#!/usr/bin/env python3

#

# Copyright 2018 Gregory Szorc <gregory.szorc@gmail.com>

#

# This software may be used and distributed according to the terms of the

# GNU General Public License version 2 or any later version.

import argparse

import pathlib

import shutil

import subprocess

import sys

def get_docker() -> str:

    docker = shutil.which('docker.io') or shutil.which('docker')

    if not docker:

        print('could not find docker executable')

        return 1

    try:

        out = subprocess.check_output([docker, '-h'], stderr=subprocess.STDOUT)

        if b'Jansens' in out:

            print('%s is the Docking System Tray; try installing docker.io' %

                  docker)

            sys.exit(1)

    except subprocess.CalledProcessError as e:

        print('error calling `%s -h`: %s' % (docker, e.output))

        sys.exit(1)

    out = subprocess.check_output([docker, 'version'],

                                  stderr=subprocess.STDOUT)

    lines = out.splitlines()

    if not any(l.startswith((b'Client:', b'Client version:')) for l in lines):

        print('`%s version` does not look like Docker' % docker)

        sys.exit(1)

    if not any(l.startswith((b'Server:', b'Server version:')) for l in lines):

        print('`%s version` does not look like Docker' % docker)

        sys.exit(1)

    return docker

def get_dockerfile(path: pathlib.Path, args: list) -> bytes:

    with path.open('rb') as fh:

        df = fh.read()

    for k, v in args:

        df = df.replace(b'%%%s%%' % k, v)

    return df

def build_docker_image(dockerfile: pathlib.Path, params: list, tag: str):

    """Build a Docker image from a templatized Dockerfile."""

    docker = get_docker()

    dockerfile_path = pathlib.Path(dockerfile)

    dockerfile = get_dockerfile(dockerfile_path, params)

    print('building Dockerfile:')

    print(dockerfile.decode('utf-8', 'replace'))

    args = [

        docker,

        'build',

        '--build-arg', 'http_proxy',

        '--build-arg', 'https_proxy',

        '--tag', tag,

        '-',

    ]

    print('executing: %r' % args)

    subprocess.run(args, input=dockerfile, check=True)

def command_build(args):

    build_args = []

    for arg in args.build_arg:

        k, v = arg.split('=', 1)

        build_args.append((k.encode('utf-8'), v.encode('utf-8')))

    build_docker_image(pathlib.Path(args.dockerfile),

                       build_args,

                       args.tag)

def command_docker(args):

    print(get_docker())

def main() -> int:

    parser = argparse.ArgumentParser()

    subparsers = parser.add_subparsers(title='subcommands')

    build = subparsers.add_parser('build', help='Build a Docker image')

    build.set_defaults(func=command_build)

    build.add_argument('--build-arg', action='append', default=[],

                        help='Substitution to perform in Dockerfile; '

                             'format: key=value')

    build.add_argument('dockerfile', help='path to Dockerfile to use')

    build.add_argument('tag', help='Tag to apply to created image')

    docker = subparsers.add_parser('docker-path', help='Resolve path to Docker')

    docker.set_defaults(func=command_docker)

    args = parser.parse_args()

    return args.func(args)

if __name__ == '__main__':

    sys.exit(main())