {
      throw new NotSupportedException(
        "Clearing is not supported in a read-only Dictionary"
      );
    }

    /// <summary>Adds an item into the Dictionary</summary>
    /// <param name="key">Key under which the item will be added</param>
    /// <param name="value">Item that will be added</param>
    void IDictionary.Add(object key, object value) {
      throw new NotSupportedException(
        "Adding items is not supported in a read-only Dictionary"
      );
    }

    /// <summary>Determines whether the specified key exists in the Dictionary</summary>
    /// <param name="key">Key that will be checked for</param>
    /// <returns>True if an item with the specified key exists in the Dictionary</returns>
    bool IDictionary.Contains(object key) {
      return this.objectDictionary.Contains(key);
    }

    /// <summary>Whether the size of the Dictionary is fixed</summary>
    bool IDictionary.IsFixedSize {
      get { return this.objectDictionary.IsFixedSize; }
    }

    /// <summary>Returns a collection of all keys in the Dictionary</summary>
    ICollection IDictionary.Keys {
      get {
        if(this.readonlyKeyCollection == null) {
          this.readonlyKeyCollection = new ReadOnlyCollection<KeyType>(
            this.typedDictionary.Keys
          );
        }

        return this.readonlyKeyCollection;
      }
    }

    /// <summary>Returns a collection of all values stored in the Dictionary</summary>
    ICollection IDictionary.Values {
      get {
        if(this.readonlyValueCollection == null) {
          this.readonlyValueCollection = new ReadOnlyCollection<ValueType>(
            this.typedDictionary.Values
          );
        }

        return this.readonlyValueCollection;
      }
    }

    /// <summary>Removes an item from the Dictionary</summary>
    /// <param name="key">Key of the item that will be removed</param>
    void IDictionary.Remove(object key) {
      throw new NotSupportedException(
        "Removing is not supported by the read-only Dictionary"
      );
    }

    /// <summary>Accesses an item in the Dictionary by its key</summary>
    /// <param name="key">Key of the item that will be accessed</param>
    /// <returns>The item with the specified key</returns>
    object IDictionary.this[object key] {
      get { return this.objectDictionary[key]; }
      set {
        throw new NotSupportedException(
          "Assigning items is not supported by the read-only Dictionary"
        );
      }
    }

    #endregion // IDictionary implementation

    #region IDictionaryEnumerator implementation

    /// <summary>Returns a new entry enumerator for the dictionary</summary>
    /// <returns>The new entry enumerator</returns>
    IDictionaryEnumerator IDictionary.GetEnumerator() {
      return this.objectDictionary.GetEnumerator();
    }

    #endregion // IDictionaryEnumerator implementation

    #region ICollection<> implementation

    /// <summary>Inserts an already prepared element into the Dictionary</summary>
    /// <param name="item">Prepared element that will be added to the Dictionary</param>
    void ICollection<KeyValuePair<KeyType, ValueType>>.Add(
      KeyValuePair<KeyType, ValueType> item
    ) {
      throw new NotSupportedException(
        "Adding items is not supported by the read-only Dictionary"
      );
    }

    /// <summary>Removes all items from the Dictionary</summary>
    void ICollection<KeyValuePair<KeyType, ValueType>>.Clear() {
      throw new NotSupportedException(
        "Clearing is not supported in a read-only Dictionary"
      );
    }

    /// <summary>Removes all items from the Dictionary</summary>
    /// <param name="itemToRemove">Item that will be removed from the Dictionary</param>
    bool ICollection<KeyValuePair<KeyType, ValueType>>.Remove(
      KeyValuePair<KeyType, ValueType> itemToRemove
    ) {
      throw new NotSupportedException(
        "Removing items is not supported in a read-only Dictionary"
      );
    }

    #endregion

    #region ICollection implementation

    /// <summary>Copies the contents of the Dictionary into an array</summary>
    /// <param name="array">Array the Dictionary contents will be copied into</param>
    /// <param name="index">
    ///   Starting index at which to begin filling the destination array
    /// </param>
    void ICollection.CopyTo(Array array, int index) {
      this.objectDictionary.CopyTo(array, index);
    }

    /// <summary>Whether the Dictionary is synchronized for multi-threaded usage</summary>
    bool ICollection.IsSynchronized {
      get { return this.objectDictionary.IsSynchronized; }
    }

    /// <summary>Synchronization root on which the Dictionary locks</summary>
    object ICollection.SyncRoot {
      get { return this.objectDictionary.SyncRoot; }
    }

    #endregion

#if !NO_SERIALIZATION
    #region ISerializable implementation

    /// <summary>Serializes the Dictionary</summary>
    /// <param name="info">
    ///   Provides the container into which the Dictionary will serialize itself
    /// </param>
    /// <param name="context">
    ///   Contextual informations about the serialization environment
    /// </param>
    void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context) {
      (this.typedDictionary as ISerializable).GetObjectData(info, context);
    }

    /// <summary>Called after all objects have been successfully deserialized</summary>
    /// <param name="sender">Nicht unterstützt</param>
    void IDeserializationCallback.OnDeserialization(object sender) {
      (this.typedDictionary as IDeserializationCallback).OnDeserialization(sender);
    }

    #endregion
#endif //!NO_SERIALIZATION

    /// <summary>The wrapped Dictionary under its type-safe interface</summary>
    private IDictionary<KeyType, ValueType> typedDictionary;
    /// <summary>The wrapped Dictionary under its object interface</summary>
    private IDictionary objectDictionary;
    /// <summary>ReadOnly wrapper for the keys collection of the Dictionary</summary>
    private ReadOnlyCollection<KeyType> readonlyKeyCollection;
    /// <summary>ReadOnly wrapper for the values collection of the Dictionary</summary>
    private ReadOnlyCollection<ValueType> readonlyValueCollection;
  }

} // namespace Nuclex.Support.Collections