using System;
using System.Collections.Generic;

namespace XCEngine.Rendering
{
    public sealed class ContextContainer : IDisposable
    {
        private readonly Dictionary<Type, ContextItem> m_items =
            new Dictionary<Type, ContextItem>();
        private bool m_disposed;

        public bool Contains<T>()
            where T : ContextItem
        {
            return m_items.ContainsKey(typeof(T));
        }

        public T Create<T>()
            where T : ContextItem, new()
        {
            ThrowIfDisposed();
            T item = new T();
            m_items[typeof(T)] = item;
            return item;
        }

        public T Get<T>()
            where T : ContextItem
        {
            ThrowIfDisposed();
            ContextItem item;
            if (!m_items.TryGetValue(
                    typeof(T),
                    out item))
            {
                throw new InvalidOperationException(
                    "Context item is not available: " +
                    typeof(T).FullName);
            }

            return (T)item;
        }

        public T GetOrCreate<T>()
            where T : ContextItem, new()
        {
            ThrowIfDisposed();
            ContextItem item;
            if (m_items.TryGetValue(
                    typeof(T),
                    out item))
            {
                return (T)item;
            }

            return Create<T>();
        }

        public void Dispose()
        {
            if (m_disposed)
            {
                return;
            }

            foreach (ContextItem item in m_items.Values)
            {
                if (item != null)
                {
                    item.Reset();
                }
            }

            m_items.Clear();
            m_disposed = true;
        }

        private void ThrowIfDisposed()
        {
            if (m_disposed)
            {
                throw new ObjectDisposedException(
                    nameof(ContextContainer));
            }
        }
    }
}