setup.sh

#!/usr/bin/env bash

TARGET_CONFIG=/etc/nixos/configuration.nix
DATE=$(date "+%F_%H-%M-%S")
BACKUP_CONFIG=/tmp/configuration_$DATE.nix
SCRIPT_DIR=$(dirname "$(readlink -f "$BASH_SOURCE")")
HOSTS_DIR=$SCRIPT_DIR/hosts
HOSTS=( $(ls $HOSTS_DIR | sed "s/\.nix//g") ) # strip .nix from end of filenames

usage() {
    echo "usage: $0 HOST"
    echo ""
    echo "Generate configuration.nix and write it to $TARGET_CONFIG."
    echo "If $TARGET_CONFIG already exists, then back it up to /tmp."
    echo "The configuration will import:"
    echo "    - common/common.nix           shared config, in this repo"
    echo "    - hosts/HOST.nix              host config, in this repo"
    echo "    - hardware-configuration.nix  platform config, generated by nixos-generate-config"
    echo ""
    echo "arguments:"
    echo "    HOST: the host to set up. Options: ${HOSTS[@]}"
}

# If exactly 1 argument is not provided
if [[ $# -ne 1 ]]; then
    echo "No host provided."
    usage
    exit 1
fi

HOST=$1

# If $HOST is not in $HOSTS
if ! printf '%s\0' "${HOSTS[@]}" | grep -Fxqz -- $HOST; then
    echo "Unknown host $HOST."
    usage
    exit 1
fi

# If configuration.nix exists, back it up to /tmp with a timestamp
if [[ -f $TARGET_CONFIG ]]; then
    echo "Backing up existing $TARGET_CONFIG to $BACKUP_CONFIG"
    cp $TARGET_CONFIG $BACKUP_CONFIG
fi

# Write the generated configuration
generate_config() {
    echo "# Generated by `realpath $BASH_SOURCE`"
    echo ""
    echo "{ config, pkgs, ...}:"
    echo ""
    echo "{"
    echo "  imports ="
    echo "    ["
    echo "      ./hardware-configuration.nix"
    echo "      $SCRIPT_DIR/hosts/$HOST.nix"
    echo "    ];"
    echo "}"
}

echo "Writing configuration to $TARGET_CONFIG"
echo ""
generate_config | sudo tee $TARGET_CONFIG