using Chernobyl.Collections.Generic.Event;
using Chernobyl.Event;
using Chernobyl.Graphics.Material.Shader.Parameters;
using Chernobyl.Graphics.Texture;
using Chernobyl.Graphics.Xna.Effects;
using Microsoft.Xna.Framework.Graphics;

namespace Chernobyl.Graphics.Xna.Controllers.Shaders
{
    /// <summary>
    /// Handles XNA texture parameters.
    /// </summary>
    public class XnaTextureParameter : XnaShaderParameter<ITexture>
    {
        /// <summary>
        /// Constructor.
        /// </summary>
        /// <param name="services">The services class that holds the services that will be injected
        /// into this class.</param>
        /// <param name="value">The initial value of the texture parameter.</param>
        /// <param name="name">The name of the texture parameter.</param>
        public XnaTextureParameter(IEventCollection<object> services, ITexture value, string name)
        {
            _value = value;
            Name = name;
            ProcessNewValue();
        }

        /// <summary>
        /// Constructor.
        /// </summary>
        /// <param name="services">The services class that holds the services that will be injected
        /// into this class.</param>
        /// <param name="effect">The <see cref="XnaEffect"/> that this parameter 
        /// belongs to.</param>
        /// <param name="effectParam">The XNA <see cref="EffectParameter"/> that 
        /// this parameter represents.</param>
        /// <param name="value">The initial value of the texture parameter.</param>
        /// <param name="name">The name of the texture parameter.</param>
        public XnaTextureParameter(IEventCollection<object> services, XnaEffect effect, EffectParameter effectParam, ITexture value, string name)
        {
            XnaEffect = effect;
            EffectParameter = effectParam;
            _value = value;
            Name = name;
            ProcessNewValue();
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="XnaTextureParameter"/> 
        /// class. This constructor is typically used for cloning (see 
        /// <see cref="ShallowClone()"/>).
        /// </summary>
        XnaTextureParameter()
        { }

        /// <summary>
        /// Applies the texture parameter to the EffectParameter of the effect
        /// applied above this texture parameter.
        /// </summary>
        public override void PreDraw()
        {
            EffectParameter.SetValue(XnaTextureValue.XnaTexture);
        }

        /// <summary>
        /// The value of the texture.
        /// </summary>
        public override ITexture Value
        {
            get { return _value; }
            set
            {
                if(ValueChangedMethod != null)
                {
                    ValueChangedEventArgs<ITexture> vce = new ValueChangedEventArgs<ITexture>(_value, value);

                    _value = value;

                    ValueChangedMethod(this, vce);
                }
                else
                    _value = value;

                ProcessNewValue();
            }
        }

        /// <summary>
        /// Creates a new instance that is a shallow copy of this instance.
        /// </summary>
        /// <returns>The new shallow copied instance.</returns>
        public override IShaderParameter<ITexture> ShallowClone()
        {
            XnaTextureParameter clone = new XnaTextureParameter();
            ShallowCopyTo(clone);
            return clone;
        }

        /// <summary>
        /// Caches the XNA texture from the Chernobyl texture. This method was 
        /// created because you should not call virtual properties/methods 
        /// (<see cref="Value"/> in this case) from the constructor.
        /// </summary>
        void ProcessNewValue()
        {
            if(_value != null)
            {
                Chernobyl.Graphics.Texture.Texture2D text = (Chernobyl.Graphics.Texture.Texture2D)_value;
                XnaTextureValue = (XnaTexture2D)text.Controller;   
            }
        }

        /// <summary>
        /// The XNA texture that was pulled from the texture <see cref="Value"/>.
        /// </summary>
        XnaTexture2D XnaTextureValue { get; set; }

        /// <summary>
        /// The backing field to <see cref="Value"/>.
        /// </summary>
        ITexture _value;
    }
}