# -*- coding: utf-8 -*-
# pylint: disable-all
#
# Copyright (c) 2012-2013 Paul Tax <paultax@gmail.com> All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
#   1. Redistributions of source code must retain the above copyright
#      notice, this list of conditions and the following disclaimer.
#
#   2. Redistributions in binary form must reproduce the above copyright
#      notice, this list of conditions and the following disclaimer in
#      the documentation and/or other materials provided with the
#      distribution.
#
#   3. Neither the name of Infrae nor the names of its contributors may
#      be used to endorse or promote products derived from this software
#      without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL INFRAE OR
# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
# EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
# PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
# PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
# LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

import hmac
from base64 import encodebytes as encodestring
from email.utils import formatdate
from hashlib import sha1 as sha
from urllib.parse import unquote, urlparse

from requests.auth import AuthBase


class S3Auth(AuthBase):

    """Attaches AWS Authentication to the given Request object."""

    service_base_url = 's3.amazonaws.com'
    # List of Query String Arguments of Interest
    special_params = [
        'acl', 'location', 'logging', 'partNumber', 'policy', 'requestPayment',
        'torrent', 'versioning', 'versionId', 'versions', 'website', 'uploads',
        'uploadId', 'response-content-type', 'response-content-language',
        'response-expires', 'response-cache-control', 'delete', 'lifecycle',
        'response-content-disposition', 'response-content-encoding', 'tagging',
        'notification', 'cors'
    ]

    def __init__(self, access_key, secret_key, service_url=None):
        if service_url:
            self.service_base_url = service_url
        self.access_key = str(access_key)
        self.secret_key = str(secret_key)

    def __call__(self, r):
        # Create date header if it is not created yet.
        if 'date' not in r.headers and 'x-amz-date' not in r.headers:
            r.headers['date'] = formatdate(
                timeval=None,
                localtime=False,
                usegmt=True)
        signature = self.get_signature(r)
        signature = signature.decode('utf-8')
        r.headers['Authorization'] = 'AWS %s:%s' % (self.access_key, signature)
        return r

    def get_signature(self, r):
        canonical_string = self.get_canonical_string(
            r.url, r.headers, r.method)
        key = self.secret_key.encode('utf-8')
        msg = canonical_string.encode('utf-8')
        h = hmac.new(key, msg, digestmod=sha)
        return encodestring(h.digest()).strip()

    def get_interesting_headers(self, headers):
        interesting_headers = {
            'content-md5': '',
            'content-type': '',
            'date': ''}
        for key in headers:
            lk = key.lower()
            try:
                if isinstance(lk, bytes):
                    lk = lk.decode('utf-8')
            except UnicodeDecodeError:
                pass
            if headers[key] and (lk in interesting_headers.keys()
                                 or lk.startswith('x-amz-')):
                interesting_headers[lk] = headers[key].strip()

        # If x-amz-date is used it supersedes the date header.
        if 'x-amz-date' in interesting_headers:
            interesting_headers['date'] = ''
        return interesting_headers

    def get_canonical_string(self, url, headers, method):
        parsedurl = urlparse(url)
        objectkey = parsedurl.path[1:]
        query_args = sorted(parsedurl.query.split('&'))

        bucket = parsedurl.netloc[:-len(self.service_base_url)]
        if len(bucket) > 1:
            # remove last dot
            bucket = bucket[:-1]

        interesting_headers = self.get_interesting_headers(headers)

        buf = '%s\n' % method
        for key in sorted(interesting_headers.keys()):
            val = interesting_headers[key]
            if key.startswith('x-amz-'):
                buf += '%s:%s\n' % (key, val)
            else:
                buf += '%s\n' % val

        # append the bucket if it exists
        if bucket != '':
            buf += '/%s' % bucket

        # add the objectkey. even if it doesn't exist, add the slash
        buf += '/%s' % objectkey

        params_found = False

        # handle special query string arguments
        for q in query_args:
            k = q.split('=')[0]
            if k in self.special_params:
                buf += '&' if params_found else '?'
                params_found = True

                try:
                    k, v = q.split('=', 1)

                except ValueError:
                    buf += q

                else:
                    # Riak CS multipart upload ids look like this, `TFDSheOgTxC2Tsh1qVK73A==`,
                    # is should be escaped to be included as part of a query string.
                    #
                    # A requests mp upload part request may look like
                    # resp = requests.put(
                    #     'https://url_here',
                    #     params={
                    #         'partNumber': 1,
                    #         'uploadId': 'TFDSheOgTxC2Tsh1qVK73A=='
                    #     },
                    #     data='some data',
                    #     auth=S3Auth('access_key', 'secret_key')
                    # )
                    #
                    # Requests automatically escapes the values in the `params` dict, so now
                    # our uploadId is `TFDSheOgTxC2Tsh1qVK73A%3D%3D`,
                    # if we sign the request with the encoded value the signature will
                    # not be valid, we'll get 403 Access Denied.
                    # So we unquote, this is no-op if the value isn't encoded.
                    buf += '{key}={value}'.format(key=k, value=unquote(v))

        return buf