# (c) 2012, Michael DeHaan <michael.dehaan@gmail.com>
#
# This file is part of Ansible
#
# Ansible is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Ansible is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.

import warnings
import os
import pipes
import socket
import random
import logging
from ansible.callbacks import vvv
from ansible import errors
from ansible import utils

# prevent paramiko warning noise -- see http://stackoverflow.com/questions/3920502/
HAVE_PARAMIKO=False
with warnings.catch_warnings():
    warnings.simplefilter("ignore")
    try:
        import paramiko
        HAVE_PARAMIKO=True
        logging.getLogger("paramiko").setLevel(logging.WARNING)
    except ImportError:
        pass

# keep connection objects on a per host basis to avoid repeated attempts to reconnect

SSH_CONNECTION_CACHE = {}
SFTP_CONNECTION_CACHE = {}


class Connection(object):
    ''' SSH based connections with Paramiko '''

    def __init__(self, runner, host, port, user, password, private_key_file, *args, **kwargs):

        self.ssh = None
        self.sftp = None
        self.runner = runner
        self.host = host
        self.port = port
        self.user = user
        self.password = password
        self.private_key_file = private_key_file

    def _cache_key(self):
        return "%s__%s__" % (self.host, self.user)

    def connect(self):
        cache_key = self._cache_key()
        if cache_key in SSH_CONNECTION_CACHE:
            self.ssh = SSH_CONNECTION_CACHE[cache_key]
        else:
            self.ssh = SSH_CONNECTION_CACHE[cache_key] = self._connect_uncached()
        return self

    def _connect_uncached(self):
        ''' activates the connection object '''

        if not HAVE_PARAMIKO:
            raise errors.AnsibleError("paramiko is not installed")

        vvv("ESTABLISH CONNECTION FOR USER: %s on PORT %s TO %s" % (self.user, self.port, self.host), host=self.host)

        ssh = paramiko.SSHClient()
        ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())

        allow_agent = True
        if self.password is not None:
            allow_agent = False
        try:
            if self.private_key_file:
                key_filename = os.path.expanduser(self.private_key_file)
            elif self.runner.private_key_file:
                key_filename = os.path.expanduser(self.runner.private_key_file)
            else:
                key_filename = None
            ssh.connect(self.host, username=self.user, allow_agent=allow_agent, look_for_keys=True,
                key_filename=key_filename, password=self.password,
                timeout=self.runner.timeout, port=self.port)
        except Exception, e:
            msg = str(e)
            if "PID check failed" in msg:
                raise errors.AnsibleError("paramiko version issue, please upgrade paramiko on the machine running ansible")
            elif "Private key file is encrypted" in msg:
                msg = 'ssh %s@%s:%s : %s\nTo connect as a different user, use -u <username>.' % (
                    self.user, self.host, self.port, msg)
                raise errors.AnsibleConnectionFailed(msg)
            else:
                raise errors.AnsibleConnectionFailed(msg)

        return ssh

    def exec_command(self, cmd, tmp_path, sudo_user, sudoable=False, executable='/bin/sh'):
        ''' run a command on the remote host '''

        bufsize = 4096
        try:
            chan = self.ssh.get_transport().open_session()
        except Exception, e:
            msg = "Failed to open session"
            if len(str(e)) > 0:
                msg += ": %s" % str(e)
            raise errors.AnsibleConnectionFailed(msg)

        if not self.runner.sudo or not sudoable:
            if executable:
                quoted_command = executable + ' -c ' + pipes.quote(cmd)
            else:
                quoted_command = cmd
            vvv("EXEC %s" % quoted_command, host=self.host)
            chan.exec_command(quoted_command)
        else:
            # sudo usually requires a PTY (cf. requiretty option), therefore
            # we give it one, and we try to initialise from the calling
            # environment
            chan.get_pty(term=os.getenv('TERM', 'vt100'),
                         width=int(os.getenv('COLUMNS', 0)),
                         height=int(os.getenv('LINES', 0)))
            shcmd, prompt = utils.make_sudo_cmd(sudo_user, executable, cmd)
            vvv("EXEC %s" % shcmd, host=self.host)
            sudo_output = ''
            try:
                chan.exec_command(shcmd)
                if self.runner.sudo_pass:
                    while not sudo_output.endswith(prompt):
                        chunk = chan.recv(bufsize)
                        if not chunk:
                            if 'unknown user' in sudo_output:
                                raise errors.AnsibleError(
                                    'user %s does not exist' % sudo_user)
                            else:
                                raise errors.AnsibleError('ssh connection ' +
                                    'closed waiting for password prompt')
                        sudo_output += chunk
                    chan.sendall(self.runner.sudo_pass + '\n')
            except socket.timeout:
                raise errors.AnsibleError('ssh timed out waiting for sudo.\n' + sudo_output)

        stdout = ''.join(chan.makefile('rb', bufsize))
        stderr = ''.join(chan.makefile_stderr('rb', bufsize))
        return (chan.recv_exit_status(), '', stdout, stderr)

    def put_file(self, in_path, out_path):
        ''' transfer a file from local to remote '''
        vvv("PUT %s TO %s" % (in_path, out_path), host=self.host)
        if not os.path.exists(in_path):
            raise errors.AnsibleFileNotFound("file or module does not exist: %s" % in_path)
        try:
            self.sftp = self.ssh.open_sftp()
        except Exception, e:
            raise errors.AnsibleError("failed to open a SFTP connection (%s)" % e)
        try:
            self.sftp.put(in_path, out_path)
        except IOError:
            raise errors.AnsibleError("failed to transfer file to %s" % out_path)

    def _connect_sftp(self):
        cache_key = "%s__%s__" % (self.host, self.user)
        if cache_key in SFTP_CONNECTION_CACHE:
            return SFTP_CONNECTION_CACHE[cache_key]
        else:
            result = SFTP_CONNECTION_CACHE[cache_key] = self.connect().ssh.open_sftp()
            return result

    def fetch_file(self, in_path, out_path):
        ''' save a remote file to the specified path '''
        vvv("FETCH %s TO %s" % (in_path, out_path), host=self.host)
        try:
            self.sftp = self._connect_sftp()
        except Exception, e:
            raise errors.AnsibleError("failed to open a SFTP connection (%s)", e)
        try:
            self.sftp.get(in_path, out_path)
        except IOError:
            raise errors.AnsibleError("failed to transfer file from %s" % in_path)

    def close(self):
        ''' terminate the connection '''
        cache_key = self._cache_key()
        SSH_CONNECTION_CACHE.pop(cache_key, None)
        SFTP_CONNECTION_CACHE.pop(cache_key, None)
        if self.sftp is not None:
            self.sftp.close()
        self.ssh.close()
        
