#!/usr/bin/python3

import os
import sys
import glob
import subprocess
import tempfile
import shutil
import re
import functools


parameters = dict(
    release='unstable',
    #mirror='http://fr.archive.ubuntu.com/ubuntu/',
    mirror='http://apt:9999/debian/',
    arch='amd64',
    image = 'unstable-amd64.qcow2',
    packages='''
        apt
        aptitude
        bash
        bash-completion
        bind9-host
        bmon
        busybox
        bzip2
        curl
        ed
        htop
        iftop
        ifupdown
        iotop
        iperf
        iproute2
        iptables
        iputils-ping
        less
        lftp
        locales
        ncdu
        ncurses-base
        ncurses-term
        net-tools
        netbase
        netcat
        nload
        openssh-client
        openssh-server
        psmisc
        python3
        ranger
        rsync
        screen
        sed
        socat
        strace
        tar
        tcpdump
        telnet
        tmux
        tree
        tzdata
        vim
        vim-nox
        vim-runtime
        w3m
        wget
        zsh
    '''.split(),
    kernel_package = 'linux-image-amd64',
    serial_console = 'ttyS0',
)


open8 = functools.partial(open, encoding='utf8')
numerical_sort = lambda y: [int(x) if x.isdigit() else x
                            for x in re.split('(\d+)', y)]


def mlstrip(s):
    return re.sub(r'^\s*', '', s, flags=re.MULTILINE)


def run(*l, **kw):
    print('run:', *l)
    return subprocess.run(*l, **kw)


def reexec_root():
    # run as root
    if os.geteuid() != 0:
        os.execvp("sudo", ["sudo"] + sys.argv)


def system_customization(device, rootdir, rootpartuuid, rootfsuuid):
    os.unlink(rootdir + '/etc/localtime')
    open8(rootdir + '/etc/zoneinfo', 'w').write('Europe/Paris\n')
    shutil.copy(rootdir + '/usr/share/zoneinfo/Europe/Paris',
                rootdir + '/etc/localtime')

    open8(rootdir + '/etc/network/interfaces', 'w').write(mlstrip(
        '''\
            auto lo
            iface lo inet loopback

            auto eth0
            iface eth0 inet dhcp
        '''))
    open8(rootdir + '/etc/hosts', 'w').write(mlstrip(
        '''\
            127.0.0.1 localhost localhost.localdomain debian

            # the following lines are desirable for IPv6 capable hosts
            ::1     localhost ip6-localhost ip6-loopback
            ff02::1 ip6-allnodes
            ff02::2 ip6-allrouters
        '''))
    open8(rootdir + '/etc/hostname', 'w').write('debian\n')
    open8(rootdir + '/etc/fstab', 'w').write(mlstrip(
        '''\
            # <device> <mount point> <type> <options> <dump>  <pass>
            PARTUUID={rid} / ext4 errors=remount-ro,relatime 0 1
        '''.format(rid=rootpartuuid)))

    # activate serial console on parameter['serial_console']
    console = parameters['serial_console']
    run([
        'ln',
        '-s',
        '/lib/systemd/system/serial-getty@.service',
        rootdir + '/etc/systemd/system/getty.target.wants/serial-getty@%s.service' % console,
        ], check=True)
    os.makedirs(rootdir + '/etc/systemd/system/serial-getty@%s.service.d' % console,
                mode=0o755)
    open8(rootdir +
        '/etc/systemd/system/serial-getty@%s.service.d/autologin.conf' % console,
        'w').write(mlstrip(
        '''\
            [Service]
            ExecStart=
            ExecStart=-/sbin/agetty --autologin root --login-pause --noclear %I 115200,38400,9600 vt102
        '''))

    open8(rootdir + '/etc/default/keyboard', 'w').write(mlstrip(
        '''\
            XKBMODEL="pc105"
            XKBLAYOUT="fr"
            XKBVARIANT="bepo"
            XKBOPTIONS=""
        '''))

    open8(rootdir + '/etc/default/locale', 'w').write(mlstrip(
        '''\
            LANG="en_US.UTF-8"
            LC_TIME="en_DK.UTF-8"
            LC_PAPER="en_GB.UTF-8"
            LC_MEASUREMENT="en_GB.UTF-8"
        '''))

    for locale in ['fr_FR', 'en_US', 'en_GB', 'en_DK', 'de_DE']:
        run([
            'localedef',
            '--prefix={}'.format(rootdir),
            '-f', 'UTF-8',
            '-i', locale,
            '{}.UTF-8'.format(locale)
            ], check=True)

    open8(rootdir + '/etc/bash.bashrc', 'a').write(mlstrip(
        '''\

            # enable bash completion in interactive shells
            if ! shopt -oq posix; then
            if [ -f /usr/share/bash-completion/bash_completion ]; then
                . /usr/share/bash-completion/bash_completion
            elif [ -f /etc/bash_completion ]; then
                . /etc/bash_completion
            fi
            fi
            alias ls="ls --color=aut"
            alias l="ls -CF"
            alias ll="l -lh"
            alias la="l -a"
            alias e="vim"
            alias rm='rm -i'
            alias cp='cp -i'
            alias mv='mv -i'
            export PAGER=less
            export EDITOR=vim
            export VISUAL=vim
        '''))

    open8(rootdir + '/etc/vim/vimrc', 'w').write(mlstrip(
        '''\
            set nocompatible
            filetype plugin indent on
            set autoindent
            set background=dark
            set backspace=2
            set hidden
            set hlsearch
            set ignorecase
            set incsearch
            set laststatus=2
            set modelines=0
            set nobackup
            set nowritebackup
            set ruler
            set scrolloff=3
            set shiftwidth=4
            set showcmd
            set showmatch
            set statusline=%<%f%h%m%r%=%l,%c\ %P
            set ts=4
            set whichwrap=<,>,[,]
            set wildmode=list:full
            syntax on
        '''))


def make_image():
    device = None
    rootdirobj = tempfile.TemporaryDirectory()
    rootdir = rootdirobj.name
    try:
        run(['qemu-img', 'create', '-f', 'qcow2', parameters['image'], '20G'],
            check=True)

        run(['modprobe', 'nbd', 'max_part=16'])

        for d in sorted(glob.glob('/dev/nbd*'), key=numerical_sort):
            if run(['qemu-nbd', '-c', d, parameters['image']]).returncode == 0:
                device = d
                break
        else:
            print('No free nbd device found for qemu-nbd')
            raise SystemExit(1)

        run([
            'sgdisk',
            '--set-alignment=8192',
            '--zap-all',
            '--largest-new=1',
            '--change-name=1:root',
            '--typecode=1:8300',
            device,
            ], check=True)

        run(['partprobe', device])
        run(['mkfs.ext4', '-q', '-L', 'root', device+'p1'], check=True)
        run(['mount', device+'p1', rootdir], check=True)

        run([
            'qemu-debootstrap',
            '--arch=' + parameters['arch'],
            '--include=' + ','.join(parameters['packages']
                                    + [parameters['kernel_package']]),
            '--components=main,universe',
            parameters['release'],
            rootdir,
            parameters['mirror'],
            ], check=True)

        rootpartuuid = (run([
            'partx',
            '--noheadings',
            '--show',
            '--output',
            'UUID',
            device+'p1'], check=True, stdout=subprocess.PIPE)
            .stdout
            .decode('utf8')
            .strip())

        rootfsuuid = [line.split()[-1]
                for line in (run([ 'tune2fs', '-l', device+'p1'],
                                 check=True, stdout=subprocess.PIPE)
                             .stdout
                             .decode('utf8')
                             .splitlines())
                if "filesystem uuid" in line.lower()][0]

        system_customization(device, rootdir, rootpartuuid, rootfsuuid)

    finally:
        if rootdir:
            run(['umount', rootdir])
        if device:
            run(['qemu-nbd', '-d', device])


def main():
    reexec_root()
    make_image()


if __name__ == '__main__':
    main()