# FredOS-Eee — Asus Eee PC 1000HG, a toy netbook running XFCE.
#
# Not built from common.nix: stylix, home-manager and hyprland would all
# compile from source for i686 (almost nothing is in cache.nixos.org for it)
# and wouldn't fit in 1GB anyway. Only locale + users are shared.
#
# Build on the server, never on the Eee — evaluating this flake alone would
# eat its 1GB.
{ config, lib, pkgs, ... }:
let
  serverKey = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIMbIdOSPjnJYQ7z7n0mHKo8T8PnAkCyIBCmT4KpsHyy/ fred@FredOS-Mediaserver";
in
{
  imports = [
    ../settings/locale.nix
    ../settings/users.nix
  ];

  nixpkgs.overlays = [
    (final: prev: {
      # partial-protected-regular-retry-linux fails on i686; the binary is fine.
      rsync = prev.rsync.overrideAttrs { doCheck = false; };
      # Tests need gjs -> spidermonkey, an hour+ of i686 compile for a check.
      libsecret = prev.libsecret.overrideAttrs { doCheck = false; };
      # libultrahdr misses -latomic on i686; icon themes only need plain convert.
      imagemagick = prev.imagemagick.override { libultrahdrSupport = false; };
      # nixpkgs' own i686 test patch no longer applies; it only touches tests.
      upower = prev.upower.overrideAttrs (o: {
        patches = lib.filter
          (p: !lib.hasSuffix "i686-test-remove-battery-check.patch" (toString p))
          o.patches;
        doCheck = false;
      });
      # 64-bit getint64 tests fail on 32-bit.
      iniparser = prev.iniparser.overrideAttrs { doCheck = false; };
    })
  ];

  # Portals (flatpak-style sandbox plumbing) drag in gnome-settings-daemon,
  # cinnamon-desktop and pulseaudio. Nothing here needs them.
  xdg.portal.enable = lib.mkForce false;
  # Plain gvfs: no gnome-online-accounts.
  services.gvfs.package = pkgs.gvfs;

  nix.settings.experimental-features = [ "nix-command" "flakes" ];
  networking.networkmanager.enable = true;

  services.xserver.enable = true;
  # IceWM (taskbar, tray and start menu in one small binary) to leave the RAM
  # for the browser; nm-applet in its tray for wifi. XFCE stays as a fallback
  # session in the login screen's chooser (log out to reach it).
  services.xserver.windowManager.icewm.enable = true;
  services.displayManager.defaultSession = "none+icewm";
  programs.nm-applet.enable = true;
  programs.nm-applet.indicator = false; # IceWM's tray is XEmbed, not appindicator
  services.xserver.desktopManager.xfce.enable = true;
  # Thunar thumbnails: tumbler -> libgepub -> webkitgtk, hours of i686 compile.
  services.tumbler.enable = lib.mkForce false;
  services.displayManager.autoLogin = {
    enable = true;
    user = "fred";
  };

  services.openssh.enable = true;
  # The server's key, so it can push closures and poke at the box. Root too:
  # `eee-update` copies unsigned closures, which only a trusted user may do.
  users.users.fred.openssh.authorizedKeys.keys = [ serverKey ];
  users.users.root.openssh.authorizedKeys.keys = [ serverKey ];

  # The Eee lives on other people's networks, so the server can't reach it.
  # Instead it holds a reverse tunnel open: server's localhost:2222 -> Eee:22
  # (`ssh eee` there). The key is made here on first start and only allowed
  # to open that one forward (hosts/FredOS-Mediaserver.nix). Plain ssh +
  # Restart=always covers reconnects; ExitOnForwardFailure retries while the
  # server still holds a dead session's port.
  systemd.services.server-tunnel = {
    wantedBy = [ "multi-user.target" ];
    wants = [ "network-online.target" ];
    after = [ "network-online.target" ];
    serviceConfig = {
      StateDirectory = "server-tunnel";
      Restart = "always";
      RestartSec = 30;
    };
    preStart = ''
      [ -f $STATE_DIRECTORY/id_ed25519 ] || \
        ${pkgs.openssh}/bin/ssh-keygen -q -t ed25519 -N "" -C "eee-tunnel" -f $STATE_DIRECTORY/id_ed25519
    '';
    script = ''
      exec ${pkgs.openssh}/bin/ssh -N -i $STATE_DIRECTORY/id_ed25519 \
        -o ServerAliveInterval=30 -o ServerAliveCountMax=3 -o ExitOnForwardFailure=yes \
        -o StrictHostKeyChecking=accept-new -o UserKnownHostsFile=$STATE_DIRECTORY/known_hosts \
        -R 2222:localhost:22 fred@nordhammer.it
    '';
  };

  # Firefox is marked unsupported on i686 (Mozilla dropped 32-bit Linux), so
  # WebKit is the only engine left that handles the modern web.
  # NetSurf: no JavaScript, so news sites load as plain pages on this CPU.
  environment.systemPackages = [
    pkgs.epiphany
    pkgs.netsurf-browser
    # netsurf ships no .desktop file, so it's missing from the menu.
    (pkgs.makeDesktopItem {
      name = "netsurf";
      desktopName = "NetSurf";
      exec = "netsurf-gtk3 %u";
      icon = "web-browser";
      categories = [ "Network" "WebBrowser" ];
    })
  ];

  # 1GB RAM: compressed swap only (disk swap is off, see hardware file).
  zramSwap.enable = true;
  # A heavy page (bbc.co.uk) used to freeze everything; now the biggest
  # process (the browser's web process) dies instead. zram lives in RAM, so
  # swap never looks full: judge on RAM alone.
  services.earlyoom.enable = true;
  services.earlyoom.freeSwapThreshold = 100;
  # Even with no disk swap it still froze: the kernel kept evicting and
  # re-reading program code from disk. MGLRU's min_ttl OOM-kills instead
  # when it can't keep the last 1s of working set in RAM.
  systemd.tmpfiles.rules = [ "w /sys/kernel/mm/lru_gen/min_ttl_ms - - - - 1000" ];

  # The NixOS manual is a big from-source build on i686 for a page nobody reads.
  documentation.nixos.enable = false;
}