using System;
using System.Collections.Generic;
using System.Linq;
using UnityEngine;

namespace UnityEditor.Graphs.Material
{
	[Title("Sub-graph/Sub-graph Node")]
	public class SubGraphNode : BaseMaterialNode, IGeneratesBodyCode, IGeneratesVertexToFragmentBlock, IGeneratesFunction, IGeneratesVertexShaderBlock
	{
		[SerializeField]
		private MaterialSubGraph m_SubGraphAsset;

		public MaterialSubGraph subGraphAsset { get { return m_SubGraphAsset; } }

		public override PreviewMode previewMode
		{
			get
			{
				if (subGraphAsset == null)
					return PreviewMode.Preview2D;

				var preview3D = subGraphAsset.outputsNode.CollectChildNodesByExecutionOrder ().Any (x => x.previewMode == PreviewMode.Preview3D);
				return preview3D ? PreviewMode.Preview3D : PreviewMode.Preview2D;
			}
		}

		public const int kMaxSlots = 16;

		public override void Init()
		{
			base.Init();
			name = "SubGraph";
			position = new Rect(position.x, position.y, Mathf.Max(300, position.width), position.height);

		}
		
		static string GetInputSlotName(int n)
		{
			return string.Format("I{0:00}", n);
		}

		static string GetOutputSlotName(int n)
		{
			return string.Format("O{0:00}", n);
		}

		public override IEnumerable<Slot> GetValidInputSlots()
		{
			// We only want to return the input slots that are internally wired to an output slot
			return base.GetValidInputSlots ().Where (slot => m_SubGraphAsset.InputInternallyWired (slot.name, this)).ToList ();
		}

		public override void NodeUI(GraphGUI host)
		{
			EditorGUI.BeginChangeCheck ();
			m_SubGraphAsset = (MaterialSubGraph)EditorGUILayout.ObjectField(GUIContent.none, m_SubGraphAsset, typeof(MaterialSubGraph), false);			
			if (EditorGUI.EndChangeCheck () && m_SubGraphAsset != null) 
			{
				SubGraphChanged (m_SubGraphAsset);
			}
		}

		private void SubGraphChanged (MaterialSubGraph sender)
		{	
			RefreshSlots (SlotType.InputSlot, inputSlots.ToList(), sender.inputsNode.slots, (s) => true);
			RefreshSlots (SlotType.OutputSlot, outputSlots.ToList(), sender.outputsNode.slots, sender.OutputInternallyWired);
			RegeneratePreviewShaders ();
		}

		private void RefreshSlots (SlotType type, IEnumerable<Slot> current, IEnumerable<Slot> updated, Func<string, bool> slotFilter)
		{
			var innerOutputSlots = updated.Where (n => slotFilter (n.name)).ToArray();
			foreach (var slot in innerOutputSlots)
			{
				var s = current.FirstOrDefault(n => n.name == slot.name);
				if (s == null)
					AddSlot (new Slot (type, slot.name, slot.title));
				else
					s.title = slot.title;
			}

			var danglingSlots = current.Except (innerOutputSlots, (ls, rs) =>  ls.name == rs.name).ToArray();
			foreach (var slot in danglingSlots)
				RemoveSlot (slot);
		}

		public void GenerateNodeCode(ShaderGenerator shaderBodyVisitor, GenerationMode generationMode)
		{
			if (m_SubGraphAsset == null)
				return;

			var outputString = new ShaderGenerator ();
			outputString.AddShaderChunk("// Subgraph for node " + GetOutputVariableNameForNode(), false);

			// Step 1...
			// find out which output slots are actually used
			//TODO: Be smarter about this and only output ones that are actually USED, not just connected
			//var validOutputSlots = NodeUtils.GetSlotsThatOutputToNodeRecurse(this, (graph as BaseMaterialGraph).masterNode);
			var validOutputSlots = outputSlots.Where (x => x.edges.Count > 0);
			foreach (var slot in validOutputSlots)
			{
				outputString.AddShaderChunk(
					"float4 "
					+ GetOutputVariableNameForSlot(slot, generationMode)
					+ " = float4(0);", false);
			}

			// Step 2...
			// Go into the subgraph
			outputString.AddShaderChunk("{", false);
			outputString.Indent();

			// Step 3...
			// For each input that is used and connects through we want to generate code.
			// First we assign the input variables to the subgraph
			foreach (var slot in slots)
			{
				if (!slot.isInputSlot)
					continue;

				// see if the input connects all the way though to the output
				// if it does allow generation
				var inputWired = m_SubGraphAsset.InputInternallyWired (slot.name, this);
				if (!inputWired)
					continue;

				var varName = m_SubGraphAsset.GetInputVariableNameForSlotByName (slot.name, this, generationMode);
				var varValue = "float4(0, 0, 0, 0);";
				var slotDefaultValue = GetSlotDefaultValue (slot.name);
				if (slotDefaultValue != null)
				{
					varValue = slotDefaultValue.GetDefaultValue (generationMode);
				}
				bool externallyWired = slot.edges.Count > 0;
				if (externallyWired)
				{
					var fromSlot = slot.edges[0].fromSlot;
					var fromNode = slot.edges[0].fromSlot.node as BaseMaterialNode;
					varValue = fromNode.GetOutputVariableNameForSlot(fromSlot, generationMode);
				}

				outputString.AddShaderChunk ("float4 " + varName + " = " + varValue + ";", false);
			}

			// Step 4...
			// Using the inputs we can now generate the shader body :)
			var bodyGenerator = new ShaderGenerator ();
			m_SubGraphAsset.GenerateNodeCode (bodyGenerator, this);
			outputString.AddShaderChunk(bodyGenerator.GetShaderString (0), false);

			// Step 5...
			// Copy the outputs to the parent context name);
			foreach (var slot in validOutputSlots)
			{
				bool internallyWired = m_SubGraphAsset.OutputInternallyWired(slot.name);
				if (internallyWired)
				{
					outputString.AddShaderChunk(
						GetOutputVariableNameForSlot(slot, generationMode)
					+ " = "
					+ m_SubGraphAsset.GetOutputVariableNameForSlotByName(slot.name, this, generationMode)
					+ ";", false);
				}
			}

			outputString.Deindent();
			outputString.AddShaderChunk("}", false);
			outputString.AddShaderChunk("// Subgraph ends", false);

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

		public void GenerateVertexToFragmentBlock (ShaderGenerator visitor, GenerationMode generationMode)
		{
			m_SubGraphAsset.GenerateVertexToFragmentBlock (visitor, GenerationMode.SurfaceShader);
		}

		public void GenerateNodeFunction(ShaderGenerator visitor, GenerationMode generationMode)
		{
			m_SubGraphAsset.GenerateNodeFunction(visitor, GenerationMode.SurfaceShader);
		}

		public void GenerateVertexShaderBlock(ShaderGenerator visitor, GenerationMode generationMode)
		{
			m_SubGraphAsset.GenerateVertexShaderBlock(visitor, GenerationMode.SurfaceShader);
		}

		public override void GeneratePropertyBlock(PropertyGenerator visitor, GenerationMode generationMode)
		{
			base.GeneratePropertyBlock (visitor, generationMode);
			m_SubGraphAsset.GeneratePropertyBlock(visitor, GenerationMode.SurfaceShader);
		}

		public override void GeneratePropertyUsages(ShaderGenerator visitor, GenerationMode generationMode)
		{
			base.GeneratePropertyUsages (visitor, generationMode);
			m_SubGraphAsset.GeneratePropertyUsages(visitor, GenerationMode.SurfaceShader);
		}

		public override void UpdatePreviewProperties()
		{
			base.UpdatePreviewProperties();

			var previewProperties = m_SubGraphAsset.GetPreviewProperties ();

			foreach (var prop in previewProperties)
				SetDependentPreviewMaterialProperty (prop);
		}
	}
}