General code cleanup for hierarchy module

rbackup/hierarchy.py

@@ -1,10 +1,14 @@
 """This module contains a class for creating a backup hierarchy."""
+
 import os.path
+import datetime
 
-class Hierarchy():
-    dest = None
 
-    def Hierarchy(self, dest):
+class Hierarchy:
+    """A class for generating the backup root hierarchy.
+    """
+
+    def __init__(self, dest):
         """Default constructor for the hierarchy class.
 
         :param dest: the root directory of the backup hierarchy
@@ -16,41 +20,81 @@ class Hierarchy():
         self.dest = dest
 
     @property
-    def etc_dir: 
+    def base_dir(self):
-        """Retrieve the /etc backup directory of this hierarchy.
-
-        :rtype: str
-        """
-        return os.path.join(self.dest, backup, etc)
-
-    @property
-    def home_dir:
-        """Retrieve the /home backup directory of this hierarchy.
-
-        :rtype: str
-        """
-        return os.path.join(self.dest, backup, home)
-
-    @property
-    def snapshot_dir:
-        """Retrieve the snapshot directory of this hierarchy.
-
-        :rtype: str
-        """
-        return os.path.join(self.dest, backup, snapshots)
-
-    @property
-    def root_home_dir:
-        """Retrieve root's home directory of this hierarchy.
-
-        :rtype: str
-        """
-        return os.path.join(self.dest, backup, root)
-
-    @property
-    def base_dir:
         """Return the base directory of this hierarchy.
 
         :rtype: str
         """
-        return dest
+        return self.dest
+
+    @property
+    def prev_snapshot(self):
+        """Return the canonical path of the previous snapshot stored in
+        this hierarchy.
+
+        This method checks whether or not '/dest/prev' is a symlink to
+        a snapshot. If it is not, then a FileExistsError is raised.
+
+        :rtype: str
+        :raises: FileExistsError if 'dest/prev' is not a symlink
+            to a snapshot
+        """
+        prevpath = os.path.join(self.base_dir, "prev")
+
+        if os.path.exists(prevpath) and not os.path.islink(prevpath):
+            raise FileExistsError(f"{prevpath} exists and is not a symlink")
+        elif not os.path.exists(prevpath):
+            raise FileNotFoundError(f"prevpath does not exist")
+
+        return os.path.realpath(prevpath)
+
+    @property
+    def prev_snapshot_link(self):
+        """Return the symlink path of the previous snapshot stored in
+        this hierarchy.
+
+        :rtype: str
+        """
+        return os.path.join(self.base_dir, "prev")
+
+    @property
+    def curr_snapshot(self):
+        """Retrieve the current date and time and use that in the path
+        for the current snapshot-to-be.
+
+        :rtype: str
+        """
+        date = datetime.datetime.utcnow().isoformat()
+        return os.path.join(self.base_dir, date.replace(":", "-"))
+
+    @property
+    def etc_dir(self):
+        """Retrieve the /etc backup directory of this hierarchy.
+
+        :rtype: str
+        """
+        return os.path.join(self.curr_snapshot, "etc")
+
+    @property
+    def home_dir(self):
+        """Retrieve the /home backup directory of this hierarchy.
+
+        :rtype: str
+        """
+        return os.path.join(self.curr_snapshot, "home")
+
+    @property
+    def snapshot_dir(self):
+        """Retrieve the snapshot directory of this hierarchy.
+
+        :rtype: str
+        """
+        return os.path.join(self.curr_snapshot, "snapshots")
+
+    @property
+    def root_home_dir(self):
+        """Retrieve root's home directory of this hierarchy.
+
+        :rtype: str
+        """
+        return os.path.join(self.curr_snapshot, "root")