{ pkgs
, inputs
, system
, lib
, ...
}:
let
  quickshell_bar = inputs.quickshell_bar.packages.${system}.default;
  att_wm = inputs.att_wm.packages.${system}.default;

  cliphist_river = pkgs.writeShellScriptBin "cliphist_river" ''
    ${lib.getExe pkgs.cliphist} list | \
    ${lib.getExe pkgs.wofi} --dmenu --insensitive | \
    ${lib.getExe pkgs.cliphist} decode | \
    ${pkgs.wl-clipboard}/bin/wl-copy
  '';

  screenshot_clip = pkgs.writeShellScriptBin "screenshot_clip" ''
    GEOM="$(${lib.getExe pkgs.slurp} -d)"
    ${lib.getExe pkgs.grim} -g "$GEOM" - | ${pkgs.wl-clipboard}/bin/wl-copy
  '';
in
{
  # att_wm is configured at compile time, dwm-style — there is no config file to
  # generate here, and the bindings live in its own src/config.zig (Alt as mod,
  # nine tags, master/monocle/tabbed). To override them without forking, build
  # with a replacement config:
  #   inputs.att_wm.packages.${system}.default.override { configFile = ./config.zig; }
  #
  # It spawns `foot` and `wmenu-run` by bare name, so both have to be on PATH;
  # cliphist_river and screenshot_clip are here for a future config.zig to spawn
  # the same way. The package also carries att_wmctl, the CLI that drives the
  # window manager over its IPC socket.
  home.packages = [
    att_wm
    pkgs.wmenu
    cliphist_river
    screenshot_clip
  ];

  # river runs $XDG_CONFIG_HOME/river/init at startup if it is executable, and
  # that is the whole of river's configuration surface — it implements no
  # window management itself, that is att_wm over river-window-management-v1.
  xdg.configFile."river/init" = {
    executable = true;
    text = ''
      #!${pkgs.runtimeShell}

      # greetd discards the session's stdio, and river/att_wm log to stderr only
      # — without this a failing window manager is a silent blank screen.
      log="''${XDG_STATE_HOME:-$HOME/.local/state}/river.log"
      mkdir -p "$(dirname "$log")"
      exec >>"$log" 2>&1
      echo "=== river init $(date -Is) ==="

      # river's session file sets no DesktopNames, so the portal backend
      # (xdg.portal.config.river in fuji/configuration.nix) needs this.
      export XDG_CURRENT_DESKTOP=river
      export XDG_SESSION_TYPE=wayland

      # Hand the session env to systemd/D-Bus, then bring up the target the
      # user services hang off — same dance the home-manager sway module does.
      ${pkgs.dbus}/bin/dbus-update-activation-environment --systemd \
        DISPLAY WAYLAND_DISPLAY XDG_CURRENT_DESKTOP XDG_SESSION_TYPE \
        NIXOS_OZONE_WL XCURSOR_THEME XCURSOR_SIZE
      systemctl --user reset-failed
      systemctl --user start river-session.target


      # The bar (same one sway and hyprland use) picks its backend from the
      # environment alone: with no $HYPRLAND_INSTANCE_SIGNATURE and no
      # $SWAYSOCK/$I3SOCK it falls through to att_wm, so nothing needs setting
      # here. It retries the connection every second, which is why starting it
      # before att_wm is fine — and why it must start after river exported
      # WAYLAND_DISPLAY, since that name is part of the socket path. Both sides
      # derive $XDG_RUNTIME_DIR/att_wm-$WAYLAND_DISPLAY.sock independently, so
      # nothing here has to agree on it.
      ${quickshell_bar}/bin/quickshell-bar &
      bar=$!

      # att_wm comes from the flake input (git.project-cloud.net/asmir/att_wm),
      # so the session runs exactly the revision flake.lock pins. Iterating on
      # it now means `nix flake update att_wm` + rebuild; to test a working tree
      # without that, run it under a nested river via the repo's run-nested.sh.
      #
      # Not exec'd: when att_wm exits we still want to tear the target down.
      # att_wm's Alt+Ctrl+Shift+q (exit_session) ends river itself.
      echo "starting ${lib.getExe att_wm}"
      ${lib.getExe att_wm}
      echo "=== att_wm exited with $? at $(date -Is) ==="

      # The bar is a child of this script rather than of att_wm, so it outlives
      # it: reap it here so an att_wm exit doesn't leave a bar floating over a
      # session with no window manager.
      kill "$bar" 2>/dev/null || true

      systemctl --user stop river-session.target
    '';
  };


  systemd.user.targets.river-session = {
    Unit = {
      Description = "river compositor session";
      Documentation = [ "man:systemd.special(7)" ];
      BindsTo = [ "graphical-session.target" ];
      Wants = [ "graphical-session-pre.target" ];
      After = [ "graphical-session-pre.target" ];
    };
  };
}