# -*- coding: utf-8 -*-
#
# Copyright 2012-2015 Spotify AB
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License 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.
#
"""
Implementation of Simple Storage Service support.
:py:class:`S3Target` is a subclass of the Target class to support S3 file
system operations. The `boto3` library is required to use S3 targets.
"""

import datetime
import itertools
import logging
import os
import os.path
import warnings
from multiprocessing.pool import ThreadPool

from urllib.parse import urlsplit

from configparser import NoSectionError

from luigi import configuration
from luigi.format import get_default_format
from luigi.parameter import OptionalParameter, Parameter
from luigi.target import FileAlreadyExists, FileSystem, FileSystemException, FileSystemTarget, AtomicLocalFile, MissingParentDirectory
from luigi.task import ExternalTask

logger = logging.getLogger('luigi-interface')

try:
    from boto3.s3.transfer import TransferConfig
    import botocore
except ImportError:
    logger.warning("Loading S3 module without the python package boto3. "
                   "Will crash at runtime if S3 functionality is used.")

# two different ways of marking a directory
# with a suffix in S3
S3_DIRECTORY_MARKER_SUFFIX_0 = '_$folder$'
S3_DIRECTORY_MARKER_SUFFIX_1 = '/'


class InvalidDeleteException(FileSystemException):
    pass


class FileNotFoundException(FileSystemException):
    pass


class DeprecatedBotoClientException(Exception):
    pass


class S3Client(FileSystem):
    """
    boto3-powered S3 client.
    """

    _s3 = None
    DEFAULT_PART_SIZE = 8388608
    DEFAULT_THREADS = 100

    def __init__(self, aws_access_key_id=None, aws_secret_access_key=None, aws_session_token=None,
                 **kwargs):
        options = self._get_s3_config()
        options.update(kwargs)
        if aws_access_key_id:
            options['aws_access_key_id'] = aws_access_key_id
        if aws_secret_access_key:
            options['aws_secret_access_key'] = aws_secret_access_key
        if aws_session_token:
            options['aws_session_token'] = aws_session_token

        self._options = options

    @property
    def s3(self):
        # only import boto3 when needed to allow top-lvl s3 module import
        import boto3

        options = dict(self._options)

        if self._s3:
            return self._s3

        aws_access_key_id = options.get('aws_access_key_id')
        aws_secret_access_key = options.get('aws_secret_access_key')

        # Removing key args would break backwards compatibility
        role_arn = options.get('aws_role_arn')
        role_session_name = options.get('aws_role_session_name')

        # In case the aws_session_token is provided use it
        aws_session_token = options.get('aws_session_token')

        if role_arn and role_session_name:
            sts_client = boto3.client('sts')
            assumed_role = sts_client.assume_role(RoleArn=role_arn,
                                                  RoleSessionName=role_session_name)
            aws_secret_access_key = assumed_role['Credentials'].get(
                'SecretAccessKey')
            aws_access_key_id = assumed_role['Credentials'].get('AccessKeyId')
            aws_session_token = assumed_role['Credentials'].get('SessionToken')
            logger.debug('using aws credentials via assumed role {} as defined in luigi config'
                         .format(role_session_name))

        for key in ['aws_access_key_id', 'aws_secret_access_key',
                    'aws_role_session_name', 'aws_role_arn', 'aws_session_token']:
            if key in options:
                options.pop(key)

        # At this stage, if no credentials provided, boto3 would handle their resolution for us
        # For finding out about the order in which it tries to find these credentials
        # please see here details
        # http://boto3.readthedocs.io/en/latest/guide/configuration.html#configuring-credentials

        if not (aws_access_key_id and aws_secret_access_key):
            logger.debug('no credentials provided, delegating credentials resolution to boto3')

        try:
            self._s3 = boto3.resource('s3',
                                      aws_access_key_id=aws_access_key_id,
                                      aws_secret_access_key=aws_secret_access_key,
                                      aws_session_token=aws_session_token,
                                      **options)
        except TypeError as e:
            logger.error(e.args[0])
            if 'got an unexpected keyword argument' in e.args[0]:
                raise DeprecatedBotoClientException(
                    "Now using boto3. Check that you're passing the correct arguments")
            raise

        return self._s3

    @s3.setter
    def s3(self, value):
        self._s3 = value

    def exists(self, path):
        """
        Does provided path exist on S3?
        """
        (bucket, key) = self._path_to_bucket_and_key(path)

        # root always exists
        if self._is_root(key):
            return True

        # file
        if self._exists(bucket, key):
            return True

        if self.isdir(path):
            return True

        logger.debug('Path %s does not exist', path)
        return False

    def remove(self, path, recursive=True):
        """
        Remove a file or directory from S3.
        :param path: File or directory to remove
        :param recursive: Boolean indicator to remove object and children
        :return: Boolean indicator denoting success of the removal of 1 or more files
        """
        if not self.exists(path):
            logger.debug('Could not delete %s; path does not exist', path)
            return False

        (bucket, key) = self._path_to_bucket_and_key(path)
        s3_bucket = self.s3.Bucket(bucket)
        # root
        if self._is_root(key):
            raise InvalidDeleteException('Cannot delete root of bucket at path %s' % path)

        # file
        if self._exists(bucket, key):
            self.s3.meta.client.delete_object(Bucket=bucket, Key=key)
            logger.debug('Deleting %s from bucket %s', key, bucket)
            return True

        if self.isdir(path) and not recursive:
            raise InvalidDeleteException('Path %s is a directory. Must use recursive delete' % path)

        delete_key_list = [{'Key': obj.key} for obj in s3_bucket.objects.filter(Prefix=self._add_path_delimiter(key))]

        # delete the directory marker file if it exists
        if self._exists(bucket, '{}{}'.format(key, S3_DIRECTORY_MARKER_SUFFIX_0)):
            delete_key_list.append({'Key': '{}{}'.format(key, S3_DIRECTORY_MARKER_SUFFIX_0)})

        if len(delete_key_list) > 0:
            n = 1000
            for i in range(0, len(delete_key_list), n):
                self.s3.meta.client.delete_objects(Bucket=bucket, Delete={'Objects': delete_key_list[i: i + n]})
            return True

        return False

    def move(self, source_path, destination_path, **kwargs):
        """
        Rename/move an object from one S3 location to another.
        :param source_path: The `s3://` path of the directory or key to copy from
        :param destination_path: The `s3://` path of the directory or key to copy to
        :param kwargs: Keyword arguments are passed to the boto3 function `copy`
        """
        self.copy(source_path, destination_path, **kwargs)
        self.remove(source_path)

    def get_key(self, path):
        """
        Returns the object summary at the path
        """
        (bucket, key) = self._path_to_bucket_and_key(path)

        if self._exists(bucket, key):
            return self.s3.ObjectSummary(bucket, key)

    def put(self, local_path, destination_s3_path, **kwargs):
        """
        Put an object stored locally to an S3 path.
        :param local_path: Path to source local file
        :param destination_s3_path: URL for target S3 location
        :param kwargs: Keyword arguments are passed to the boto function `put_object`
        """
        self._check_deprecated_argument(**kwargs)

        # put the file
        self.put_multipart(local_path, destination_s3_path, **kwargs)

    def put_string(self, content, destination_s3_path, **kwargs):
        """
        Put a string to an S3 path.
        :param content: Data str
        :param destination_s3_path: URL for target S3 location
        :param kwargs: Keyword arguments are passed to the boto3 function `put_object`
        """
        self._check_deprecated_argument(**kwargs)
        (bucket, key) = self._path_to_bucket_and_key(destination_s3_path)

        # put the file
        self.s3.meta.client.put_object(
            Key=key, Bucket=bucket, Body=content, **kwargs)

    def put_multipart(self, local_path, destination_s3_path, part_size=DEFAULT_PART_SIZE, **kwargs):
        """
        Put an object stored locally to an S3 path
        using S3 multi-part upload (for files > 8Mb).
        :param local_path: Path to source local file
        :param destination_s3_path: URL for target S3 location
        :param part_size: Part size in bytes. Default: 8388608 (8MB)
        :param kwargs: Keyword arguments are passed to the boto function `upload_fileobj` as ExtraArgs
        """
        self._check_deprecated_argument(**kwargs)

        from boto3.s3.transfer import TransferConfig
        # default part size for boto3 is 8Mb, changing it to fit part_size
        # provided as a parameter
        transfer_config = TransferConfig(multipart_chunksize=part_size)

        (bucket, key) = self._path_to_bucket_and_key(destination_s3_path)

        self.s3.meta.client.upload_fileobj(
            Fileobj=open(local_path, 'rb'), Bucket=bucket, Key=key, Config=transfer_config, ExtraArgs=kwargs)

    def copy(self, source_path, destination_path, threads=DEFAULT_THREADS, start_time=None, end_time=None,
             part_size=DEFAULT_PART_SIZE, **kwargs):
        """
        Copy object(s) from one S3 location to another. Works for individual keys or entire directories.
        When files are larger than `part_size`, multipart uploading will be used.
        :param source_path: The `s3://` path of the directory or key to copy from
        :param destination_path: The `s3://` path of the directory or key to copy to
        :param threads: Optional argument to define the number of threads to use when copying (min: 3 threads)
        :param start_time: Optional argument to copy files with modified dates after start_time
        :param end_time: Optional argument to copy files with modified dates before end_time
        :param part_size: Part size in bytes
        :param kwargs: Keyword arguments are passed to the boto function `copy` as ExtraArgs
        :returns tuple (number_of_files_copied, total_size_copied_in_bytes)
        """

        # don't allow threads to be less than 3
        threads = 3 if threads < 3 else threads

        if self.isdir(source_path):
            return self._copy_dir(source_path, destination_path, threads=threads,
                                  start_time=start_time, end_time=end_time, part_size=part_size, **kwargs)

        # If the file isn't a directory just perform a simple copy
        else:
            return self._copy_file(source_path, destination_path, threads=threads, part_size=part_size, **kwargs)

    def _copy_file(self, source_path, destination_path, threads=DEFAULT_THREADS, part_size=DEFAULT_PART_SIZE, **kwargs):
        src_bucket, src_key = self._path_to_bucket_and_key(source_path)
        dst_bucket, dst_key = self._path_to_bucket_and_key(destination_path)
        transfer_config = TransferConfig(max_concurrency=threads, multipart_chunksize=part_size)
        item = self.get_key(source_path)
        copy_source = {
            'Bucket': src_bucket,
            'Key': src_key
        }

        self.s3.meta.client.copy(copy_source, dst_bucket, dst_key, Config=transfer_config, ExtraArgs=kwargs)

        return 1, item.size

    def _copy_dir(self, source_path, destination_path, threads=DEFAULT_THREADS,
                  start_time=None, end_time=None, part_size=DEFAULT_PART_SIZE, **kwargs):
        start = datetime.datetime.now()
        copy_jobs = []
        management_pool = ThreadPool(processes=threads)
        transfer_config = TransferConfig(max_concurrency=threads, multipart_chunksize=part_size)
        src_bucket, src_key = self._path_to_bucket_and_key(source_path)
        dst_bucket, dst_key = self._path_to_bucket_and_key(destination_path)
        src_prefix = self._add_path_delimiter(src_key)
        dst_prefix = self._add_path_delimiter(dst_key)
        key_path_len = len(src_prefix)
        total_size_bytes = 0
        total_keys = 0
        for item in self.list(source_path, start_time=start_time, end_time=end_time, return_key=True):
            path = item.key[key_path_len:]
            # prevents copy attempt of empty key in folder
            if path != '' and path != '/':
                total_keys += 1
                total_size_bytes += item.size
                copy_source = {
                    'Bucket': src_bucket,
                    'Key': src_prefix + path
                }
                the_kwargs = {'Config': transfer_config, 'ExtraArgs': kwargs}
                job = management_pool.apply_async(self.s3.meta.client.copy,
                                                  args=(copy_source, dst_bucket, dst_prefix + path),
                                                  kwds=the_kwargs)
                copy_jobs.append(job)
        # Wait for the pools to finish scheduling all the copies
        management_pool.close()
        management_pool.join()
        # Raise any errors encountered in any of the copy processes
        for result in copy_jobs:
            result.get()
        end = datetime.datetime.now()
        duration = end - start
        logger.info('%s : Complete : %s total keys copied in %s' %
                    (datetime.datetime.now(), total_keys, duration))
        return total_keys, total_size_bytes

    def get(self, s3_path, destination_local_path):
        """
        Get an object stored in S3 and write it to a local path.
        """
        (bucket, key) = self._path_to_bucket_and_key(s3_path)
        # download the file
        self.s3.meta.client.download_file(bucket, key, destination_local_path)

    def get_as_bytes(self, s3_path):
        """
        Get the contents of an object stored in S3 as bytes

        :param s3_path: URL for target S3 location
        :return: File contents as pure bytes
        """
        (bucket, key) = self._path_to_bucket_and_key(s3_path)
        obj = self.s3.Object(bucket, key)
        contents = obj.get()['Body'].read()
        return contents

    def get_as_string(self, s3_path, encoding='utf-8'):
        """
        Get the contents of an object stored in S3 as string.

        :param s3_path: URL for target S3 location
        :param encoding: Encoding to decode bytes to string
        :return: File contents as a string
        """
        content = self.get_as_bytes(s3_path)
        return content.decode(encoding)

    def isdir(self, path):
        """
        Is the parameter S3 path a directory?
        """
        (bucket, key) = self._path_to_bucket_and_key(path)

        s3_bucket = self.s3.Bucket(bucket)

        # root is a directory
        if self._is_root(key):
            return True

        for suffix in (S3_DIRECTORY_MARKER_SUFFIX_0,
                       S3_DIRECTORY_MARKER_SUFFIX_1):
            try:
                self.s3.meta.client.get_object(
                    Bucket=bucket, Key=key + suffix)
            except botocore.exceptions.ClientError as e:
                if not e.response['Error']['Code'] in ['NoSuchKey', '404']:
                    raise
            else:
                return True

        # files with this prefix
        key_path = self._add_path_delimiter(key)
        s3_bucket_list_result = list(itertools.islice(
            s3_bucket.objects.filter(Prefix=key_path), 1))
        if s3_bucket_list_result:
            return True

        return False

    is_dir = isdir  # compatibility with old version.

    def mkdir(self, path, parents=True, raise_if_exists=False):
        if raise_if_exists and self.isdir(path):
            raise FileAlreadyExists()

        bucket, key = self._path_to_bucket_and_key(path)
        if self._is_root(key):
            # isdir raises if the bucket doesn't exist; nothing to do here.
            return

        path = self._add_path_delimiter(path)

        if not parents and not self.isdir(os.path.dirname(path)):
            raise MissingParentDirectory()

        return self.put_string("", path)

    def listdir(self, path, start_time=None, end_time=None, return_key=False):
        """
        Get an iterable with S3 folder contents.
        Iterable contains absolute paths for which queried path is a prefix.

        :param path: URL for target S3 location
        :param start_time: Optional argument to list files with modified (offset aware) datetime after start_time
        :param end_time: Optional argument to list files with modified (offset aware) datetime before end_time
        :param return_key: Optional argument, when set to True will return boto3's ObjectSummary (instead of the filename)
        """
        (bucket, key) = self._path_to_bucket_and_key(path)

        # grab and validate the bucket
        s3_bucket = self.s3.Bucket(bucket)

        key_path = self._add_path_delimiter(key)
        key_path_len = len(key_path)
        for item in s3_bucket.objects.filter(Prefix=key_path):
            last_modified_date = item.last_modified
            if (
                # neither are defined, list all
                (not start_time and not end_time) or
                # start defined, after start
                (start_time and not end_time and start_time < last_modified_date) or
                # end defined, prior to end
                (not start_time and end_time and last_modified_date < end_time) or
                (start_time and end_time and start_time <
                 last_modified_date < end_time)  # both defined, between
            ):
                if return_key:
                    yield item
                else:
                    yield self._add_path_delimiter(path) + item.key[key_path_len:]

    def list(self, path, start_time=None, end_time=None, return_key=False):  # backwards compat
        """
        Get an iterable with S3 folder contents.
        Iterable contains paths relative to queried path.

        :param path: URL for target S3 location
        :param start_time: Optional argument to list files with modified (offset aware) datetime after start_time
        :param end_time: Optional argument to list files with modified (offset aware) datetime before end_time
        :param return_key: Optional argument, when set to True will return boto3's ObjectSummary (instead of the filename)
        """
        key_path_len = len(self._add_path_delimiter(path))
        for item in self.listdir(path, start_time=start_time, end_time=end_time, return_key=return_key):
            if return_key:
                yield item
            else:
                yield item[key_path_len:]

    @staticmethod
    def _get_s3_config(key=None):
        defaults = dict(configuration.get_config().defaults())
        try:
            config = dict(configuration.get_config().items('s3'))
        except (NoSectionError, KeyError):
            return {}
        # So what ports etc can be read without us having to specify all dtypes
        for k, v in config.items():
            try:
                config[k] = int(v)
            except ValueError:
                pass
        if key:
            return config.get(key)
        section_only = {k: v for k, v in config.items() if k not in defaults or v != defaults[k]}

        return section_only

    @staticmethod
    def _path_to_bucket_and_key(path):
        (scheme, netloc, path, query, fragment) = urlsplit(path,
                                                           allow_fragments=False)
        question_mark_plus_query = '?' + query if query else ''
        path_without_initial_slash = path[1:] + question_mark_plus_query
        return netloc, path_without_initial_slash

    @staticmethod
    def _is_root(key):
        return (len(key) == 0) or (key == '/')

    @staticmethod
    def _add_path_delimiter(key):
        return key if key[-1:] == '/' or key == '' else key + '/'

    @staticmethod
    def _check_deprecated_argument(**kwargs):
        """
        If `encrypt_key` or `host` is part of the arguments raise an exception
        :return: None
        """
        if 'encrypt_key' in kwargs:
            raise DeprecatedBotoClientException(
                'encrypt_key deprecated in boto3. Please refer to boto3 documentation for encryption details.')
        if 'host' in kwargs:
            raise DeprecatedBotoClientException(
                'host keyword deprecated and is replaced by region_name in boto3.\n'
                'example: region_name=us-west-1\n'
                'For region names, refer to the amazon S3 region documentation\n'
                'https://docs.aws.amazon.com/general/latest/gr/rande.html#s3_region')

    def _exists(self, bucket, key):
        try:
            self.s3.Object(bucket, key).load()
        except botocore.exceptions.ClientError as e:
            if e.response['Error']['Code'] in ['NoSuchKey', '404']:
                return False
            else:
                raise

        return True


class AtomicS3File(AtomicLocalFile):
    """
    An S3 file that writes to a temp file and puts to S3 on close.

    :param kwargs: Keyword arguments are passed to the boto function `initiate_multipart_upload`
    """

    def __init__(self, path, s3_client, **kwargs):
        self.s3_client = s3_client
        super(AtomicS3File, self).__init__(path)
        self.s3_options = kwargs

    def move_to_final_destination(self):
        self.s3_client.put_multipart(
            self.tmp_path, self.path, **self.s3_options)


class ReadableS3File:
    def __init__(self, s3_key):
        self.s3_key = s3_key.get()['Body']
        self.buffer = []
        self.closed = False
        self.finished = False

    def read(self, size=None):
        f = self.s3_key.read(size)
        return f

    def close(self):
        self.s3_key.close()
        self.closed = True

    def __del__(self):
        self.close()

    def __exit__(self, exc_type, exc, traceback):
        self.close()

    def __enter__(self):
        return self

    def _add_to_buffer(self, line):
        self.buffer.append(line)

    def _flush_buffer(self):
        output = b''.join(self.buffer)
        self.buffer = []
        return output

    def readable(self):
        return True

    def writable(self):
        return False

    def seekable(self):
        return False

    def __iter__(self):
        key_iter = self.s3_key.__iter__()

        has_next = True
        while has_next:
            try:
                # grab the next chunk
                chunk = next(key_iter)

                # split on newlines, preserving the newline
                for line in chunk.splitlines(True):

                    if not line.endswith(os.linesep):
                        # no newline, so store in buffer
                        self._add_to_buffer(line)
                    else:
                        # newline found, send it out
                        if self.buffer:
                            self._add_to_buffer(line)
                            yield self._flush_buffer()
                        else:
                            yield line
            except StopIteration:
                # send out anything we have left in the buffer
                output = self._flush_buffer()
                if output:
                    yield output
                has_next = False
        self.close()


class S3Target(FileSystemTarget):
    """
    Target S3 file object

    :param kwargs: Keyword arguments are passed to the boto function `initiate_multipart_upload`
    """

    fs = None

    def __init__(self, path, format=None, client=None, **kwargs):
        super(S3Target, self).__init__(path)
        if format is None:
            format = get_default_format()

        self.path = path
        self.format = format
        self.fs = client or S3Client()
        self.s3_options = kwargs

    def open(self, mode='r'):
        if mode not in ('r', 'w'):
            raise ValueError("Unsupported open mode '%s'" % mode)

        if mode == 'r':
            s3_key = self.fs.get_key(self.path)
            if not s3_key:
                raise FileNotFoundException(
                    "Could not find file at %s" % self.path)

            fileobj = ReadableS3File(s3_key)
            return self.format.pipe_reader(fileobj)
        else:
            return self.format.pipe_writer(AtomicS3File(self.path, self.fs, **self.s3_options))


class S3FlagTarget(S3Target):
    """
    Defines a target directory with a flag-file (defaults to `_SUCCESS`) used
    to signify job success.

    This checks for two things:

    * the path exists (just like the S3Target)
    * the _SUCCESS file exists within the directory.

    Because Hadoop outputs into a directory and not a single file,
    the path is assumed to be a directory.

    This is meant to be a handy alternative to AtomicS3File.

    The AtomicFile approach can be burdensome for S3 since there are no directories, per se.

    If we have 1,000,000 output files, then we have to rename 1,000,000 objects.
    """

    fs = None

    def __init__(self, path, format=None, client=None, flag='_SUCCESS'):
        """
        Initializes a S3FlagTarget.

        :param path: the directory where the files are stored.
        :type path: str
        :param client:
        :type client:
        :param flag:
        :type flag: str
        """
        if format is None:
            format = get_default_format()

        if path[-1] != "/":
            raise ValueError("S3FlagTarget requires the path to be to a "
                             "directory.  It must end with a slash ( / ).")
        super(S3FlagTarget, self).__init__(path, format, client)
        self.flag = flag

    def exists(self):
        hadoopSemaphore = self.path + self.flag
        return self.fs.exists(hadoopSemaphore)


class S3EmrTarget(S3FlagTarget):
    """
    Deprecated. Use :py:class:`S3FlagTarget`
    """

    def __init__(self, *args, **kwargs):
        warnings.warn("S3EmrTarget is deprecated. Please use S3FlagTarget")
        super(S3EmrTarget, self).__init__(*args, **kwargs)


class S3PathTask(ExternalTask):
    """
    A external task that to require existence of a path in S3.
    """
    path = Parameter()

    def output(self):
        return S3Target(self.path)


class S3EmrTask(ExternalTask):
    """
    An external task that requires the existence of EMR output in S3.
    """
    path = Parameter()

    def output(self):
        return S3EmrTarget(self.path)


class S3FlagTask(ExternalTask):
    """
    An external task that requires the existence of EMR output in S3.
    """
    path = Parameter()
    flag = OptionalParameter(default=None)

    def output(self):
        return S3FlagTarget(self.path, flag=self.flag)
