docker

#!/usr/bin/env python
from __future__ import print_function
from contextlib import closing
import json
import os
import socket
import subprocess
import sys

try:
    from urllib2 import urlopen, URLError
except:
    from urllib.request import urlopen
    from urllib.error import URLError

try:
    from ConfigParser import ConfigParser
except:
    from configparser import ConfigParser


def load_config(filepath):
    cfg = ConfigParser()
    with open(CONF_PATH) as conf:
        cfg.readfp(conf)
        return [(s[0].strip(), s[1].strip()) for s in cfg.items('dockers')]


CONF_PATH = os.path.join(
    os.environ['HOME'],
    '.dewya'
)
DOCKERS = load_config(CONF_PATH)
FORWARD_PORT = 4243


def getch():
    """Get single character from user.
    http://code.activestate.com/recipes/134892/
    """

    import sys
    import tty
    import termios
    fd = sys.stdin.fileno()
    old_settings = termios.tcgetattr(fd)
    try:
        tty.setraw(sys.stdin.fileno())
        ch = sys.stdin.read(1)
    finally:
        termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)
    return ch


def forward_port(docker_uri):
    """Forward local port to remote unix domain socket."""

    host, port = docker_uri[6:], FORWARD_PORT

    # execute unix=>tcp port forwarding on server
    socat_cmd = 'ssh -f {} "socat {} {}" &>/dev/null'.format(
        host,
        'TCP4-LISTEN\:{},fork,reuseaddr'.format(port),
        'UNIX-CONNECT\:/var/run/docker.sock',
    )
    subprocess.call(socat_cmd, shell=True)

    # kill previous instance (fight with dangling connections)
    kill_cmd = "kill `pgrep -f 'ssh -fN -L{port}.*{host}'` &>/dev/null".format(
        port=port,
        host=host
    ),
    subprocess.call(kill_cmd, shell=True)

    # execute port forwarding in background
    forward_cmd = 'ssh -fN -L4243:127.0.0.1:{port} {host} &>/dev/null'.format(
        port=port,
        host=host
    ),
    subprocess.call(forward_cmd, shell=True)

    return 'tcp://localhost:{}'.format(port)


def main():
    if not sys.stdout.isatty() or not sys.stdin.isatty():
        print('dewya cannot be used in pipes', file=sys.stderr)
        return -3

    # if connection already configured in environment
    if 'DOCKER_HOST' in os.environ:
        docker_uri = os.environ['DOCKER_HOST']
        os.environ['DOCKER_PS1'] = docker_uri
    else:
        for num, (name, addr) in enumerate(DOCKERS):
            print('{}. {} ({})'.format(num, name, addr))

        # read the id of awaited docker from user
        num = None
        while True:
            num = ord(getch())
            if num in [3, 4]:
                return -1
            elif num > 47 and num < (48 + len(DOCKERS)):
                num -= 48
                break

            print(
                'Please press {}'.format(
                    ','.join(map(str, xrange(len(DOCKERS))))
                )
            )

        docker_uri = DOCKERS[num][1]
        os.environ['DOCKER_PS1'] = DOCKERS[num][0]

    # forward port for "remote" docker
    if docker_uri.startswith('ssh:'):
        docker_uri = forward_port(docker_uri)

    # check docker availability and fetch version
    url = 'http://{}/version'.format(docker_uri[6:])
    version = None
    try:
        with closing(urlopen(url, timeout=5)) as r:
            version = json.loads(r.read().decode('utf-8'))['Version']
    except (socket.timeout, URLError):
        print('docker connection failed', file=sys.stderr)
        return -2

    # set path to real docker bin
    client_path = '/usr/local/Cellar/docker/{}/bin'.format(version)
    os.environ['PATH'] = '{}:{}'.format(client_path, os.environ['PATH'])

    # configure env for docker client
    os.environ['DOCKER_HOST'] = docker_uri

    # ... and some nifty addon for shell prompt
    ps1_docker = '\[\e[1;34m\]$DOCKER_PS1\[\e[00m\]|'
    os.environ['PS1'] = ps1_docker + os.environ['PS1']

    # re-create requested command and run it
    docker_bin = '{}/docker'.format(client_path)
    args = [docker_bin]
    args.extend(sys.argv[1:])
    subprocess.call(args)

    # ... and start subshell
    shell = os.environ['SHELL']
    os.execl(shell, shell)


if __name__ == '__main__':
    if not len(DOCKERS):
        print('Please create config file ~/.dewya', file=sys.stderr)
    sys.exit(main())