from sfa.util.xrn import urn_to_hrn
from sfa.util.method import Method

from sfa.trust.credential import Credential

from sfa.storage.parameter import Parameter, Mixed


class GetCredential(Method):
    """
    Retrive a credential for an object
    If cred == None then the behavior reverts to GetSelfCredential

    @param hrn human readable name of object (hrn or urn)
    @param cred credential object specifying rights of the caller
    @param type type of object (user | slice | node | authority )

    @return the string representation of a credential object  
    """

    interfaces = ['registry']

    accepts = [
        Mixed(Parameter(str, "Credential string"),
              Parameter(type([str]), "List of credentials")),
        Parameter(str, "Human readable name (hrn or urn)"),
        Mixed(Parameter(str, "Record type"),
              Parameter(None, "Type not specified")),
    ]

    returns = Parameter(str, "String representation of a credential object")

    def call(self, creds, xrn, type):

        if type:
            hrn = urn_to_hrn(xrn)[0]
        else:
            hrn, type = urn_to_hrn(xrn)

        # check creds
        valid_creds = self.api.auth.checkCredentials(creds, 'getcredential')
        self.api.auth.verify_object_belongs_to_me(hrn)

        # log the call
        origin_hrn = Credential(
            string=valid_creds[0]).get_gid_caller().get_hrn()
        self.api.logger.info("interface: %s\tcaller-hrn: %s\ttarget-hrn: %s\tmethod-name: %s" %
                             (self.api.interface, origin_hrn, hrn, self.name))

        return self.api.manager.GetCredential(self.api, xrn, type, self.api.auth.client_gid.get_urn())