using System;
using System.Collections;
using System.Collections.Generic;
using GamecraftModdingAPI.App;
using GamecraftModdingAPI.Utility;
using Rewired.Internal;
using Svelto.DataStructures;
using Svelto.Tasks;
using Svelto.Tasks.ExtraLean;
using Svelto.Tasks.ExtraLean.Unity;
using UnityEngine;

namespace GamecraftModdingAPI.Interface.IMGUI
{
    /// <summary>
    /// Keeps track of UIElement instances.
    /// This also handles displaying and processing them during the MonoBehaviour.OnGUI phase of screen updates.
    /// Most of this functionality is handled implicitly by the included UIElement implementations,
    /// but this is left as a public API so it can be expanded.
    /// </summary>
    public static class IMGUIManager
    {
        internal static OnGuiRunner ImguiScheduler = new OnGuiRunner("GamecraftModdingAPI_IMGUIScheduler");
        
        private static Dictionary<string, UIElement> _activeElements = new Dictionary<string,UIElement>();

        /// <summary>
        /// Add an UIElement instance to be managed by IMGUIManager.
        /// </summary>
        /// <param name="e">The UIElement instance.</param>
        public static void AddElement(UIElement e)
        {
            if (!ExistsElement(e))
            {
                _activeElements[e.Name] = e;
            }
        }
        
        /// <summary>
        /// Determine whether the UIElement instance is already tracked by IMGUIManager.
        /// </summary>
        /// <param name="name">The UIElement's unique name.</param>
        /// <returns>Whether the UIElement instance is already tracked by IMGUIManager (true) or not (false).</returns>
        public static bool ExistsElement(string name)
        {
            return _activeElements.ContainsKey(name);
        }

        /// <summary>
        /// Determine whether the UIElement instance is already tracked by IMGUIManager.
        /// </summary>
        /// <param name="element">The UIElement instance.</param>
        /// <returns>Whether the UIElement instance is already tracked by IMGUIManager (true) or not (false).</returns>
        public static bool ExistsElement(UIElement element)
        {
            return ExistsElement(element.Name);
        }

        /// <summary>
        /// Remove an UIElement instance from IMGUIManager.
        /// The UIElement will become invisible and stop generating events.
        /// </summary>
        /// <param name="name">The UIElement's unique name.</param>
        /// <returns>Whether the UIElement instance existed in IMGUIManager (true) or not (false).</returns>
        public static bool RemoveElement(string name)
        {
            if (ExistsElement(name))
            {
                return _activeElements.Remove(name);
            }

            return false;
        }
        
        /// <summary>
        /// Remove an UIElement instance from IMGUIManager.
        /// The UIElement will become invisible and stop generating events.
        /// </summary>
        /// <param name="element">The UIElement instance.</param>
        /// <returns>Whether the UIElement instance existed in IMGUIManager (true) or not (false).</returns>
        public static bool RemoveElement(UIElement element)
        {
            return RemoveElement(element.Name);
        }

        private static void OnGUI()
        {
            foreach (var element in _activeElements.Values)
            {
                if (element.Enabled)
                    element.OnGUI();
                /*try
                {
                    if (elements[i].Enabled)
                        elements[i].OnGUI();
                }
                catch (ArgumentException)
                {
                    // ignore these, since this is (hopefully) just Unity being dumb
                }
                catch (Exception e)
                {
                    Logging.MetaDebugLog($"Element '{elements[i].Name}' threw exception:\n{e.ToString()}");
                }*/
                
            }
        }

        private static IEnumerator<TaskContract> OnGUIAsync()
        {
            yield return (new Svelto.Tasks.Enumerators.WaitForSecondsEnumerator(5)).Continue(); // wait for some startup
            while (true)
            {
                yield return Yield.It;
                GUI.skin = Constants.Default;
                OnGUI();
            }
        }

        internal static void Init()
        {
            OnGUIAsync().RunOn(ImguiScheduler);
        }
    }
}