#!/usr/bin/env dash

# shellcheck source=/dev/null
SHELL_LIBRARY_VERSION="1.1.3" . %SHELL_LIBRARY_PATH

help() {
    cat << EOF
This is a NixOS System flake update manager.

Usage:
    $NAME [--branch <branchname>] [--help]

Options:
    --branch | -b  BRANCHNAME
                                select a branch to update from.
    --mode | -m  MODE
                                select a mode to update with
    --help   | -h
                                output this help.
EOF
    exit "$1";
}
default_branch=$(mktmp);
BRANCH="";

while [ "$#" -gt 0 ];do
    case "$1" in
        "--help" | "-h")
            help 0;
            ;;
        "--branch" | "-b")
            if [ -n "$2" ];then
                BRANCH="$2";
            else
                error "$1 requires an argument";
                help 1;
            fi
            shift 2;
            ;;
        "--mode" | "-m")
            if [ -n "$2" ];then
                MODE="$2";
            else
                error "$1 requires an argument";
                help 1;
            fi
            shift 2;
            ;;
        *)
            error "the option $1 does not exist!";
            help 1;
            ;;
    esac
done


cd /etc/nixos || die "No /etc/nixos";
msg "Starting system update...";
git remote update origin --prune > /dev/null 2>&1;
if ! [ "$BRANCH" = "" ];then
    git switch "$BRANCH" > /dev/null 2>&1 && msg2 "Switched to branch '$BRANCH'";
fi
msg2 "Updating git repository...";
git pull --rebase;

git remote show origin | grep 'HEAD' | cut -d':' -f2 | sed -e 's/^ *//g' -e 's/ *$//g' > "$default_branch" &

msg2 "Updating system...";
if [ -n "$MODE" ]; then
    nixos-rebuild "$MODE";
else
    nixos-rebuild switch;
fi

git switch "$(cat "$default_branch")" > /dev/null 2>&1 && msg2 "Switched to branch '$(cat "$default_branch")'";
msg "Finished Update!";

# vim: ft=sh