//------------------------------------------------------------------------------
// <copyright file="StringDictionary.cs" company="Microsoft">
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>                                                                
//------------------------------------------------------------------------------

/*
 */
namespace System.Collections.Specialized {
    using System.Runtime.InteropServices;
    using System.Diagnostics;
    using System;
    using System.Collections;
    using System.ComponentModel.Design.Serialization;
    using System.Globalization;
    using System.Collections.Generic;
    
    /// <devdoc>
    ///    <para>Implements a hashtable with the key strongly typed to be
    ///       a string rather than an object. </para>
    ///    <para>Consider this class obsolete - use Dictionary&lt;String, String&gt; instead
    ///       with a proper StringComparer instance.</para>
    /// </devdoc>
    [Serializable]
    [DesignerSerializer("System.Diagnostics.Design.StringDictionaryCodeDomSerializer, " + AssemblyRef.SystemDesign, "System.ComponentModel.Design.Serialization.CodeDomSerializer, " + AssemblyRef.SystemDesign)]
    // @
    public class StringDictionary : IEnumerable {

        // For compatibility, we want the Keys property to return values in lower-case.
        // That means using ToLower in each property on this type.  Also for backwards
        // compatibility, we will be converting strings to lower-case, which has a 
        // problem for some Georgian alphabets.  Can't really fix it now though...
        internal Hashtable contents = new Hashtable();

        
        /// <devdoc>
        /// <para>Initializes a new instance of the StringDictionary class.</para>
        /// <para>If you're using file names, registry keys, etc, you want to use
        /// a Dictionary&lt;String, Object&gt; and use 
        /// StringComparer.OrdinalIgnoreCase.</para>
        /// </devdoc>
        public StringDictionary() {
        }

        /// <devdoc>
        /// <para>Gets the number of key-and-value pairs in the StringDictionary.</para>
        /// </devdoc>
        public virtual int Count {
            get {
                return contents.Count;
            }
        }

        
        /// <devdoc>
        /// <para>Indicates whether access to the StringDictionary is synchronized (thread-safe). This property is 
        ///    read-only.</para>
        /// </devdoc>
        public virtual bool IsSynchronized {
            get {
                return contents.IsSynchronized;
            }
        }

        /// <devdoc>
        ///    <para>Gets or sets the value associated with the specified key.</para>
        /// </devdoc>
        public virtual string this[string key] {
            get {
                if( key == null ) {
                    throw new ArgumentNullException("key");
                }

                return (string) contents[key.ToLower(CultureInfo.InvariantCulture)];
            }
            set {
                if( key == null ) {
                    throw new ArgumentNullException("key");
                }

                contents[key.ToLower(CultureInfo.InvariantCulture)] = value;
            }
        }

        /// <devdoc>
        /// <para>Gets a collection of keys in the StringDictionary.</para>
        /// </devdoc>
        public virtual ICollection Keys {
            get {
                return contents.Keys;
            }
        }

        
        /// <devdoc>
        /// <para>Gets an object that can be used to synchronize access to the StringDictionary.</para>
        /// </devdoc>
        public virtual object SyncRoot {
            get {
                return contents.SyncRoot;
            }
        }

        /// <devdoc>
        /// <para>Gets a collection of values in the StringDictionary.</para>
        /// </devdoc>
        public virtual ICollection Values {
            get {
                return contents.Values;
            }
        }

        /// <devdoc>
        /// <para>Adds an entry with the specified key and value into the StringDictionary.</para>
        /// </devdoc>
        public virtual void Add(string key, string value) {
            if( key == null ) {
                throw new ArgumentNullException("key");
            }

            contents.Add(key.ToLower(CultureInfo.InvariantCulture), value);
        }

        /// <devdoc>
        /// <para>Removes all entries from the StringDictionary.</para>
        /// </devdoc>
        public virtual void Clear() {
            contents.Clear();
        }

        /// <devdoc>
        ///    <para>Determines if the string dictionary contains a specific key</para>
        /// </devdoc>
        public virtual bool ContainsKey(string key) {
            if( key == null ) {
                throw new ArgumentNullException("key");
            }

            return contents.ContainsKey(key.ToLower(CultureInfo.InvariantCulture));
        }

        /// <devdoc>
        /// <para>Determines if the StringDictionary contains a specific value.</para>
        /// </devdoc>
        public virtual bool ContainsValue(string value) {
            return contents.ContainsValue(value);
        }

        /// <devdoc>
        /// <para>Copies the string dictionary values to a one-dimensional <see cref='System.Array'/> instance at the 
        ///    specified index.</para>
        /// </devdoc>
        public virtual void CopyTo(Array array, int index) {
            contents.CopyTo(array, index);
        }

        /// <devdoc>
        ///    <para>Returns an enumerator that can iterate through the string dictionary.</para>
        /// </devdoc>
        public virtual IEnumerator GetEnumerator() {
            return contents.GetEnumerator();
        }

        /// <devdoc>
        ///    <para>Removes the entry with the specified key from the string dictionary.</para>
        /// </devdoc>
        public virtual void Remove(string key) {
            if( key == null ) {
                throw new ArgumentNullException("key");
            }

            contents.Remove(key.ToLower(CultureInfo.InvariantCulture));
        }

        /// <summary>
        /// Make this StringDictionary subservient to some other collection.
        /// <para>Some code was replacing the contents field with a Hashtable created elsewhere.
        /// While it may not have been incorrect, we don't want to encourage that pattern, because
        /// it will replace the IEqualityComparer in the Hashtable, and creates a possibly-undesirable
        /// link between two seemingly different collections.  Let's discourage that somewhat by
        /// making this an explicit method call instead of an internal field assignment.</para>
        /// </summary>
        /// <param name="useThisHashtableInstead">Replaces the backing store with another, possibly aliased Hashtable.</param>
        internal void ReplaceHashtable(Hashtable useThisHashtableInstead) {
            contents = useThisHashtableInstead;
        }

        internal IDictionary<string, string> AsGenericDictionary() {
            return new GenericAdapter(this);
        }

#region GenericAdapter
        //
    // This class is used to make StringDictionary implement IDictionary<string,string> indirectly. 
    // This is done to prevent StringDictionary be serialized as IDictionary<string,string> and break its serialization by DataContractSerializer due to a bug in the serialization code.
    private class GenericAdapter : IDictionary<string, string>
    {

        StringDictionary m_stringDictionary;

        internal GenericAdapter(StringDictionary stringDictionary) {
            m_stringDictionary = stringDictionary;
        }

        #region IDictionary<string, string> Members
        public void Add(string key, string value) {

            // GenericAdapter.Add has the semantics of Item property to make ProcessStartInfo.Environment deserializable by DataContractSerializer.
            // ProcessStartInfo.Environment property does not have a setter
            // and so during deserialization the serializer initializes the property by calling get_Environment and 
            // then populates it via IDictionary<,>.Add per item.
            // However since get_Environment gives the current snapshot of environment variables we might try to insert a key that already exists.
            // (For Example 'PATH') causing an exception. This implementation ensures that we overwrite values in case of duplication.

            this[key] =  value;
        }

        public bool ContainsKey(string key) {
            return m_stringDictionary.ContainsKey(key);
        }

        public void Clear() {
            m_stringDictionary.Clear();
        }

        public int Count {
            get {
                return m_stringDictionary.Count;
            }
        }

        // Items added to allow StringDictionary to provide IDictionary<string, string> support.
        ICollectionToGenericCollectionAdapter _values;
        ICollectionToGenericCollectionAdapter _keys;

        // IDictionary<string,string>.Item vs StringDictioanry.Item
        // IDictionary<string,string>.get_Item         i. KeyNotFoundException when the property is retrieved and key is not found.
        // StringBuilder.get_Item                      i. Returns null in case the key is not found.
        public string this[string key] {
            get {
                if (key == null) {
                    throw new ArgumentNullException("key");
                }

                if (!m_stringDictionary.ContainsKey(key)) throw new KeyNotFoundException();

                return m_stringDictionary[key];
            }
            set {
                if (key == null) {
                    throw new ArgumentNullException("key");
                }

                m_stringDictionary[key] = value;
            }
        }

        // This method returns a read-only view of the Keys in the StringDictinary.
        public ICollection<string> Keys {
            get {
                if( _keys == null ) {
                    _keys = new ICollectionToGenericCollectionAdapter(m_stringDictionary, KeyOrValue.Key);
                }
                return _keys;
            }
        }

        // This method returns a read-only view of the Values in the StringDictionary.
        public ICollection<string> Values {
            get {
                if( _values == null ) {
                    _values = new ICollectionToGenericCollectionAdapter(m_stringDictionary, KeyOrValue.Value);
                }
                return _values;
            }
        }

        // IDictionary<string,string>.Remove vs StringDictionary.Remove.
        // IDictionary<string,string>.Remove-  i. Returns a bool status that represents success\failure.
        //                                    ii. Returns false in case key is not found.
        // StringDictionary.Remove             i. Does not return the status and does nothing in case key is not found.
        public bool Remove(string key) {

            // Check if the key is not present and return false.
            if (!m_stringDictionary.ContainsKey(key)) return false;

            // We call the virtual StringDictionary.Remove method to ensure any subClass gets the expected behavior.
            m_stringDictionary.Remove(key);

            // If the above call has succeeded we simply return true.
            return true;
        }


        public bool TryGetValue(string key, out string value) {
            if (!m_stringDictionary.ContainsKey(key)) {
                value = null;
                return false;
            }

            value = m_stringDictionary[key];
            return true;
        }

        void ICollection<KeyValuePair<string, string>>.Add(KeyValuePair<string, string> item) {
            m_stringDictionary.Add(item.Key, item.Value);
        }

        bool ICollection<KeyValuePair<string, string>>.Contains(KeyValuePair<string, string> item) {
            string value;
            return TryGetValue(item.Key, out value) && value.Equals(item.Value);
        }

        void ICollection<KeyValuePair<string, string>>.CopyTo(KeyValuePair<string, string>[] array, int arrayIndex) {
            if( array == null )
                throw new ArgumentNullException("array", SR.GetString(SR.ArgumentNull_Array));
            if( arrayIndex < 0 )
                throw new ArgumentOutOfRangeException("arrayIndex", SR.GetString(SR.ArgumentOutOfRange_NeedNonNegNum));
            if( array.Length - arrayIndex < Count )
                throw new ArgumentException(SR.GetString(SR.Arg_ArrayPlusOffTooSmall));

            int index = arrayIndex;

            foreach (DictionaryEntry entry in m_stringDictionary) {
                array[index++] = new KeyValuePair<string, string>((string)entry.Key, (string)entry.Value);
            }
        }

        bool ICollection<KeyValuePair<string,string>>.IsReadOnly {
            get {
                return false;
            }
        }

        // ICollection<KeyValuePair<string, string>>.Remove vs StringDictionary.Remove
        // ICollection<KeyValuePair<string, string>>.Remove - i. Return status.
        //                                                   ii. Returns false in case the items is not found.
        // StringDictionary.Remove                            i. Does not return a status and does nothing in case the key is not found.
        bool ICollection<KeyValuePair<string, string>>.Remove(KeyValuePair<string, string> item) {

            // If the item is not found return false.
            ICollection<KeyValuePair<string, string>> iCollection = this;
            if( !iCollection.Contains(item) ) return false;

            // We call the virtual StringDictionary.Remove method to ensure any subClass gets the expected behavior.
            m_stringDictionary.Remove(item.Key);

            // If the above call has succeeded we simply return true.
            return true;
        }

        IEnumerator IEnumerable.GetEnumerator() {
            return this.GetEnumerator();
        }

        // The implementation asummes that this.GetEnumerator().Current can be casted to DictionaryEntry.
        // and although StringDictionary.GetEnumerator() returns IEnumerator and is a virtual method
        // it should be ok to take that assumption since it is an implicit contract.
        public IEnumerator<KeyValuePair<string, string>> GetEnumerator()
        {
            foreach (DictionaryEntry dictionaryEntry in m_stringDictionary)
                yield return new KeyValuePair<string, string>((string)dictionaryEntry.Key, (string)dictionaryEntry.Value);
        }

        internal enum KeyOrValue // Used internally for IDictionary<string, string> support 
        {
            Key,
            Value
        }

        // This Adapter converts StringDictionary.Keys and StringDictionary.Values to ICollection<string>
        // Since StringDictionary implements a virtual StringDictionary.Keys and StringDictionary.Values 
        private class ICollectionToGenericCollectionAdapter : ICollection<string> {

            StringDictionary _internal;
            KeyOrValue _keyOrValue;

            public ICollectionToGenericCollectionAdapter(StringDictionary source, KeyOrValue keyOrValue) {
                if (source == null) throw new ArgumentNullException("source");

                _internal = source;
                _keyOrValue = keyOrValue;
            }

            public void Add(string item) {
                ThrowNotSupportedException();
            }

            public void Clear() {
                ThrowNotSupportedException();
            }

            public void ThrowNotSupportedException() {
                if( _keyOrValue == KeyOrValue.Key ) {
                    throw new NotSupportedException(SR.GetString(SR.NotSupported_KeyCollectionSet)); //Same as KeyCollection/ValueCollection
                }
                throw new NotSupportedException(SR.GetString(SR.NotSupported_ValueCollectionSet)); //Same as KeyCollection/ValueCollection
            }


            public bool Contains(string item) {
                // The underlying backing store for the StringDictionary is a HashTable so we 
                // want to delegate Contains to respective ContainsKey/ContainsValue functionality 
                // depending upon whether we are using Keys or Value collections.            

                if( _keyOrValue == KeyOrValue.Key ) {
                    return _internal.ContainsKey(item);
                }
                return _internal.ContainsValue(item);
            }

            public void CopyTo(string[] array, int arrayIndex) {
                var collection = GetUnderlyingCollection();
                collection.CopyTo(array, arrayIndex);
            }

            public int Count {
                get {
                    return _internal.Count;  // hashtable count is same as key/value count.
                }
            }

            public bool IsReadOnly {
                get {
                    return true; //Same as KeyCollection/ValueCollection
                }
            }

            public bool Remove(string item) {
                ThrowNotSupportedException();
                return false;
            }

            private ICollection GetUnderlyingCollection() {
                if( _keyOrValue == KeyOrValue.Key ) {
                    return (ICollection) _internal.Keys;
                }
                return (ICollection) _internal.Values;
            }

            public IEnumerator<string> GetEnumerator() {
                ICollection collection = GetUnderlyingCollection();

                // This is doing the same as collection.Cast<string>()
                foreach (string entry in collection) {
                    yield return entry;
                }
            }

            IEnumerator IEnumerable.GetEnumerator() {
                return GetUnderlyingCollection().GetEnumerator();
            }
        }
        #endregion
    }
#endregion
    }
}