include_guard "dhcp_server"

template dhcp_server {
    alias("_arg0") addr;
    alias("_arg1") prefix;
    alias("_arg2") range_start;
    alias("_arg3") range_end;
    alias("_arg4") routers;
    alias("_arg5") dns_servers;

    # Choose lease file.
    concat("/var/lib/dhcp/dhcpd-", addr, ".leases") leases_file;

    # Create leases file if it doesn't exist.
    file_stat(leases_file) stat;
    If (stat.succeeded) { print(); } Else {
        file_write(leases_file, "");
    };

    # Create a temporary directory.
    concat("/run/ncd-dhcp-server-", addr) run_dir;
    run({"/bin/rm", "-rf", run_dir}, {});
    run({"/bin/mkdir", run_dir}, {"/bin/rm", "-rf", run_dir});

    # Compute path for dhcp.conf.
    concat(run_dir, "/dhcp.conf") dhcp_conf_path;

    # This is a template for dhcp.conf.
    var("
default-lease-time 43200;
max-lease-time 43200;
log-facility local7;
ddns-update-style none;
local-address <LOCAL_ADDRESS>;

subnet <NETWORK> netmask <NETMASK> {
        authoritative;
        range <RANGE_START> <RANGE_END>;
        option routers <ROUTERS>;
        option domain-name-servers <DNS_SERVERS>;
}
"   ) config_template;

    # Compute some of the variables.
    ipv4_net_from_addr_and_prefix(addr, prefix) network;
    ipv4_prefix_to_mask(prefix) netmask;
    implode(", ", routers) routers_str;
    implode(", ", dns_servers) dns_servers_str;

    # Perform substitutions.
    var({"<LOCAL_ADDRESS>", "<NETWORK>", "<NETMASK>", "<RANGE_START>", "<RANGE_END>", "<ROUTERS>", "<DNS_SERVERS>"}) regex;
    var({addr, network, netmask, range_start, range_end, routers_str, dns_servers_str}) replace;
    regex_replace(config_template, regex, replace) config_data;

    # Write dhcp.conf.
    file_write(dhcp_conf_path, config_data);

    # Start dhcpd.
    daemon({"/usr/sbin/dhcpd", "-f", "-cf", dhcp_conf_path, "-user", "dhcp", "-group", "dhcp", "--no-pid", "-lf", leases_file});
}