#!/usr/bin/python3
# Style Guide: https://www.python.org/dev/peps/pep-0008/

import argparse
import configparser
import libvirt
from pathlib import Path
import subprocess
import sys
import time

import fcntoolbox.bscp as bscp

log_function = lambda x : print(x)
log_file = sys.stdout

parser = argparse.ArgumentParser()
parser.add_argument("selection", type=str, choices=["is-active", "is-volume-open", "vol-backup", "vol-serve"])
parser.add_argument("--dom", "-d", type=str)
parser.add_argument("--vol", type=str)

args = parser.parse_args()

config = configparser.RawConfigParser()
config.read("/etc/fcntoolbox/config.ini")
confvirt = config['virt']

def is_active(dom_name):
  conn = libvirt.openReadOnly(None)
  if conn == None:
    print('Failed to open connection to the hypervisor')
    sys.exit(1)

  dom = conn.lookupByName(dom_name)
  return dom.isActive()

def is_volume_open(volpath):
  if not Path(volpath).exists():
    raise FileNotFoundError("Cannot find volume '{}'".format(volpath))
  lvd_out = subprocess.check_output(['lvdisplay', volpath]).decode()
  #   split lines v           v remove header
  lvinfo = lvd_out.split("\n")[1:]
  lvinfo = [line.strip() for line in lvinfo]
  # Find line starting with "# open"
  lvopen = list(filter(lambda line : line.find("# open") == 0, lvinfo))
  # Read after "# open"
  lvopen = lvopen[0][len("# open"):].strip()
  return lvopen != "0"

def create_backup_snapshot(vol_str):
  snap_path = Path("{}_snap_{}".format(vol_str, time.strftime("%Y-%m-%d")))
  snapshot_size = '10G'
  subprocess.call(['lvcreate', '--snapshot', '--size', snapshot_size, '--name', snap_path.name, vol_str], stdout = subprocess.DEVNULL, stderr = log_file)
  return snap_path

def backup(dom_name, vol_str):
  vol_path = Path(vol_str)
  if not vol_path.exists():
    raise FileNotFoundError("Cannot find volume '{}'".format(vol_str))
  
  conn = libvirt.open(None)
  if conn == None:
    print('Failed to open connection to the hypervisor')
    sys.exit(1)
  
  dom = conn.lookupByName(dom_name)
  is_active = dom.isActive()
  if is_active:
    #try:
    #  dom.fSTrim(None, 4096)
    #except libvirt.libvirtError as e:
    #  print(e)
    dom.suspend()
  
  snap_path = create_backup_snapshot(vol_str)
  
  if is_active:
    dom.resume()
  
  remote_vol_str = '/dev/{}/{}'.format(confvirt['remote_vg'], vol_path.name)
  bscp.remote_command = confvirt['remote_command']
  bscp.bscp(str(snap_path), confvirt['remote_host'], remote_vol_str, 64 * 1024, 'sha1')

def bscp_device_function(filename):
  allowed_volumes = set(confvirt['allowed_volumes'].split(','))
  if not filename in allowed_volumes:
    return None
  filename = str(create_backup_snapshot(filename))
  if is_volume_open(filename):
    return None
  else:
    return filename

if args.selection == 'is-active':
  if args.dom is None:
    parser.error("is-active requires --domain.")
  if is_active(args.dom):
    sys.exit(0)
  else:
    sys.exit(1)
elif args.selection == 'is-volume-open':
  if args.vol is None:
    parser.error("is-volume-open requires --vol.")
  if is_volume_open(args.vol):
    sys.exit(0)
  else:
    sys.exit(1)
elif args.selection == 'vol-backup':
  if args.dom is None or args.vol is None:
    parser.error("vol-backup requires --domain and --vol.")
  backup(args.dom, args.vol)
elif args.selection == 'vol-serve':
  log_function = lambda x : None
  log_file = subprocess.DEVNULL
  bscp.device_function =  bscp_device_function
  bscp.serve()