using System;
using System.Collections.Generic;
using System.Linq;
using UnityEditor;

namespace UnityEngine.TerrainTools
{
    [Serializable]
    internal class Layer
    {
        public bool IsSelected;
        public TerrainLayer AssignedLayer;
    }

    internal class TerrainToolboxLayer
    {
        // add a list of terrain layers to terrain, and have an option of clear existing ones
        public static void AddLayersToTerrain(TerrainData terrainData, List<TerrainLayer> layers, bool clearExisting)
        {
            if (terrainData == null || layers == null)
                return;

            if (clearExisting)
            {
                terrainData.SetTerrainLayersRegisterUndo(layers.ToArray(), "Clearing layers");
            }
            else
            {
                // check and remove existing layers
                var filteredLayers = layers.Where(i => !terrainData.terrainLayers.Contains(i)).ToArray();
                int oldLength = terrainData.terrainLayers.Length;
                int newLength = oldLength + filteredLayers.Length;
                var newArray = new TerrainLayer[newLength];
                terrainData.terrainLayers.CopyTo(newArray, 0);
                filteredLayers.CopyTo(newArray, oldLength);
                terrainData.SetTerrainLayersRegisterUndo(newArray, "Add terrain layers");
            }			
        }

        // add layer to terrain
        public static void AddLayerToTerrain(TerrainData terrainData, TerrainLayer inputLayer)
        {
            if (inputLayer == null)
                return;

            var layers = terrainData.terrainLayers;
            for (var idx = 0; idx < layers.Length; ++idx)
            {
                if (layers[idx] == inputLayer)
                    return;
            }

            int newIndex = layers.Length;
            var newarray = new TerrainLayer[newIndex + 1];
            Array.Copy(layers, 0, newarray, 0, newIndex);
            newarray[newIndex] = inputLayer;
            terrainData.SetTerrainLayersRegisterUndo(newarray, "Add terrain layer");
        }

        public static void CopyTerrainLayers(Terrain fromTerrain, Terrain toTerrain)
        {
            // wipe out existing layers and splatmaps
            RemoveAllLayers(toTerrain.terrainData);

            toTerrain.terrainData.terrainLayers = fromTerrain.terrainData.terrainLayers;
        }

        public static void RemoveAllLayers(TerrainData terrainData)
        {
            terrainData.SetTerrainLayersRegisterUndo(new TerrainLayer[0], "Remove All terrain layer");
        }

        // remove a single layer and clear splatmap
        public static void RemoveLayerFromTerrain(TerrainData terrainData, int index)
        {

            int width = terrainData.alphamapWidth;
            int height = terrainData.alphamapHeight;
            float[,,] alphamap = terrainData.GetAlphamaps(0, 0, width, height);
            int alphaCount = alphamap.GetLength(2);

            int newAlphaCount = alphaCount - 1;
            float[,,] newalphamap = new float[height, width, newAlphaCount];

            // move further alphamaps one index below
            for (int y = 0; y < height; ++y)
            {
                for (int x = 0; x < width; ++x)
                {
                    for (int a = 0; a < index; ++a)
                        newalphamap[y, x, a] = alphamap[y, x, a];
                    for (int a = index + 1; a < alphaCount; ++a)
                        newalphamap[y, x, a - 1] = alphamap[y, x, a];
                }
            }

            // normalize weights in new alpha map
            for (int y = 0; y < height; ++y)
            {
                for (int x = 0; x < width; ++x)
                {
                    float sum = 0.0F;
                    for (int a = 0; a < newAlphaCount; ++a)
                        sum += newalphamap[y, x, a];
                    if (sum >= 0.01)
                    {
                        float multiplier = 1.0F / sum;
                        for (int a = 0; a < newAlphaCount; ++a)
                            newalphamap[y, x, a] *= multiplier;
                    }
                    else
                    {
                        // in case all weights sum to pretty much zero (e.g.
                        // removing splat that had 100% weight), assign
                        // everything to 1st splat texture (just like
                        // initial terrain).
                        for (int a = 0; a < newAlphaCount; ++a)
                            newalphamap[y, x, a] = (a == 0) ? 1.0f : 0.0f;
                    }
                }
            }

            // remove splat from terrain prototypes
            var layers = terrainData.terrainLayers;
            var newSplats = new TerrainLayer[layers.Length - 1];
            for (int a = 0; a < index; ++a)
                newSplats[a] = layers[a];
            for (int a = index + 1; a < alphaCount; ++a)
                newSplats[a - 1] = layers[a];
            int group = Undo.GetCurrentGroup();
            Undo.SetCurrentGroupName("Remove terrain layer");
            terrainData.SetTerrainLayersRegisterUndo(newSplats, "Remove Layer");
            var undoObjects = new List<Object>();
            undoObjects.AddRange(terrainData.alphamapTextures);
            Undo.RegisterCompleteObjectUndo(undoObjects.ToArray(), "Apply Modified Alphamaps");
            Undo.CollapseUndoOperations(Undo.GetCurrentGroup());
            terrainData.SetAlphamaps(0, 0, newalphamap);
        }
    }
}