Add tests for a read-only mode for the journal

This will be necessary for a read-only mode Larch in
general.

4 files changed, 62 insertions, 4 deletions

diff --git a/larch/__init__.py b/larch/__init__.py
index cc83b85..52b02d4 100644
--- a/larch/__init__.py
+++ b/larch/__init__.py
@@ -27,7 +27,7 @@ from refcountstore import RefcountStore
 from lru import LRUCache
 from uploadqueue import UploadQueue
 from idpath import IdPath
-from journal import Journal
+from journal import Journal, ReadOnlyMode
 from nodestore_disk import NodeStoreDisk, LocalFS, FormatProblem
 from nodestore_memory import NodeStoreMemory
 
diff --git a/larch/journal.py b/larch/journal.py
index ff6498d..1c18056 100644
--- a/larch/journal.py
+++ b/larch/journal.py
@@ -20,6 +20,12 @@ import os
 import tracing
 
 
+class ReadOnlyMode(Exception):
+
+    def __str__(self):
+        return 'Larch B-tree is in read-only mode, no changes allowed'
+
+
 class Journal(object):
 
     '''A journal layer on top of a virtual filesystem.
@@ -58,8 +64,9 @@ class Journal(object):
     
     flag_basename = 'metadata'
     
-    def __init__(self, fs, storedir):
+    def __init__(self, allow_writes, fs, storedir):
         logging.debug('Initializing Journal for %s' % storedir)
+        self.allow_writes = allow_writes
         self.fs = fs
         self.storedir = storedir
         if not self.storedir.endswith(os.sep):
diff --git a/larch/journal_tests.py b/larch/journal_tests.py
index 8d55b57..ac6f0ce 100644
--- a/larch/journal_tests.py
+++ b/larch/journal_tests.py
@@ -27,7 +27,7 @@ class JournalTests(unittest.TestCase):
     def setUp(self):
         self.tempdir = tempfile.mkdtemp()
         self.fs = larch.LocalFS()
-        self.j = larch.Journal(self.fs, self.tempdir)
+        self.j = larch.Journal(True, self.fs, self.tempdir)
         
     def tearDown(self):
         shutil.rmtree(self.tempdir)
@@ -175,3 +175,54 @@ class JournalTests(unittest.TestCase):
         j2 = larch.Journal(self.fs, self.tempdir)
         self.assertTrue(j2.exists(filename))
 
+
+class ReadOnlyJournalTests(unittest.TestCase):
+
+    def setUp(self):
+        self.tempdir = tempfile.mkdtemp()
+        self.fs = larch.LocalFS()
+        self.rw = larch.Journal(True, self.fs, self.tempdir)
+        self.ro = larch.Journal(False, self.fs, self.tempdir)
+        
+    def tearDown(self):
+        shutil.rmtree(self.tempdir)
+
+    def join(self, *args):
+        return os.path.join(self.tempdir, *args)
+
+    def test_does_not_know_random_directory_initially(self):
+        self.assertFalse(self.ro.exists(self.join('foo')))
+
+    def test_creating_directory_raises_error(self):
+        self.assertRaises(larch.ReadOnlyMode, self.ro.makedirs, 'foo')
+
+    def test_calling_rollback_raises_error(self):
+        self.assertRaises(larch.ReadOnlyMode, self.ro.rollback)
+
+    def test_readonly_mode_does_not_check_for_directory_creation(self):
+        dirname = self.rw.join('foo/bar')
+        self.rw.makedirs(dirname)
+        self.assertFalse(self.ro.exists(dirname))
+
+    def test_write_file_raisees_error(self):
+        self.assertRaises(larch.ReadOnlyMode, 
+                          self.ro.overwrite_file, 'foo', 'bar')
+
+    def test_readonly_mode_does_not_check_for_new_file(self):
+        self.rw.ovewrite_file('foo', 'bar')
+        self.assertFalse(self.ro.exists('foo'))
+
+    def test_readonly_mode_does_not_check_for_modified_file(self):
+        self.rw.ovewrite_file('foo', 'first')
+        self.rw.commit()
+        self.assertEqual(self.ro.cat('foo'), 'first')
+        self.rw.ovewrite_file('foo', 'second')
+        self.assertEqual(self.ro.cat('foo'), 'first')
+
+    def test_readonly_mode_does_not_know_file_is_deleted_in_journal(self):
+        filename = self.join('foo/bar')
+        self.rw.overwrite_file(filename, 'bar')
+        self.rw.commit()
+        self.rw.remove(filename)
+        self.assertEqual(self.ro.cat(filename), 'bar')
+
diff --git a/larch/nodestore_disk.py b/larch/nodestore_disk.py
index 01cae30..c216f50 100644
--- a/larch/nodestore_disk.py
+++ b/larch/nodestore_disk.py
@@ -130,7 +130,7 @@ class NodeStoreDisk(larch.NodeStore):
         self.upload_queue = larch.UploadQueue(self._really_put_node, 
                                               self.upload_max)
         self.vfs = vfs if vfs != None else LocalFS()
-        self.journal = larch.Journal(self.vfs, dirname)
+        self.journal = larch.Journal(True, self.vfs, dirname)
         self.idpath = larch.IdPath(os.path.join(dirname, self.nodedir), 
                                    DIR_DEPTH, DIR_BITS, DIR_SKIP)