Add monotonic randomness support

Doing this required a refactoring of how timestamp/randomness values
were generated. We've broken these into "provider" implementations
with the "default" provider being the implementation that exists today,
e.g. randomness values are random even on identical timestamp values.

A "monotonic" provider has been added which monotonically increments
the first randomness value on timestamp collision until an overflow.

Additionally, the API has been broken out into a subpackage so we can
stay agnostic to the provider and just plug it in. Work has been done
to maintain the existing package interface for backwards compatibility.

tests/test_module.py

@@ -37,9 +37,8 @@ def test_module_has_submodule_interface(submodule):
         assert hasattr(mod, i)
 
 
-def test_module_exposes_api_and_ulid_interfaces_via_all():
+def test_module_exposes_api_interfaces_via_all():
     """
-    Assert that :mod:`~ulid` exposes the :attr:`~ulid.api.__all__` and :attr:`~ulid.ulid.__all__`
-    attributes in its public interface.
+    Assert that :mod:`~ulid` exposes the :attr:`~ulid.api.__all__` attributes in its public interface.
     """
-    assert mod.__all__ == api.__all__ + ulid.__all__
+    assert mod.__all__ == api.__all__

ulid/__init__.py

@@ -7,29 +7,29 @@
     :copyright: (c) 2017 Andrew Hawker.
     :license: Apache 2.0, see LICENSE for more details.
 """
-from . import api, ulid
+from .api import default, monotonic
 
-create = api.create
-from_bytes = api.from_bytes
-from_int = api.from_int
-from_randomness = api.from_randomness
-from_str = api.from_str
-from_timestamp = api.from_timestamp
-from_uuid = api.from_uuid
-new = api.new
-parse = api.parse
+create = default.create
+from_bytes = default.from_bytes
+from_int = default.from_int
+from_randomness = default.from_randomness
+from_str = default.from_str
+from_timestamp = default.from_timestamp
+from_uuid = default.from_uuid
+new = default.new
+parse = default.parse
 
-MIN_TIMESTAMP = api.MIN_TIMESTAMP
-MAX_TIMESTAMP = api.MAX_TIMESTAMP
-MIN_RANDOMNESS = api.MIN_RANDOMNESS
-MAX_RANDOMNESS = api.MAX_RANDOMNESS
-MIN_ULID = api.MIN_ULID
-MAX_ULID = api.MAX_ULID
+MIN_TIMESTAMP = default.MIN_TIMESTAMP
+MAX_TIMESTAMP = default.MAX_TIMESTAMP
+MIN_RANDOMNESS = default.MIN_RANDOMNESS
+MAX_RANDOMNESS = default.MAX_RANDOMNESS
+MIN_ULID = default.MIN_ULID
+MAX_ULID = default.MAX_ULID
 
-Timestamp = ulid.Timestamp
-Randomness = ulid.Randomness
-ULID = ulid.ULID
+Timestamp = default.Timestamp
+Randomness = default.Randomness
+ULID = default.ULID
 
-__all__ = api.__all__ + ulid.__all__
+__all__ = default.__all__
 
 __version__ = '0.2.0'

ulid/api/__init__.py

@@ -0,0 +1,31 @@
+"""
+    ulid/api
+    ~~~~~~~~
+
+    Defines the public API of the `ulid` package.
+"""
+from .. import consts, ulid
+from . import default
+
+create = default.create
+from_bytes = default.from_bytes
+from_int = default.from_int
+from_randomness = default.from_randomness
+from_str = default.from_str
+from_timestamp = default.from_timestamp
+from_uuid = default.from_uuid
+new = default.new
+parse = default.parse
+
+MIN_TIMESTAMP = consts.MIN_TIMESTAMP
+MAX_TIMESTAMP = consts.MAX_TIMESTAMP
+MIN_RANDOMNESS = consts.MIN_RANDOMNESS
+MAX_RANDOMNESS = consts.MAX_RANDOMNESS
+MIN_ULID = consts.MIN_ULID
+MAX_ULID = consts.MAX_ULID
+
+Timestamp = ulid.Timestamp
+Randomness = ulid.Randomness
+ULID = ulid.ULID
+
+__all__ = default.__all__