// ==++==
// 
//   Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// ==--==
//------------------------------------------------------------------------------
//------------------------------------------------------------------------------
// <OWNER>[....]</OWNER>
// 

namespace System.Collections {

    using System;
    using System.Security.Permissions;

    // Useful base class for typed read/write collections where items derive from object
    [Serializable]
[System.Runtime.InteropServices.ComVisible(true)]
    public abstract class DictionaryBase : IDictionary {
        Hashtable hashtable;

        protected Hashtable InnerHashtable { 
            get { 
                if (hashtable == null)
                    hashtable = new Hashtable();
                return hashtable;
            }
        }

        protected IDictionary Dictionary {
            get { return (IDictionary) this; }
        }

        public int Count {
            // to avoid newing inner list if no items are ever added
            get { return hashtable == null ? 0 : hashtable.Count; }
        }

        bool IDictionary.IsReadOnly {
            get { return InnerHashtable.IsReadOnly; }
        }

        bool IDictionary.IsFixedSize {
            get { return InnerHashtable.IsFixedSize; }
        }

        bool ICollection.IsSynchronized {
            get { return InnerHashtable.IsSynchronized; }
        }

        ICollection IDictionary.Keys {
            get {
                return InnerHashtable.Keys;
            }
        }

        Object ICollection.SyncRoot {
            get { return InnerHashtable.SyncRoot; }
        }

        ICollection IDictionary.Values {
            get {
                return InnerHashtable.Values;
            }
        }

        public void CopyTo(Array array, int index) {
            InnerHashtable.CopyTo(array, index);
        }

        object IDictionary.this[object key] {
            get {
                object currentValue = InnerHashtable[key];
                OnGet(key, currentValue);
                return currentValue; 
            }
            set { 
                OnValidate(key, value);
                bool keyExists = true;
                Object temp = InnerHashtable[key];
                if( temp == null) {
                    keyExists = InnerHashtable.Contains(key);
                }

                OnSet(key, temp, value); 
                InnerHashtable[key] = value; 
                try {
                    OnSetComplete(key, temp, value); 
                }
                catch {
                   if( keyExists) {
                       InnerHashtable[key] = temp; 
                   }
                   else {
                       InnerHashtable.Remove(key);
                   }
                   throw;
                }
            }
        }

        bool IDictionary.Contains(object key) {
            return InnerHashtable.Contains(key);
        }

        void IDictionary.Add(object key, object value) {
            OnValidate(key, value);
            OnInsert(key, value); 
            InnerHashtable.Add(key, value);
            try {
                OnInsertComplete(key, value);
            }
            catch {
                InnerHashtable.Remove(key);
                throw;
            }
        }

        public void Clear() {
            OnClear();
            InnerHashtable.Clear();
            OnClearComplete();
        }

        void IDictionary.Remove(object key) {
            if(InnerHashtable.Contains(key)) {
                Object temp = InnerHashtable[key];
                OnValidate(key, temp);
                OnRemove(key, temp);

                InnerHashtable.Remove(key);
                try {
                    OnRemoveComplete(key, temp);
                }
                catch {
                    InnerHashtable.Add(key, temp);
                    throw;
                }
            }
        }

        public IDictionaryEnumerator GetEnumerator() {
            return InnerHashtable.GetEnumerator();
        }

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

        protected virtual object OnGet(object key, object currentValue) {
            return currentValue;
        }

        protected virtual void OnSet(object key, object oldValue, object newValue) { 
        }

        protected virtual void OnInsert(object key, object value) { 
        }

        protected virtual void OnClear() { 
        }

        protected virtual void OnRemove(object key, object value) { 
        }

        protected virtual void OnValidate(object key, object value) {
        }
        
        protected virtual void OnSetComplete(object key, object oldValue, object newValue) { 
        }

        protected virtual void OnInsertComplete(object key, object value) { 
        }

        protected virtual void OnClearComplete() { 
        }

        protected virtual void OnRemoveComplete(object key, object value) { 
        }
        
    }

}