import sys
import os
import argparse
import getpass
import pathlib
import xdg.BaseDirectory
import yaml
import datetime
import pytz
import subprocess
from pprint import pprint


def find_config_file(user_conf):
    conf_list = [
            'runon.yaml',
            '.runon.yaml',
            os.path.join(xdg.BaseDirectory.xdg_config_home, 'runon', 'runon.yaml'),
            os.path.join(xdg.BaseDirectory.xdg_config_home, 'runon', 'runon.default.yaml')
            ]
    if user_conf:
        conf_list = [ user_conf ]
    for conf in conf_list:
        if os.path.exists(conf):
            return conf
    return None


def read_yaml(conf_file):
    try:
        with open(conf_file, 'r') as file:
            conf = yaml.safe_load(file)
            conf['stamp'] = datetime.datetime.fromtimestamp(os.path.getmtime(conf_file), tz=pytz.UTC)
        return conf
    except yaml.YAMLError as e:
        print(f'ERROR: bad configuration file:')
        print(e)
        sys.exit(1)
    return conf

def list_osnames(conf_file):
    conf = read_yaml(conf_file)
    osnames = []
    for key in conf:
        if (type(conf[key]) is dict) and conf[key].get('image'):
            osnames.append(key)
    return osnames


def load_config(conf_file, osname):
    user_vars = {
            'osname': osname,
            'user': getpass.getuser(),
            'uid': os.getuid(),
            'home': pathlib.Path.home(),
            }
    conf = read_yaml(conf_file)
    osconf = conf.get(osname)
    if not osconf:
        print(f"ERROR: cannot find configuration for distribution {osname}")
        sys.exit(1)

    osconf['stamp'] = conf.get('stamp')
    osconf['osname'] = osname
    for k in [ 'dockerfile', 'packages', 'environment', 'binds' ]:
        if osconf.get(k):
            osconf[k] = [ s.format(**user_vars) for s in osconf[k]]
    return osconf


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


def build_image(conf, update, verbose):
    osname = conf.get('osname')
    image_name = 'runon-{}'.format(osname)
    cache_dir = os.path.join(xdg.BaseDirectory.xdg_cache_home, 'runon')
    cache_file = os.path.join(cache_dir, image_name)

    if not update and os.path.exists(cache_file):
        ts_image = datetime.datetime.fromtimestamp(os.path.getmtime(cache_file), tz=pytz.UTC)
        ts_conf = conf.get('stamp')
        if verbose:
            print('config: {}'.format(ts_conf))
            print('image:  {}'.format(ts_image))
        if ts_image and ts_image > ts_conf:
            if verbose:
                print('image: {} up-to-date'.format(image_name))
            return image_name

    image = conf.get('image')
    dockerfile = conf.get('dockerfile')
    pkginstall = conf.get('pkginstall')
    packages = conf.get('packages')
    if not dockerfile:
        dockerfile = []
    if image:
        dockerfile.insert(0, 'FROM {}'.format(image))
    if packages:
        for p in packages:
            dockerfile.append(pkginstall.format(p))

    if verbose:
        print('Dockerfile:')
        for l in dockerfile:
            print(' * {}'.format(l))
        print('Building image {} ...'.format(image_name))
    cmd = ['podman', 'build']
    if update:
        cmd.append('--no-cache')
    cmd += ['-t', image_name, '-']
    ret = subprocess.run(cmd,
                         input='\n'.join(dockerfile).encode('utf-8'),
                         stderr=subprocess.STDOUT, check=True)

    if not os.path.exists(cache_dir):
        os.mkdir(cache_dir)
    with open(cache_file, 'w') as file:
        if verbose:
            print('cache: {}'.format(cache_file))
        file.write('')

    return image_name


def run_image(name, conf, command, verbose):
    volumes = {
            }
    environment = {}
    if conf.get('binds'):
        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]
            if os.path.exists(vol):
                volumes[vol] = { 'bind': bind, 'mode': mode }
    if conf.get('environment'):
        for v in conf['environment']:
            e = v.split('=')
            if len(e) == 1:
                e.append(os.getenv(e[0]))
            environment[e[0]] = e[1]

    cmd = ['podman', 'run', '--rm', '--interactive', '--tty', '--userns=keep-id', '--net=host' ]
    for e in environment:
        cmd += [ '-e', '{}={}'.format(e, environment[e]) ]
    for v in volumes:
        cmd += [ '-v', ':'.join([v, volumes[v]['bind'], volumes[v]['mode']]) ]
    cmd += [ '--workdir', os.getcwd() ]
    cmd += [ name ]
    if command:
        cmd += command
    if verbose:
        print('executing: {}\n'.format(' '.join(cmd)))
    ret = subprocess.run(cmd)
    return ret.returncode


def main():
    osname = None
    run_name = os.path.basename(os.sys.argv[0])
    if run_name == "runon":
        pass
    elif run_name.startswith("runon_"):
        osname = run_name[len("runon_"):]
    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, '
                            '"edit" to open the current config file in a text editor.')
    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

    conf_file = find_config_file(args.config)
    if not conf_file:
        print('ERROR: config file not found')
        sys.exit(1)

    if args.osname == 'list':
        osnames = list_osnames(conf_file)
        print('Available distributions:')
        for o in sorted(osnames):
            print('  {}'.format(o))
        print()
        return 0
    elif args.osname == 'edit':
        cmd = [ 'xdg-open', conf_file ]
        ret = subprocess.run(cmd, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL);
        return 0

    if args.link:
        make_osname_link(sys.argv[0], args.osname)

    conf = load_config(conf_file, args.osname)
    image_name = build_image(conf, args.update, args.verbose)
    ret = run_image(image_name, conf, args.command, args.verbose)
    return ret