package_cache/server.py

   1 # Copyright
   2
   3 import email.utils as _email_utils
   4 import mimetypes as _mimetypes
   5 import os as _os
   6 import urllib.error as _urllib_error
   7 import urllib.request as _urllib_request
   8
   9 from . import __version__
  10
  11
  12 class InvalidFile (ValueError):
  13     def __init__(self, url):
  14         super(InvalidFile, self).__init__('invalid file {!r}'.format(url))
  15         self.url = url
  16
  17
  18 class Server (object):
  19     def __init__(self, sources, cache):
  20         self.sources = sources
  21         self.cache = cache
  22         self.opener = _urllib_request.build_opener()
  23         self.opener.addheaders = [
  24             ('User-agent', 'Package-cache/{}'.format(__version__)),
  25             ]
  26
  27     def __call__(self, environ, start_response):
  28         try:
  29             return self._serve_request(
  30                 environ=environ, start_response=start_response)
  31         except InvalidFile:
  32             start_response('404 Not Found', [])
  33         except _urllib_error.HTTPError as e:
  34             print('{} {}'.format(e.code, e.reason))
  35             start_response('{} {}'.format(e.code, e.reason), [])
  36         return [b'']
  37
  38     def _serve_request(self, environ, start_response):
  39         method = environ['REQUEST_METHOD']
  40         url = environ.get('PATH_INFO', None)
  41         if url is None:
  42             raise InvalidFile(url=url)
  43         cache_path = self._get_cache_path(url=url)
  44         if not _os.path.exists(path=cache_path):
  45             self._get_file_from_sources(url=url, path=cache_path)
  46         if not _os.path.isfile(path=cache_path):
  47             raise InvalidFile(url=url)
  48         return self._serve_file(
  49             path=cache_path, environ=environ, start_response=start_response)
  50
  51     def _get_cache_path(self, url):
  52         relative_path = url.lstrip('/').replace('/', _os.path.sep)
  53         cache_path = _os.path.abspath(_os.path.join(self.cache, relative_path))
  54         check_relative_path = _os.path.relpath(
  55             path=cache_path, start=self.cache)
  56         if check_relative_path.startswith(_os.pardir + _os.path.sep):
  57             raise InvalidFile(url=url)
  58         return cache_path
  59
  60     def _get_file_from_sources(self, url, path):
  61         dirname = _os.path.dirname(path)
  62         if not _os.path.isdir(dirname):
  63             _os.makedirs(dirname, exist_ok=True)
  64         for i, source in enumerate(self.sources):
  65             source_url = source.rstrip('/') + url
  66             try:
  67                 self._get_file(url=source_url, path=path)
  68             except _urllib_error.HTTPError:
  69                 if i == len(self.sources) - 1:
  70                     raise
  71             else:
  72                 return
  73
  74     def _get_file(self, url, path):
  75         with self.opener.open(url) as response:
  76             content_length = int(response.getheader('Content-Length'))
  77             with open(path, 'wb') as f:
  78                 block_size = 8192
  79                 while True:
  80                     data = response.read(block_size)
  81                     f.write(data)
  82                     if len(data) < block_size:
  83                         break
  84
  85     def _serve_file(self, path, environ, start_response):
  86         headers = {
  87             'Content-Length': self._get_content_length(path=path),
  88             'Content-Type': self._get_content_type(path=path),
  89             'Last-Modified': self._get_last_modified(path=path),
  90             }
  91         f = open(path, 'rb')
  92         if 'wsgi.file_wrapper' in environ:
  93             file_iterator = environ['wsgi.file_wrapper'](f)
  94         else:
  95             file_iterator = iter(lambda: f.read(block_size), '')
  96         start_response('200 OK', list(headers.items()))
  97         return file_iterator
  98
  99     def _get_content_length(self, path):
 100         """Content-Length value per RFC 2616
 101
 102         Content-Length:
 103           https://tools.ietf.org/html/rfc2616#section-14.13
 104         """
 105         return str(_os.path.getsize(path))
 106
 107     def _get_content_type(self, path):
 108         """Content-Type value per RFC 2616
 109
 110         Content-Type:
 111           https://tools.ietf.org/html/rfc2616#section-14.17
 112         Media types:
 113           https://tools.ietf.org/html/rfc2616#section-3.7
 114         """
 115         mimetype, charset = _mimetypes.guess_type(url=path)
 116         if charset:
 117             return '{}; charset={}'.format(mimetype, charset)
 118         else:
 119             return mimetype
 120
 121     def _get_last_modified(self, path):
 122         """Last-Modified value per RFC 2616
 123
 124         Last-Modified:
 125           https://tools.ietf.org/html/rfc2616#section-14.29
 126         Date formats:
 127           https://tools.ietf.org/html/rfc2616#section-3.3.1
 128           https://tools.ietf.org/html/rfc1123#page-55
 129           https://tools.ietf.org/html/rfc822#section-5
 130         """
 131         mtime = _os.path.getmtime(path)
 132         return _email_utils.formatdate(
 133             timeval=mtime, localtime=False, usegmt=True)