# Night light — a scheduled blue-light filter via hyprsunset (Hyprland's own
# gamma/temperature tool). Warm at night, identity (no shift) by day;
# hyprsunset's time-based `profile` entries handle the schedule and pick the
# right state on session start. Opt-in via nomarchy.nightlight.enable.
#
# The hyprsunset HM service module is provided by home-manager; this only
# configures it. Override anything with plain services.hyprsunset.* options.
#
# nomarchy-nightlight is the menu/Waybar toggle: it starts/stops the hyprsunset
# *service* (so `systemctl --user is-active` is the single source of truth and
# the screen restores to true colours when stopped), letting you force the
# filter off for colour-sensitive work and back on without touching the config.
{ config, lib, pkgs, ... }:

let
  cfg = config.nomarchy.nightlight;

  # Toggle/status helper, on PATH so the menu and both the generated and
  # whole-swap Waybars can drive it by name. Self-gates: when the unit doesn't
  # exist (night-light not enabled) `status` prints nothing, so the Waybar
  # module hides itself — same pattern as the power-profile indicator.
  nomarchy-nightlight = pkgs.writeShellScriptBin "nomarchy-nightlight" ''
    unit=hyprsunset.service
    if ! systemctl --user cat "$unit" >/dev/null 2>&1; then
      [ "''${1:-}" = status ] && exit 0
      notify-send "Night light" "Not enabled — set nomarchy.nightlight.enable."
      exit 0
    fi
    case "''${1:-toggle}" in
      status)
        if systemctl --user is-active --quiet "$unit"; then
          printf '{"text":"󰖔","tooltip":"Night light on — warm on schedule (click to disable)","class":"on"}\n'
        else
          printf '{"text":"󰖙","tooltip":"Night light off (click to enable)","class":"off"}\n'
        fi ;;
      on)  systemctl --user start "$unit" ;;
      off) systemctl --user stop "$unit" ;;
      toggle)
        if systemctl --user is-active --quiet "$unit"; then
          systemctl --user stop "$unit"
          notify-send "Night light off" "Screen back to true colours."
        else
          systemctl --user start "$unit"
          notify-send "Night light on" "Warm filter follows your schedule."
        fi ;;
      *) echo "usage: nomarchy-nightlight [toggle|status|on|off]" >&2; exit 64 ;;
    esac
  '';
in
{
  config = {
    services.hyprsunset = lib.mkIf cfg.enable {
      enable = true;
      settings.profile = [
        # Daytime: identity = no colour change.
        { time = cfg.sunrise; identity = true; }
        # Night: shift to the warm temperature.
        { time = cfg.sunset; temperature = cfg.temperature; }
      ];
    };

    # Always on PATH (it self-gates at runtime), so a static whole-swap Waybar
    # can exec it even when night-light is off without the call failing.
    home.packages = [ nomarchy-nightlight ];
  };
}