using System.Collections.Generic;
using UnityEngine;

namespace Golems
{
    /// <summary>
    /// A gross singleton collection of all the Ghost Object Behaviours
    /// which require rendering via Albert Ghost Memory This is purely
    /// convenience for the AlbertGhostMemory to access Ghost Object Behaviours
    /// and for Ghost Object Behaviours to register/unregister themselves.
    /// </summary>
    public class GhostObjectCollection
    {
        /// <summary>
        /// The active singleton of GhostObjectCollection
        /// </summary>
        private static GhostObjectCollection m_Instance;

        public static GhostObjectCollection Instance
        {
            get
            {
                if (m_Instance == null) new GhostObjectCollection();
                return m_Instance;
            }
        }
        
        /// <summary>
        /// Collection of all the Ghost Object Behaviours which require rendering
        /// </summary>
        public List<GhostObjectBehaviour> GhostObjectBehaviours { get; private set; }
        
        /// <summary>
        /// Flag if there's anything Ghost Object Behaviours which require rendering
        /// </summary>
        public bool HasSomethingToRender()=> GhostObjectBehaviours != null && GhostObjectBehaviours.Count > 0;
        
        /// <summary>
        /// The number of objects rendered in AlbertGhostMemoryPass.
        /// This is reset in AlbertGhostMemoryPass.Execute() and incremented in
        /// DrawObjectsDefault().
        /// ComposeOutlinePass uses this in AddRenderPasses, if it's zero screen copy Blit is avoided.
        ///
        /// N.B This is a sketchy place to do this sort of thing, full acknowledged but it's quick, easy and works...
        /// </summary>
        public int NumberOfObjectsRendered = 0;

        private GhostObjectCollection()
        {
            m_Instance = this;
            GhostObjectBehaviours = new List<GhostObjectBehaviour>();
        }
        
        /// <summary>
        /// Add the passed Ghost Object Behaviour to Albert Ghost Memory pass
        /// </summary>
        public void AddGhostObjectBehaviour(GhostObjectBehaviour ghostObjectBehaviour)
        {
            if (ghostObjectBehaviour == null) return;
            GhostObjectBehaviours.Add(ghostObjectBehaviour);
        }
        
        /// <summary>
        /// Remove the passed Ghost Object Behaviour to Albert Ghost Memory pass
        /// </summary>
        public void RemoveGhostObjectBehaviour(GhostObjectBehaviour ghostObjectBehaviour)
        {
            if (ghostObjectBehaviour == null) return;
            GhostObjectBehaviours.Remove(ghostObjectBehaviour);
        }
    }
}