#! /bin/bash
# /usr/bin/pacman2pacman-get
#
# Version 1.1
#
# Copyright (C) 2014 Joseph Graham <joseph@t67.eu>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.


# Where Pacman2pacman will look to find .torrent files.
torrents='http://repo.parabolagnulinux.org/torrents/'

pkg_cache_location='/var/cache/pacman/pkg'

# Pacman2pacman should be called like this from /etc/pacman.conf:
# XferCommand = /usr/bin/pacman2pacman-get %u %o

# Check that the args are not empty.
[[ -z ${1} ]] && { echo "The first argument should be the download url." ; exit 1 ; }
[[ -z ${2} ]] && { echo "The second argument should be the local filename, plus a “.part” extension." ; exit 1 ; }

url="${1}"  # The download url.
filename="${2}"  # This is where the downloaded file needs to be saved
                 # or hardlinked

# Check if transmission daemon is running.
if ! systemctl show --property='ActiveState' transmission | grep -q 'ActiveState=active'
then
    echo 'Error: The transmission daemon is not running.'
    exit 1
fi

torrent_url="${torrents}${url##*/}.torrent"

cd "${pkg_cache_location}"

# Find the name of the package that will be displayed
pname="${url##*/}"
pname="${pname%%-[[:digit:]]*}"

# Check for a .torrent.
if curl -O -f -L -s -A 'Pacman2pacman' "${torrent_url}"
then
    # Add the torrent to transmission
    transmission-remote -a "${url##*/}.torrent" -w "${pkg_cache_location}" &>/dev/null

    # The torrent is now downloading. To get info about the torrent in
    # order to display a progress bar we need to know it's id.

    # Find out the id of the torrent
    id=$(transmission-remote -l | grep "${url##*/}")
    id="${id## }"
    id="${id## }"
    id="${id## }"
    id="${id## }"
    id="${id## }"
    id="${id## }"
    id="${id## }"
    id="${id## }"
    id="${id## }"
    id="${id## }"
    id="${id## }"  # Once should be enough but somehow it's not so I do
                   # it loads of times.
    id="${id%% *}"

    # If there is an error there will be an asterix displayed on the
    # end of the id. We must remove it.
    id="${id%\*}"

    if ! [[ ${id} =~ [[:digit:]] ]]
    then
        echo 'Error.'
        exit 1
    fi

    # Display a progress bar until it's finished and then hardlink it to
    # the right place.
    progress='0%'

    echo -n "Pacman2pacman download: ${pname}: ${progress}"

    until [[ "${progress}" == '100%' ]]
    do
        progress=$(transmission-remote -t "${id}" -i | grep 'Percent Done:')
        progress="${progress##* }"  # Remove stuff we don't want

        printf "\rPacman2pacman download: %s: %s   " "${pname}" "${progress}"

        sleep 0.7
    done

    echo

    ln -f "${pkg_cache_location}/${url##*/}" "${filename}" || exit 1

else
    # There's no .torrent so we download it by just HTTP.

    # We must do some complicated stuff to customise the progress
    # meter how we want it, to make it consistent with the progress
    # bar when we download stuff with transmission.

    progress='0%'

    echo -n "Pacman2pacman download: ${pname}: ${progress}"

    # The first loop gets rid of all the backspace and `#'es and
    # stuff. The second loop isolates the percent done number.
    curl -# -f -L -o "${filename}" -A 'Pacman2pacman' "${url}" 2>&1 |
    while read -N 1 char
    do
        [[ "${char}" =~ [[:digit:].%\ ] ]] && echo -n "${char}"
    done |
    while read -d '%' word
    do
        progress="${word}%"

        # For consistency with the transmission progress bar:
        [[ "${progress}" == '100.0%' ]] && progress='100%'

        printf "\rPacman2pacman download: %s: %s   " "${pname}" "${progress}"
    done

    echo

    [[ -f "${filename}" ]] || exit 1
fi

exit