using System.Collections.Generic;

namespace gaemstone.Bloxel.WorldGen;

// FIXME: There is an issue with this generator where it doesn't generate grass and dirt properly.
public class SurfaceGrassGenerator
	: IWorldGenerator
{
	public static readonly string IDENTIFIER = nameof(SurfaceGrassGenerator);

	private const int AIR_BLOCKS_NEEDED = 12;
	private const int DIRT_BLOCKS_BENEATH = 3;

	public string Identifier { get; } = IDENTIFIER;

	public IEnumerable<string> Dependencies { get; } = new[]{
		BasicWorldGenerator.IDENTIFIER
	};

	public IEnumerable<(Neighbor, string)> NeighborDependencies { get; } = new[]{
		(Neighbor.Up, BasicWorldGenerator.IDENTIFIER)
	};

	public void Populate(Chunk chunk)
	{
		var up = chunk.Neighbors[Neighbor.Up]!;
		for (var lx = 0; lx < Chunk.LENGTH; lx++)
			for (var lz = 0; lz < Chunk.LENGTH; lz++)
			{
				var numAirBlocks = 0;
				var blockIndex = 0;
				for (var ly = Chunk.LENGTH + AIR_BLOCKS_NEEDED - 1; ly >= 0; ly--)
				{
					var block = ly >= Chunk.LENGTH
						? up.Storage[lx, ly - Chunk.LENGTH, lz]
						: chunk.Storage[lx, ly, lz];
					if (block.IsAir)
					{
						numAirBlocks++;
						blockIndex = 0;
					}
					else if (numAirBlocks >= AIR_BLOCKS_NEEDED || blockIndex > 0)
					{
						if (ly < Chunk.LENGTH)
						{
							if (blockIndex == 0)
								chunk.Storage[lx, ly, lz] = Block.GRASS;
							else if (blockIndex <= DIRT_BLOCKS_BENEATH)
								chunk.Storage[lx, ly, lz] = Block.DIRT;
						}
						blockIndex++;
						numAirBlocks = 0;
					}
				}
			}
	}
}