using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.Graphics;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace RhythmBullet.Zer01HD.Utilities.ContentSystem
{
    public delegate void ContentSystemUpdate(String fileName, float completed);

    public class ContentSystem
    {
        public event ContentSystemUpdate ContentSystemListeners;
        Thread thread;
        readonly ContentManager contentManager;
        readonly Queue<LoadableContent> queue;
        Dictionary<string, IDisposable> assets;
        public readonly Dictionary<Type, IContentPathModifier> contentPathModifier;
        volatile float progress;
        public ContentSystem(ContentManager contentManager)
        {
            this.contentManager = contentManager;
            assets = new Dictionary<string, IDisposable>();
            queue = new Queue<LoadableContent>();
            contentPathModifier = new Dictionary<Type, IContentPathModifier>();
        }

        private void Load(string assetName, Type type, bool usePathModifier)
        {
            string path = assetName;
            if (usePathModifier)
            {
                IContentPathModifier handler = contentPathModifier[type];
                path = handler.Modify(assetName);

            }
            assets.Add(assetName, contentManager.Load<IDisposable>(path));

            Debug.WriteLine("Loaded asset: " + assetName);
        }

        public T Get<T>(string assetName)
        {
            lock (queue)
            {
                return (T)assets[assetName];
            }
        }

        public void Queue<T>(string assetName, bool usePathModifier = true) where T : IDisposable
        {
            lock (queue)
            {
                if (!assets.ContainsKey(assetName))
                {
                    queue.Enqueue(new LoadableContent(assetName, typeof(T), usePathModifier));
                    Debug.WriteLine("Queued asset: " + assetName);
                }
                else
                {
                    throw new InvalidOperationException("Did not queue asset due to asset with same name being loaded: " + assetName);
                }
            }
        }

        /// <summary>
        /// Called whenever a batch of assets should be loaded from the queue. Safe to call once every frame.
        /// </summary>
        public void Update()
        {
            if (queue.Count > 0 && (thread == null || !thread.IsAlive))
            {
                ThreadStart threadStart = new ThreadStart(LoadBatch);
                thread = new Thread(threadStart);
                thread.Start();
            }
        }

        private void LoadBatch()
        {
            int totalTasks = queue.Count;
            int tasksCompleted = 0;
            while (queue.Count != 0)
            {
                lock (queue)
                {
                    LoadableContent content = queue.Dequeue();
                    Load(content.assetName, content.type, content.usePathModifier);
                    tasksCompleted++;
                    progress = (float)tasksCompleted / totalTasks;
                    OnProgress(content.assetName, progress);
                }
            }
        }
        /// <summary>
        /// Removes the asset from the list of assets in the system.
        /// Cannot remove from queue.
        /// </summary>
        /// <param name="name">the string name used to load the asset</param>
        public void Remove(string name)
        {
            lock (queue)
            {
                if (assets.ContainsKey(name))
                {
                    assets[name].Dispose();
                    assets.Remove(name);
                }
            }
        }

        /// <summary>
        /// Clears the queue.
        /// </summary>
        public void ClearQueue()
        {
            lock (queue)
            {
                queue.Clear();
            }
        }

        /// <summary>
        /// Unloads everything from both queue and loaded list while properly disposing of the assets loaded.
        /// </summary>
        public void UnloadAll()
        {
            lock (queue)
            {
                contentManager.Unload();
                assets.Clear();
                ClearQueue();
                Debug.WriteLine("Unloaded all assets.");
            }
        }

        public bool Done
        {
            get
            {
                return queue.Count == 0;
            }
        }

        protected virtual void OnProgress(string fileName, float progress)
        {
            ContentSystemListeners?.Invoke(fileName, progress);
        }

        public float Progress
        {
            get
            {
                return progress;
            }
        }
    }
}