import hashlib
import os
from itertools import chain

from django.conf import settings
from django.core.cache import cache
from django.core.exceptions import PermissionDenied
from django.core.signing import b64_encode
from django.http import Http404, HttpResponse, HttpResponseNotModified
from django.shortcuts import get_object_or_404
from django.views.decorators.http import etag
from shapely.geometry import box

from c3nav.mapdata.cache import MapHistory
from c3nav.mapdata.middleware import no_language
from c3nav.mapdata.models import Level, MapUpdate, Source
from c3nav.mapdata.render import MapRenderer, get_render_level_ids, get_tile_access_cookie, set_tile_access_cookie
from c3nav.mapdata.render.engines import ImageRenderEngine


@no_language()
def tile(request, level, zoom, x, y):
    zoom = int(zoom)
    if not (0 <= zoom <= 10):
        raise Http404

    # calculate bounds
    x, y = int(x), int(y)
    size = 256/2**zoom
    minx = size * x
    miny = size * (-y-1)
    maxx = minx + size
    maxy = miny + size

    # add one pixel so tiles can overlap to avoid rendering bugs in chrome or webkit
    maxx += size / 256
    miny -= size / 256

    # error 404 if tiles is out of bounds
    bounds = Source.max_bounds()
    if not box(*chain(*bounds)).intersects(box(minx, miny, maxx, maxy)):
        raise Http404

    # is this a valid level?
    cache_key = MapUpdate.current_cache_key()
    level = int(level)
    if level not in get_render_level_ids(cache_key):
        raise Http404

    # decode access permissions
    access_permissions = get_tile_access_cookie(request)

    # init renderer
    renderer = MapRenderer(level, minx, miny, maxx, maxy, scale=2 ** zoom, access_permissions=access_permissions)
    tile_cache_key = renderer.cache_key
    update_cache_key = renderer.update_cache_key

    # check browser cache
    etag = '"'+b64_encode(hashlib.sha256(
        ('%d-%d-%d-%d:%s:%s' % (level, zoom, x, y, tile_cache_key, settings.SECRET_TILE_KEY)).encode()
    ).digest()).decode()+'"'
    if_none_match = request.META.get('HTTP_IF_NONE_MATCH')
    if if_none_match == etag:
        return HttpResponseNotModified()

    data = None
    tile_dirname, last_update_filename, tile_filename, tile_cache_update_cache_key = '', '', '', ''

    # get tile cache last update
    if settings.CACHE_TILES:
        tile_dirname = os.path.sep.join((settings.TILES_ROOT, str(level), str(zoom), str(x), str(y)))
        last_update_filename = os.path.join(tile_dirname, 'last_update')
        tile_filename = os.path.join(tile_dirname, renderer.access_cache_key+'.png')

        # get tile cache last update
        tile_cache_update_cache_key = 'mapdata:tile-cache-update:%d-%d-%d-%d' % (level, zoom, x, y)
        tile_cache_update = cache.get(tile_cache_update_cache_key, None)
        if tile_cache_update is None:
            try:
                with open(last_update_filename) as f:
                    tile_cache_update = f.read()
            except FileNotFoundError:
                pass

        if tile_cache_update != update_cache_key:
            os.system('rm -rf '+os.path.join(tile_dirname, '*'))
        else:
            try:
                with open(tile_filename, 'rb') as f:
                    data = f.read()
            except FileNotFoundError:
                pass

    if data is None:
        image = renderer.render(ImageRenderEngine)
        data = image.render()

        if settings.CACHE_TILES:
            os.makedirs(tile_dirname, exist_ok=True)
            with open(tile_filename, 'wb') as f:
                f.write(data)
            with open(last_update_filename, 'w') as f:
                f.write(update_cache_key)
            cache.get(tile_cache_update_cache_key, update_cache_key, 60)

    response = HttpResponse(data, 'image/png')
    response['ETag'] = etag
    response['X-ETag-Unencoded'] = '%d-%d-%d-%d:%s' % (level, zoom, x, y, tile_cache_key)
    response['Cache-Control'] = 'no-cache'
    response['Vary'] = 'Cookie'
    response['X-Access-Restrictions'] = ', '.join(str(s) for s in renderer.unlocked_access_restrictions) or '0'

    return response


@no_language()
def tile_access(request):
    response = HttpResponse(content_type='text/plain')
    set_tile_access_cookie(request, response)
    response['Cache-Control'] = 'no-cache'
    return response


@etag(lambda *args, **kwargs: MapUpdate.current_cache_key())
@no_language()
def history(request, level, mode, format):
    if not request.user.is_superuser:
        raise PermissionDenied
    level = get_object_or_404(Level, pk=level)

    if mode == 'composite' and level.on_top_of_id is not None:
        raise Http404

    history = MapHistory.open_level(level.pk, mode)
    if format == 'png':
        response = HttpResponse(content_type='image/png')
        history.to_image().save(response, format='PNG')
    elif format == 'data':
        response = HttpResponse(content_type='application/octet-stream')
        history.write(response)
    else:
        raise ValueError
    response['Cache-Control'] = 'no-cache'
    return response