from __future__ import unicode_literals

import base64
import hashlib
import hmac
import time

from datetime import datetime

from requests.auth import AuthBase

try:
    from urllib.parse import urlparse, urlencode
except ImportError:
    from urlparse import urlparse
    from urllib import urlencode


def safe_decode(value):
    return value.decode('utf-8') if hasattr(value, 'decode') else value


class AwsV2Auth(AuthBase):
    def __init__(self, key, secret):
        self.key = key
        self.secret = secret

    def __call__(self, request):
        date = datetime.utcnow().strftime('%a, %d %b %Y %H:%M:%S +0000')
        request.headers['x-amz-date'] = date
        signature = self.sign(request.method, request.url, request.headers)
        request.headers['Authorization'] = 'AWS {0}:{1}'.format(self.key,
                                                                signature)
        return request

    def sign(self, method, url, headers, expires=None):
        parsed = urlparse(url)
        path = parsed.path
        if parsed.query in ['acl', 'cors', 'delete', 'lifecycle', 'location',
                            'logging', 'notification', 'partnumber', 'policy',
                            'response-content-disposition',
                            'response-content-type',
                            'response-content-encoding',
                            'response-content-language',
                            'response-cache-control', 'response-expires',
                            'requestpayment', 'tagging', 'torrent', 'uploadid',
                            'uploads', 'versionid', 'versioning', 'versions',
                            'website']:
            path += '?' + parsed.query
        sig_headers = sorted([[k.lower(), v]
                              for k, v in headers.items()
                              if k.lower().startswith('x-amz-')],
                             key=lambda i: i[0])
        sig_headers = "\n".join((":".join((key, safe_decode(value)))
                                 for key, value in sig_headers))
        parts = [method,
                 safe_decode(headers.get('Content-MD5', '')),
                 safe_decode(headers.get('Content-Type', '')),
                 # date provided in x-amz-date if not from Expires
                 str(expires) if expires is not None else ""]
        if sig_headers:
            parts.append(sig_headers)
        parts.append(path)

        string_to_sign = "\n".join(parts)
        return base64.b64encode(hmac.new(
            self.secret.encode('utf-8'),
            string_to_sign.encode('utf-8'),
            digestmod=hashlib.sha1,
        ).digest()).decode('utf-8')

    def pre_sign(self, url, method='GET', headers=None, expires=None):
        if expires is None:
            expires = int(time.time()) + 3600
        if headers is None:
            headers = {}
        sig = self.sign(method, url, headers, expires)
        qs = urlencode({'Expires': expires,
                        'Signature': sig,
                        'AWSAccessKeyId': self.key})
        return '{0}?{1}'.format(url, qs)
