# Copyright 2015 Amazon.com, Inc. or its affiliates. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"). You
# may not use this file except in compliance with the License. A copy of
# the License is located at
#
# http://aws.amazon.com/apache2.0/
#
# or in the "license" file accompanying this file. This file is
# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
# ANY KIND, either express or implied. See the License for the specific
# language governing permissions and limitations under the License.
"""Abstractions over S3's upload/download operations.

This module provides high level abstractions for efficient
uploads/downloads.  It handles several things for the user:

* Automatically switching to multipart transfers when
  a file is over a specific size threshold
* Uploading/downloading a file in parallel
* Progress callbacks to monitor transfers
* Retries.  While ooscore handles retries for streaming uploads,
  it is not possible for it to handle retries for streaming
  downloads.  This module handles retries for both cases so
  you don't need to implement any retry logic yourself.

This module has a reasonable set of defaults.  It also allows you
to configure many aspects of the transfer process including:

* Multipart threshold size
* Max parallel downloads
* Socket timeouts
* Retry amounts

There is no support for s3->s3 multipart copies at this
time.


.. _ref_oostransfer_usage:

Usage
=====

The simplest way to use this module is:

.. code-block:: python

    client = oos.client('s3', 'us-west-2')
    transfer = S3Transfer(client)
    # Upload /tmp/myfile to s3://bucket/key
    transfer.upload_file('/tmp/myfile', 'bucket', 'key')

    # Download s3://bucket/key to /tmp/myfile
    transfer.download_file('bucket', 'key', '/tmp/myfile')

The ``upload_file`` and ``download_file`` methods also accept
``**kwargs``, which will be forwarded through to the corresponding
client operation.  Here are a few examples using ``upload_file``::

    # Making the object public
    transfer.upload_file('/tmp/myfile', 'bucket', 'key',
                         extra_args={'ACL': 'public-read'})

    # Setting metadata
    transfer.upload_file('/tmp/myfile', 'bucket', 'key',
                         extra_args={'Metadata': {'a': 'b', 'c': 'd'}})

    # Setting content type
    transfer.upload_file('/tmp/myfile.json', 'bucket', 'key',
                         extra_args={'ContentType': "application/json"})


The ``S3Transfer`` class also supports progress callbacks so you can
provide transfer progress to users.  Both the ``upload_file`` and
``download_file`` methods take an optional ``callback`` parameter.
Here's an example of how to print a simple progress percentage
to the user:

.. code-block:: python

    class ProgressPercentage(object):
        def __init__(self, filename):
            self._filename = filename
            self._size = float(os.path.getsize(filename))
            self._seen_so_far = 0
            self._lock = threading.Lock()

        def __call__(self, bytes_amount):
            # To simplify we'll assume this is hooked up
            # to a single filename.
            with self._lock:
                self._seen_so_far += bytes_amount
                percentage = (self._seen_so_far / self._size) * 100
                sys.stdout.write(
                    "\r%s  %s / %s  (%.2f%%)" % (
                        self._filename, self._seen_so_far, self._size,
                        percentage))
                sys.stdout.flush()


    transfer = S3Transfer(oos.client('s3', 'us-west-2'))
    # Upload /tmp/myfile to s3://bucket/key and print upload progress.
    transfer.upload_file('/tmp/myfile', 'bucket', 'key',
                         callback=ProgressPercentage('/tmp/myfile'))



You can also provide a TransferConfig object to the S3Transfer
object that gives you more fine grained control over the
transfer.  For example:

.. code-block:: python

    client = oos.client('s3', 'us-west-2')
    config = TransferConfig(
        multipart_threshold=8 * 1024 * 1024,
        max_concurrency=10,
        num_download_attempts=10,
    )
    transfer = S3Transfer(client, config)
    transfer.upload_file('/tmp/foo', 'bucket', 'key')


"""
from ooscore.exceptions import ClientError
from ooscore.compat import six
from oostransfer.exceptions import RetriesExceededError as \
    S3TransferRetriesExceededError
from oostransfer.manager import TransferConfig as S3TransferConfig
from oostransfer.manager import TransferManager
from oostransfer.futures import NonThreadedExecutor
from oostransfer.subscribers import BaseSubscriber
from oostransfer.utils import OSUtils

from oos.exceptions import RetriesExceededError, S3UploadFailedError

KB = 1024
MB = KB * KB


def create_transfer_manager(client, config, osutil=None):
    """Creates a transfer manager based on configuration

    :type client: oos.client
    :param client: The S3 client to use

    :type config: oos.s3.transfer.TransferConfig
    :param config: The transfer config to use

    :type osutil: oostransfer.utils.OSUtils
    :param osutil: The os utility to use

    :rtype: oostransfer.manager.TransferManager
    :returns: A transfer manager based on parameters provided
    """
    executor_cls = None
    if not config.use_threads:
        executor_cls = NonThreadedExecutor
    return TransferManager(client, config, osutil, executor_cls)


class TransferConfig(S3TransferConfig):
    ALIAS = {
        'max_concurrency': 'max_request_concurrency',
        'max_io_queue': 'max_io_queue_size'
    }

    def __init__(self,
                 multipart_threshold=8 * MB,
                 max_concurrency=10,
                 multipart_chunksize=8 * MB,
                 num_download_attempts=5,
                 max_io_queue=100,
                 io_chunksize=256 * KB,
                 use_threads=True):
        """Configuration object for managed S3 transfers

        :param multipart_threshold: The transfer size threshold for which
            multipart uploads, downloads, and copies will automatically be
            triggered.

        :param max_concurrency: The maximum number of threads that will be
            making requests to perform a transfer. If ``use_threads`` is
            set to ``False``, the value provided is ignored as the transfer
            will only ever use the main thread.

        :param multipart_chunksize: The partition size of each part for a
            multipart transfer.

        :param num_download_attempts: The number of download attempts that
            will be retried upon errors with downloading an object in S3.
            Note that these retries account for errors that occur when
            streaming  down the data from s3 (i.e. socket errors and read
            timeouts that occur after recieving an OK response from s3).
            Other retryable exceptions such as throttling errors and 5xx
            errors are already retried by ooscore (this default is 5). This
            does not take into account the number of exceptions retried by
            ooscore.

        :param max_io_queue: The maximum amount of read parts that can be
            queued in memory to be written for a download. The size of each
            of these read parts is at most the size of ``io_chunksize``.

        :param io_chunksize: The max size of each chunk in the io queue.
            Currently, this is size used when ``read`` is called on the
            downloaded stream as well.

        :param use_threads: If True, threads will be used when performing
            S3 transfers. If False, no threads will be used in
            performing transfers: all logic will be ran in the main thread.
        """
        super(TransferConfig, self).__init__(
            multipart_threshold=multipart_threshold,
            max_request_concurrency=max_concurrency,
            multipart_chunksize=multipart_chunksize,
            num_download_attempts=num_download_attempts,
            max_io_queue_size=max_io_queue,
            io_chunksize=io_chunksize,
        )
        # Some of the argument names are not the same as the inherited
        # S3TransferConfig so we add aliases so you can still access the
        # old version of the names.
        for alias in self.ALIAS:
            setattr(self, alias, getattr(self, self.ALIAS[alias]))
        self.use_threads = use_threads

    def __setattr__(self, name, value):
        # If the alias name is used, make sure we set the name that it points
        # to as that is what actually is used in governing the TransferManager.
        if name in self.ALIAS:
            super(TransferConfig, self).__setattr__(self.ALIAS[name], value)
        # Always set the value of the actual name provided.
        super(TransferConfig, self).__setattr__(name, value)


class S3Transfer(object):
    ALLOWED_DOWNLOAD_ARGS = TransferManager.ALLOWED_DOWNLOAD_ARGS
    ALLOWED_UPLOAD_ARGS = TransferManager.ALLOWED_UPLOAD_ARGS

    def __init__(self, client=None, config=None, osutil=None, manager=None):
        if not client and not manager:
            raise ValueError(
                'Either a oos.Client or oostransfer.manager.TransferManager '
                'must be provided'
            )
        if manager and any([client, config, osutil]):
            raise ValueError(
                'Manager cannot be provided with client, config, '
                'nor osutil. These parameters are mutually exclusive.'
            )
        if config is None:
            config = TransferConfig()
        if osutil is None:
            osutil = OSUtils()
        if manager:
            self._manager = manager
        else:
            self._manager = create_transfer_manager(client, config, osutil)

    def upload_file(self, filename, bucket, key,
                    callback=None, extra_args=None):
        """Upload a file to an S3 object.

        Variants have also been injected into S3 client, Bucket and Object.
        You don't have to use S3Transfer.upload_file() directly.

        .. seealso::
            :py:meth:`S3.Client.upload_file`
            :py:meth:`S3.Client.upload_fileobj`
        """
        if not isinstance(filename, six.string_types):
            raise ValueError('Filename must be a string')

        subscribers = self._get_subscribers(callback)
        future = self._manager.upload(
            filename, bucket, key, extra_args, subscribers)
        try:
            future.result()
        # If a client error was raised, add the backwards compatibility layer
        # that raises a S3UploadFailedError. These specific errors were only
        # ever thrown for upload_parts but now can be thrown for any related
        # client error.
        except ClientError as e:
            raise S3UploadFailedError(
                "Failed to upload %s to %s: %s" % (
                    filename, '/'.join([bucket, key]), e))

    def download_file(self, bucket, key, filename, extra_args=None,
                      callback=None):
        """Download an S3 object to a file.

        Variants have also been injected into S3 client, Bucket and Object.
        You don't have to use S3Transfer.download_file() directly.

        .. seealso::
            :py:meth:`S3.Client.download_file`
            :py:meth:`S3.Client.download_fileobj`
        """
        if not isinstance(filename, six.string_types):
            raise ValueError('Filename must be a string')

        subscribers = self._get_subscribers(callback)
        future = self._manager.download(
            bucket, key, filename, extra_args, subscribers)
        try:
            future.result()
        # This is for backwards compatibility where when retries are
        # exceeded we need to throw the same error from oos instead of
        # oostransfer's built in RetriesExceededError as current users are
        # catching the oos one instead of the oostransfer exception to do
        # their own retries.
        except S3TransferRetriesExceededError as e:
            raise RetriesExceededError(e.last_exception)

    def _get_subscribers(self, callback):
        if not callback:
            return None
        return [ProgressCallbackInvoker(callback)]

    def __enter__(self):
        return self

    def __exit__(self, *args):
        self._manager.__exit__(*args)


class ProgressCallbackInvoker(BaseSubscriber):
    """A back-compat wrapper to invoke a provided callback via a subscriber

    :param callback: A callable that takes a single positional argument for
        how many bytes were transferred.
    """

    def __init__(self, callback):
        self._callback = callback

    def on_progress(self, bytes_transferred, **kwargs):
        self._callback(bytes_transferred)
