#!/bin/bash
set -e

apt()
{
        (set -x; command apt "$@")
}

[ "$(id -u)" = 0 ] || exec sudo bash "$0" "$@"

basics='etckeeper git info par ssh tmux vim w3m'
#xorg='xorg xterm i3'
xorg='xorg xterm'
media='libdbus-glib-1-2 mpv pulseaudio'
apt install --no-upgrade $basics $xorg $media

apt_backport()
{
    (
        set -e
        apt install --no-upgrade debhelper
        SOURCES_DIR=$1
        TARGET_URL=$2
        TARGET_PKG=$3
        case "$TARGET_PKG" in
                '' | */*) exit 1 ;;
        esac
        mkdir -p "$SOURCES_DIR"
        cd "$SOURCES_DIR"

        if [ -e "$TARGET_PKG" ]
        then
                cd "$TARGET_PKG"
                git pull --ff-only
        else
                rm -rf "$TARGET_PKG"~tmp
                git clone --depth=1 "$TARGET_URL" "$TARGET_PKG"~tmp
                mv -T "$TARGET_PKG"~tmp "$TARGET_PKG"
                cd "$TARGET_PKG"
        fi

        arch=$(dpkg-architecture -q DEB_BUILD_ARCH)
        version=$(dpkg-parsechangelog --show-field Version)
        pkgs=$(dh_listpackages)
        debs=
        for pkg in $pkgs
        do
                debs="$debs ${pkg}_${version}_${arch}.deb"
        done

        for deb in $debs
        do
                [ -e ../"$deb" ] && continue || true
                # We are missing a deb, therefore build.

                if command -v mk-build-deps >/dev/null
                then
                        mk-build-deps "$TARGET_PKG" --install
                else
                        # We could 'apt install devscripts' but it pulls
                        # in like 50MB of perl deps, possibly nullifying
                        # the savings from removing unneeded build deps.

                        # However, we cannot simply use 'apt build-dep'
                        # because that would use the build-deps from the
                        # version of the package in the repo, which may
                        # differ from the source version.

                        # Arguably we do want to try that though, since
                        # it's a backport...

                        if [ "$try_newer_build_deps" ]
                        then
                                build_deps=$(get_build_deps)
                                apt install $build_deps
                        else
                                apt build-dep "$TARGET_PKG"
                        fi
                fi
                fakeroot ./debian/rules binary
                break
        done

        set --
        for deb in $debs
        do
                set -- "$@" ../"$deb"
        done
        apt install "$@"
    )
}

get_build_deps()
{
        # credit: Archemar @ https://unix.stackexchange.com/a/648927
        build_deps=$(dpkg-checkbuilddeps 2>&1 |
                sed -n -e 's/dpkg-checkbuilddeps:\serror:\sUnmet build dependencies: //gp' \
                       -e 's/[\(][^)]*[\)] //g')
}

try_newer_build_deps=y
apt_backport /usr/local/src https://salsa.debian.org/i3-team/i3-wm.git i3-wm