#!/usr/bin/python
## vim:set et ts=2 sw=2 ai:
# Send email reminders to users having sizable homedirs.
##
# Copyright (c) 2013 Philipp Kern <phil@philkern.de>
# Copyright (c) 2013 Peter Palfrader <peter@palfrader.org>
# Copyright (c) 2013 Luca Filipozzi <lfilipoz@debian.org>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

from __future__ import print_function

from collections import defaultdict
import email
import email.mime.text
import glob
import logging
import os.path
import platform
import pwd
import random
import subprocess
import struct
import time
import StringIO

# avoid base64 encoding for utf-8
email.charset.add_charset('utf-8', email.charset.SHORTEST, email.charset.QP)

SENDMAIL = ['/usr/sbin/sendmail', '-t', '-oi']
#SENDMAIL = ['/bin/cat']

EXPLANATIONS = [
u"""\
{hostname} /home is growing close to full.  If you have anything in there that
you no longer need, please clean it up.""" # By Martin Zobel-Helas
,u"""\
Can you please look at your $HOME on {hostname} and remove files which you
no longer need (such as old sources).""" # By Martin Michlmayr
,u"""\
Thanks for your porting effort on {hostname}!

Please note that /home is running short of diskspace, so please remove files
you do not need anymore.""" # By Bill Allombert
  # Please add more from your archive!
  ]

REPORT_SIZES = [
    { 'days':  5, 'size': 10240 },
    { 'days': 10, 'size':  1024 },
    { 'days': 30, 'size':   100 },
    { 'days': 60, 'size':    60 },
    { 'days': 90, 'size':    30 }
  ]
USER_EXCLUSION_LIST = ['lost+found']
MAIL_FROM = 'debian-admin (via Cron) <bulk@admin.debian.org>'
MAIL_TO = '{username}@{hostname}.debian.org'
MAIL_CC = 'debian-admin (bulk sink) <bulk@admin.debian.org>'
MAIL_REPLYTO = 'debian-admin <dsa@debian.org>'
MAIL_SUBJECT = 'Please clean up ~{username} on {hostname}.debian.org'
MAIL_TEXT = u"""\
Hi {name}!

{explanation}

For your information, you last logged into {hostname} {days_ago} days ago, and
your home directory there is {homedir_size} MB in size.

If you currently do not use {hostname}, please keep ~{username} under 30 MB,
if possible.  Please assist us in freeing up space by deleting schroots, also.

Thanks,

Debian System Administration Team via Cron

PS: replies not required.
"""

class Error(Exception):
  pass

class SendmailError(Error):
  pass

class LastLog(object):
  LASTLOG_STRUCT = '=L32s256s'

  def __init__(self, fname='/var/log/lastlog'):
    record_size = struct.calcsize(self.LASTLOG_STRUCT)
    self.records = {}
    with open(fname, 'r') as fp:
      uid = -1
      for record in iter(lambda: fp.read(record_size), ''):
        uid += 1
        last_login, _, _ = list(struct.unpack(self.LASTLOG_STRUCT, record))
        if last_login == 0:
          continue
        try:
          self.records[pwd.getpwuid(uid).pw_name] = last_login
        except KeyError:
          continue

  def last_login_for_user(self, username):
    return self.records.get(username, 0)

class HomedirReminder(object):
  def __init__(self):
    self.lastlog = LastLog()
    self.generate_homedir_list()

  def parse_utmp(self):
    self.utmp_records = defaultdict(list)
    for wtmpfile in glob.glob('/var/log/wtmp*'):
      for entry in utmp.UtmpRecord(wtmpfile):
        # TODO: Login, does not account for non-idle sessions.
        self.utmp_records[entry.ut_user].append(entry.ut_tv[0])
    for username, timestamps in self.utmp_records.iteritems():
      self.utmp_records[username] = sorted(timestamps)[-1]

  def last_login_for_user(self, username):
    return self.lastlog.last_login_for_user(username)

  def generate_homedir_list(self):
    self.homedir_sizes = {}
    for direntry in glob.glob('/home/*'):
      username = os.path.basename(direntry)
      try:
        pwinfo = pwd.getpwnam(username)
      except KeyError:
        if os.path.isdir(direntry):
          logging.warning('Directory %s exists on %s but there is no %s user', direntry, platform.node(), username)
        continue
      homedir = pwinfo.pw_dir

      if username in USER_EXCLUSION_LIST:
        continue
      # Ignore errors from du.
      command = ['/usr/bin/du', '-ms', homedir]
      p = subprocess.Popen(command,
                           stdout=subprocess.PIPE,
                           stderr=subprocess.PIPE)
      (stdout, stderr) = p.communicate()
      if p.returncode != 0:
        logging.info('%s failed:', ' '.join(command))
        logging.info(stderr)
      try:
        size = int(stdout.split('\t')[0])
      except ValueError:
        logging.error('Could not convert size output from %s: %s',
                      ' '.join(command), stdout)
        continue
      self.homedir_sizes[username] = size

  def send_mail(self, **kwargs):
    msg = email.mime.text.MIMEText(MAIL_TEXT.format(**kwargs), _charset='UTF-8')
    msg['From'] = MAIL_FROM.format(**kwargs)
    msg['To'] = MAIL_TO.format(**kwargs)
    if MAIL_CC != "": msg['Cc'] = MAIL_CC.format(**kwargs)
    if MAIL_REPLYTO != "": msg['Reply-To'] = MAIL_REPLYTO.format(**kwargs)
    msg['Subject'] = MAIL_SUBJECT.format(**kwargs)
    msg['Precedence'] = "bulk"
    msg['Auto-Submitted'] = "auto-generated by mail-big-homedirs"
    p = subprocess.Popen(SENDMAIL, stdin=subprocess.PIPE)
    p.communicate(msg.as_string())
    logging.debug(msg.as_string())
    if p.returncode != 0:
      raise SendmailError

  def run(self):
    current_time = time.time()
    for username, homedir_size in self.homedir_sizes.iteritems():
      last_login = self.last_login_for_user(username)
      logging.info('user %s: size %dMB, last login: %d', username, homedir_size, last_login)
      days_ago = int( (current_time - last_login) / 3600 / 24 )

      reportsize = None
      for e in REPORT_SIZES:
        if days_ago >= e['days']: reportsize = e['size']

      if reportsize is not None and homedir_size > reportsize:
        logging.warning('Homedir of user %s is %d and did not login for a while', username, homedir_size)
        try:
          name = pwd.getpwnam(username).pw_gecos.decode('utf-8')
          name = name.split(',', 1)[0]
          name = name.split(' ', 1)[0]
        except:
          name = username
        explanation = EXPLANATIONS[random.randint(0,len(EXPLANATIONS)-1)]
        explanation = explanation.format(hostname=platform.node())
        self.send_mail(hostname=platform.node(),
                       username=username,
                       name=name,
                       explanation=explanation,
                       homedir_size=homedir_size,
                       days_ago=days_ago)

if __name__ == '__main__':
  logging.basicConfig()
  # DEBUG for debugging, ERROR for production.
  logging.getLogger().setLevel(logging.ERROR)
  HomedirReminder().run()