import boto
import os
import logging
import hashlib

from boto.s3.key import Key
from uuid import uuid4
from flask import url_for


logger = logging.getLogger(__name__)


class FakeUserfiles(object):
  def prepare_for_drop(self, mime_type):
    return ('http://fake/url', uuid4())

  def store_file(self, file_like_obj, content_type):
    raise NotImplementedError()

  def get_file_url(self, file_id, expires_in=300):
    return ('http://fake/url')

  def get_file_checksum(self, file_id):
    return 'abcdefg'


class S3FileWriteException(Exception):
  pass


class S3Userfiles(object):
  def __init__(self, path, s3_access_key, s3_secret_key, bucket_name):
    self._initialized = False
    self._bucket_name = bucket_name
    self._access_key = s3_access_key
    self._secret_key = s3_secret_key
    self._prefix = path
    self._s3_conn = None
    self._bucket = None

  def _initialize_s3(self):
    if not self._initialized:
      self._s3_conn = boto.connect_s3(self._access_key, self._secret_key)
      self._bucket = self._s3_conn.get_bucket(self._bucket_name)
      self._initialized = True

  def prepare_for_drop(self, mime_type):
    """ Returns a signed URL to upload a file to our bucket. """
    self._initialize_s3()
    logger.debug('Requested upload url with content type: %s' % mime_type)
    file_id = str(uuid4())
    full_key = os.path.join(self._prefix, file_id)
    k = Key(self._bucket, full_key)
    url = k.generate_url(300, 'PUT', headers={'Content-Type': mime_type},
                         encrypt_key=True)
    return (url, file_id)

  def store_file(self, file_like_obj, content_type):
    self._initialize_s3()
    file_id = str(uuid4())
    full_key = os.path.join(self._prefix, file_id)
    k = Key(self._bucket, full_key)
    logger.debug('Setting s3 content type to: %s' % content_type)
    k.set_metadata('Content-Type', content_type)
    bytes_written = k.set_contents_from_file(file_like_obj, encrypt_key=True,
                                             rewind=True)

    if bytes_written == 0:
      raise S3FileWriteException('Unable to write file to S3')

    return file_id

  def get_file_url(self, file_id, expires_in=300, mime_type=None):
    self._initialize_s3()
    full_key = os.path.join(self._prefix, file_id)
    k = Key(self._bucket, full_key)
    headers = None
    if mime_type:
      headers={'Content-Type': mime_type}
    
    return k.generate_url(expires_in, headers=headers)

  def get_file_checksum(self, file_id):
    self._initialize_s3()
    full_key = os.path.join(self._prefix, file_id)
    k = self._bucket.lookup(full_key)
    return k.etag[1:-1][:7]


def upload_userfile_endpoint(file_id):
  raise NotImplementedError()


def download_userfile_endpoint(file_id):
  raise NotImplementedError()


class LocalUserfiles(object):
  def __init__(self, path):
    self._root_path = path
    self._buffer_size = 64 * 1024  # 64 KB

  def prepare_for_drop(self, mime_type):
    file_id = str(uuid4())
    return (url_for('upload_userfile_endpoint', file_id=file_id), file_id)

  def store_file(self, file_like_obj, content_type):
    file_id = str(uuid4())
    path = os.path.join(self._root_path, file_id)
    with open(path, 'w') as to_write:
      while True:
        try:
          buf = file_like_obj.read(self._buffer_size)
          if not buf:
            break
          to_write.write(buf)
        except IOError:
          break

    return file_id

  def get_file_url(self, file_id, expires_in=300):
    return url_for('download_userfile_endpoint', file_id=file_id)

  def get_file_checksum(self, file_id):
    path = os.path.join(self._root_path, file_id)
    sha_hash = hashlib.sha256()
    with open(path, 'r') as to_hash:
      while True:
        buf = to_hash.read(self._buffer_size)
        if not buf:
          break
        sha_hash.update(buf)
    return sha_hash.hexdigest()[:7]


class Userfiles(object):
  def __init__(self, app=None):
    self.app = app
    if app is not None:
      self.state = self.init_app(app)
    else:
      self.state = None

  def init_app(self, app):
    storage_type = app.config.get('USERFILES_TYPE', 'LocalUserfiles')
    path = app.config.get('USERFILES_PATH', '')

    if storage_type == 'LocalUserfiles':
      app.add_url_rule('/userfiles/<file_id>', 'upload_userfile_endpoint',
                       upload_userfile_endpoint, methods=['PUT'])
      app.add_url_rule('/userfiles/<file_id>', 'download_userfile_endpoint',
                       download_userfile_endpoint, methods=['GET'])
      userfiles = LocalUserfiles(path)

    elif userfiles_type == 'S3Userfiles':
      access_key = app.config.get('USERFILES_AWS_ACCESS_KEY', '')
      secret_key = app.config.get('USERFILES_AWS_SECRET_KEY', '')
      bucket = app.config.get('USERFILES_S3_BUCKET', '')
      userfiles = S3Userfiles(path, access_key, secret_key, bucket)

    else:
      userfiles = FakeUserfiles()

    # register extension with app
    app.extensions = getattr(app, 'extensions', {})
    app.extensions['userfiles'] = userfiles
    return userfiles

  def __getattr__(self, name):
    return getattr(self.state, name, None)