"""
Parses roster entries out of Host directives from SSH config

.. code-block:: bash

    salt-ssh --roster sshconfig '*' -r "echo hi"
"""

import collections
import fnmatch
import logging
import os
import re

import salt.utils.files
import salt.utils.stringutils

log = logging.getLogger(__name__)

_SSHConfRegex = collections.namedtuple("_SSHConfRegex", ["target_field", "pattern"])
_ROSTER_FIELDS = (
    _SSHConfRegex(target_field="user", pattern=r"\s+User (.*)"),
    _SSHConfRegex(target_field="port", pattern=r"\s+Port (.*)"),
    _SSHConfRegex(target_field="priv", pattern=r"\s+IdentityFile (.*)"),
)


def _get_ssh_config_file(opts):
    """
    :return: Path to the .ssh/config file - usually <home>/.ssh/config
    """
    ssh_config_file = opts.get("ssh_config_file")
    if not os.path.isfile(ssh_config_file):
        raise OSError("Cannot find SSH config file")
    if not os.access(ssh_config_file, os.R_OK):
        raise OSError("Cannot access SSH config file: {}".format(ssh_config_file))
    return ssh_config_file


def parse_ssh_config(lines):
    """
    Parses lines from the SSH config to create roster targets.

    :param lines: Individual lines from the ssh config file
    :return: Dictionary of targets in similar style to the flat roster
    """
    # transform the list of individual lines into a list of sublists where each
    # sublist represents a single Host definition
    hosts = []
    for line in lines:
        line = salt.utils.stringutils.to_unicode(line)
        if not line or line.startswith("#"):
            continue
        elif line.startswith("Host "):
            hosts.append([])
        hosts[-1].append(line)

    # construct a dictionary of Host names to mapped roster properties
    targets = collections.OrderedDict()
    for host_data in hosts:
        target = collections.OrderedDict()
        hostnames = host_data[0].split()[1:]
        for line in host_data[1:]:
            for field in _ROSTER_FIELDS:
                match = re.match(field.pattern, line)
                if match:
                    target[field.target_field] = match.group(1)
        for hostname in hostnames:
            targets[hostname] = target

    # apply matching for glob hosts
    wildcard_targets = []
    non_wildcard_targets = []
    for target in targets.keys():
        if "*" in target or "?" in target:
            wildcard_targets.append(target)
        else:
            non_wildcard_targets.append(target)
    for pattern in wildcard_targets:
        for candidate in non_wildcard_targets:
            if fnmatch.fnmatch(candidate, pattern):
                targets[candidate].update(targets[pattern])
        del targets[pattern]

    # finally, update the 'host' to refer to its declaration in the SSH config
    # so that its connection parameters can be utilized
    for target in targets:
        targets[target]["host"] = target
    return targets


def targets(tgt, tgt_type="glob", **kwargs):
    """
    Return the targets from the flat yaml file, checks opts for location but
    defaults to /etc/salt/roster
    """
    ssh_config_file = _get_ssh_config_file(__opts__)
    with salt.utils.files.fopen(ssh_config_file, "r") as fp:
        all_minions = parse_ssh_config([line.rstrip() for line in fp])
    rmatcher = RosterMatcher(all_minions, tgt, tgt_type)
    matched = rmatcher.targets()
    return matched


class RosterMatcher:
    """
    Matcher for the roster data structure
    """

    def __init__(self, raw, tgt, tgt_type):
        self.tgt = tgt
        self.tgt_type = tgt_type
        self.raw = raw

    def targets(self):
        """
        Execute the correct tgt_type routine and return
        """
        try:
            return getattr(self, "ret_{}_minions".format(self.tgt_type))()
        except AttributeError:
            return {}

    def ret_glob_minions(self):
        """
        Return minions that match via glob
        """
        minions = {}
        for minion in self.raw:
            if fnmatch.fnmatch(minion, self.tgt):
                data = self.get_data(minion)
                if data:
                    minions[minion] = data
        return minions

    def get_data(self, minion):
        """
        Return the configured ip
        """
        if isinstance(self.raw[minion], str):
            return {"host": self.raw[minion]}
        if isinstance(self.raw[minion], dict):
            return self.raw[minion]
        return False
