"""
(c) 2008-2013, holger krekel
"""
class XSpec:
    """ Execution Specification: key1=value1//key2=value2 ...
        * keys need to be unique within the specification scope
        * neither key nor value are allowed to contain "//"
        * keys are not allowed to contain "="
        * keys are not allowed to start with underscore
        * if no "=value" is given, assume a boolean True value
    """
    # XXX allow customization, for only allow specific key names
    popen = ssh = socket = python = chdir = nice = \
            dont_write_bytecode = execmodel = None

    def __init__(self, string):
        self._spec = string
        self.env = {}
        for keyvalue in string.split("//"):
            i = keyvalue.find("=")
            if i == -1:
                key, value = keyvalue, True
            else:
                key, value = keyvalue[:i], keyvalue[i+1:]
            if key[0] == "_":
                raise AttributeError("%r not a valid XSpec key" % key)
            if key in self.__dict__:
                raise ValueError("duplicate key: %r in %r" %(key, string))
            if key.startswith("env:"):
                self.env[key[4:]] = value
            else:
                setattr(self, key, value)

    def __getattr__(self, name):
        if name[0] == "_":
            raise AttributeError(name)
        return None

    def __repr__(self):
        return "<XSpec %r>" %(self._spec,)
    def __str__(self):
        return self._spec

    def __hash__(self):
        return hash(self._spec)
    def __eq__(self, other):
        return self._spec == getattr(other, '_spec', None)
    def __ne__(self, other):
        return self._spec != getattr(other, '_spec', None)

    def _samefilesystem(self):
        return bool(self.popen and not self.chdir)

