/// <summary>
/// Dvornik
///kostiantyn-dvornik.blogspot.com/2013/12/unity-split-terrain-script.html
/// </summary>
using UnityEngine;
using UnityEditor;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
using System.Collections.Generic;

/// <summary>
/// Split terrain.
/// </summary>
public class SplitTerrain : EditorWindow {

    string num = "4";

    List<TerrainData> terrainData = new List<TerrainData>();
    List<GameObject> terrainGo = new List<GameObject>();

    Terrain parentTerrain;

    static int terrainsCount = 4;

    // Add submenu
    [MenuItem("Terrain/Split Terrain")]
    static void Init()
    {

        // Get existing open window or if none, make a new one:
        SplitTerrain window = (SplitTerrain)EditorWindow.GetWindow(typeof(SplitTerrain));

        window.minSize =  new Vector2( 100f,100f );
        window.maxSize =  new Vector2( 200f,200f );

        window.autoRepaintOnSceneChange = true;
        window.title = "Resize terrain";
        window.Show();


    }

    /// <summary>
    /// Determines whether this instance is power of two the specified x.
    /// </summary>
    /// <returns>
    /// <c>true</c> if this instance is power of two the specified x; otherwise, <c>false</c>.
    /// </returns>
    /// <param name='x'>
    /// If set to <c>true</c> x.
    /// </param>
    bool IsPowerOfTwo(int x)
    {
        return (x & (x - 1)) == 0;
    }

    void SplitIt()
    {

        if ( Selection.activeGameObject == null )
        {
            Debug.LogWarning("No terrain was selected");
            return;
        }


        parentTerrain = Selection.activeGameObject.GetComponent(typeof(Terrain)) as Terrain;

        if ( parentTerrain == null )
        {
            Debug.LogWarning("Current selection is not a terrain");
            return;
        }

        //Split terrain
        for ( int i=0; i< terrainsCount; i++)
        {

            EditorUtility.DisplayProgressBar("Split terrain","Process " + i, (float) i / terrainsCount );

            TerrainData td = new TerrainData();
            GameObject tgo = Terrain.CreateTerrainGameObject( td );

            tgo.name = parentTerrain.name + " " + i;

            terrainData.Add( td );
            terrainGo.Add ( tgo );

            Terrain genTer = tgo.GetComponent(typeof(Terrain)) as Terrain;
            genTer.terrainData = td;

            AssetDatabase.CreateAsset(td, "Assets/" + genTer.name+ ".asset");


            // Assign splatmaps
            genTer.terrainData.splatPrototypes = parentTerrain.terrainData.splatPrototypes;

            // Assign detail prototypes
            genTer.terrainData.detailPrototypes = parentTerrain.terrainData.detailPrototypes;

            // Assign tree information
            genTer.terrainData.treePrototypes = parentTerrain.terrainData.treePrototypes;


            // Copy parent terrain propeties
            #region parent properties
            genTer.basemapDistance = parentTerrain.basemapDistance;
            genTer.castShadows = parentTerrain.castShadows;
            genTer.detailObjectDensity = parentTerrain.detailObjectDensity;
            genTer.detailObjectDistance = parentTerrain.detailObjectDistance;
            genTer.heightmapMaximumLOD = parentTerrain.heightmapMaximumLOD;
            genTer.heightmapPixelError = parentTerrain.heightmapPixelError;
            genTer.treeBillboardDistance = parentTerrain.treeBillboardDistance;
            genTer.treeCrossFadeLength = parentTerrain.treeCrossFadeLength;
            genTer.treeDistance = parentTerrain.treeDistance;
            genTer.treeMaximumFullLODCount = parentTerrain.treeMaximumFullLODCount;

            #endregion

            //Start processing it

            // Translate peace to position
            #region translate peace to right position

            Vector3 parentPosition = parentTerrain.GetPosition();

            int terraPeaces = (int) Mathf.Sqrt( terrainsCount );

            float spaceShiftX = parentTerrain.terrainData.size.z / terraPeaces;
            float spaceShiftY = parentTerrain.terrainData.size.x / terraPeaces;

            float xWShift = (i % terraPeaces ) * spaceShiftX;
            float zWShift = ( i / terraPeaces ) * spaceShiftY;

            tgo.transform.position = new Vector3( tgo.transform.position.x + zWShift,
                                                  tgo.transform.position.y,
                                                  tgo.transform.position.z + xWShift );

            // Shift last position
            tgo.transform.position = new Vector3( tgo.transform.position.x + parentPosition.x,
                                                  tgo.transform.position.y + parentPosition.y,
                                                  tgo.transform.position.z + parentPosition.z
                                                 );



            #endregion

            // Split height
            #region split height

            Debug.Log ( "Split height" );

            //Copy heightmap
            td.heightmapResolution = parentTerrain.terrainData.heightmapResolution /  terraPeaces;

            //Keep y same
            td.size = new Vector3( parentTerrain.terrainData.size.x / terraPeaces,
                                   parentTerrain.terrainData.size.y,
                                   parentTerrain.terrainData.size.z / terraPeaces
                                  );

            float[,] parentHeight = parentTerrain.terrainData.GetHeights(0,0, parentTerrain.terrainData.heightmapResolution, parentTerrain.terrainData.heightmapResolution );

            float[,] peaceHeight = new float[ parentTerrain.terrainData.heightmapResolution / terraPeaces + 1,
                                              parentTerrain.terrainData.heightmapResolution / terraPeaces + 1
                                            ];

            // Shift calc
            int heightShift = parentTerrain.terrainData.heightmapResolution / terraPeaces;

            int startX = 0;
            int startY = 0;

            int endX = 0;
            int endY = 0;
            /*
            if ( i==0 )
            {
                startX = startY = 0;
                endX = endY = parentTerrain.terrainData.heightmapResolution / terraPeaces + 1;
            }

            if ( i==1 )
            {
                startX = startY = 0;
                endX = parentTerrain.terrainData.heightmapResolution / terraPeaces + 1;
                endY = parentTerrain.terrainData.heightmapResolution / terraPeaces + 1;
            }

            if ( i==2 )
            {
                startX = startY = 0;
                endX = parentTerrain.terrainData.heightmapResolution / terraPeaces + 1;
                endY = parentTerrain.terrainData.heightmapResolution / terraPeaces + 1;
            }

            if ( i==3 )
            {
                startX = startY = 0;
                endX = parentTerrain.terrainData.heightmapResolution / terraPeaces + 1;
                endY = parentTerrain.terrainData.heightmapResolution / terraPeaces + 1;
            }
                */
                endX = parentTerrain.terrainData.heightmapResolution / terraPeaces ;
                endY = parentTerrain.terrainData.heightmapResolution / terraPeaces ;
            // iterate
            for ( int x=startX;x< endX;x++)
            {

                EditorUtility.DisplayProgressBar("Split terrain","Split height", (float) x / ( endX - startX ));

                for ( int y=startY;y< endY;y++)
                {

                    int xShift=0;
                    int yShift=0;

                    //
                    /*
                    if ( i==0 )
                    {
                        xShift = 0;
                        yShift = 0;
                    }

                    //
                    if ( i==1 )
                    {
                        xShift = heightShift;
                        yShift = 0;
                    }

                    //
                    if ( i==2 )
                    {
                        xShift = 0;
                        yShift = heightShift;
                    }

                    if ( i==3 )
                    {
                        xShift = heightShift;
                        yShift = heightShift;
                    }
                    */
                    xShift=heightShift*(i%terraPeaces);
                    yShift=heightShift*(i/terraPeaces);
                    float ph = parentHeight[ x + xShift,y + yShift];

                    peaceHeight[x ,y ] = ph;

                }

            }

            EditorUtility.ClearProgressBar();

            // Set heightmap to child
            genTer.terrainData.SetHeights( 0,0, peaceHeight );
            #endregion

            // Split splat map
            #region split splat map

            td.alphamapResolution = parentTerrain.terrainData.alphamapResolution /  terraPeaces;

            float[,,] parentSplat = parentTerrain.terrainData.GetAlphamaps(0,0, parentTerrain.terrainData.alphamapResolution, parentTerrain.terrainData.alphamapResolution );

            float[,,] peaceSplat = new float[ parentTerrain.terrainData.alphamapResolution / terraPeaces ,
                                              parentTerrain.terrainData.alphamapResolution / terraPeaces,
                                              parentTerrain.terrainData.alphamapLayers
                                            ];

            // Shift calc
            int splatShift = parentTerrain.terrainData.alphamapResolution / terraPeaces;

            startX = startY = 0;
                endX = parentTerrain.terrainData.alphamapResolution / terraPeaces;
                endY = parentTerrain.terrainData.alphamapResolution / terraPeaces;
            // iterate
            for ( int s=0;s<parentTerrain.terrainData.alphamapLayers;s++)
            {
                for ( int x=startX;x< endX;x++)
                {

                    EditorUtility.DisplayProgressBar("Split terrain","Split splat", (float) x / ( endX - startX ));

                    for ( int y=startY;y< endY;y++)
                    {

                        int xShift=0;
                        int yShift=0;

                        //
                        xShift=splatShift*(i%terraPeaces);
                        yShift=splatShift*(i/terraPeaces);
                        float ph = parentSplat[x + xShift,y + yShift, s];
                        peaceSplat[x ,y, s] = ph;

                    }


                }
            }

            EditorUtility.ClearProgressBar();

            // Set heightmap to child
            genTer.terrainData.SetAlphamaps( 0,0, peaceSplat );
            #endregion


            AssetDatabase.SaveAssets();



        }

        EditorUtility.ClearProgressBar();



    }

    void OnGUI()
    {

        if(GUILayout.Button("Split terrain"))
        {

            SplitIt();
        }

        terrainsCount=EditorGUILayout.IntField(terrainsCount);
    }



}