[PATCH 07/21] Add a new lookaside module

[Mathieu Bridon]

From: Mathieu Bridon <bochecha at daitauha.fr>

At the moment this doesn't do much: it only stores the 3
lookaside-related parameters we have (a download url, an upload url and
a hash type), but eventually it will become a full-fledged lookaside
cache client.

Using a property for it makes it trivial for downstreams to override it
if they need to use their own implementation of a lookaside cache
client.

And using a cached property means we won't reinitialize the
CGILookasideCache object every time we access the
Commands.lookasidecache attribute.
---
 src/pyrpkg/__init__.py  | 16 ++++++++++++++++
 src/pyrpkg/lookaside.py | 30 ++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)
 create mode 100644 src/pyrpkg/lookaside.py

diff --git a/src/pyrpkg/__init__.py b/src/pyrpkg/__init__.py
index 9e706b4..b06c68b 100644
--- a/src/pyrpkg/__init__.py
+++ b/src/pyrpkg/__init__.py
@@ -39,7 +39,9 @@ except ImportError:
     pass
 
 from pyrpkg.errors import HashtypeMixingError, rpkgError, rpkgAuthError
+from pyrpkg.lookaside import CGILookasideCache
 from pyrpkg.sources import SourcesFile
+from pyrpkg.utils import cached_property
 
 
 # Setup our logger
@@ -166,6 +168,20 @@ class Commands(object):
     # that we can do clone actions without knowing things like the spec
     # file or rpm data.
 
+    @cached_property
+    def lookasidecache(self):
+        """A helper to interact with the lookaside cache
+
+        This is a pyrpkg.lookaside.CGILookasideCache instance, providing all
+        the needed stuff to communicate with a Fedora-style lookaside cache.
+
+        Downstream users of the pyrpkg API may override this property with
+        their own, returning their own implementation of a lookaside cache
+        helper object.
+        """
+        return CGILookasideCache(
+            self.lookasidehash, self.lookaside, self.lookaside_cgi)
+
     @property
     def path(self):
         return self._path
diff --git a/src/pyrpkg/lookaside.py b/src/pyrpkg/lookaside.py
new file mode 100644
index 0000000..f7d191e
--- /dev/null
+++ b/src/pyrpkg/lookaside.py
@@ -0,0 +1,30 @@
+# Copyright (c) 2015 - Red Hat Inc.
+#
+# This program is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation; either version 2 of the License, or (at your
+# option) any later version.  See http://www.gnu.org/copyleft/gpl.html for
+# the full text of the license.
+
+
+"""Interact with a lookaside cache
+
+This module contains everything needed to upload and download source files the
+way it is done by Fedora, RHEL, and other distributions maintainers.
+"""
+
+
+class CGILookasideCache(object):
+    """A class to interact with a CGI-based lookaside cache"""
+    def __init__(self, hashtype, download_url, upload_url):
+        """Constructor
+
+        Args:
+            hashtype (str): The hash algorithm to use for uploads. (e.g 'md5')
+            download_url (str): The URL used to download source files.
+            upload_url (str): The URL of the CGI script called when uploading
+                source files.
+        """
+        self.hashtype = hashtype
+        self.download_url = download_url
+        self.upload_url = upload_url
-- 
2.1.0