#!/usr/bin/env dash

# shellcheck source=/dev/null
SHELL_LIBRARY_VERSION="2.1.1" . %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