text: # This file is dual licensed under the terms of the Apache License, Version
  # 2.0, and the BSD License. See the LICENSE file in the root of this repository
  # for complete details.
  
  
  import string
  import re
  
  from setuptools.extern.pyparsing import stringStart, stringEnd, originalTextFor, ParseException
  from setuptools.extern.pyparsing import ZeroOrMore, Word, Optional, Regex, Combine
  from setuptools.extern.pyparsing import Literal as L  # noqa
  from setuptools.extern.six.moves.urllib import parse as urlparse
  
  from .markers import MARKER_EXPR, Marker
  from .specifiers import LegacySpecifier, Specifier, SpecifierSet
  
  
  class InvalidRequirement(ValueError):
      """
      An invalid requirement was found, users should refer to PEP 508.
      """
  
  
  ALPHANUM = Word(string.ascii_letters + string.digits)
  
  LBRACKET = L("[").suppress()
  RBRACKET = L("]").suppress()
  LPAREN = L("(").suppress()
  RPAREN = L(")").suppress()
  COMMA = L(",").suppress()
  SEMICOLON = L(";").suppress()
  AT = L("@").suppress()
  
  PUNCTUATION = Word("-_.")
  IDENTIFIER_END = ALPHANUM | (ZeroOrMore(PUNCTUATION) + ALPHANUM)
  IDENTIFIER = Combine(ALPHANUM + ZeroOrMore(IDENTIFIER_END))
  
  NAME = IDENTIFIER("name")
  EXTRA = IDENTIFIER
  
  URI = Regex(r'[^ ]+')("url")
  URL = (AT + URI)
  
  EXTRAS_LIST = EXTRA + ZeroOrMore(COMMA + EXTRA)
  EXTRAS = (LBRACKET + Optional(EXTRAS_LIST) + RBRACKET)("extras")
  
  VERSION_PEP440 = Regex(Specifier._regex_str, re.VERBOSE | re.IGNORECASE)
  VERSION_LEGACY = Regex(LegacySpecifier._regex_str, re.VERBOSE | re.IGNORECASE)
  
  VERSION_ONE = VERSION_PEP440 ^ VERSION_LEGACY
  VERSION_MANY = Combine(VERSION_ONE + ZeroOrMore(COMMA + VERSION_ONE),
                         joinString=",", adjacent=False)("_raw_spec")
  _VERSION_SPEC = Optional(((LPAREN + VERSION_MANY + RPAREN) | VERSION_MANY))
  _VERSION_SPEC.setParseAction(lambda s, l, t: t._raw_spec or '')
  
  VERSION_SPEC = originalTextFor(_VERSION_SPEC)("specifier")
  VERSION_SPEC.setParseAction(lambda s, l, t: t[1])
  
  MARKER_EXPR = originalTextFor(MARKER_EXPR())("marker")
  MARKER_EXPR.setParseAction(
      lambda s, l, t: Marker(s[t._original_start:t._original_end])
  )
  MARKER_SEPERATOR = SEMICOLON
  MARKER = MARKER_SEPERATOR + MARKER_EXPR
  
  VERSION_AND_MARKER = VERSION_SPEC + Optional(MARKER)
  URL_AND_MARKER = URL + Optional(MARKER)
  
  NAMED_REQUIREMENT = \
      NAME + Optional(EXTRAS) + (URL_AND_MARKER | VERSION_AND_MARKER)
  
  REQUIREMENT = stringStart + NAMED_REQUIREMENT + stringEnd
  
  
  class Requirement(object):
      """Parse a requirement.
  
      Parse a given requirement string into its parts, such as name, specifier,
      URL, and extras. Raises InvalidRequirement on a badly-formed requirement
      string.
      """
  
      # TODO: Can we test whether something is contained within a requirement?
      #       If so how do we do that? Do we need to test against the _name_ of
      #       the thing as well as the version? What about the markers?
      # TODO: Can we normalize the name and extra name?
  
      def __init__(self, requirement_string):
          try:
              req = REQUIREMENT.parseString(requirement_string)
          except ParseException as e:
              raise InvalidRequirement(
                  "Invalid requirement, parse error at \"{0!r}\"".format(
                      requirement_string[e.loc:e.loc + 8]))
  
          self.name = req.name
          if req.url:
              parsed_url = urlparse.urlparse(req.url)
              if not (parsed_url.scheme and parsed_url.netloc) or (
                      not parsed_url.scheme and not parsed_url.netloc):
                  raise InvalidRequirement("Invalid URL given")
              self.url = req.url
          else:
              self.url = None
          self.extras = set(req.extras.asList() if req.extras else [])
          self.specifier = SpecifierSet(req.specifier)
          self.marker = req.marker if req.marker else None
  
      def __str__(self):
          parts = [self.name]
  
          if self.extras:
              parts.append("[{0}]".format(",".join(sorted(self.extras))))
  
          if self.specifier:
              parts.append(str(self.specifier))
  
          if self.url:
              parts.append("@ {0}".format(self.url))
  
          if self.marker:
              parts.append("; {0}".format(self.marker))
  
          return "".join(parts)
  
      def __repr__(self):
          return "<Requirement({0!r})>".format(str(self))
  