{ config, lib, pkgs, ... }:

with lib;

let
  cfg = config.nix-nos.routing;

  routeType = types.submodule {
    options = {
      destination = mkOption {
        type = types.str;
        description = "Destination network in CIDR notation";
        example = "192.168.100.0/24";
      };

      gateway = mkOption {
        type = types.nullOr types.str;
        default = null;
        description = "Gateway IP address (null for blackhole routes)";
        example = "192.168.1.1";
      };

      interface = mkOption {
        type = types.nullOr types.str;
        default = null;
        description = "Outbound interface name";
        example = "eth0";
      };

      metric = mkOption {
        type = types.nullOr types.int;
        default = null;
        description = "Route metric/preference";
      };
    };
  };

in {
  options.nix-nos.routing = {
    staticRoutes = mkOption {
      type = types.listOf routeType;
      default = [];
      description = "Static route configurations";
      example = literalExpression ''
        [
          {
            destination = "10.0.0.0/8";
            gateway = "192.168.1.1";
            interface = "eth0";
          }
          {
            destination = "192.0.2.0/24";
            gateway = null;  # blackhole route
          }
        ]
      '';
    };
  };

  config = mkIf (config.nix-nos.enable && cfg.staticRoutes != []) {
    # Add static routes using NixOS networking.localCommands
    networking.localCommands = concatMapStringsSep "\n" (route:
      let
        routeCmd = "${pkgs.iproute2}/bin/ip route add ${route.destination}";
        viaClause = optionalString (route.gateway != null) " via ${route.gateway}";
        devClause = optionalString (route.interface != null) " dev ${route.interface}";
        metricClause = optionalString (route.metric != null) " metric ${toString route.metric}";
        blackholeClause = optionalString (route.gateway == null && route.interface == null) " blackhole";
      in
      "${routeCmd}${viaClause}${devClause}${metricClause}${blackholeClause} || true"
    ) cfg.staticRoutes;
  };
}