#!/usr/bin/env bash
set -e

# use_nix.sh - Script to update NixOS configuration
# Usage: use_nix.sh [--rebuild] [--upgrade] [--re-flake]

function check_root() {
    if [[ $EUID -ne 0 ]]; then
        echo "This script must be run as root" >&2
        exit 1
    fi
}

function show_usage() {
    echo "Usage: $0 [--rebuild] [--upgrade] [--re-flake]"
    echo "  --no-rebuild    Disable automatic run of nixos-rebuild after copying files"
    echo "  --upgrade    Upgrade installed packages to match flake.lock"
    echo "  --update [inputs]     Update the flake.lock file to latest"
    echo "  --re-flake   Delete the flake.lock, forcing to fetch the latest in-branch commits"
}

AUTO_REBUILD=1
UPGRADE=0
RE_FLAKE=0
UPDATE=0

FLAKES_TO_UPDATE=()

# Parse arguments
prev_arg=""
for arg in "$@"; do
    case $arg in
        --no-rebuild) AUTO_REBUILD=0 ;;
        --upgrade) UPGRADE=1 ;;
        --update) UPDATE=1 ;;
        --re-flake) RE_FLAKE=1 ;;
        --help|-h) show_usage; exit 0 ;;
        *)
            if [ "${arg:0:2}" != "--" ]; then
                case $prev_arg in
                    --update) FLAKES_TO_UPDATE+=($arg) ;;
                    *) echo "No argument needet for: $prev_arg"; show_usage; exit 1 ;;
                esac
                continue
            fi;
            echo "Unknown option: $arg"; show_usage; exit 1 ;;
    esac
    prev_arg=$arg
done

# Check if source directory exists
if [[ ! -d "root-conf/nixos" ]]; then
    echo "Error: Source directory 'root-conf/nixos' not found!" >&2
    exit 1
fi

if [[ $UPDATE -eq 1 ]]; then
    echo "Updatening flake.lock $FLAKES_TO_UPDATE"
    cd root-conf/nixos
    nix flake update $FLAKES_TO_UPDATE
    cd -
fi

check_root

# Backup existing configuration
if [[ -d /etc/nixos ]]; then
    echo "Backing up existing configuration to /etc/nixos.bak"
    rm -rf /etc/nixos.bak 2>/dev/null || true
    cp -r /etc/nixos /etc/nixos.bak
    rm -rf /etc/nixos/*
else
    mkdir -p /etc/nixos
fi

# Copy new configuration
echo "Copying files to /etc/nixos/"
cp -r root-conf/nixos/* /etc/nixos/

if [[ $RE_FLAKE -eq 1 ]]; then
    echo "Deleting flake.lock"
    rm /etc/nixos/flake.lock 2>/dev/null || true
    rm root-conf/nixos/flake.lock 2>/dev/null || true
fi

ARGS=""
if [[ $AUTO_REBUILD -eq 1 ]]; then
    ARGS+="switch "
else
    ARGS+="boot "
fi

if [[ $UPGRADE -eq 1 ]]; then
    ARGS+="--upgrade "
fi
ARGS+="--flake /etc/nixos"

echo "Running:  nixos-rebuild $ARGS"
nixos-rebuild $ARGS
cp /etc/nixos/flake.lock root-conf/nixos/flake.lock

diff -r /etc/nixos.bak root-conf/nixos | colordiff --nobanner
echo "Done!"