# Evaluation-time tests: broken configs must fail with exactly the expected
# assertion messages, and a valid one with none.
{ self, pkgs }:
let
  inherit (pkgs) lib;

  evalRouter =
    router:
    (import "${pkgs.path}/nixos/lib/eval-config.nix" {
      system = "x86_64-linux";
      modules = [
        self.nixosModules.router
        {
          boot.loader.grub.enable = false;
          fileSystems."/" = {
            device = "x";
            fsType = "ext4";
          };
          system.stateVersion = "25.05";
          router = lib.recursiveUpdate {
            enable = true;
            wan.interface = "eth0";
          } router;
        }
      ];
    }).config;

  lan = overrides: lib.recursiveUpdate {
    interface = "eth1";
    ipv4.address = "192.168.10.1";
    dhcp.pool = { start = "192.168.10.100"; end = "192.168.10.199"; };
  } overrides;

  failed = router: map (a: a.message) (lib.filter (a: !a.assertion) (evalRouter router).assertions);

  cases = {
    valid = { router.lans.main = lan { }; expect = [ ]; };
    noManagement = {
      router.lans.main = lan { allowManagement = false; };
      expect = [ "locked out" ];
    };
    wanIsLan = {
      router.lans.main = lan { interface = "eth0"; };
      expect = [ "WAN interface `eth0` is also used by a LAN" ];
    };
    sharedInterface = {
      router.lans = {
        a = lan { };
        b = lan { ipv4.address = "192.168.20.1"; dhcp.pool = { start = "192.168.20.100"; end = "192.168.20.199"; }; };
      };
      expect = [ "two LANs share the same interface" ];
    };
    badAddress = {
      router.lans.main = lan { ipv4.address = "192.168.10.300"; dhcp.enable = false; };
      expect = [ "`192.168.10.300` is not a valid IPv4 address" ];
    };
    poolOutsideSubnet = {
      router.lans.main = lan { dhcp.pool = { start = "192.168.11.100"; end = "192.168.11.199"; }; };
      expect = [ "pool is not inside 192.168.10.0/24" ];
    };
    poolReversed = {
      router.lans.main = lan { dhcp.pool = { start = "192.168.10.199"; end = "192.168.10.100"; }; };
      expect = [ "starts after it ends" ];
    };
    poolContainsRouter = {
      router.lans.main = lan { dhcp.pool = { start = "192.168.10.1"; end = "192.168.10.50"; }; };
      expect = [ "contains the router's own address 192.168.10.1" ];
    };
    overlappingLans = {
      router.lans = {
        a = lan { };
        b = lan { interface = "eth2"; ipv4.address = "192.168.10.2"; };
      };
      expect = [ "`a` (192.168.10.0/24) and `b` (192.168.10.0/24) overlap" ];
    };
    pdOnOneLan = {
      router = {
        wan.ipv6.enable = true;
        lans.main = lan { ipv6.pd = true; };
      };
      expect = [ ];
    };
    pdOnTwoLans = {
      router = {
        wan.ipv6.enable = true;
        lans = {
          a = lan { ipv6.pd = true; };
          b = lan {
            interface = "eth2";
            ipv4.address = "192.168.20.1";
            dhcp.pool = { start = "192.168.20.100"; end = "192.168.20.199"; };
            ipv6.pd = true;
          };
        };
      };
      expect = [ "delegated /64 cannot be split" ];
    };
    pdWithoutWanIpv6 = {
      router.lans.main = lan { ipv6.pd = true; };
      expect = [ "router.wan.ipv6.enable is false" ];
    };
    pppoeMissingCredentials = {
      router = {
        wan.ipv4.type = "pppoe";
        lans.main = lan { };
      };
      expect = [
        "pppoe.username must be set"
        "pppoe.passwordFile must be set"
      ];
    };
    pppoeValid = {
      router = {
        wan = {
          ipv4 = {
            type = "pppoe";
            pppoe = {
              vlan = 7;
              username = "user@isp";
              passwordFile = "/var/lib/secrets/pppoe";
            };
          };
          ipv6.enable = true;
        };
        lans.main = lan { ipv6.pd = true; };
      };
      expect = [ ];
    };
    nonOverlappingLans = {
      router.lans = {
        a = lan { };
        b = lan { interface = "eth2"; ipv4.address = "192.168.20.1"; dhcp.pool = { start = "192.168.20.100"; end = "192.168.20.199"; }; };
      };
      expect = [ ];
    };
  };

  problems = lib.concatLists (
    lib.mapAttrsToList (
      name: c:
      let
        got = failed c.router;
        missing = lib.filter (e: !lib.any (m: lib.hasInfix e m) got) c.expect;
      in
      lib.optional (missing != [ ] || lib.length got != lib.length c.expect)
        "${name}: expected ${builtins.toJSON c.expect}, got ${builtins.toJSON got}"
    ) cases
  );

  # Assertions alone do not force every option (e.g. networkd unit checks), so
  # fully evaluate the system for the configs that are meant to be valid.
  fullEval =
    name:
    let
      r = builtins.tryEval (builtins.seq (evalRouter cases.${name}.router).system.build.toplevel.drvPath true);
    in
    lib.optional (!r.success) "${name}: full system evaluation failed";
  fullEvalProblems = lib.concatMap fullEval [
    "valid"
    "pdOnOneLan"
    "pppoeValid"
  ];

  subnet = (evalRouter { lans.main = lan { ipv4.prefixLength = 20; ipv4.address = "172.16.37.1"; dhcp.enable = false; }; }).router.lans.main.ipv4.subnet;
  subnetProblem = lib.optional (subnet != "172.16.32.0/20") "derived subnet: expected 172.16.32.0/20, got ${subnet}";
in
pkgs.runCommand "router-assertion-tests" { } (
  if problems ++ subnetProblem ++ fullEvalProblems == [ ] then
    "touch $out"
  else
    ''
      printf '%s\n' ${lib.escapeShellArgs (problems ++ subnetProblem ++ fullEvalProblems)} >&2
      exit 1
    ''
)