using System;
using System.Linq;
using System.ComponentModel;
using System.Collections.Generic;
using System.Collections;

#if NETFX_CORE
    using specialized = System.Collections.Specialized;
#else
    using specialized = PlatformSupport.Collections.Specialized;
#endif

namespace PlatformSupport.Collections.ObjectModel
{
    public class ObservableDictionary<TKey, TValue> : IDictionary<TKey, TValue>, specialized.INotifyCollectionChanged, INotifyPropertyChanged
    {
        private const string CountString = "Count";
        private const string IndexerName = "Item[]";
        private const string KeysName = "Keys";
        private const string ValuesName = "Values";

        private IDictionary<TKey, TValue> _Dictionary;
        protected IDictionary<TKey, TValue> Dictionary
        {
            get { return _Dictionary; }
        }

#region Constructors
        public ObservableDictionary()
        {
            _Dictionary = new Dictionary<TKey, TValue>();
        }
        public ObservableDictionary(IDictionary<TKey, TValue> dictionary)
        {
            _Dictionary = new Dictionary<TKey, TValue>(dictionary);
        }
        public ObservableDictionary(IEqualityComparer<TKey> comparer)
        {
            _Dictionary = new Dictionary<TKey, TValue>(comparer);
        }
        public ObservableDictionary(int capacity)
        {
            _Dictionary = new Dictionary<TKey, TValue>(capacity);
        }
        public ObservableDictionary(IDictionary<TKey, TValue> dictionary, IEqualityComparer<TKey> comparer)
        {
            _Dictionary = new Dictionary<TKey, TValue>(dictionary, comparer);
        }
        public ObservableDictionary(int capacity, IEqualityComparer<TKey> comparer)
        {
            _Dictionary = new Dictionary<TKey, TValue>(capacity, comparer);
        }
#endregion

#region IDictionary<TKey,TValue> Members

        public void Add(TKey key, TValue value)
        {
            Insert(key, value, true);
        }

        public bool ContainsKey(TKey key)
        {
            return Dictionary.ContainsKey(key);
        }

        public ICollection<TKey> Keys
        {
            get { return Dictionary.Keys; }
        }

        public bool Remove(TKey key)
        {
            if (key == null) throw new ArgumentNullException("key");

            TValue value;
            Dictionary.TryGetValue(key, out value);
            var removed = Dictionary.Remove(key);
            if (removed)

                //OnCollectionChanged(NotifyCollectionChangedAction.Remove, new KeyValuePair<TKey, TValue>(key, value));
                OnCollectionChanged();


            return removed;
        }

        public bool TryGetValue(TKey key, out TValue value)
        {
            return Dictionary.TryGetValue(key, out value);
        }

        public ICollection<TValue> Values
        {
            get { return Dictionary.Values; }
        }

        public TValue this[TKey key]
        {
            get
            {
                return Dictionary[key];
            }
            set
            {
                Insert(key, value, false);
            }
        }

#endregion

#region ICollection<KeyValuePair<TKey,TValue>> Members

        public void Add(KeyValuePair<TKey, TValue> item)
        {
            Insert(item.Key, item.Value, true);
        }

        public void Clear()
        {
            if (Dictionary.Count > 0)
            {
                Dictionary.Clear();
                OnCollectionChanged();
            }
        }

        public bool Contains(KeyValuePair<TKey, TValue> item)
        {
            return Dictionary.Contains(item);
        }

        public void CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)
        {
            Dictionary.CopyTo(array, arrayIndex);
        }

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

        public bool IsReadOnly
        {
            get { return Dictionary.IsReadOnly; }
        }

        public bool Remove(KeyValuePair<TKey, TValue> item)
        {
            return Remove(item.Key);
        }

#endregion

#region IEnumerable<KeyValuePair<TKey,TValue>> Members

        public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
        {
            return Dictionary.GetEnumerator();
        }

#endregion

#region IEnumerable Members

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

#endregion

#region INotifyCollectionChanged Members

        public event specialized.NotifyCollectionChangedEventHandler CollectionChanged;

#endregion

#region INotifyPropertyChanged Members

        public event PropertyChangedEventHandler PropertyChanged;

#endregion

        public void AddRange(IDictionary<TKey, TValue> items)
        {
            if (items == null) throw new ArgumentNullException("items");

            if (items.Count > 0)
            {
                if (Dictionary.Count > 0)
                {
                    if (items.Keys.Any((k) => Dictionary.ContainsKey(k)))
                        throw new ArgumentException("An item with the same key has already been added.");
                    else
                        foreach (var item in items) Dictionary.Add(item);
                }
                else
                    _Dictionary = new Dictionary<TKey, TValue>(items);

                OnCollectionChanged(specialized.NotifyCollectionChangedAction.Add, items.ToArray());
            }
        }

        private void Insert(TKey key, TValue value, bool add)
        {
            if (key == null) throw new ArgumentNullException("key");

            TValue item;
            if (Dictionary.TryGetValue(key, out item))
            {
                if (add) throw new ArgumentException("An item with the same key has already been added.");
                if (Equals(item, value)) return;
                Dictionary[key] = value;

                OnCollectionChanged(specialized.NotifyCollectionChangedAction.Replace, new KeyValuePair<TKey, TValue>(key, value), new KeyValuePair<TKey, TValue>(key, item));
            }
            else
            {
                Dictionary[key] = value;

                OnCollectionChanged(specialized.NotifyCollectionChangedAction.Add, new KeyValuePair<TKey, TValue>(key, value));
            }
        }

        private void OnPropertyChanged()
        {
            OnPropertyChanged(CountString);
            OnPropertyChanged(IndexerName);
            OnPropertyChanged(KeysName);
            OnPropertyChanged(ValuesName);
        }

        protected virtual void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }

        private void OnCollectionChanged()
        {
            OnPropertyChanged();
            if (CollectionChanged != null) CollectionChanged(this, new specialized.NotifyCollectionChangedEventArgs(specialized.NotifyCollectionChangedAction.Reset));
        }

        private void OnCollectionChanged(specialized.NotifyCollectionChangedAction action, KeyValuePair<TKey, TValue> changedItem)
        {
            OnPropertyChanged();
            if (CollectionChanged != null) CollectionChanged(this, new specialized.NotifyCollectionChangedEventArgs(action, changedItem));
        }

        private void OnCollectionChanged(specialized.NotifyCollectionChangedAction action, KeyValuePair<TKey, TValue> newItem, KeyValuePair<TKey, TValue> oldItem)
        {
            OnPropertyChanged();
            if (CollectionChanged != null) CollectionChanged(this, new specialized.NotifyCollectionChangedEventArgs(action, newItem, oldItem));
        }

        private void OnCollectionChanged(specialized.NotifyCollectionChangedAction action, IList newItems)
        {
            OnPropertyChanged();
            if (CollectionChanged != null) CollectionChanged(this, new specialized.NotifyCollectionChangedEventArgs(action, newItems));
        }
    }
}