let
  lib = import <nixpkgs/lib>;

  getDevices = net:
    if net ? devices && builtins.isAttrs net.devices then
      net.devices
    else
      throw "config/network.nix must define devices as an attrset.";

  getLocalDevices = devices:
    lib.filterAttrs (deviceName: device:
      if !builtins.isAttrs device then
        throw "Device '${deviceName}' must be an attrset."
      else if !(device ? type) || !builtins.isString device.type then
        throw "Device '${deviceName}' must define type as a string."
      else if !(device ? ip) || !builtins.isString device.ip || device.ip == "" then
        throw "Device '${deviceName}' must define ip as a non-empty string."
      else
        device.type == "local"
    ) devices;

  validateReservationShape = deviceName: reservation:
    let
      _ = if !builtins.isAttrs reservation then throw "Device '${deviceName}' reservation must be an attrset." else null;
      _hw =
        if reservation ? hw_address && builtins.isString reservation.hw_address && reservation.hw_address != "" then
          null
        else
          throw "Device '${deviceName}' reservation must define hw_address as a non-empty string.";
      _host =
        if reservation ? hostname && builtins.isString reservation.hostname && reservation.hostname != "" then
          null
        else
          throw "Device '${deviceName}' reservation must define hostname as a non-empty string.";
    in
      reservation;
in
{
  inherit getDevices getLocalDevices validateReservationShape;
}