#    This file is part of the Minecraft Overviewer.
#
#    Minecraft Overviewer is free software: you can redistribute it and/or
#    modify it under the terms of the GNU General Public License as published
#    by the Free Software Foundation, either version 3 of the License, or (at
#    your option) any later version.
#
#    Minecraft Overviewer is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
#    Public License for more details.
#
#    You should have received a copy of the GNU General Public License along
#    with the Overviewer.  If not, see <http://www.gnu.org/licenses/>.

import numpy
from PIL import Image, ImageDraw
import os.path
import hashlib
import logging

import nbt
import textures

"""
This module has routines related to rendering one particular chunk into an
image

"""

# General note about pasting transparent image objects onto an image with an
# alpha channel:
# If you use the image as its own mask, it will work fine only if the alpha
# channel is binary. If there's any translucent parts, then the alpha channel
# of the dest image will have its alpha channel modified. To prevent this:
# first use im.split() and take the third item which is the alpha channel and
# use that as the mask. Then take the image and use im.convert("RGB") to strip
# the image from its alpha channel, and use that as the source to paste()

def get_lvldata(filename):
    """Takes a filename and returns the Level struct, which contains all the
    level info"""
    return nbt.load(filename)[1]['Level']

def get_blockarray(level):
    """Takes the level struct as returned from get_lvldata, and returns the
    Block array, which just contains all the block ids"""
    return numpy.frombuffer(level['Blocks'], dtype=numpy.uint8).reshape((16,16,128))

def get_blockarray_fromfile(filename):
    """Same as get_blockarray except takes a filename and uses get_lvldata to
    open it. This is a shortcut"""
    level = get_lvldata(filename)
    return get_blockarray(level)

def get_skylight_array(level):
    """Returns the skylight array. Remember this is 4 bits per block, so divide
    the z component by 2 when accessing the array. and mask off the top or
    bottom 4 bits if it's odd or even respectively
    """
    return numpy.frombuffer(level['SkyLight'], dtype=numpy.uint8).reshape((16,16,64))

def get_blockdata_array(level):
    """Returns the ancillary data from the 'Data' byte array.  Data is packed
    in a similar manner to skylight data"""
    return numpy.frombuffer(level['Data'], dtype=numpy.uint8).reshape((16,16,64))

def iterate_chunkblocks(xoff,yoff):
    """Iterates over the 16x16x128 blocks of a chunk in rendering order.
    Yields (x,y,z,imgx,imgy)
    x,y,z is the block coordinate in the chunk
    imgx,imgy is the image offset in the chunk image where that block should go
    """
    for x in xrange(15,-1,-1):
        for y in xrange(16):
            imgx = xoff + x*12 + y*12
            imgy = yoff - x*6 + y*6 + 128*12 + 16*12//2
            for z in xrange(128):
                yield x,y,z,imgx,imgy
                imgy -= 12


# This set holds blocks ids that can be seen through, for occlusion calculations
transparent_blocks = set([0, 6, 8, 9, 18, 20, 37, 38, 39, 40, 44, 50, 51, 52, 53,
    59, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 74, 75, 76, 77, 78, 79, 81, 83, 85])

def render_and_save(chunkfile, cachedir, cave=False):
    """Used as the entry point for the multiprocessing workers (since processes
    can't target bound methods) or to easily render and save one chunk
    
    Returns the image file location"""
    a = ChunkRenderer(chunkfile, cachedir)
    try:
        return a.render_and_save(cave)
    except ChunkCorrupt:
        # This should be non-fatal, but should print a warning
        pass
    except Exception, e:
        import traceback
        traceback.print_exc()
        raise
    except KeyboardInterrupt:
        print
        print "You pressed Ctrl-C. Exiting..."
        # Raise an exception that is an instance of Exception. Unlike
        # KeyboardInterrupt, this will re-raise in the parent, killing the
        # entire program, instead of this process dying and the parent waiting
        # forever for it to finish.
        raise Exception()

class ChunkCorrupt(Exception):
    pass

class ChunkRenderer(object):
    def __init__(self, chunkfile, cachedir):
        """Make a new chunk renderer for the given chunkfile.
        chunkfile should be a full path to the .dat file to process
        cachedir is a directory to save the resulting chunk images to
        """
        if not os.path.exists(chunkfile):
            raise ValueError("Could not find chunkfile")
        self.chunkfile = chunkfile
        destdir, filename = os.path.split(self.chunkfile)
        self.blockid = ".".join(filename.split(".")[1:3])

        # Cachedir here is the base directory of the caches. We need to go 2
        # levels deeper according to the chunk file. Get the last 2 components
        # of destdir and use that
        moredirs, dir2 = os.path.split(destdir)
        _, dir1 = os.path.split(moredirs)
        self.cachedir = os.path.join(cachedir, dir1, dir2)

        if not os.path.exists(self.cachedir):
            try:
                os.makedirs(self.cachedir)
            except OSError, e:
                import errno
                if e.errno != errno.EEXIST:
                    raise

    def _load_level(self):
        """Loads and returns the level structure"""
        if not hasattr(self, "_level"):
            try:
                self._level = get_lvldata(self.chunkfile)
            except Exception, e:
                logging.warning("Error opening chunk file %s. It may be corrupt. %s", self.chunkfile, e)
                raise ChunkCorrupt(str(e))
        return self._level
    level = property(_load_level)
        
    def _load_blocks(self):
        """Loads and returns the block array"""
        if not hasattr(self, "_blocks"):
            self._blocks = get_blockarray(self._load_level())
        return self._blocks
    blocks = property(_load_blocks)

    def _hash_blockarray(self):
        """Finds a hash of the block array"""
        if hasattr(self, "_digest"):
            return self._digest
        h = hashlib.md5()
        h.update(self.level['Blocks'])

        # If the render algorithm changes, change this line to re-generate all
        # the chunks automatically:
        h.update("1")

        digest = h.hexdigest()
        # 6 digits ought to be plenty
        self._digest = digest[:6]
        return self._digest

    def find_oldimage(self, cave):
        # Get the name of the existing image. No way to do this but to look at
        # all the files
        oldimg = oldimg_path = None
        for filename in os.listdir(self.cachedir):
            if filename.startswith("img.{0}.{1}.".format(self.blockid,
                    "cave" if cave else "nocave")) and \
                    filename.endswith(".png"):
                oldimg = filename
                oldimg_path = os.path.join(self.cachedir, oldimg)
                break
        return oldimg, oldimg_path

    def render_and_save(self, cave=False):
        """Render the chunk using chunk_render, and then save it to a file in
        the same directory as the source image. If the file already exists and
        is up to date, this method doesn't render anything.
        """
        blockid = self.blockid

        oldimg, oldimg_path = self.find_oldimage(cave)

        if oldimg:
            # An image exists? Instead of checking the hash which is kinda
            # expensive (for tens of thousands of chunks, yes it is) check if
            # the mtime of the chunk file is newer than the mtime of oldimg
            if os.path.getmtime(self.chunkfile) <= os.path.getmtime(oldimg_path):
                # chunkfile is older than the image, don't even bother checking
                # the hash
                return oldimg_path

        # Reasons for the code to get to this point:
        # 1) An old image doesn't exist
        # 2) An old image exists, but the chunk was more recently modified (the
        #    image was NOT checked if it was valid)
        # 3) An old image exists, the chunk was not modified more recently, but
        #    the image was invalid and deleted (sort of the same as (1))

        # What /should/ the image be named, go ahead and hash the block array
        dest_filename = "img.{0}.{1}.{2}.png".format(
                blockid,
                "cave" if cave else "nocave",
                self._hash_blockarray(),
                )

        dest_path = os.path.join(self.cachedir, dest_filename)

        if oldimg:
            if dest_filename == oldimg:
                # There is an existing file, the chunk has a newer mtime, but the
                # hashes match.
                # Before we return it, update its mtime so the next round
                # doesn't have to check the hash
                os.utime(dest_path, None)
                return dest_path
            else:
                # Remove old image for this chunk. Anything already existing is
                # either corrupt or out of date
                os.unlink(oldimg_path)

        # Render the chunk
        img = self.chunk_render(cave=cave)
        # Save it
        try:
            img.save(dest_path)
        except:
            os.unlink(dest_path)
            raise
        # Return its location
        return dest_path

    def chunk_render(self, img=None, xoff=0, yoff=0, cave=False):
        """Renders a chunk with the given parameters, and returns the image.
        If img is given, the chunk is rendered to that image object. Otherwise,
        a new one is created. xoff and yoff are offsets in the image.
        
        For cave mode, all blocks that have any direct sunlight are not
        rendered, and blocks are drawn with a color tint depending on their
        depth."""
        blocks = self.blocks
        if cave:
            skylight = get_skylight_array(self.level)
            # Cave mode. Actually go through and 0 out all blocks that are not in a
            # cave, so that it only renders caves.

            # 1st task: this array is 2 blocks per byte, expand it so we can just
            # do a bitwise and on the arrays
            skylight_expanded = numpy.empty((16,16,128), dtype=numpy.uint8)
            # Even elements get the lower 4 bits
            skylight_expanded[:,:,::2] = skylight & 0x0F
            # Odd elements get the upper 4 bits
            skylight_expanded[:,:,1::2] = skylight >> 4

            # Places where the skylight is not 0 (there's some amount of skylight
            # touching it) change it to something that won't get rendered, AND
            # won't get counted as "transparent".
            blocks = blocks.copy()
            blocks[skylight_expanded != 0] = 21

        blockData = get_blockdata_array(self.level)
        blockData_expanded = numpy.empty((16,16,128), dtype=numpy.uint8)
        # Even elements get the lower 4 bits
        blockData_expanded[:,:,::2] = blockData & 0x0F
        # Odd elements get the upper 4 bits
        blockData_expanded[:,:,1::2] = blockData >> 4


        # Each block is 24x24
        # The next block on the X axis adds 12px to x and subtracts 6px from y in the image
        # The next block on the Y axis adds 12px to x and adds 6px to y in the image
        # The next block up on the Z axis subtracts 12 from y axis in the image

        # Since there are 16x16x128 blocks in a chunk, the image will be 384x1728
        # (height is 128*12 high, plus the size of the horizontal plane: 16*12)
        if not img:
            img = Image.new("RGBA", (384, 1728), (38,92,255,0))

        for x,y,z,imgx,imgy in iterate_chunkblocks(xoff,yoff):
            blockid = blocks[x,y,z]

            # the following blocks don't have textures that can be pre-computed from the blockid
            # alone.  additional data is required.
            # TODO torches, redstone torches, crops, ladders, stairs, 
            #      levers, doors, buttons, and signs all need to be handled here (and in textures.py)

            ## minecart track, crops, ladder, doors, etc.
            if blockid in textures.special_blocks:
             # also handle furnaces here, since one side has a different texture than the other
                ancilData = blockData_expanded[x,y,z]
                try:
                    t = textures.specialblockmap[(blockid, ancilData)]
                except KeyError:
                    t = None

            else:
                t = textures.blockmap[blockid]
            if not t:
                continue

            # Check if this block is occluded
            if cave and (
                    x == 0 and y != 15 and z != 127
            ):
                # If it's on the x face, only render if there's a
                # transparent block in the y+1 direction OR the z-1
                # direction
                if (
                    blocks[x,y+1,z] not in transparent_blocks and
                    blocks[x,y,z+1] not in transparent_blocks
                ):
                    continue
            elif cave and (
                    y == 15 and x != 0 and z != 127
            ):
                # If it's on the facing y face, only render if there's
                # a transparent block in the x-1 direction OR the z-1
                # direction
                if (
                    blocks[x-1,y,z] not in transparent_blocks and
                    blocks[x,y,z+1] not in transparent_blocks
                ):
                    continue
            elif cave and (
                    y == 15 and x == 0
            ):
                # If it's on the facing edge, only render if what's
                # above it is transparent
                if (
                    blocks[x,y,z+1] not in transparent_blocks
                ):
                    continue
            elif (
                    # Normal block or not cave mode, check sides for
                    # transparentcy or render unconditionally if it's
                    # on a shown face
                    x != 0 and y != 15 and z != 127 and
                    blocks[x-1,y,z] not in transparent_blocks and
                    blocks[x,y+1,z] not in transparent_blocks and
                    blocks[x,y,z+1] not in transparent_blocks
            ):
                # Don't render if all sides aren't transparent and
                # we're not on the edge
                continue

            # Draw the actual block on the image. For cave images,
            # tint the block with a color proportional to its depth
            if cave:
                img.paste(Image.blend(t[0],depth_colors[z],0.3), (imgx, imgy), t[1])
            else:
                img.paste(t[0], (imgx, imgy), t[1])

            # Draw edge lines
            if blockid in (44,): # step block
               increment = 6
            elif blockid in (78,): # snow
               increment = 9
            else:
               increment = 0

            if blockid not in transparent_blocks or blockid in (78,): #special case snow so the outline is still drawn
                draw = ImageDraw.Draw(img)
                if x != 15 and blocks[x+1,y,z] == 0:
                    draw.line(((imgx+12,imgy+increment), (imgx+22,imgy+5+increment)), fill=(0,0,0), width=1)
                if y != 0 and blocks[x,y-1,z] == 0:
                    draw.line(((imgx,imgy+6+increment), (imgx+12,imgy+increment)), fill=(0,0,0), width=1)

        return img


# Render 128 different color images for color coded depth blending in cave mode
def generate_depthcolors():
    depth_colors = []
    r = 255
    g = 0
    b = 0
    for z in range(128):
        img = Image.new("RGB", (24,24), (r,g,b))
        depth_colors.append(img)
        if z < 32:
            g += 7
        elif z < 64:
            r -= 7
        elif z < 96:
            b += 7
        else:
            g -= 7

    return depth_colors
depth_colors = generate_depthcolors()