#!/bin/bash

set -e                  # exit on error
set -o pipefail         # exit on pipeline error
set -u                  # treat unset variable as error
#set -x

SCRIPT_DIR="$(dirname "$(readlink -f "$0")")"

CMD=(setup_host install_pkg finish_up)

function help() {
    # if $1 is set, use $1 as headline message in help()
    if [ -z ${1+x} ]; then
        echo -e "This script builds Ubuntu from scratch"
        echo -e
    else
        echo -e $1
        echo
    fi
    echo -e "Supported commands : ${CMD[*]}"
    echo -e
    echo -e "Syntax: $0 [start_cmd] [-] [end_cmd]"
    echo -e "\trun from start_cmd to end_end"
    echo -e "\tif start_cmd is omitted, start from first command"
    echo -e "\tif end_cmd is omitted, end with last command"
    echo -e "\tenter single cmd to run the specific command"
    echo -e "\tenter '-' as only argument to run all commands"
    echo -e
    exit 0
}

function find_index() {
    local ret;
    local i;
    for ((i=0; i<${#CMD[*]}; i++)); do
        if [ "${CMD[i]}" == "$1" ]; then
            index=$i;
            return;
        fi
    done
    help "Command not found : $1"
}

function check_host() {
    if [ $(id -u) -ne 0 ]; then
        echo "This script should be run as 'root'"
        exit 1
    fi

    export HOME=/root
    export LC_ALL=C
}

function setup_host() {
    echo "=====> running setup_host ..."

    echo "ubuntu-fs-live" > /etc/hostname

    # we need to install systemd first, to configure machine id
    apt-get update
    apt-get install -y libterm-readline-gnu-perl systemd-sysv

    #configure machine id
    dbus-uuidgen > /etc/machine-id
    ln -fs /etc/machine-id /var/lib/dbus/machine-id

    # don't understand why, but multiple sources indicate this
    dpkg-divert --local --rename --add /sbin/initctl
    ln -s /bin/true /sbin/initctl
}

function install_pkg() {
    echo "=====> running install_pkg ... will take a long time ..."
    apt-get -y upgrade

    # install live linux packages
    apt-get install -y \
    ubuntu-standard \
    casper \
    lupin-casper \
    discover \
    laptop-detect \
    os-prober \
    network-manager \
    resolvconf \
    net-tools \
    wireless-tools \
    wpagui \
    locales \
    linux-generic

    # graphic installer - ubiquity
    apt-get install -y \
    ubiquity \
    ubiquity-casper \
    ubiquity-frontend-gtk \
    ubiquity-slideshow-ubuntu \
    ubiquity-ubuntu-artwork

    # install graphics and desktop
    apt-get install -y \
    plymouth-theme-ubuntu-logo \
    ubuntu-gnome-desktop \
    ubuntu-gnome-wallpapers

    # useful tools
    apt-get install -y \
    clamav-daemon \
    terminator \
    apt-transport-https \
    curl \
    vim \
    nano \
    less

    # purge
    apt-get purge -y \
    transmission-gtk \
    transmission-common \
    gnome-mahjongg \
    gnome-mines \
    gnome-sudoku \
    aisleriot \
    hitori

    # remove unused and clean up apt cache
    apt-get autoremove -y

    # final touch
    dpkg-reconfigure locales
    dpkg-reconfigure resolvconf

    # network manager
    cat <<EOF > /etc/NetworkManager/NetworkManager.conf
[main]
rc-manager=resolvconf
plugins=ifupdown,keyfile
dns=dnsmasq

[ifupdown]
managed=false
EOF
    dpkg-reconfigure network-manager

    apt-get clean -y
}

function finish_up() { 
    echo "=====> finish_up"

    # truncate machine id (why??)
    truncate -s 0 /etc/machine-id

    # remove diversion (why??)
    rm /sbin/initctl
    dpkg-divert --rename --remove /sbin/initctl

    rm -rf /tmp/* ~/.bash_history
}

# =============   main  ================

check_host

# check number of args
if [[ $# == 0 || $# > 3 ]]; then help; fi

# loop through args
dash_flag=false
start_index=0
end_index=${#CMD[*]}
for ii in "$@";
do
    if [[ $ii == "-" ]]; then
        dash_flag=true
        continue
    fi
    find_index $ii
    if [[ $dash_flag == false ]]; then
        start_index=$index
    else
        end_index=$(($index+1))
    fi
done
if [[ $dash_flag == false ]]; then
    end_index=$(($start_index + 1))
fi

# loop through the commands
for ((ii=$start_index; ii<$end_index; ii++)); do
    ${CMD[ii]}
done

echo "$0 - Initial build is done!"