using UnityEngine;

namespace UnityEditor.Graphs.Material
{
	[Title("Art/Blend Node")]
	class BlendNode : Function2Input, IGeneratesFunction
	{
		public override void Init()
		{
			name = "BlendNode";
			base.Init();
		}
		
		public enum Operation {
			Normal,
			Additive,
		}
		
		[SerializeField]
		private Operation m_Operation;
		[SerializeField]
		private float m_Blend = 0.5f;

		private static readonly string[] kOpNames = new[] 
		{
			"normal",
			"add"
		};

		protected override string GetFunctionName() { return "unity_blend_"+ kOpNames[(int)m_Operation] +"_"+precision; }
		protected override string GetFunctionCallBody (string input1Value, string input2Value)
		{
			return GetFunctionName() + "("+input1Value+", "+input2Value+", "+m_Blend+")";
		}

		protected void AddOperationBody (ShaderGenerator visitor, string name, string body, string precision)
		{
			var outputString = new ShaderGenerator ();
			outputString.AddShaderChunk("inline "+precision+"4 unity_blend_"+name+"_"+precision+" ("+precision+"4 arg1, "+precision+"4 arg2, "+precision+" blend)", false);
			outputString.AddShaderChunk("{", false); outputString.Indent();
			outputString.AddShaderChunk(body, false);
			outputString.Deindent(); outputString.AddShaderChunk("}", false);
			
			visitor.AddShaderChunk (outputString.GetShaderString (0), true);
		}

		public override void NodeUI (Graphs.GraphGUI host)
		{
			base.NodeUI(host);

			EditorGUI.BeginChangeCheck ();
			m_Blend = GUILayout.HorizontalSlider(m_Blend, 0f, 1f, GUILayout.Width(64));
			m_Operation = (Operation)EditorGUILayout.EnumPopup (m_Operation);
			if (EditorGUI.EndChangeCheck ())
				RegeneratePreviewShaders ();
		}
		
		public void GenerateNodeFunction(ShaderGenerator visitor, GenerationMode generationMode)
		{
			foreach (var precision in m_PrecisionNames)
			{
				AddOperationBody (visitor, kOpNames[(int)Operation.Normal], "return lerp(arg1, arg2, blend);", precision);
				AddOperationBody (visitor, kOpNames[(int)Operation.Additive], "return (arg1 + arg2) * blend;", precision);
			}
		}
	}
}