using System;
using System.Linq;
using UnityEngine;

namespace UnityEditor.Graphs.Material
{
	[Title("Fractal/Perlin Node")]
	class PerlinNode : TextureNode, IGeneratesFunction, IGeneratesBodyCode
	{
		public override bool hasPreview { get { return true; } }

		[SerializeField]
		private int m_Iterations = 4;

		[SerializeField]
		private float m_Decay = 0.5f;

		[SerializeField]
		private float m_Frequency = 2.0f;

		public override void Init()
		{
			name = "Perlin";
			base.Init ();
		}

		public void GenerateNodeFunction(ShaderGenerator visitor, GenerationMode generationMode)
		{
			var outputString = new ShaderGenerator();
			foreach (var precision in m_PrecisionNames)
			{
				outputString.AddShaderChunk("inline " + precision + "4 unity_perlin_" + precision + " ("
					+ "sampler2D textureID, "
					+ "int iterations, "
					+ precision + " decay, "
					+ precision + " frequency, "
					+ precision + "2 p"
					+ ")", false);
				outputString.AddShaderChunk("{", false);
				outputString.Indent();
				outputString.AddShaderChunk(precision + "4 sum = " + precision + "4(0, 0, 0, 0);", false);
				outputString.AddShaderChunk(precision + " amp = 0.5;", false);
				outputString.AddShaderChunk("for(int n = 0; n < iterations; n++)", false);
				outputString.AddShaderChunk("{", false);
				outputString.Indent();
				outputString.AddShaderChunk("sum += amp * tex2D (textureID, p);", false);
				outputString.AddShaderChunk("p *= frequency;", false);
				outputString.AddShaderChunk("amp *= decay;", false);
				outputString.Deindent();
				outputString.AddShaderChunk("}", false);
				outputString.AddShaderChunk("return sum;", false);
				outputString.Deindent();
				outputString.AddShaderChunk("}", false);
			}

			visitor.AddShaderChunk(outputString.GetShaderString(0), true);
		}

		public override void GenerateNodeCode(ShaderGenerator visitor, GenerationMode generationMode)
		{
			var outputSlot = FindOutputSlot(kOutputSlotName);
			if (outputSlot == null)
				return;

			var uvSlot = FindInputSlot(kUVSlotName);
			if (uvSlot == null)
				return;

			var uvName = "IN.meshUV0";
			if (uvSlot.edges.Count > 0)
			{
				var fromNode = uvSlot.edges[0].fromSlot.node as BaseMaterialNode;
				uvName = fromNode.GetOutputVariableNameForSlot(uvSlot.edges[0].fromSlot, generationMode);
			}

			string body = "unity_perlin_" + precision + "(" + GetPropertyName () + ", " + m_Iterations + ", " + m_Decay + ", " + m_Frequency + ", " + uvName + ".xy)";
			visitor.AddShaderChunk("float4 " + GetOutputVariableNameForSlot(outputSlot, generationMode) + " = " + body + ";", true);
		}

		static float Slider(string title, float value, float from, float to)
		{
			GUILayout.BeginHorizontal();
			GUILayout.Label(title);
			value = GUILayout.HorizontalSlider(value, from, to, GUILayout.Width(64));
			GUILayout.EndHorizontal();
			return value;
		}

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

			EditorGUI.BeginChangeCheck();
			m_Iterations = (int)Slider("Iterations", (float)m_Iterations, 1, 8);
			m_Decay = Slider("Decay", m_Decay, -1f, 1f);
			m_Frequency = Slider("Frequency", m_Frequency, 0f, 5f);
			if (EditorGUI.EndChangeCheck())
				RegeneratePreviewShaders();
		}		
	}
}