Add AppHandler.next_counter_value() magic

this is now used by `BatchHandler.consume_batch_id()` and hopefully is
able to auto-magically create a dedicated counter table if the
underlying db engine is not postgres.  at least that part seems to
work for tests using sqlite

docs/api/rattail/batch/handlers.rst

@@ -15,6 +15,8 @@
 
    .. autoattribute:: batch_model_class
 
+   .. automethod:: consume_batch_id
+
    .. automethod:: make_batch
 
    .. automethod:: make_basic_batch
@@ -113,6 +115,8 @@
 
    .. automethod:: remove_row
 
+   .. automethod:: get_effective_rows
+
    .. automethod:: executable
 
    .. automethod:: why_not_execute

rattail/app.py

@@ -30,6 +30,7 @@ import os
 # import re
 import tempfile
 import warnings
+import logging
 
 import six
 
@@ -41,6 +42,9 @@ from rattail.config import parse_list
 from rattail.core import get_uuid
 
 
+log = logging.getLogger(__name__)
+
+
 class AppHandler(object):
     """
     Base class and default implementation for top-level Rattail app handler.
@@ -170,6 +174,29 @@ class AppHandler(object):
         """
         return load_object(spec)
 
+    def next_counter_value(self, session, key, **kwargs):
+        """
+        Return the next counter value for the given key.
+
+        :param session: Current session for Rattail DB.
+
+        :param key: Unique key indicating the counter for which the
+           next value should be fetched.
+
+        :returns: Next value as integer.
+        """
+        dialect = session.bind.url.get_dialect().name
+        if dialect != 'postgresql':
+            log.debug("non-postgresql database detected; will use workaround")
+            from rattail.db.util import CounterMagic
+            magic = CounterMagic(self.config)
+            return magic.next_value(session, key)
+
+        # normal (uses postgresql sequence)
+        sql = "select nextval('{}_seq')".format(key)
+        value = session.execute(sql).scalar()
+        return value
+
     def get_active_stores(self, session, **kwargs):
         """
         Returns the list of "active" stores.  A store is considered

rattail/batch/handlers.py

@@ -2,7 +2,7 @@
 ################################################################################
 #
 #  Rattail -- Retail Software Framework
-#  Copyright © 2010-2021 Lance Edgar
+#  Copyright © 2010-2022 Lance Edgar
 #
 #  This file is part of Rattail.
 #
@@ -119,6 +119,22 @@ class BatchHandler(object):
             return False
         return True
 
+    def consume_batch_id(self, session, as_str=False):
+        """
+        Consumes a new batch ID from the generator, and returns it.
+
+        :param session: Current session for Rattail DB.
+
+        :param as_str: Flag indicating whether the return value should be a
+           string, as opposed to the default of integer.
+
+        :returns: Batch ID as integer, or zero-padded string of 8 chars.
+        """
+        batch_id = self.app.next_counter_value(session, 'batch_id')
+        if as_str:
+            return '{:08d}'.format(batch_id)
+        return batch_id
+
     def make_basic_batch(self, session, user=None, progress=None, **kwargs):
         """
         Make a new "basic" batch, with no customization beyond what is provided
@@ -712,6 +728,23 @@ class BatchHandler(object):
         batch.executed_by = user
         return result
 
+    def get_effective_rows(self, batch):
+        """
+        Should return the set of rows from the given batch which are
+        considered "effective" - i.e. when the batch is executed,
+        these rows should be processed whereas the remainder should
+        not.
+
+        :param batch: A
+           :class:`~rattail.db.model.batch.vendorcatalog.VendorCatalogBatch`
+           instance.
+
+        :returns: List of
+           :class:`~rattail.db.model.batch.vendorcatalog.VendorCatalogBatchRow`
+           instances.
+        """
+        return batch.active_rows()
+
     def execute(self, batch, progress=None, **kwargs):
         """
         Execute the given batch, according to the given kwargs.  This is really

rattail/batch/vendorcatalog.py

@@ -55,6 +55,16 @@ class VendorCatalogHandler(BatchHandler):
     case_cost_diff_threshold = None
     unit_cost_diff_threshold = None
 
+    def allow_future(self):
+        """
+        Returns boolean indicating whether "future" cost changes
+        should be allowed.
+
+        :returns: ``True`` if future cost changes allowed; else ``False``.
+        """
+        return self.config.getbool('rattail.batch', 'vendor_catalog.allow_future',
+                                   default=False)
+
     def should_populate(self, batch):
         # all vendor catalogs must come from data file
         return True
@@ -118,7 +128,8 @@ class VendorCatalogHandler(BatchHandler):
                                                    require=True)
         parser.session = session
         parser.vendor = batch.vendor
-        batch.effective = parser.parse_effective_date(path)
+        if not batch.effective:
+            batch.effective = parser.parse_effective_date(path)
 
         def append(row, i):
             self.add_row(batch, row)

rattail/db/util.py

@@ -2,7 +2,7 @@
 ################################################################################
 #
 #  Rattail -- Retail Software Framework
-#  Copyright © 2010-2018 Lance Edgar
+#  Copyright © 2010-2022 Lance Edgar
 #
 #  This file is part of Rattail.
 #
@@ -30,6 +30,7 @@ import re
 import pprint
 import logging
 
+import sqlalchemy as sa
 from sqlalchemy import orm
 
 # TODO: Deprecate/remove these imports.
@@ -39,6 +40,27 @@ from rattail.db.config import engine_from_config, get_engines, get_default_engin
 log = logging.getLogger(__name__)
 
 
+class CounterMagic(object):
+    """
+    Provides magic counter values, to simulate PostgreSQL sequence.
+    """
+
+    def __init__(self, config):
+        self.config = config
+        self.metadata = sa.MetaData()
+
+    def next_value(self, session, key):
+        """
+        Increment and return the next counter value for given key.
+        """
+        engine = session.bind
+        table = sa.Table('counter_{}'.format(key), self.metadata,
+                         sa.Column('value', sa.Integer(), primary_key=True))
+        table.create(engine, checkfirst=True)
+        result = engine.execute(table.insert())
+        return result.lastrowid
+
+
 class QuerySequence(object):
     """
     Simple wrapper for a SQLAlchemy (or Django, or other?) query, to make it

tests/batch/test_handlers.py

@@ -0,0 +1,67 @@
+# -*- coding: utf-8; -*-
+
+from __future__ import unicode_literals, absolute_import
+
+import os
+from unittest import TestCase
+
+import sqlalchemy as sa
+
+from rattail.batch import handlers as mod
+from rattail.config import make_config
+from rattail.db import Session
+
+
+class TestBatchHandler(TestCase):
+
+    def setUp(self):
+        self.config = self.make_config()
+        self.handler = self.make_handler()
+
+    def make_config(self):
+        return make_config([], extend=False)
+
+    def make_handler(self):
+        return mod.BatchHandler(self.config)
+
+    def test_consume_batch_id(self):
+        engine = sa.create_engine('sqlite://')
+        model = self.config.get_model()
+        model.Base.metadata.create_all(bind=engine)
+        session = Session(bind=engine)
+
+        # first id is 1
+        result = self.handler.consume_batch_id(session)
+        self.assertEqual(result, 1)
+
+        # second is 2; test string version
+        result = self.handler.consume_batch_id(session, as_str=True)
+        self.assertEqual(result, '00000002')
+
+    def test_get_effective_rows(self):
+        engine = sa.create_engine('sqlite://')
+        model = self.config.get_model()
+        model.Base.metadata.create_all(bind=engine)
+        session = Session(bind=engine)
+
+        # make batch w/ 3 rows
+        user = model.User(username='patty')
+        batch = model.NewProductBatch(id=1, created_by=user)
+        batch.data_rows.append(model.NewProductBatchRow())
+        batch.data_rows.append(model.NewProductBatchRow())
+        batch.data_rows.append(model.NewProductBatchRow())
+        self.assertEqual(len(batch.data_rows), 3)
+
+        # all rows should be effective by default
+        result = self.handler.get_effective_rows(batch)
+        self.assertEqual(len(result), 3)
+
+        # unless we mark one as "removed"
+        batch.data_rows[1].removed = True
+        result = self.handler.get_effective_rows(batch)
+        self.assertEqual(len(result), 2)
+
+        # or if we delete one
+        batch.data_rows.pop(-1)
+        result = self.handler.get_effective_rows(batch)
+        self.assertEqual(len(result), 1)

tests/batch/test_vendorcatalog.py

@@ -28,6 +28,18 @@ class TestProductBatchHandler(TestCase):
     def make_handler(self):
         return mod.VendorCatalogHandler(self.config)
 
+    def test_allow_future(self):
+
+        # off by default
+        result = self.handler.allow_future()
+        self.assertFalse(result)
+
+        # but can be enabled via config
+        self.config.setdefault('rattail.batch', 'vendor_catalog.allow_future',
+                               'true')
+        result = self.handler.allow_future()
+        self.assertTrue(result)
+
     def test_populate_from_file(self):
         engine = sa.create_engine('sqlite://')
         model = self.config.get_model()