nixos/hosts/yarn/default.nix

{
  pkgs,
  lib,
  username,
  inputs,
  site_config,
  ...
}:
{
  imports = [
    ../../modules/desktop-common.nix
    ../../modules/desktop-jovian.nix
    ../../modules/no-rgb.nix
    ./disk.nix
    ./impermanence.nix
    ./lact.nix
    ./vr.nix
    ./forza-trigger
    ../../modules/desktop-game-mods.nix

    inputs.impermanence.nixosModules.impermanence
  ];

  fileSystems."/media/games" = {
    device = "/dev/disk/by-uuid/1878136e-765d-4784-b204-3536ab4fdac8";
    fsType = "f2fs";
    options = [ "nofail" ];
  };

  systemd.targets = {
    sleep.enable = false;
    suspend.enable = false;
    hibernate.enable = false;
    hybrid-sleep.enable = false;
  };

  networking.hostId = "abf570f9";

  # Static IP for consistent SSH access
  networking.networkmanager.ensureProfiles.profiles.enp7s0-static = {
    connection = {
      id = "enp7s0-static";
      type = "ethernet";
      interface-name = "enp7s0";
      autoconnect = true;
    };
    ipv4 = {
      method = "manual";
      address1 = "${site_config.hosts.yarn.ip}/24,${site_config.lan.gateway}";
      dns = lib.concatMapStrings (n: "${n};") site_config.dns_servers;
    };
    ipv6.method = "disabled";
  };

  services.openssh = {
    enable = true;
    ports = [ 22 ];
    settings = {
      PasswordAuthentication = false;
      PermitRootLogin = "yes";
    };
  };

  users.users.${username}.openssh.authorizedKeys.keys = [
    site_config.ssh_keys.laptop
  ];

  users.users.root.openssh.authorizedKeys.keys = [
    site_config.ssh_keys.laptop
    site_config.ssh_keys.ci_deploy
  ];

  programs.steam = {
    remotePlay.openFirewall = true;
    localNetworkGameTransfers.openFirewall = true;
  };

  environment.systemPackages = [ pkgs.jovian-stubs ];

  # yarn is not a Steam Deck
  jovian.devices.steamdeck.enable = false;

  # PS5 DualSense adaptive triggers in Forza Horizon 4 / 5.
  services.forzaTrigger.enable = true;

  # Declarative game-file mods on top of Steam.
  #
  # fh5-no-intro: stub the 40 MB T10/Microsoft Studios cold-start splash.
  #   Two copies live in the install (SD + hires); engine picks one based on
  #   the installed asset profile, so stub both. PCGamingWiki documents both
  #   paths under "Skip intro video".
  #
  # fh5-optiscaler: drop OptiScaler v0.9.1 + a FH5-tuned OptiScaler.ini into
  #   the install dir to enable FSR 4 INT8 on this RDNA 3 Navi 32 box.
  #   OptiScaler intercepts FH5's DLSS/XeSS calls and reroutes them through
  #   the bundled FFX SDK. Settings flipped from upstream defaults:
  #     Fsr4Update         auto -> true   # FSR 4 path required for INT8 RDNA 3
  #     Dxgi               auto -> false  # FH5 wiki: required for 0.9
  #     DlssReactiveMaskBias auto -> 0.65 # FH5 wiki: fixes flickering lights, reduces car ghosting
  #
  #   Required one-time per-game setup in Steam (Proton picker is not
  #   declarable from NixOS; launch options are written declaratively below):
  #     1. Properties -> Compatibility: force "GE-Proton" (proton-ge-bin is
  #        already in extraCompatPackages; pick the latest installed).
  #        Steam must be closed when the launch options write happens, or
  #        Steam will overwrite our localconfig.vdf edit on shutdown.
  #     2. In-game: switch the Upscaling option from FSR 2.2 to DLSS or XeSS
  #        (FSR 2 inputs aren't intercepted). Press Insert to open the Opti
  #        overlay and set the FFX upscaler to FSR 4.
  #
  #   Caveats:
  #   - OptiScaler.ini is dropped with mode = "init" so in-game overlay edits
  #     persist. The awk-patched template below is only written on first apply
  #     (or after manual deletion). To push a new default into an existing
  #     install: rm OptiScaler.ini in the FH5 dir, then `systemctl start
  #     game-mods`. The DLLs and other static assets stay mode = "create" so
  #     they're updated on every OptiScaler version bump.
  #   - OptiScaler's installation page warns against use with online games.
  #     FH5 has no kernel-mode anti-cheat but Playground does server-side
  #     telemetry. Use at your own risk.
  #
  # fh5-vkd3d-no-hvv: append `VKD3D_CONFIG=no_upload_hvv` to FH5's launch
  #   options. Disables vkd3d-proton's host-visible VRAM upload heap, which
  #   works around a Proton stutter/crash on this box. Kept as its own mod
  #   (no files, just env) so the workaround can be removed independently of
  #   OptiScaler when a future Proton release fixes the underlying issue.
  services.gameMods =
    let
      optiPkg = pkgs.optiscaler;
      # OptiScaler.ini ships with CRLF line endings, so we use awk with explicit
      # RS/ORS to keep the rewrites line-ending agnostic. The regex is matched
      # against the CR-stripped record, the original CRLF is restored on output.
      optiIni = pkgs.runCommand "OptiScaler-fh5.ini" { } ''
        awk -v RS='\r\n' -v ORS='\r\n' '
          /^Fsr4Update=auto$/           { print "Fsr4Update=true"; next }
          /^Dxgi=auto$/                 { print "Dxgi=false"; next }
          /^DlssReactiveMaskBias=auto$/ { print "DlssReactiveMaskBias=0.65"; next }
          { print }
        ' ${optiPkg}/OptiScaler.ini > $out
      '';
      fromOpti = relpath: {
        source = "${optiPkg}/${relpath}";
        mode = "create";
      };
    in
    {
      enable = true;
      mods."fh5-no-intro" = {
        steamAppId = 1551360;
        files."media/UI/Videos/T10_MS_Combined.bk2".empty = true;
        files."media/UI/Videos/hires/T10_MS_Combined.bk2".empty = true;
      };
      mods."fh5-optiscaler" = {
        steamAppId = 1551360;
        # RDNA 3 (Navi 32) FSR 4 path on Linux:
        #   PROTON_FSR4_UPGRADE=1            opts FH5 into Proton's FSR 4 upgrade.
        #   DXIL_SPIRV_CONFIG=wmma_rdna3_... fixes broken visuals on RDNA 3 per
        #                                    the OptiScaler FSR4 wiki.
        # Other FH5-targeting mods (e.g. fh5-vkd3d-no-hvv) append their own
        # entries to this list; the module joins them and adds %command%.
        launchOptions = [
          "PROTON_FSR4_UPGRADE=1"
          "DXIL_SPIRV_CONFIG=wmma_rdna3_workaround"
        ];
        files = {
          # OptiScaler.dll is renamed to dxgi.dll so FH5's DLL search order
          # picks it up as the dxgi shim per the OptiScaler FH5 wiki page.
          "dxgi.dll" = fromOpti "OptiScaler.dll";
          "OptiScaler.ini" = {
            source = optiIni;
            # init: drop the patched template once, then leave it alone so
            # the in-game overlay can persist user tweaks.
            mode = "init";
          };
        }
        // lib.genAttrs [
          "D3D12_Optiscaler/D3D12Core.dll"
          "amd_fidelityfx_dx12.dll"
          "amd_fidelityfx_framegeneration_dx12.dll"
          "amd_fidelityfx_upscaler_dx12.dll"
          "amd_fidelityfx_vk.dll"
          "dlssg_to_fsr3_amd_is_better.dll"
          "fakenvapi.dll"
          "fakenvapi.ini"
          "libxell.dll"
          "libxess.dll"
          "libxess_dx11.dll"
          "libxess_fg.dll"
        ] fromOpti;
      };
      mods."fh5-vkd3d-no-hvv" = {
        steamAppId = 1551360;
        launchOptions = [ "VKD3D_CONFIG=no_upload_hvv" ];
      };
    };
}