using System;
using System.Collections;
using System.Linq;
using TransportGame.Generator;
using TransportGame.Model;
using TransportGame.Utils;
using UnityEngine;

public class TerrainGeneratorScript : MonoBehaviour
{
	private Map map = null;

	public int TerrainWidth = 1024;
	public int TerrainHeight = 1024;
	public GameObject WaterObject;
    public Texture2D[] Textures;

	// Use this for initialization
	void Start()
	{
		StartCoroutine(GenerateMap());
	}

	private void GenerateTerrainThread()
	{
		CityGenerator generator = new CityGenerator();
		map = generator.Generate(TerrainWidth, TerrainHeight);
	}
    
	private Mesh GenerateWater()
	{
		Mesh water = new Mesh();
		water.name = "water";
		water.vertices = new[] { 
			new Vector3(0, map.WaterLevel, 0), 
			new Vector3(0, map.WaterLevel, map.Height), 
			new Vector3(map.Width, map.WaterLevel, 0), 
			new Vector3(map.Width, map.WaterLevel, map.Height)
		};
		water.triangles = new[] { 0, 1, 2, 2, 1, 3 };
		water.uv = new[] {
			new Vector2(0, 0),
			new Vector2(0, 1),
			new Vector2(1, 0),
			new Vector2(1, 1)
		};
		water.RecalculateNormals();

		return water;
	}

	private IEnumerator GenerateMap()
	{
		// Generate terrain
		foreach (var i in Task.RunAsync(GenerateTerrainThread))
			yield return i;

		// Generate terrain data
		TerrainData terrainData = new TerrainData();
		terrainData.heightmapResolution = Mathf.Max(map.Height, map.Width) + 1;
		terrainData.size = new Vector3(map.Width, map.Biome.Height, map.Height);
		terrainData.SetDetailResolution(1024, 8);
		terrainData.SetHeights(0, 0, map.Heightmap);
		terrainData.name = "Generated Terrain Data";
        yield return null;
        
        if (map.Biome.Textures != null)
        {
            SplatPrototype[] prototypes = new SplatPrototype[map.Biome.Textures.Length];
            
            for (int i = 0; i < map.Biome.Textures.Length; i++)
            {
                Texture2D texture = Textures.FirstOrDefault(tex => tex != null && tex.name == map.Biome.Textures[i].Source);

                if (texture == null)
                    throw new Exception("Texture " + map.Biome.Textures[i].Source + " not found!");

                prototypes[i] = new SplatPrototype();
                prototypes[i].texture = texture;
            }

            terrainData.splatPrototypes = prototypes;

            yield return null;
        }

		// Create terrain object
		GameObject terrain = Terrain.CreateTerrainGameObject(terrainData);
		terrain.name = "Generated Terrain";
		yield return null;

		Terrain terrainComp = terrain.GetComponent<Terrain>();
		terrainComp.heightmapPixelError = 1;
		yield return null;

		// Set water
		if (WaterObject != null)
		{
			MeshFilter waterMesh = WaterObject.GetComponent<MeshFilter>();
			waterMesh.mesh = GenerateWater();
		}
        yield return null;

		// Set up textures
        SetupSplatmaps(terrainData);
	}

    private void SetupSplatmaps(TerrainData terrainData)
    {
        float[, ,] splatData = new float[terrainData.alphamapWidth, terrainData.alphamapHeight, terrainData.alphamapLayers];
        Expression[] expressions = new Expression[terrainData.alphamapLayers];

        for (int y = 0; y < terrainData.alphamapHeight; y++)
            for (int x = 0; x < terrainData.alphamapWidth; x++)
            {
                float y_01 = (float)y / (float)terrainData.alphamapHeight;
                float x_01 = (float)x / (float)terrainData.alphamapWidth;

                int ix = Mathf.RoundToInt(x_01 * TerrainWidth);
                int iy = Mathf.RoundToInt(y_01 * TerrainHeight);

                // Get height
                float height = map.GetHeight(ix, iy);
                
                // Get steepness
                float steepness = map.GetSteepness(ix, iy);
                
                // Go through each texture layer
                float[] weights = new float[terrainData.alphamapLayers];
                float sum = 0;

                for (int t = 0; t < terrainData.alphamapLayers; t++)
                {
                    // Set up expression
                    if (expressions[t] == null)
                    {
                        expressions[t] = new Expression(map.Biome.Textures[t].Expression);
                        expressions[t].ParseExpression();
                    }

                    expressions[t].Variables["height"] = height;
                    expressions[t].Variables["steepness"] = steepness;
                    expressions[t].Variables["maxHeight"] = terrainData.size.y;
                    expressions[t].Variables["waterLevel"] = map.WaterLevel - 1f;

                    // Obtain weight
                    weights[t] = expressions[t].Evaluate();
                    sum += weights[t];
                }

                // Normalize and copy weights
                for (int t = 0; t < terrainData.alphamapLayers; t++)
                {
                    splatData[x, y, t] = weights[t] / sum;
                }
            }

        terrainData.SetAlphamaps(0, 0, splatData);
    }

	// Update is called once per frame
	void Update()
	{
	}
}