using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Data;
using System.Windows.Threading;

namespace Tango.Core
{
    public static class SynchronizedObservableCollectionConfig
    {
        public static bool DisableSynchronization { get; set; }
    }

    public class SynchronizedObservableCollection<T> : ObservableCollection<T>
    {
        private object _sync_lock = new object();
        private object _modify_lock = new object();
        private SynchronizedObservableCollectionDispatcher _dispatcher;

        public bool DisableSynchronization { get; set; } = SynchronizedObservableCollectionConfig.DisableSynchronization;

        public SynchronizedObservableCollection() : base()
        {
            if (!DisableSynchronization)
            {
                _dispatcher = new SynchronizedObservableCollectionDispatcher();
                BindingOperations.EnableCollectionSynchronization(this, _modify_lock);
            }
        }

        public SynchronizedObservableCollection(IEnumerable<T> collection) : base(collection)
        {
            if (!DisableSynchronization)
            {
                _dispatcher = new SynchronizedObservableCollectionDispatcher();
                BindingOperations.EnableCollectionSynchronization(this, _modify_lock);
            }
        }

        protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
        {
            if (!DisableSynchronization)
            {
                lock (_modify_lock)
                {
                    _dispatcher.Invoke(() =>
                    {
                        base.OnCollectionChanged(e);
                    });
                }
            }
            else
            {
                base.OnCollectionChanged(e);
            }
        }

        protected override void InsertItem(int index, T item)
        {
            if (!DisableSynchronization)
            {
                lock (_modify_lock)
                {
                    base.InsertItem(index, item);
                }
            }
            else
            {
                base.InsertItem(index, item);
            }
        }

        protected override void RemoveItem(int index)
        {
            if (!DisableSynchronization)
            {
                lock (_modify_lock)
                {
                    base.RemoveItem(index);
                }
            }
            else
            {
                base.RemoveItem(index);
            }
        }

        protected override void ClearItems()
        {
            if (!DisableSynchronization)
            {
                lock (_modify_lock)
                {
                    base.ClearItems();
                }
            }
            else
            {
                base.ClearItems();
            }
        }
    }

    internal class SynchronizedObservableCollectionDispatcher
    {
        internal Dispatcher Dispatcher { get; set; }

        internal SynchronizedObservableCollectionDispatcher()
        {
            if (Application.Current != null)
            {
                Dispatcher = Application.Current.Dispatcher;
            }
        }

        internal void Invoke(Action action)
        {
            if (Dispatcher != null)
            {
                Dispatcher.Invoke(action);
            }
            else
            {
                action();
            }
        }
    }
}