# The MIT License
#
# Copyright 2012 Sony Mobile Communications. All rights reserved.
#
# 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.

""" Gerrit SSH Client. """

from os.path import abspath, expanduser, isfile
import re
import socket

from .error import GerritError

from paramiko import SSHClient, SSHConfig
from paramiko.ssh_exception import SSHException


def _extract_version(version_string, pattern):
    """ Extract the version from `version_string` using `pattern`.

    Return the version as a string, with leading/trailing whitespace
    stripped.

    """
    if version_string:
        match = pattern.match(version_string.strip())
        if match:
            return match.group(1)
    return ""


class GerritSSHCommandResult(object):

    """ Represents the results of a Gerrit command run over SSH. """

    def __init__(self, command, stdin, stdout, stderr):
        self.command = command
        self.stdin = stdin
        self.stdout = stdout
        self.stderr = stderr

    def __repr__(self):
        return "<GerritSSHCommandResult [%s]>" % self.command


class GerritSSHClient(SSHClient):

    """ Gerrit SSH Client, wrapping the paramiko SSH Client. """

    def __init__(self, hostname):
        """ Initialise and connect to SSH. """
        super(GerritSSHClient, self).__init__()
        self.remote_version = None
        self.hostname = hostname
        self.connected = False

    def _connect(self):
        """ Connect to the remote if not already connected. """
        if self.connected:
            return
        self.load_system_host_keys()
        configfile = expanduser("~/.ssh/config")
        if not isfile(configfile):
            raise GerritError("ssh config file '%s' does not exist" %
                              configfile)

        config = SSHConfig()
        config.parse(open(configfile))
        data = config.lookup(self.hostname)
        if not data:
            raise GerritError("No ssh config for host %s" % self.hostname)
        if not 'hostname' in data or not 'port' in data or not 'user' in data:
            raise GerritError("Missing configuration data in %s" % configfile)
        key_filename = None
        if 'identityfile' in data:
            key_filename = abspath(expanduser(data['identityfile']))
            if not isfile(key_filename):
                raise GerritError("Identity file '%s' does not exist" %
                                  key_filename)
        try:
            port = int(data['port'])
        except ValueError:
            raise GerritError("Invalid port: %s" % data['port'])
        try:
            self.connect(hostname=data['hostname'],
                         port=port,
                         username=data['user'],
                         key_filename=key_filename)
            self.connected = True
        except socket.error as e:
            raise GerritError("Failed to connect to server: %s" % e)

        try:
            version_string = self._transport.remote_version
            pattern = re.compile(r'^.*GerritCodeReview_([a-z0-9-\.]*) .*$')
            self.remote_version = _extract_version(version_string, pattern)
        except AttributeError:
            self.remote_version = None

    def exec_command(self, command, bufsize=1, timeout=None, get_pty=False):
        """ Execute the command.

        Make sure we're connected and then execute the command.

        Return a tuple of stdin, stdout, stderr.

        """
        self._connect()
        return super(GerritSSHClient, self).\
            exec_command(command, bufsize, timeout, get_pty)

    def get_remote_version(self):
        """ Return the version of the remote Gerrit server. """
        if self.remote_version is None:
            result = self.run_gerrit_command("version")
            version_string = result.stdout.read()
            pattern = re.compile(r'^gerrit version (.*)$')
            self.remote_version = _extract_version(version_string, pattern)
        return self.remote_version

    def run_gerrit_command(self, command):
        """ Run the given command.

        Run `command` and return a `GerritSSHCommandResult`.

        Raise `ValueError` if `command` is not a string.

        """
        if not isinstance(command, basestring):
            raise ValueError("command must be a string")
        gerrit_command = "gerrit " + command

        try:
            stdin, stdout, stderr = self.exec_command(gerrit_command)
        except SSHException as err:
            raise GerritError("Command execution error: %s" % err)
        return GerritSSHCommandResult(command, stdin, stdout, stderr)