using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Xna.Framework;

namespace FirzLib.MapSystem
{
    class HeightmapChunk
    {
        Vector2 minPos, maxPos;
        int indexCount;
        int indexOffset;
        const int MinChunkSize = 10;
        bool bottomChunk;
        HeightmapChunk[] childChunks;

        public HeightmapChunk(Vector2 minPos, Vector2 maxPos, Vector2 mapSize, int offset, ref int[] indices)
        {
            this.minPos = minPos;
            this.maxPos = maxPos;
            indexOffset = offset;
            Vector2 ChunkSize = (maxPos-minPos);
            if (ChunkSize.X > 2 * MinChunkSize && ChunkSize.Y > 2 * MinChunkSize)
            {
                childChunks = new HeightmapChunk[4];
                childChunks[0] = new HeightmapChunk(minPos, minPos+ChunkSize/2.0f,mapSize,offset, ref indices);
                childChunks[1] = new HeightmapChunk(minPos + Vector2.UnitX * ChunkSize.X / 2.0f, maxPos - Vector2.UnitY * ChunkSize.Y / 2.0f, mapSize, offset + childChunks[0].indexCount, ref indices);
                childChunks[2] = new HeightmapChunk(minPos + Vector2.UnitY * ChunkSize.Y / 2.0f, maxPos - Vector2.UnitX * ChunkSize.X / 2.0f, mapSize, childChunks[1].indexOffset + childChunks[1].indexCount, ref indices);
                childChunks[3] = new HeightmapChunk(minPos + ChunkSize / 2.0f, maxPos, mapSize, childChunks[2].indexOffset + childChunks[2].indexCount, ref indices);
                indexCount = childChunks[0].indexCount + childChunks[1].indexCount + childChunks[2].indexCount + childChunks[3].indexCount;
                bottomChunk = false;
            }
            else
            {
                int count = 0;
                int sizeX=(int)mapSize.X;
                for(int x=(int)minPos.X; x<maxPos.X; x++)
                    for (int y = (int)minPos.Y; y < maxPos.Y; y++)
                    {
                        indices[offset + count] = x + y * sizeX;
                        indices[offset + count + 1] = x + 1 + y * sizeX;
                        indices[offset + count + 2] = x + 1 + (y+1) * sizeX;
                        indices[offset + count + 3] = indices[offset + count];
                        indices[offset + count + 4] = indices[offset + count + 2];
                        indices[offset + count + 5] = x + (y+1) * sizeX;
                        count+=6;
                    }
                indexCount = count-6;
                bottomChunk = true;
            }
        }
    }
}