import os

from landscape.lib.fs import read_file
from landscape.constants import APT_PREFERENCES_SIZE_LIMIT

from landscape.monitor.plugin import DataWatcher


class AptPreferences(DataWatcher):
"""
Report the system APT preferences configuration.
"""

persist_name = "apt-preferences"
message_type = "apt-preferences"
message_key = "data"
run_interval = 900 # 15 minutes
scope = "package"
size_limit = APT_PREFERENCES_SIZE_LIMIT

def __init__(self, etc_apt_directory="/etc/apt"):
self._etc_apt_directory = etc_apt_directory

def get_data(self):
"""Return a C{dict} mapping APT preferences files to their contents.

If no APT preferences configuration is set at all on the system, then
simply return C{None}
"""
data = {}
read_unicode = lambda filename: unicode(read_file(filename))
preferences_filename = os.path.join(self._etc_apt_directory,
u"preferences")
if os.path.exists(preferences_filename):
data[preferences_filename] = read_unicode(preferences_filename)

preferences_directory = os.path.join(self._etc_apt_directory,
u"preferences.d")
if os.path.isdir(preferences_directory):
for entry in os.listdir(preferences_directory):
filename = os.path.join(preferences_directory, entry)
if os.path.isfile(filename):
data[filename] = read_unicode(filename)

if data == {}:
return None

item_size_limit = self.size_limit / len(data.keys())
for filename, contents in data.iteritems():
if len(filename) + len(contents) > item_size_limit:
truncated_contents_size = item_size_limit - len(filename)
data[filename] = data[filename][0:truncated_contents_size]

return data

def run(self):
return self.exchange(urgent=True)