#!/usr/bin/env python3

import sys
import argparse
import docker
import dockerpty
import io
import json
import getpass
import platform
import os
import re
import xdg.BaseDirectory
import configparser
import subprocess
from pprint import pprint


def natural_sortkey(string):
    tokenize = re.compile(r'(\d+)|(\D+)').findall
    return tuple(int(num) if num else alpha for num, alpha in tokenize(string))

def read_ini(user_confname, osname=''):
    ini_list = [ 'runon.conf', '.runon.conf', os.path.join(xdg.BaseDirectory.xdg_config_home, 'runon', 'runon.conf'), '/etc/runon/runon.conf' ]
    defaults = {
        'osname': osname,
        'user': getpass.getuser()
    }
    if user_confname:
        ini_list.insert(0, user_confname)
    ini = configparser.ConfigParser(defaults=defaults, interpolation=configparser.ExtendedInterpolation())
    ini.read(ini_list)
    return ini

def list_osnames(user_confname):
    ini = read_ini(user_confname)
    return ini.sections()

def load_config(user_confname, osname):
    ini = read_ini(user_confname, osname)
    if not ini.has_section(osname):
        print('ERROR: cannot find configuration for distribution "{}"'.format(osname))
        sys.exit(1)
    conf = {}
    fields = [ 'dockerfile', 'pkginstall', 'packages', 'environment', 'binds', 'user', 'osname' ]
    try:
        for f in fields:
            conf[f] = ini.get(osname, f)
    except configparser.NoOptionError as e:
        print('ERROR: {}'.format(e))
        sys.exit(1)
    for f in [ 'dockerfile', 'environment', 'binds' ]:
        conf[f] = [ i for i in conf[f].split('\n') if i ]
    for f in [ 'packages' ]:
        conf[f] = conf[f].split()
    return conf


def make_osname_link(binpath, osname):
    link = os.path.join(os.path.dirname(binpath), osname)
    try:
        os.symlink('runon', link)
    except FileExistsError:
        pass

def make_image_name(osname):
    user = getpass.getuser()
    name = 'runon-{}-{}'.format(osname, user)
    return name


def build_image(client, conf, update, verbose):
    packages = conf['packages']
    dockerfile = conf['dockerfile']
    pkginstall = conf['pkginstall']
    for p in packages:
        dockerfile.append(pkginstall.format(p))
    tag = make_image_name(conf['osname'])
    try:
        if verbose:
            # fallback to external command 'docker build' as there is
            # no way to follow the build progress with API.
            print('Building image {} ...'.format(tag))
            cmd = ['docker', 'build']
            if update:
                cmd.append('--no-cache')
            cmd += ['-t', tag, '-']
            ret = subprocess.run(cmd,
                                 input='\n'.join(dockerfile).encode('utf-8'),
                                 stderr=subprocess.STDOUT, check=True)
            image = client.images.get(tag)
        else:
            with io.BytesIO('\n'.join(dockerfile).encode('utf-8')) as fd:
                image, logs = client.images.build(tag=tag, fileobj=fd, rm=True, nocache=update)
            if verbose:
                print('Built image {} / {}'.format(image.tags[0], image.short_id))
                for l in logs:
                    print(l.get('stream', '').strip('\n'))
    except (docker.errors.BuildError, KeyboardInterrupt, subprocess.CalledProcessError, docker.errors.ImageNotFound) as e:
        print('Build Error: {}'.format(e))
        print()
        print('with dockerfile:')
        for line in dockerfile:
            print('  {}'.format(line))
        sys.exit(1)
    return image


def create_container(client, image, conf, command, verbose):
    volumes = {}
    environment = {}
    for mnt in conf['binds']:
        mnt = mnt.split(':')
        if mnt[-1] in ['ro','rw']:
            mode = mnt[-1]
            del mnt[-1]
        else:
            mode = 'rw'
        mnt = mnt[:2]
        bind = mnt[-1]
        vol = mnt[0]
        volumes[vol] = { 'bind': bind, 'mode': mode }
    hostname = platform.node()
    for v in conf['environment']:
        e = v.split('=')
        if len(e) == 1:
            e.append(os.getenv(e[0]))
        environment[e[0]] = e[1]
    #environment['debian_chroot']=conf['osname']
    user='{}:{}'.format(os.getuid(), os.getgid())
    pwd=os.getcwd()

    container = client.containers.create(image, command,
                                         detach=False, stdin_open=True, tty=True,
                                         auto_remove=True,
                                         hostname=hostname,
                                         volumes=volumes,
                                         environment=environment,
                                         user=user,
                                         network_mode='host',
                                         working_dir=pwd
                                         )
    return container


def run_container(client, container):
    try:
        dockerpty.start(client.api, container.id)
        container.reload()  # to update attrs fields
    except docker.errors.APIError as e:
        print('ERROR: {}'.format(e))
        sys.exit(1)
    ret = container.attrs['State']['ExitCode']
    return ret


def main():
    osname = None
    run_name = os.path.basename(os.sys.argv[0])
    if run_name == 'runos':
        pass
    elif run_name.startswith('runon'):
        m = re.match('runon[-_]?(.*)$', run_name)
        if m:
            osname = m[1]
    else:
        osname = run_name

    parser = argparse.ArgumentParser()
    if osname:
        parser.description = 'run commands on "{}" distribution'.format(osname)
    else:
        parser.description = 'run commands on any distribution'
        parser.add_argument('osname',
                            help = 'distribution name to run on, '
                            '"list" to dump all available distributions')
    parser.epilog = '(c) 2021 Gilles Grandou <gilles@grandou.net>'

    parser.add_argument('-v', '--verbose', action='store_true',
                        help='verbose output')
    parser.add_argument('-c', '--config',
                        help='specify config file')
    parser.add_argument('-u', '--update', action='store_true',
                        help='force image update')
    parser.add_argument('-l', '--link', action='store_true',
                        help='create a symlink to call "osname" as a shortcut to "runon osname"')
    parser.add_argument('command', nargs='*', default=None,
                        help = 'command to execute')

    args = parser.parse_args()
    if osname:
        args.osname = osname

    if args.osname == 'list':
        osnames = list_osnames(args.config)
        print('Available distributions:')
        for o in sorted(osnames, key=natural_sortkey):
            print('  {}'.format(o))
        print()
        if args.link:
            for o in osnames:
                make_osname_link(sys.argv[0], args.osname)
        return 0

    client = docker.from_env()
    conf = load_config(args.config, args.osname)
    if args.link:
        make_osname_link(sys.argv[0], args.osname)
    image = build_image(client, conf, args.update, args.verbose)
    container = create_container(client, image, conf, args.command, args.verbose)
    ret = run_container(client, container)
    return ret


if __name__ == '__main__':
    ret = main()
    sys.exit(ret)