1 files changed, 87 insertions, 0 deletions
diff --git a/cloudinit/mergers/m_list.py b/cloudinit/mergers/m_list.py
new file mode 100644
index 00000000..62999b4e
--- /dev/null
+++ b/cloudinit/mergers/m_list.py
@@ -0,0 +1,87 @@
+# 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/>.
+
+DEF_MERGE_TYPE = 'replace'
+MERGE_TYPES = ('append', 'prepend', DEF_MERGE_TYPE, 'no_replace')
+
+
+def _has_any(what, *keys):
+    for k in keys:
+        if k in what:
+            return True
+    return False
+
+
+class Merger(object):
+    def __init__(self, merger, opts):
+        self._merger = merger
+        # Affects merging behavior...
+        self._method = DEF_MERGE_TYPE
+        for m in MERGE_TYPES:
+            if m in opts:
+                self._method = m
+                break
+        # Affect how recursive merging is done on other primitives
+        self._recurse_str = _has_any(opts, 'recurse_str')
+        self._recurse_dict = _has_any(opts, 'recurse_dict')
+        self._recurse_array = _has_any(opts, 'recurse_array', 'recurse_list')
+
+    def __str__(self):
+        return ('ListMerger: (method=%s,recurse_str=%s,'
+                'recurse_dict=%s,recurse_array=%s)') % (self._method,
+                                                        self._recurse_str,
+                                                        self._recurse_dict,
+                                                        self._recurse_array)
+
+    def _on_tuple(self, value, merge_with):
+        return tuple(self._on_list(list(value), merge_with))
+
+    def _on_list(self, value, merge_with):
+        if (self._method == 'replace' and
+            not isinstance(merge_with, (tuple, list))):
+            return merge_with
+
+        # Ok we now know that what we are merging with is a list or tuple.
+        merged_list = []
+        if self._method == 'prepend':
+            merged_list.extend(merge_with)
+            merged_list.extend(value)
+            return merged_list
+        elif self._method == 'append':
+            merged_list.extend(value)
+            merged_list.extend(merge_with)
+            return merged_list
+
+        def merge_same_index(old_v, new_v):
+            if self._method == 'no_replace':
+                # Leave it be...
+                return old_v
+            if isinstance(new_v, (list, tuple)) and self._recurse_array:
+                return self._merger.merge(old_v, new_v)
+            if isinstance(new_v, (str, basestring)) and self._recurse_str:
+                return self._merger.merge(old_v, new_v)
+            if isinstance(new_v, (dict)) and self._recurse_dict:
+                return self._merger.merge(old_v, new_v)
+            return new_v
+
+        # Ok now we are replacing same indexes
+        merged_list.extend(value)
+        common_len = min(len(merged_list), len(merge_with))
+        for i in xrange(0, common_len):
+            merged_list[i] = merge_same_index(merged_list[i], merge_with[i])
+        return merged_list