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

namespace UnityEditor.Graphs.Material
{
	abstract class FunctionMultiInput : BaseMaterialNode, IGeneratesBodyCode
	{
		private const string kOutputSlotName = "Output";
		private const string kBaseInputSlotName = "Input";

		public override bool hasPreview { get { return true; } }

		public override void Init()
		{
			base.Init ();
			AddSlot (new Slot (SlotType.OutputSlot, kOutputSlotName));

			AddSlot (new Slot (SlotType.InputSlot, GetInputSlotName (0)));
			AddSlot (new Slot (SlotType.InputSlot, GetInputSlotName (1)));
		}

		protected bool IsInputSlotConnected (int index)
		{
			var inputSlot = GetValidInputSlots ().FirstOrDefault(x => x.name == GetInputSlotName (index));
			if (inputSlot == null)
			{
				Debug.LogError("Invalid slot configuration on node: " + name);
				return false;
			}

			return inputSlot.edges.Count > 0;
		}

		private static string GetInputSlotName (int index) { return kBaseInputSlotName + (index); }

		public override void InputEdgeChanged(Edge e)
		{
			base.InputEdgeChanged(e);

			int inputSlotCount = GetValidInputSlots().Count();

			if (IsInputSlotConnected(inputSlotCount - 1))
				AddSlot(new Slot(SlotType.InputSlot, GetInputSlotName(inputSlotCount)));
			else if (inputSlotCount > 2)
			{
				var lastSlot = inputSlots.FirstOrDefault (x => x.name == GetInputSlotName (inputSlotCount - 1));
				if (lastSlot != null)
					RemoveSlot (lastSlot);
			}
		}

		protected abstract string GetFunctionName();

		public void GenerateNodeCode(ShaderGenerator visitor, GenerationMode generationMode)
		{
			var outputSlot = outputSlots.FirstOrDefault (x => x.name == kOutputSlotName);

			if (outputSlot == null)
			{
				Debug.LogError ("Invalid slot configuration on node: " + name);
				return;
			}

			var inputSlots = GetValidInputSlots ();
			int inputSlotCount = inputSlots.Count ();

			// build up a list of the valid input connections
			var inputValues = new List<string> (inputSlotCount);
			MaterialWindow.DebugMaterialGraph ("Generating On Node: " + GetOutputVariableNameForNode () + " - Preview is: " + generationMode);
			inputValues.AddRange (inputSlots.Select (inputSlot => GetSlotValue (inputSlot, generationMode)));
			visitor.AddShaderChunk (precision + "4 " + GetOutputVariableNameForSlot (outputSlot, generationMode) + " = " + GetFunctionCallBody (inputValues) + ";", true);
		}

		protected virtual string GetFunctionCallBody(List<string> inputValues)
		{
			string functionCall = inputValues[0];
			for (int q = 1; q < inputValues.Count; ++q)
				functionCall = GetFunctionName () + " (" + functionCall + ", " + inputValues[q] + ")";
			return functionCall;
		}
	}
}