from __future__ import (
    absolute_import,
)

from foolscap.constraint import (
    ByteStringConstraint,
)
from foolscap.api import (
    ListOf,
)
from foolscap.remoteinterface import (
    RemoteMethodSchema,
    RemoteInterface,
)

from allmydata.interfaces import (
    RIStorageServer,
)

# The Foolscap convention seems to be to try to constrain inputs to valid
# values.  So we'll try to limit the number of tokens a client can supply.
# Foolscap may be moving away from this so we may eventually drop this as
# well.  Though it may still make sense on a non-Foolscap protocol (eg HTTP)
# which Tahoe-LAFS may eventually support.
#
# In any case, for now, pick some fairly arbitrary value.  I am deliberately
# picking a small number here and expect to have to raise.  However, ideally,
# a client could accomplish a lot with a few tokens while also not wasting a
# lot of value.
MAXIMUM_TOKENS_PER_CALL = 10

# This is the length of a serialized Ristretto-flavored PrivacyPass pass
# (there's a lot of confusion between "tokens" and "passes" here, sadly).
#
# The pass is a combination of base64-encoded token preimages and unblinded
# token signatures.
TOKEN_LENGTH = 177

# Take those values and turn them into the appropriate Foolscap constraint
# objects.  Foolscap seems to have a convention of representing these as
# CamelCase module-level values so I replicate that here.
Token = ByteStringConstraint(maxLength=TOKEN_LENGTH, minLength=TOKEN_LENGTH)
TokenList = ListOf(Token, maxLength=MAXIMUM_TOKENS_PER_CALL)


def add_tokens(schema):
    """
    Add a ``tokens`` parameter to the given method schema.

    :param foolscap.remoteinterface.RemoteMethodSchema schema: An existing
        method schema to modify.

    :return foolscap.remoteinterface.RemoteMethodSchema: A schema like
        ``schema`` but with one additional required argument.
    """
    return add_arguments(schema, [(b"tokens", TokenList)])


def add_arguments(schema, kwargs):
    """
    Create a new schema like ``schema`` but with the arguments given by
    ``kwargs`` prepended to the signature.

    :param foolscap.remoteinterface.RemoteMethodSchema schema: The existing
        schema.

    :param list[(bytes, foolscap.IConstraint)] kwargs: The arguments to
        prepend to the signature of ``schema``.

    :return foolscap.remoteinterface.RemoteMethodSchema: The new schema
        object.
    """
    new_kwargs = dict(schema.argConstraints)
    new_kwargs.update(kwargs)
    modified_schema = RemoteMethodSchema(**new_kwargs)
    # Initialized from **new_kwargs, RemoteMethodSchema.argumentNames is in
    # some arbitrary, probably-incorrect order.  This breaks user code which
    # tries to use positional arguments.  Put them back in the order they were
    # in originally (in the input ``schema``), prepended with the newly added
    # arguments.
    modified_schema.argumentNames = (
        # The new arguments
        list(argName for (argName, _) in kwargs) +
        # The original arguments in the original order
        schema.argumentNames
    )
    return modified_schema



class RITokenAuthorizedStorageServer(RemoteInterface):
    """
    An object which can store and retrieve shares, subject to token-based
    authorization.

    This is much the same as ``allmydata.interfaces.RIStorageServer`` but
    several of its methods take an additional ``tokens`` parameter.  Clients
    are expected to supply suitable tokens and only after the tokens have been
    validated is service provided.
    """
    __remote_name__ = (
        "RITokenAuthorizedStorageServer.tahoe.privatestorage.io"
    )

    get_version = RIStorageServer["get_version"]

    allocate_buckets = add_tokens(RIStorageServer["allocate_buckets"])

    add_lease = add_tokens(RIStorageServer["add_lease"])

    renew_lease = add_tokens(RIStorageServer["renew_lease"])

    get_buckets = RIStorageServer["get_buckets"]

    slot_readv = RIStorageServer["slot_readv"]

    slot_testv_and_readv_and_writev = add_tokens(
        RIStorageServer["slot_testv_and_readv_and_writev"],
    )

    advise_corrupt_share = RIStorageServer["advise_corrupt_share"]