# This will leave the top X layers of the selected area.
# The area underneath will be set to Air or what the user chooses.
# copied from topsoil.py - all credit to codewarrior0 (assuming he is the author)
from numpy import zeros
import itertools
from pymclevel import alphaMaterials
from pymclevel.level import extractHeights

am = alphaMaterials

#naturally occuring materials
blocks = [
  am.Grass,
  am.Dirt,
  am.Stone,
  am.Bedrock,
  am.Sand,
  am.Gravel,
  am.GoldOre,
  am.IronOre,
  am.CoalOre,
  am.LapisLazuliOre,
  am.DiamondOre,
  am.RedstoneOre,
  am.RedstoneOreGlowing,
  am.Netherrack,
  am.SoulSand,
  am.Clay,
  am.Glowstone
]
blocktypes = [b.ID for b in blocks]

def naturalBlockmask():
    blockmask = zeros((256,), dtype='bool')
    blockmask[blocktypes] = True
    return blockmask

inputs = (
  ("Layers to keep", (1, 1, 128)),
  ("Fill under with:", alphaMaterials.Air),
)

def perform(level, box, options):
    depth = options["Layers to keep"]
    blocktype = options["Fill under with:"]

    #compute a truth table that we can index to find out whether a block
    # is naturally occuring and should be considered in a heightmap
    blockmask = naturalBlockmask()

    #iterate through the slices of each chunk in the selection box
    for chunk, slices, point in level.getChunkSlices(box):
        # slicing the block array is straightforward. blocks will contain only
        # the area of interest in this chunk.
        blocks = chunk.Blocks[slices]
        data = chunk.Data[slices]

        # use indexing to look up whether or not each block in blocks is
        # naturally-occuring. these blocks will "count" for column height.
        maskedBlocks = blockmask[blocks]

        heightmap = extractHeights(maskedBlocks)

        for x, z in itertools.product(*map(xrange, heightmap.shape)):
            h = heightmap[x, z]
            # Take 'lowest point' through 'naturally occuring'
            # then subtract users 'depth' input and set it all as air
            blocks[x, z, 0:(h - depth)] = blocktype.ID
            data[x, z, 0:(h - depth)] = blocktype.blockData

        #remember to do this to make sure the chunk is saved
        chunk.chunkChanged()