"""
Module containing the classes that are used for remote listing

:author: Daniel Abercrombie <dabercro@mit.edu> \n
         Max Goncharov <maxi@mit.edu>
"""

import logging
import re
import time
import subprocess
from datetime import datetime

import XRootD.client    # pylint: disable=import-error

from . import redirectors
from .. import config


LOG = logging.getLogger(__name__)


class Lister(object):
    """
    The protoype of the listing facility

    :param int thread_num: This optional parameter is only used to
                           Create a separate logger for this object
    :param str site: Used for reading the correct configuration
    """

    def __init__(self, thread_num, site):
        config_dict = config.config_dict()
        self.log = logging.getLogger(__name__ if thread_num is None else \
                                         '%s--thread%i' % (__name__, thread_num))
        self.ignore_list = config_dict.get('IgnoreDirectories', [])
        self.path_prefix = config_dict.get('PathPrefix', {}).get(site, '')
        self.tries = config_dict.get('Retries', 0) + 1

        self.fallback_tries = 5


    def ls_directory(self, path):
        """
        Prototype function that lists the directories

        :param str path: The full path, of the directory to list.
        """
        pass


    def reconnect(self):
        """
        A prototype for reconnecting to the remote servers
        """
        pass


    def list(self, path, retries=0):
        """
        Return the directory contents at the given path.
        The ``list`` member is expected of every object passed to :py:mod:`datatypes`.

        :param str path: The full LFN, of the directory to list.
        :param int retries: Number of attempts so far
        :returns: A bool indicating the success, a list of directories, and a list of files.
                  The list of directories consists of tuples of (directory name, mod time).
                  The list of files consistents of tuples of (file name, size, mod time).
                  The modification times are in seconds from epoch and the file size is in bytes.
        :rtype: bool, list, list
        """
        # Skip over paths that include part of the list of ignored directories
        for pattern in self.ignore_list:
            if pattern in path:
                self.log.warning('Ignoring %s because of ignored pattern %s', path, pattern)
                return False, [], []

        if retries >= self.tries:
            self.log.error('Giving up on %s due to too many retries', path)
            return False, [], []

        if retries:
            self.reconnect()

        # FileSystem only works with ending slashes for some sites (not all, but let's be safe)
        path = self.path_prefix + path + ('/' if path[-1] != '/' else '')

        okay, directories, files = self.ls_directory(path)

        if not okay and self.fallback_tries and \
                not self.path_prefix and len(path.strip('/').split('/')) < 4:

            self.fallback_tries -= 1

            # Try to fall back on /cms
            self.path_prefix = '/cms'
            self.log.warning('Trying to fall back to using suffix %s', self.path_prefix)
            okay, directories, files = self.list(path, self.tries - 1)

            if not okay:
                self.log.warning('Fallback did not work, reverting')
                self.path_prefix = ''

        if not okay:
            okay, directories, files = self.list(path, retries + 1)

        return okay, directories, files


def ct_timestamp(line):
    """
    Takes a time string from gfal and extracts the time since epoch

    :param str line: The line from the gfal-ls call including month, day, and year
                     in some format with lots of hypens
    :returns: Timestamp's time since epoch
    :rtype: int
    """

    fields = line.split('-')
    if ':' in fields[-1]:
        fields[-1] = datetime.now().year
    month = time.strptime(fields[0], '%b').tm_mon
    datestr = str(month) + '-' + str(fields[1]) + '-' + str(fields[2])

    epoch = int(time.mktime(time.strptime(datestr, '%m-%d-%Y')))
    return epoch


class GFalLister(Lister):
    """
    An object to list a site through ``gfal-ls`` calls
    """

    def __init__(self, site, backend, thread_num=None):
        super(GFalLister, self).__init__(thread_num, site)
        self.backend = backend


    def ls_directory(self, path):
        """
        Gets the contents of a path

        :param str path: The full LFN, of the directory to list.
        :returns: A bool indicating the success, a list of directories, and a list of files.
        :rtype: bool, list, list
        """

        directories = []
        files = []

        full_path = self.backend + '/' + str(path)

        cmd = 'gfal-ls -l ' + full_path
        process = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE,
                                   bufsize=4096, shell=True)
        strout, error = process.communicate()
        if process.returncode != 0:
            self.log.error(error)
            return False, directories, files

        for line in strout.split('\n'):
            fields = line.strip().split()
            if len(fields) < 1:
                continue
            item_name = fields[-1]
            item_size = int(fields[4])
            tstamp = ct_timestamp(fields[5] + '-' + fields[6] + '-' + fields[7])

            if fields[0].startswith('d'):
                directories.append((item_name, tstamp))
            else:
                files.append((item_name, item_size, tstamp))

        return True, directories, files


class XRootDSubShell(Lister):
    """
    Very similar to the :py:class:`XRootDLister`,
    but uses a subshell through `pexpect`.
    """
    def __init__(self, site, door, thread_num=None):
        super(XRootDSubShell, self).__init__(thread_num, site)

        self.shell = subprocess.Popen(['xrdfs', door],
                                      stdin=subprocess.PIPE,
                                      stdout=subprocess.PIPE,
                                      stderr=subprocess.STDOUT)
        self.uri = door


    def __del__(self):
        self.shell.communicate('quit')


    def ls_directory(self, path):

        self.log.debug('Directly listing %s with %s', path, self.uri)

        self.shell.stdin.write('ls -l %s\n' % path)
        self.shell.stdin.write('\n') # send one extra [ENTER] to make an empty prompt appear
        self.shell.stdin.flush()
        self.shell.stdout.readline().strip() # Read out the original prompt line

        directories = []
        files = []
        okay = True

        while True:
            line = self.shell.stdout.readline().strip()

            self.log.debug(line)

            if line.endswith('>'): # stop reading at the empty prompt (otherwise readline hangs)
                break

            # Parse the line
            # First check that it matches the expected format
            match = re.match( # (d)rwx (YYYY-MM-DD HH:MM:SS)     (size) (name)
                r'(d|\-).{3}\s(\d{4}\-\d{2}\-\d{2}\s\d{2}:\d{2}:\d{2})\s*(\d*)\s([^\s]*)',
                line)

            if match:
                # Get the timestamp
                mtime = time.mktime(time.strptime(match.group(2), '%Y-%m-%d %H:%M:%S'))
                # Get the relative name
                name = match.group(4).split('/')[-1]
                if match.group(1) == 'd':  # Directory
                    directories.append((name, mtime))
                else:                    # File
                    files.append((name, int(match.group(3)), mtime))
            elif re.match(r'.*\[\d+\].*', line):
                # Otherwise, we probably have an error on our hands
                okay = False
                self.log.error(line)

        return okay, directories, files



class XRootDLister(Lister):
    """
    A class that holds two XRootD connections.
    If the primary connection fails to list a directory,
    then a fallback connection is used.
    This keeps the load of listing from hitting more than half
    of a site's doors at a time.

    :param str site: The site that this connection is to.
    :param str door: The URL of the door that will get the most load
    :param int thread_num: This optional parameter is only used to
                           Create a separate logger for this object
    """
    def __init__(self, site, door, thread_num=None):
        super(XRootDLister, self).__init__(thread_num, site)

        self.conn = XRootD.client.FileSystem(door)

        self.log.info('Connection created at %s', door)


    def ls_directory(self, path):
        """
        Gets the contents of the previously defined redirector at a given path

        :param str path: The full LFN, of the directory to list.
        :returns: A bool indicating the success, a list of directories, and a list of files.
        :rtype: bool, list, list
        """

        self.log.debug('Using door at %s to list directory %s', self.conn.url, path)

        # http://xrootd.org/doc/python/xrootd-python-0.1.0/modules/client/filesystem.html#XRootD.client.FileSystem.dirlist
        status, dir_list = self.conn.dirlist(path, flags=XRootD.client.flags.DirListFlags.STAT)

        directories = []
        files = []

        self.log.debug('For %s, directory listing good: %s', path, bool(dir_list))

        # If there's a directory listing, parse it
        if dir_list:
            for entry in dir_list.dirlist:
                if entry.statinfo.flags & XRootD.client.flags.StatInfoFlags.IS_DIR:
                    directories.append((entry.name.lstrip('/'), entry.statinfo.modtime))
                else:
                    files.append((entry.name.lstrip('/'), entry.statinfo.size,
                                  entry.statinfo.modtime))

        okay = bool(status.ok)

        # If status isn't perfect, analyze the error
        if not okay:

            self.log.warning('While listing %s: %s', path, status.message)
            self.log.debug('Directory List: %s', dir_list)
            self.log.debug('Okay: %i', okay)

        self.log.debug('From %s returning status %i with %i directories and %i files.',
                       path, okay, len(directories), len(files))

        return okay, directories, files


class NoPath(Exception):
    """
    An exception for when there is no known path to the remote site
    """
    pass


# This starts off bad, but the prod.py modules will
# fix this to point to the imported siteinfo.get_gfal_location
GFAL_LOCATION = lambda _: ''


def get_listers(site):
    """
    Picks out a suitable lister for a site based on the configuration file.
    Returns the type of Lister and arguments for its construction

    :param str site:
    :returns: Lister constructor and arguments for construction
              that can be passed directly to
              :py:function:`dynamo_consistency.datatypes.create_dirinfo`
    :rtype: Lister, list of tuples
    :raises NoPath: When a way to list the remote site cannot be determined
    """

    config_dict = config.config_dict()
    access = config_dict.get('AccessMethod', {})
    if access.get(site) == 'SRM':
        num_threads = int(config_dict.get('GFALThreads'))
        LOG.info('threads = %i', num_threads)

        backend = GFAL_LOCATION(site)

        if not backend:
            raise NoPath('No path for gfal command for %s' % site)

        params = [(site, backend, x) for x in xrange(num_threads)]
        return GFalLister, params


    # Get the redirector for a site
    # The redirector can be used for a double check (not implemented yet...)
    # The redir_list is used for the original listing
    num_threads = int(config_dict.get('NumThreads'))

    balancer, door_list = redirectors.get_redirector(site)
    LOG.debug('Full redirector list: %s', door_list)

    if site in config_dict.get('UseLoadBalancer', []) or \
            (balancer and not door_list):
        num_threads = 1
        door_list = [balancer]

    if not door_list:
        raise NoPath('No doors found for %s' % site)

    while num_threads > len(door_list):
        if len(door_list) % 2:
            door_list.extend(door_list)
        else:
            # If even number of redirectors and not using both, stagger them
            door_list.extend(door_list[1:])
            door_list.append(door_list[0])

    # Strip off the extra threads
    door_list = door_list[:num_threads]

    # Create DirectoryInfo for each directory to search (set in configuration file)
    # The search is done with XRootDLister objects that have two doors and the thread
    # number as initialization arguments.


    constructor = XRootDSubShell if access.get(site) == 'directx' else XRootDLister
    params = [(site, door, thread_num) for thread_num, door in enumerate(door_list)]

    return constructor, params
