#!/usr/bin/env python3
import configparser
import fcntl
import json
import glob
import logging
import os
import socket
import ssl
import struct
import subprocess
import sys
import time
import xml.etree.ElementTree as ET
from urllib.request import Request, urlopen
from urllib.error import HTTPError, URLError


MCS_SYSCONF_DIR = '@ENGINE_SYSCONFDIR@'
MCS_ETC_PATH  = os.path.join(MCS_SYSCONF_DIR, 'columnstore')
CMAPI_CONFIG_PATH = os.path.join(MCS_ETC_PATH, 'cmapi_server.conf')
MCS_CONFIG_PATH = os.path.join(MCS_ETC_PATH, 'Columnstore.xml')
SM_CONFIG_PATH = os.path.join(MCS_ETC_PATH, 'storagemanager.cnf')
MCS_BIN_DIR = '@ENGINE_BINDIR@'
SAVEBRM = os.path.join(MCS_BIN_DIR, 'save_brm')
EM_FILE_SUFFIX = '_em'
EM_FILE_SIZE_THRESHOLD = 1000
HALF_A_MINUTE = 30
NUMBER_OF_FILES_TO_KEEP = 40
DEFAULT_EM_LOCAL_PATH_PREFIX = ''
LOCALHOST = '127.0.0.1'
# according to https://www.ibm.com/docs/en/storage-sentinel/1.1.2?topic=installation-map-your-local-host-loopback-address
LOCALHOSTS = (
    '127.0.0.1',
    'localhost', 'localhost.localdomain',
    'localhost4', 'localhost4.localdomain4',
    '::1',
    'localhost6', 'localhost6.localdomain6',
)
API_VERSION = '0.4.0'
API_PORT = '8640'
BRM_BACKUP_PATH = '/tmp/columnstore_tmp_files/rdwrscratch/'
BRM_BACKUP_PATH_PART = '{}_BRM_saves'


def get_api_key():
    """Get API key from cmapi config file.

    :return: return api key
    :rtype: str
    """
    cmapi_config = configparser.ConfigParser()
    cmapi_config.read(CMAPI_CONFIG_PATH)
    # dequote?
    return cmapi_config.get('Authentication', 'x-api-key', fallback='')


def get_unverified_context():
    ctx = ssl.create_default_context()
    ctx.check_hostname = False
    ctx.verify_mode = ssl.CERT_NONE
    return ctx


def cmapi_available():
    """Check if CMAPI server is running.

    :return: is CMAPI running or not
    :rtype: bool
    """
    logging.error('Detecting CMAPI is up and running.')
    url = 'https://{}:{}/notfound'.format(LOCALHOST, API_PORT)
    request = Request(method='POST', url=url)
    ctx = get_unverified_context()
    try:
        with urlopen(request, context=ctx, timeout=HALF_A_MINUTE) as req:
            _ = req.read().decode('utf-8')
    except HTTPError as exc:
        if exc.code == 404:
            return True
    except URLError:
        logging.info('CMAPI seems to be unavailable.')
    except Exception:
        logging.error(
            'Undefined error while trying to check CMAPI availabale.',
            exc_info=True
        )
    return False


def get_ip_address_by_nic(ifname):
    """Get ip address for nic.

    :param ifname: network intarface name
    :type ifname: str
    :return: ip address
    :rtype: str
    """
    # doesn't work on windows,
    # OpenBSD and probably doesn't on FreeBSD/pfSense either
    ip_addr = ''
    try:
        s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
        ip_addr = socket.inet_ntoa(
            fcntl.ioctl(
                s.fileno(),
                0x8915,  # SIOCGIFADDR "socket ioctl get interface address"
                struct.pack('256s', bytes(ifname[:15], 'utf-8'))
            )[20:24]
        )
    except Exception as exc:
        logging.error(
            'Exception while getting IP address of an "{}" interface'.format(
                ifname
            ),
            exc_info=True
        )
    finally:
        s.close()
    return ip_addr


def is_primary_fallback(current_hostname):
    """Detect is node primary or not without cmapi.

    :param current_hostname: hostname or FQDN
    :type current_hostname: str
    :return: is node primary
    :rtype: bool
    """
    logging.error(
        'Current DBRM_Controller/IPAddr is {}'.format(current_hostname)
    )
    hostnames = set()
    for _, nic_name in socket.if_nameindex():
        ip_addr = get_ip_address_by_nic(nic_name)
        try:
            hostnames_3tuple = socket.gethostbyaddr(ip_addr)
            hostnames.update([hostnames_3tuple[0], *hostnames_3tuple[1]])
        except:
            pass
    logging.error('Found hostnames {}.'.format(hostnames))
    return current_hostname in LOCALHOSTS or current_hostname in hostnames


def is_node_primary(conf_root):
    """Detect is current node primary or not.

    :param conf_root: xml config root element
    :type conf_root: xml.etree.ElementTree.ElementTree
    :return: primary or not
    :rtype: bool
    """
    if cmapi_available():
        url = 'https://{}:{}/cmapi/{}/node/primary'.format(
            LOCALHOST, API_PORT, API_VERSION
        )
        ctx = get_unverified_context()
        # Actually for this endpoint no need to provide api key cause it's
        # not required
        request = Request(
            method='GET', url=url, headers={'x-api-key': get_api_key()}
        )

        success = False
        try:
            with urlopen(request, context=ctx, timeout=HALF_A_MINUTE) as req:
                response = req.read()
            success = True
        except HTTPError as exc:
            logging.warning(
                'Something goes wrong while requesting primary status through api. Got response code "{}" with reason "{}".'.format(
                    exc.code, exc.reason
                )
            )
        except URLError:
            logging.warning(
                'CMAPI became unavailable while trying to request primary status.'
            )
        except Exception:
            logging.error(
                'Undefined exception while trying to request primary status.',
                exc_info=True
            )

        if success:
            dict_response = json.loads(response.decode('utf-8'))
            is_primary = dict_response.get('is_primary', False)
            if is_primary and is_primary in ('True', 'true'):
                is_primary = True
            else:
                is_primary = False
            return is_primary

    logging.info('Trying to detect primary without cmapi running.')
    # text in tag have to be hostname or FQDN
    return is_primary_fallback(conf_root.find('./DBRM_Controller/IPAddr').text)


def get_file_size(file_path):
    """ Returns the size of the file in bytes. """
    try:
        size = os.path.getsize(file_path)
        return size
    except OSError as e:
        logging.error('OSError in get_file_size(): {}.'.format(e))
        return None
    

def em_is_empty(file_path_prefix):
    """Returns True if EM file size is less than EM_FILE_SIZE_THRESHOLD 
        or its argument is None.

    :rtype: Bool
    """
    # Add error message if EM is empty
    if file_path_prefix is None:
        is_em_empty = True
    else:
        filesize = get_file_size(file_path_prefix + EM_FILE_SUFFIX)
        is_em_empty = filesize < EM_FILE_SIZE_THRESHOLD
    if is_em_empty:
        logging.error('EM file is none or its size {} is less than {} bytes.'.format(filesize, EM_FILE_SIZE_THRESHOLD))
    return is_em_empty


def clean_up_backup_brm_files(save_brm_dir_path):
    """ Removes all but 5 last usable sets of BRM files in the specified directory.
        Usable in the context means having non-empty EM.
    """
    filenames = os.listdir(save_brm_dir_path)
    filenames.sort(reverse=True)
    files_to_remove = filenames[NUMBER_OF_FILES_TO_KEEP:]
    for filename in files_to_remove:
        file_path = os.path.join(save_brm_dir_path, filename)
        logging.error('Clean up {}.'.format(file_path))
        try:
            os.remove(file_path)
        except OSError as e:
            logging.error('OSError exception happens removing {}: {}.'.format(file_path, e))


def remove_files_by_prefix_if_exist(file_path_prefix):
    """ Removes files with the given prefix if they exist. """
    if file_path_prefix is None:
        logging.error(
            'file_path_prefix is None. Cannot remove files.',
            exc_info=True
        )
        return
    try:

        files_paths = glob.glob(file_path_prefix + '*')
        for file_path in files_paths:
            os.remove(file_path)
    except OSError as e:
        logging.error(
            'Error removing file: {} - {}'.format(file_path, e.strerror),
            exc_info=True
        )


def get_config_root_from_file(file_path):
    """Returns XML root element from file.

    :param file_path: xml config path
    :return: XML root element or None
    :rtype: Element or None
    """
    try:
        cs_config = ET.parse(file_path)
        return cs_config.getroot()
    except (FileNotFoundError, AttributeError, ValueError):
        logging.error(
            'Exception while loading Columnstore.xml. Continue anyway.',
            exc_info=True
        )
    return None

def get_epoch_prefix():
    """Returns a prefix with epoch time

    :rtype: String
    """
    epoch_time = int(time.time())
    
    return 'backup_{}'.format(epoch_time)


def get_save_brm_dir_path(a_mcs_config_root):
    """Returns a path that SM treats as local

    :param file_path: xml config XML root
    :rtype
    """
    save_brm_dir_path = BRM_BACKUP_PATH
    if a_mcs_config_root is not None:
        try:
            system_temp_file_dir = a_mcs_config_root.find('./SystemConfig/SystemTempFileDir').text
            hdfs_rdwr_scratch = a_mcs_config_root.find('./SystemConfig/hdfsRdwrScratch').text
            # There is a danger to have no '/' in the end of system_temp_file_dir
            # or have two of them there. In both cases save_brm will fail to store
            # files locally.
            save_brm_dir_path = system_temp_file_dir + hdfs_rdwr_scratch
        except AttributeError:
            logging.error('Exception while getting SystemTempFileDir and hdfsRdwrScratch from Columnstore.xml', exc_info=True)
    
    return save_brm_dir_path


def get_save_brm_path_prefix(a_mcs_config_root):
    """Returns a path that SM treats as local

    :param file_path: xml config XML root
    :rtype: String
    """
    epoch_prefix = get_epoch_prefix()
    return get_save_brm_dir_path(a_mcs_config_root) + '/' + BRM_BACKUP_PATH_PART.format(epoch_prefix)


def call_save_brm(path):
    """Calls save_brm first and then tries to call it with local path. 

    :param file_path: xml config XML root
    :rtype: None
    """
    savebrm_cmd = SAVEBRM + ' ' + path
    try:
        subprocess.check_call(savebrm_cmd, shell=True)
    except subprocess.CalledProcessError as exc:
        logging.error('The call to {} exits with {}.'.format(savebrm_cmd, exc.returncode))
        return None
    except OSError:
        logging.error('Os error while calling savebrm', exc_info=True)
        return None
    return path


def call_save_brm_locally(a_mcs_config_root):
    """Calls save_brm first and then tries to call it with local path. 

    :param file_path: xml config XML root
    :rtype: None
    """
    local_path = get_save_brm_path_prefix(a_mcs_config_root)
    return call_save_brm(local_path)


def call_save_brm_with_local_fallback(a_mcs_config_root):
    """Calls save_brm first and then tries to call it with local path. 

    :param file_path: xml config XML root
    :rtype: None
    """
    try:
        subprocess.check_call(SAVEBRM, shell=True)
    except subprocess.CalledProcessError as exc:
        logging.error('The primary call to {} exits with {}.'.format(exc.cmd, exc.returncode))
        backup_path = get_save_brm_path_prefix(a_mcs_config_root)
        logging.error('Back up BRM files locally to {}.'.format(backup_path))
        backup_cmd = SAVEBRM + ' ' + backup_path
        try:
            subprocess.check_call(backup_cmd, shell=True)
        except subprocess.CalledProcessError:
            logging.error('The backup call to {} exits with {}.'.format(exc.cmd, exc.returncode))
        except OSError:
            logging.error('Os error while calling savebrm during the backup', exc_info=True)

        sys.exit(1)
    except OSError:
        logging.error('Os error while calling savebrm', exc_info=True)
        sys.exit(1)


if __name__ == '__main__':
    mcs_config_root = get_config_root_from_file(MCS_CONFIG_PATH)
    # config_root can be None
    if is_node_primary(mcs_config_root):
        em_local_path_prefix = call_save_brm_locally(mcs_config_root)
        if not em_local_path_prefix or em_is_empty(em_local_path_prefix):
            # remove_files_by_prefix_if_exist(em_local_path_prefix)
            logging.error('Exiting with error.')
            sys.exit(1)
        
        clean_up_backup_brm_files(get_save_brm_dir_path(mcs_config_root))

        call_save_brm(DEFAULT_EM_LOCAL_PATH_PREFIX)

    sys.exit(0)