Add ConfigDirectoryContext framework

amanuensis/config/context.py

@@ -0,0 +1,134 @@
+import os
+import re
+
+from amanuensis.config.loader import json_ro, json_rw
+from amanuensis.errors import MissingConfigError, ConfigAlreadyExistsError
+
+
+def is_guid(s):
+	return re.match(r'[0-9a-z]{32}', s.lower())
+
+
+class ConfigDirectoryContext():
+	"""
+	Base class for CRUD operations on config files in a config
+	directory.
+	"""
+	def __init__(self, path):
+		self.path = path
+		if not os.path.isdir(self.path):
+			raise MissingConfigError(path)
+
+	def new(self, filename):
+		"""
+		Creates a JSON file that doesn't already exist.
+		"""
+		if not filename.endswith('.json'):
+			filename = f'{filename}.json'
+		fpath = os.path.join(self.path, filename)
+		if os.path.isfile(fpath):
+			raise ConfigAlreadyExistsError(fpath)
+		return json_rw(fpath, new=True)
+
+	def read(self, filename):
+		"""
+		Loads a JSON file in read-only mode.
+		"""
+		if not filename.endswith('.json'):
+			filename = f'{filename}.json'
+		fpath = os.path.join(self.path, filename)
+		if not os.path.isfile(fpath):
+			raise MissingConfigError(path)
+		return json_ro(fpath)
+
+	def edit(self, filename):
+		"""
+		Loads a JSON file in write mode.
+		"""
+		if not filename.endswith('.json'):
+			filename = f'{filename}.json'
+		fpath = os.path.join(self.path, filename)
+		if not os.path.isfile(fpath):
+			raise MissingConfigError(path)
+		return json_rw(fpath, new=False)
+
+	def delete(self, filename):
+		"""Deletes a file."""
+		if not filename.endswith('.json'):
+			filename = f'{filename}.json'
+		fpath = os.path.join(self.path, filename)
+		if not os.path.isfile(fpath):
+			raise MissingConfigError(path)
+		os.delete(fpath)
+
+
+class IndexDirectoryContext(ConfigDirectoryContext):
+	"""
+	A lookup layer for getting config directory contexts for lexicon
+	or user directories.
+	"""
+	def __init__(self, path, cdc_type):
+		super().__init__(path)
+		self.cdc_type = cdc_type
+
+	def __getitem__(self, key):
+		"""
+		Returns a context to the given item. key is treated as the
+		item's id if it's a guid string, otherwise it's treated as
+		the item's indexed name and run through the index first.
+		"""
+		if not is_guid(key):
+			with self.index() as index:
+				iid = index.get(key)
+				if not iid:
+					raise MissingConfigError(key)
+				key = iid
+		return self.cdc_type(os.path.join(self.path, key))
+
+	def index(self, edit=False):
+		if edit:
+			return self.edit('index')
+		else:
+			return self.read('index')
+
+
+class RootConfigDirectoryContext(ConfigDirectoryContext):
+	"""
+	Context for the config directory with links to the lexicon and
+	user contexts.
+	"""
+	def __init__(self, path):
+		super().__init__(path)
+		self.lexicon = IndexDirectoryContext(
+			os.path.join(self.path, 'lexicon'),
+			LexiconConfigDirectoryContext)
+		self.user = IndexDirectoryContext(
+			os.path.join(self.path, 'user'),
+			UserConfigDirectoryContext)
+
+
+class LexiconConfigDirectoryContext(ConfigDirectoryContext):
+	"""
+	A config context for a lexicon's config directory.
+	"""
+	def __init__(self, path):
+		super().__init__(path)
+		self.draft = ConfigDirectoryContext(os.path.join(self.path, 'draft'))
+		self.src = ConfigDirectoryContext(os.path.join(self.path, 'src'))
+
+	def config(edit=False):
+		if edit:
+			return self.edit('config')
+		else:
+			return self.read('config')
+
+
+class UserConfigDirectoryContext(ConfigDirectoryContext):
+	"""
+	A config context for a user's config directory.
+	"""
+	def config(edit=False):
+		if edit:
+			return self.edit('config')
+		else:
+			return self.read('config')

amanuensis/config/loader.py

@@ -46,7 +46,9 @@ class ReadOnlyOrderedDict(OrderedDict):
 			raise AttributeError(key)
 		return self[key]
 
+
 class open_lock():
+	"""A context manager that opens a file with the specified file lock"""
 	def __init__(self, path, mode, lock_type):
 		self.fd = open(path, mode, encoding='utf8')
 		fcntl.lockf(self.fd, lock_type)
@@ -58,15 +60,25 @@ class open_lock():
 		fcntl.lockf(self.fd, fcntl.LOCK_UN)
 		self.fd.close()
 
+
 class open_sh(open_lock):
+	"""A context manager that opens a file with a shared lock"""
 	def __init__(self, path, mode):
 		super().__init__(path, mode, fcntl.LOCK_SH)
 
+
 class open_ex(open_lock):
+	"""A context manager that opens a file with an exclusive lock"""
 	def __init__(self, path, mode):
 		super().__init__(path, mode, fcntl.LOCK_EX)
 
+
 class json_ro(open_sh):
+	"""
+	A context manager that opens a file in a shared, read-only mode.
+	The contents of the file are read as JSON and returned as a read-
+	only OrderedDict.
+	"""
 	def __init__(self, path):
 		super().__init__(path, 'r')
 		self.config = None
@@ -75,16 +87,32 @@ class json_ro(open_sh):
 		self.config = json.load(self.fd, object_pairs_hook=ReadOnlyOrderedDict)
 		return self.config
 
+
 class json_rw(open_ex):
-	def __init__(self, path):
-		super().__init__(path, 'r+')
+	"""
+	A context manager that opens a file with an exclusive lock. The
+	file mode defaults to r+, which requires that the file exist. The
+	file mode can be set to w+ to create a new file by setting the new
+	kwarg in the ctor. The contents of the file are read as JSON and
+	returned in an AttrOrderedDict. Any changes to the context dict
+	will be written out to the file when the context manager exits.
+	"""
+	def __init__(self, path, new=False):
+		mode = 'w+' if new else 'r+'
+		super().__init__(path, mode)
 		self.config = None
+		self.new = new
 
 	def __enter__(self):
+		if not self.new:
 			self.config = json.load(self.fd, object_pairs_hook=AttrOrderedDict)
+		else:
+			self.config = AttrOrderedDict()
 		return self.config
 
 	def __exit__(self, exc_type, exc_value, traceback):
+		# Only write the enw value out if there wasn't an exception
+		if not exc_type:
 			self.fd.seek(0)
 			json.dump(self.config, self.fd, allow_nan=False, indent='\t')
 			self.fd.truncate()

amanuensis/errors.py

@@ -3,6 +3,15 @@ class AmanuensisError(Exception):
 
 class MissingConfigError(AmanuensisError):
 	"""A config file is missing that was expected to be present"""
+	def __init__(self, path):
+		super.__init__(self, "A config file or directory was expected to "
+			f"exist, but could not be found: {path}")
+
+class ConfigAlreadyExistsError(AmanuensisError):
+	"""Attempted to create a config, but it already exists"""
+	def __init__(self, path):
+		super.__init__(self, "Attempted to create a config, but it already "
+			f"exists: {path}")
 
 class MalformedConfigError(AmanuensisError):
 	"""A config file could not be read and parsed"""