From 5b3fbd3befbb037186bbfa5b901cc2ded3cd43b2 Mon Sep 17 00:00:00 2001
From: Lars Wirzenius <liw@liw.fi>
Date: Fri, 19 Oct 2018 20:00:56 +0300
Subject: Add: PersistentStore

---
 muck/__init__.py   |  1 +
 muck/pers.py       | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 muck/pers_tests.py | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 110 insertions(+)
 create mode 100644 muck/pers.py
 create mode 100644 muck/pers_tests.py

diff --git a/muck/__init__.py b/muck/__init__.py
index 5e20126..69831f1 100644
--- a/muck/__init__.py
+++ b/muck/__init__.py
@@ -22,3 +22,4 @@ from .change import (
     create_change_from_log_entry,
 )
 from .mem import MemoryStore
+from .pers import PersistentStore
diff --git a/muck/pers.py b/muck/pers.py
new file mode 100644
index 0000000..aa4f4c1
--- /dev/null
+++ b/muck/pers.py
@@ -0,0 +1,55 @@
+# Copyright (C) 2018  Lars Wirzenius
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+import json
+import os
+
+import muck
+
+
+class PersistentStore:
+
+    def __init__(self, dirname):
+        self._dirname = dirname
+        self._log = ChangeLogWriter(self._changelog_filename())
+
+    def _changelog_filename(self):
+        return os.path.join(self._dirname, 'changelog')
+
+    def append_change(self, chg):
+        self._log.append(chg)
+
+    def load_memory_store(self):
+        ms = muck.MemoryStore()
+        for chg in self._changelog_reader():
+            ms.change(chg)
+        return ms
+
+    def _changelog_reader(self):
+        with open(self._changelog_filename()) as f:
+            for line in f:
+                entry = json.loads(line.strip())
+                yield muck.create_change_from_log_entry(entry)
+
+
+class ChangeLogWriter:
+
+    def __init__(self, filename):
+        mode = os.O_WRONLY | os.O_APPEND | os.O_CREAT
+        self._fd = os.open(filename, mode, 0o666)
+
+    def append(self, chg):
+        line = json.dumps(chg.as_dict())
+        os.write(self._fd, line.encode('UTF-8'))
diff --git a/muck/pers_tests.py b/muck/pers_tests.py
new file mode 100644
index 0000000..69a1023
--- /dev/null
+++ b/muck/pers_tests.py
@@ -0,0 +1,54 @@
+# Copyright (C) 2018  Lars Wirzenius
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+import shutil
+import tempfile
+import unittest
+
+import muck
+
+
+class PersistentStoreTests(unittest.TestCase):
+
+    def setUp(self):
+        self.tempdir = tempfile.mkdtemp()
+        self.ps = muck.PersistentStore(self.tempdir)
+
+    def tearDown(self):
+        shutil.rmtree(self.tempdir)
+
+    def test_initially_loads_empty_memory_store(self):
+        ms = self.ps.load_memory_store()
+        self.assertEqual(len(ms), 0)
+
+    def test_appends_to_change_log(self):
+        meta = {
+            'id': 'id-1',
+            'rev': 'rev-1',
+        }
+        res = {
+            'foo': 'bar',
+        }
+
+        chg = muck.CreateChange(meta, res)
+        self.ps.append_change(chg)
+
+        ms = self.ps.load_memory_store()
+        self.assertEqual(len(ms), 1)
+        self.assertEqual(
+            ms.as_dict(),
+            {
+                'id-1': (meta, res),
+            })
-- 
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