strategies.py

# Copyright 2019 PrivateStorage.io, LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""
Hypothesis strategies for property testing.
"""

from base64 import (
    urlsafe_b64encode,
)

import attr

from hypothesis.strategies import (
    one_of,
    just,
    binary,
    characters,
    text,
    integers,
    sets,
    lists,
    tuples,
    dictionaries,
    fixed_dictionaries,
    builds,
)

from twisted.web.test.requesthelper import (
    DummyRequest,
)

from allmydata.interfaces import (
    StorageIndex,
    LeaseRenewSecret,
    LeaseCancelSecret,
    WriteEnablerSecret,
)

from allmydata.client import (
    config_from_string,
)

from ..model import (
    Pass,
    RandomToken,
)


def _merge_dictionaries(dictionaries):
    result = {}
    for d in dictionaries:
        result.update(d)
    return result


def _tahoe_config_quote(text):
    return text.replace(u"%", u"%%")


def _config_string_from_sections(divided_sections):
    sections = _merge_dictionaries(divided_sections)
    return u"".join(list(
        u"[{name}]\n{items}\n".format(
            name=name,
            items=u"\n".join(
                u"{key} = {value}".format(key=key, value=_tahoe_config_quote(value))
                for (key, value)
                in contents.items()
            )
        )
        for (name, contents) in sections.items()
    ))


def tahoe_config_texts(storage_client_plugins):
    """
    Build the text of complete Tahoe-LAFS configurations for a node.
    """
    return builds(
        lambda *sections: _config_string_from_sections(
            sections,
        ),
        fixed_dictionaries(
            {
                "storageclient.plugins.{}".format(name): configs
                for (name, configs)
                in storage_client_plugins.items()
            },
        ),
        fixed_dictionaries(
            {
                "node": fixed_dictionaries(
                    {
                        "nickname": node_nicknames(),
                    },
                ),
                "client": fixed_dictionaries(
                    {
                        "storage.plugins": just(
                            u",".join(storage_client_plugins.keys()),
                        ),
                    },
                ),
            },
        ),
    )


def tahoe_configs(storage_client_plugins=None):
    """
    Build complete Tahoe-LAFS configurations for a node.
    """
    if storage_client_plugins is None:
        storage_client_plugins = {}
    return tahoe_config_texts(
        storage_client_plugins,
    ).map(
        lambda config_text: lambda basedir, portnumfile: config_from_string(
            basedir,
            portnumfile,
            config_text.encode("utf-8"),
        ),
    )

def node_nicknames():
    """
    Builds Tahoe-LAFS node nicknames.
    """
    return text(
        min_size=0,
        max_size=16,
        alphabet=characters(
            blacklist_categories={
                # Surrogates
                u"Cs",
                # Unnamed and control characters
                u"Cc",
            },
        ),
    )


def configurations():
    """
    Build configuration values for the server-side plugin.
    """
    return just({})


def client_configurations():
    """
    Build configuration values for the client-side plugin.
    """
    return just({})


def vouchers():
    """
    Build unicode strings in the format of vouchers.
    """
    return binary(
        min_size=32,
        max_size=32,
    ).map(
        urlsafe_b64encode,
    ).map(
        lambda voucher: voucher.decode("ascii"),
    )


def random_tokens():
    """
    Build random tokens as unicode strings.
    """
    return binary(
        min_size=32,
        max_size=32,
    ).map(
        urlsafe_b64encode,
    ).map(
        lambda token: RandomToken(token.decode("ascii")),
    )


def zkaps():
    """
    Build random ZKAPs as ``Pass` instances.
    """
    return binary(
        min_size=32,
        max_size=32,
    ).map(
        urlsafe_b64encode,
    ).map(
        lambda zkap: Pass(zkap.decode("ascii")),
    )


def request_paths():
    """
    Build lists of unicode strings that represent the path component of an
    HTTP request.

    :see: ``requests``
    """


def requests(paths=request_paths()):
    """
    Build objects providing ``twisted.web.iweb.IRequest``.
    """
    return builds(
        DummyRequest,
        paths,
    )


def storage_indexes():
    """
    Build Tahoe-LAFS storage indexes.
    """
    return binary(
        min_size=StorageIndex.minLength,
        max_size=StorageIndex.maxLength,
    )


def lease_renew_secrets():
    """
    Build Tahoe-LAFS lease renewal secrets.
    """
    return binary(
        min_size=LeaseRenewSecret.minLength,
        max_size=LeaseRenewSecret.maxLength,
    )


def lease_cancel_secrets():
    """
    Build Tahoe-LAFS lease cancellation secrets.
    """
    return binary(
        min_size=LeaseCancelSecret.minLength,
        max_size=LeaseCancelSecret.maxLength,
    )


def write_enabler_secrets():
    """
    Build Tahoe-LAFS write enabler secrets.
    """
    return binary(
        min_size=WriteEnablerSecret.minLength,
        max_size=WriteEnablerSecret.maxLength,
    )


def sharenums():
    """
    Build Tahoe-LAFS share numbers.
    """
    return integers(
        min_value=0,
        max_value=255,
    )


def sharenum_sets():
    """
    Build sets of Tahoe-LAFS share numbers.
    """
    return sets(
        sharenums(),
        min_size=1,
        max_size=255,
    )


def sizes():
    """
    Build Tahoe-LAFS share sizes.
    """
    return integers(
        # Size 0 data isn't data, it's nothing.
        min_value=1,
        # Just for practical purposes...
        max_value=2 ** 16,
    )


def offsets():
    """
    Build Tahoe-LAFS share offsets.
    """
    return integers(
        min_value=0,
        # Just for practical purposes...
        max_value=2 ** 16,
    )


def bytes_for_share(sharenum, size):
    """
    :return bytes: marginally distinctive bytes of a certain length for the
        given share number
    """
    if 0 <= sharenum <= 255:
        return (unichr(sharenum) * size).encode("latin-1")
    raise ValueError("Sharenum must be between 0 and 255 inclusive.")


def shares():
    """
    Build Tahoe-LAFS share data.
    """
    return tuples(
        sharenums(),
        sizes()
    ).map(
        lambda num_and_size: bytes_for_share(*num_and_size),
    )


def data_vectors():
    """
    Build Tahoe-LAFS data vectors.
    """
    return lists(
        tuples(
            offsets(),
            shares(),
        ),
        # An empty data vector doesn't make much sense.  If you have no data
        # to write, you should probably use slot_readv instead.  Also,
        # Tahoe-LAFS explodes if you pass an empty data vector -
        # storage/server.py, OSError(ENOENT) from `os.listdir(bucketdir)`.
        min_size=1,
        # Just for practical purposes...
        max_size=8,
    )


def test_vectors():
    """
    Build Tahoe-LAFS test vectors.
    """
    return lists(
        # XXX TODO
        just(None),
        min_size=0,
        max_size=0,
    )


@attr.s(frozen=True)
class TestAndWriteVectors(object):
    """
    Provide an alternate structure for the values required by the
    ``tw_vectors`` parameter accepted by
    ``RIStorageServer.slot_testv_and_readv_and_writev``.
    """
    test_vector = attr.ib()
    write_vector = attr.ib()
    new_length = attr.ib()

    def for_call(self):
        """
        Construct a value suitable to be passed as ``tw_vectors`` to
        ``slot_testv_and_readv_and_writev``.
        """
        return (self.test_vector, self.write_vector, self.new_length)


def test_and_write_vectors():
    """
    Build Tahoe-LAFS test and write vectors for a single share.
    """
    return builds(
        TestAndWriteVectors,
        test_vectors(),
        data_vectors(),
        one_of(
            just(None),
            sizes(),
        ),
    )


def test_and_write_vectors_for_shares():
    """
    Build Tahoe-LAFS test and write vectors for a number of shares.
    """
    return dictionaries(
        sharenums(),
        test_and_write_vectors(),
        # An empty dictionary wouldn't make much sense.  And it provokes a
        # NameError from Tahoe, storage/server.py:479, `new_length` referenced
        # before assignment.
        min_size=1,
        # Just for practical purposes...
        max_size=4,
    )


def announcements():
    """
    Build announcements for the ZKAPAuthorizer plugin.
    """
    return just({})