import os

import errno

import urlparse

from django.conf import settings

from django.core.exceptions import ImproperlyConfigured, SuspiciousOperation

from django.utils.encoding import force_unicode

from django.utils.text import get_valid_filename

from django.utils._os import safe_join

from django.core.files import locks, File

from django.core.files.move import file_move_safe

__all__ = ('Storage', 'FileSystemStorage', 'DefaultStorage', 'default_storage')

class Storage(object):

    """

    A base storage class, providing some default behaviors that all other

    storage systems can inherit or override, as necessary.

    """

    # The following methods represent a public interface to private methods.

    # These shouldn't be overridden by subclasses unless absolutely necessary.

    def open(self, name, mode='rb', mixin=None):

        """

        Retrieves the specified file from storage, using the optional mixin

        class to customize what features are available on the File returned.

        """

        file = self._open(name, mode)

        if mixin:

            # Add the mixin as a parent class of the File returned from storage.

            file.__class__ = type(mixin.__name__, (mixin, file.__class__), {})

        return file

    def save(self, name, content):

        """

        Saves new content to the file specified by name. The content should be a

        proper File object, ready to be read from the beginning.

        """

        # Get the proper name for the file, as it will actually be saved.

        if name is None:

            name = content.name

        name = self.get_available_name(name)

        name = self._save(name, content)

        # Store filenames with forward slashes, even on Windows

        return force_unicode(name.replace('\\', '/'))

    # These methods are part of the public API, with default implementations.

    def get_valid_name(self, name):

        """

        Returns a filename, based on the provided filename, that's suitable for

        use in the target storage system.

        """

        return get_valid_filename(name)

    def get_available_name(self, name):

        """

        Returns a filename that's free on the target storage system, and

        available for new content to be written to.

        """

        # If the filename already exists, keep adding an underscore to the name

        # of the file until the filename doesn't exist.

        while self.exists(name):

            try:

                dot_index = name.rindex('.')

            except ValueError: # filename has no dot

                name += '_'

            else:

                name = name[:dot_index] + '_' + name[dot_index:]

        return name

    def path(self, name):

        """

        Returns a local filesystem path where the file can be retrieved using

        Python's built-in open() function. Storage systems that can't be

        accessed using open() should *not* implement this method.

        """

        raise NotImplementedError("This backend doesn't support absolute paths.")

    # The following methods form the public API for storage systems, but with

    # no default implementations. Subclasses must implement *all* of these.

    def delete(self, name):

        """

        Deletes the specified file from the storage system.

        """

        raise NotImplementedError()

    def exists(self, name):

        """

        Returns True if a file referened by the given name already exists in the

        storage system, or False if the name is available for a new file.

        """

        raise NotImplementedError()

    def listdir(self, path):

        """

        Lists the contents of the specified path, returning a 2-tuple of lists;

        the first item being directories, the second item being files.

        """

        raise NotImplementedError()

    def size(self, name):

        """

        Returns the total size, in bytes, of the file specified by name.

        """

        raise NotImplementedError()

    def url(self, name):

        """

        Returns an absolute URL where the file's contents can be accessed

        directly by a web browser.

        """

        raise NotImplementedError()

class FileSystemStorage(Storage):

    """

    Standard filesystem storage

    """

    def __init__(self, location=settings.MEDIA_ROOT, base_url=settings.MEDIA_URL):

        self.location = os.path.abspath(location)

        self.base_url = base_url

    def _open(self, name, mode='rb'):

        return File(open(self.path(name), mode))

    def _save(self, name, content):

        full_path = self.path(name)

        directory = os.path.dirname(full_path)

        if not os.path.exists(directory):

            os.makedirs(directory)

        elif not os.path.isdir(directory):

            raise IOError("%s exists and is not a directory." % directory)

        # There's a potential race condition between get_available_name and

        # saving the file; it's possible that two threads might return the

        # same name, at which point all sorts of fun happens. So we need to

        # try to create the file, but if it already exists we have to go back

        # to get_available_name() and try again.

        while True:

            try:

                # This file has a file path that we can move.

                if hasattr(content, 'temporary_file_path'):

                    file_move_safe(content.temporary_file_path(), full_path)

                    content.close()

                # This is a normal uploadedfile that we can stream.

                else:

                    # This fun binary flag incantation makes os.open throw an

                    # OSError if the file already exists before we open it.

                    fd = os.open(full_path, os.O_WRONLY | os.O_CREAT | os.O_EXCL | getattr(os, 'O_BINARY', 0))

                    try:

                        locks.lock(fd, locks.LOCK_EX)

                        for chunk in content.chunks():

                            os.write(fd, chunk)

                    finally:

                        locks.unlock(fd)

                        os.close(fd)

            except OSError, e:

                if e.errno == errno.EEXIST:

                    # Ooops, the file exists. We need a new file name.

                    name = self.get_available_name(name)

                    full_path = self.path(name)

                else:

                    raise

            else:

                # OK, the file save worked. Break out of the loop.

                break

        if settings.FILE_UPLOAD_PERMISSIONS is not None:

            os.chmod(full_path, settings.FILE_UPLOAD_PERMISSIONS)

        return name

    def delete(self, name):

        name = self.path(name)

        # If the file exists, delete it from the filesystem.

        if os.path.exists(name):

            os.remove(name)

    def exists(self, name):

        return os.path.exists(self.path(name))

    def listdir(self, path):

        path = self.path(path)

        directories, files = [], []

        for entry in os.listdir(path):

            if os.path.isdir(os.path.join(path, entry)):

                directories.append(entry)

            else:

                files.append(entry)

        return directories, files

    def path(self, name):

        try:

            path = safe_join(self.location, name)

        except ValueError:

            raise SuspiciousOperation("Attempted access to '%s' denied." % name)

        return os.path.normpath(path)

    def size(self, name):

        return os.path.getsize(self.path(name))

    def url(self, name):

        if self.base_url is None:

            raise ValueError("This file is not accessible via a URL.")

        return urlparse.urljoin(self.base_url, name).replace('\\', '/')

def get_storage_class(import_path):

    try:

        dot = import_path.rindex('.')

    except ValueError:

        raise ImproperlyConfigured("%s isn't a storage module." % import_path)

    module, classname = import_path[:dot], import_path[dot+1:]

    try:

        mod = __import__(module, {}, {}, [''])

    except ImportError, e:

        raise ImproperlyConfigured('Error importing storage module %s: "%s"' % (module, e))

    try:

        return getattr(mod, classname)

    except AttributeError:

        raise ImproperlyConfigured('Storage module "%s" does not define a "%s" class.' % (module, classname))

DefaultStorage = get_storage_class(settings.DEFAULT_FILE_STORAGE)

default_storage = DefaultStorage()