Use a set of helper/parsing classes to perform system configuration

Previously file modification of system configuration was done
in a functional and hard to test manner. Now instead this patch
allows for a manner that provides a nice object oriented
interface to those objects as well as makes it possible to test
those parsing entities without having to invoke distro class code.
   - Created parsers for:
    - /etc/sysconfig
    - /etc/hostname
    - resolv.conf
    - /etc/hosts

Moved duplicated functionality into the root level distro class including:
 - apply_hostname
 - set_hostname
 - *various shared configuration file names/paths*

1 files changed, 88 insertions, 0 deletions

diff --git a/cloudinit/distros/parsers/hostname.py b/cloudinit/distros/parsers/hostname.py
new file mode 100644
index 00000000..617b3c36
--- /dev/null
+++ b/cloudinit/distros/parsers/hostname.py
@@ -0,0 +1,88 @@
+# vi: ts=4 expandtab
+#
+#    Copyright (C) 2012 Yahoo! Inc.
+#
+#    Author: Joshua Harlow <harlowja@yahoo-inc.com>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License version 3, as
+#    published by the Free Software Foundation.
+#
+#    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 General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from StringIO import StringIO
+
+from cloudinit.distros.parsers import chop_comment
+
+
+# Parser that knows how to work with /etc/hostname format
+class HostnameConf(object):
+    def __init__(self, text):
+        self._text = text
+        self._contents = None
+
+    def parse(self):
+        if self._contents is None:
+            self._contents = self._parse(self._text)
+
+    def __str__(self):
+        self.parse()
+        contents = StringIO()
+        for (line_type, components) in self._contents:
+            if line_type == 'blank':
+                contents.write("%s\n" % (components[0]))
+            elif line_type == 'all_comment':
+                contents.write("%s\n" % (components[0]))
+            elif line_type == 'hostname':
+                (hostname, tail) = components
+                contents.write("%s%s\n" % (hostname, tail))
+        # Ensure trailing newline
+        contents = contents.getvalue()
+        if not contents.endswith("\n"):
+            contents += "\n"
+        return contents
+
+    @property
+    def hostname(self):
+        self.parse()
+        for (line_type, components) in self._contents:
+            if line_type == 'hostname':
+                return components[0]
+        return None
+
+    def set_hostname(self, your_hostname):
+        your_hostname = your_hostname.strip()
+        if not your_hostname:
+            return
+        self.parse()
+        replaced = False
+        for (line_type, components) in self._contents:
+            if line_type == 'hostname':
+                components[0] = str(your_hostname)
+                replaced = True
+        if not replaced:
+            self._contents.append(('hostname', [str(your_hostname), '']))
+
+    def _parse(self, contents):
+        entries = []
+        hostnames_found = set()
+        for line in contents.splitlines():
+            if not len(line.strip()):
+                entries.append(('blank', [line]))
+                continue
+            (head, tail) = chop_comment(line.strip(), '#')
+            if not len(head):
+                entries.append(('all_comment', [line]))
+                continue
+            entries.append(('hostname', [head, tail]))
+            hostnames_found.add(head)
+        if len(hostnames_found) > 1:
+            raise IOError("Multiple hostnames (%s) found!"
+                           % (hostnames_found))
+        return entries