##
## imagestorage.py
## Login : <uli@pu.smp.net>
## Started on  Mon Jul  4 16:02:14 2011 Uli Fouquet
## $Id$
## 
## Copyright (C) 2011 Uli Fouquet
## This program 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 2 of the License, or
## (at your option) any later version.
## 
## This program 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 this program; if not, write to the Free Software
## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
##
"""A storage for image files.
"""
import grok
import hashlib
import os
from StringIO import StringIO
from ZODB.blob import Blob
from persistent import Persistent
from hurry.file.interfaces import IFileRetrieval
from zope.container.contained import Contained
from waeup.sirp.image import WAeUPImageFile
from waeup.sirp.utils.helpers import cmp_files

def md5digest(fd):
    """Get an MD5 hexdigest for the file stored in `fd`.

    `fd`
      a file object open for reading.

    """
    return hashlib.md5(fd.read()).hexdigest()

class Basket(grok.Container):
    """A basket holds a set of image files with same hash.
    """
    def _del(self):
        """Remove temporary files associated with local blobs.

        A basket holds files as Blob objects. Unfortunately, if a
        basket was not committed (put into ZODB), those blobs linger
        around as real files in some temporary directory and won't be
        removed.

        This is a helper function to remove all those uncommitted
        blobs that has to be called explicitly, for instance in tests.
        """
        key_list = self.keys()
        for key in key_list:
            item = self[key]
            if getattr(item, '_p_oid', None):
                # Don't mess around with blobs in ZODB
                continue
            fd = item.open('r')
            name = getattr(fd, 'name', None)
            fd.close()
            if name is not None and os.path.exists(name):
                os.unlink(name)
            del self[key]
        return

    def getInternalId(self, fd):
        for key, val in self.items():
            fd.seek(0)
            fd_stored = val.open('r')
            if cmp_files(fd, fd_stored):
                fd_stored.close()
                return key
            fd_stored.close()
        return None

    @property
    def curr_id(self):
        num = 1
        while True:
            if str(num) not in self.keys():
                return str(num)
            num += 1
            if num <= 0:
                name = getattr(self, '__name__', None)
                raise ValueError('Basket full: %s' % name)

    def storeFile(self, fd, filename):
        internal_id = self.getInternalId(fd)
        if internal_id is None:
            internal_id = self.curr_id
            self[internal_id] = Blob(fd.read())
        return internal_id

    def retrieveFile(self, basket_id):
        if basket_id in self.keys():
            return self[basket_id].open('r')
        return None

class ImageStorage(grok.Container):
    """A container for image files.
    """
    def _del(self):
        for basket in self.values():
            try:
                basket._del()
            except:
                pass

    def storeFile(self, fd, filename):
        fd.seek(0)
        digest = md5digest(fd)
        fd.seek(0)
        if not digest in self.keys():
            self[digest] = Basket()
        basket_id = self[digest].storeFile(fd, filename)
        full_id = "%s-%s" % (digest, basket_id)
        return full_id

    def retrieveFile(self, file_id):
        if not '-' in file_id:
            return None
        full_id, basket_id = file_id.split('-', 1)
        if not full_id in self.keys():
            return None
        return self[full_id].retrieveFile(basket_id)

class ImageStorageFileRetrieval(Persistent):
    grok.implements(IFileRetrieval)

    def getImageStorage(self):
        site = grok.getSite()
        if site is None:
            return None
        return site.get('images', None)

    def isImageStorageEnabled(self):
        site = grok.getSite()
        if site is None:
            return False
        if site.get('images', None) is None:
            return False
        return True

    def getFile(self, data):
        # ImageStorage is disabled, so give fall-back behaviour for
        # testing without ImageStorage
        if not self.isImageStorageEnabled():
            return StringIO(data)
        storage = self.getImageStorage()
        if storage is None:
            raise ValueError('Cannot find an image storage')
        return storage.retrieveFile(data)

    def createFile(self, filename, f):
        if not self.isImageStorageEnabled():
            return WAeUPImageFile(filename, f.read())
        storage = self.getImageStorage()
        if storage is None:
            raise ValueError('Cannot find an image storage')
        file_id = storage.storeFile(f, filename)
        return WAeUPImageFile(filename, file_id)