from mimetypes import guess_type
from StringIO import StringIO
import urlparse
import os

from django.core.exceptions import ImproperlyConfigured
from django.core.filestorage.base import Storage, RemoteFile
from django.core.filestorage.filesystem import FileSystemStorage
from django.utils.functional import curry
from django.conf import settings

ACCESS_KEY_NAME = 'AWS_ACCESS_KEY_ID'
SECRET_KEY_NAME = 'AWS_SECRET_ACCESS_KEY'

try:
    from _lib.amazon.S3 import AWSAuthConnection, QueryStringAuthGenerator
except ImportError:
    raise ImproperlyConfigured, "Could not load amazon's S3 bindings.\
    \nSee http://developer.amazonwebservices.com/connect/entry.jspa?externalID=134"

class S3Storage(Storage):
    """Amazon Simple Storage Service"""

    def __init__(self, bucket=settings.AWS_STORAGE_BUCKET_NAME, 
            access_key=None, secret_key=None, acl='public-read', 
            calling_format=settings.AWS_CALLING_FORMAT):
        self.bucket = bucket
        self.acl = acl

        if not access_key and not secret_key:
             access_key, secret_key = self._get_access_keys()

        self.connection = AWSAuthConnection(access_key, secret_key, 
                            calling_format=calling_format)
        self.generator = QueryStringAuthGenerator(access_key, secret_key, 
                            calling_format=calling_format, is_secure=False)

    def _get_access_keys(self):
        access_key = getattr(settings, ACCESS_KEY_NAME, None)
        secret_key = getattr(settings, SECRET_KEY_NAME, None)
        if (access_key or secret_key) and (not access_key or not secret_key):
            access_key = os.environ.get(ACCESS_KEY_NAME)
            secret_key = os.environ.get(SECRET_KEY_NAME)

        if access_key and secret_key:
            # Both were provided, so use them
            return access_key, secret_key

        return None, None

    def _get_connection(self):
        return AWSAuthConnection(*self._get_access_keys())

    def _put_file(self, filename, raw_contents):
        content_type = guess_type(filename)[0] or "application/x-octet-stream"
        headers = {'x-amz-acl':  self.acl, 'Content-Type': content_type}
        response = self.connection.put(self.bucket, filename, raw_contents, headers)

    def url(self, filename):
        return self.generator.make_bare_url(self.bucket, filename)

    def filesize(self, filename):
        response = self.connection.make_request('HEAD', self.bucket, filename)
        return int(response.getheader('Content-Length'))

    def open(self, filename, mode='rb'):
        response = self.connection.get(self.bucket, filename)
        writer = curry(self._put_file, filename)
        return RemoteFile(self, response.object.data, mode, writer)

    def exists(self, filename):
        response = self.connection.make_request('HEAD', self.bucket, filename)
        return response.status == 200

    def save(self, filename, raw_contents):
        filename = self.get_available_filename(filename)
        self._put_file(filename, raw_contents)
        return filename

    def delete(self, filename):
        self.connection.delete(self.bucket, filename)

    def get_available_filename(self, filename):
        """ Overwrite existing file with the same name. """
        return filename