# Automatic audio-output follow for docks / external monitors (#87 round
# 2). The WirePlumber priority rules (modules/nixos/dock-audio-rules.nix)
# only decide among sinks when there is NO stored user default — but
# WirePlumber persists every explicit pick (menu, pavucontrol, pactl) in
# its default-nodes state, and that stored default outranks priority. So
# on any machine where a device was ever picked, docking never moves the
# default — Bernardo's T14s dock test, 2026-07-12. This watcher makes the
# switch explicit: when a dock-class sink appears (same regexes as the
# wireplumber rules — imported from that file, single source of truth) it
# `pactl set-default-sink`s it and toasts. EasyEffects needs no handling:
# EE 8's useDefaultOutputDevice defaults to true, so its output follows
# the default device and effects stay in the chain (a user who pinned a
# device inside EE keeps their pin — that's an explicit choice). Unplug
# needs no handling either: the stored dock sink vanishes and WirePlumber
# falls back by priority to the built-in output. A manual pick made while
# docked sticks until the next plug event (a plug is treated as intent).
{ config, lib, pkgs, ... }:

let
  cfg   = config.nomarchy;
  rules = import ../nixos/dock-audio-rules.nix;
  dockSinkRe = lib.concatStringsSep "|"
    (map (m: lib.removePrefix "~" m."node.name")
      (lib.concatMap (r: r.matches) rules."monitor.alsa.rules"));

  watcher = pkgs.writeShellScript "nomarchy-dock-audio" ''
    set -euo pipefail
    PACTL=${pkgs.pulseaudio}/bin/pactl
    JQ=${pkgs.jq}/bin/jq
    TAB=$(printf '\t')

    # Self-gate: no PipeWire pulse socket (nomarchy.audio off, TTY-only
    # session) means nothing to watch — exit clean, stay dead.
    rt="''${XDG_RUNTIME_DIR:-/run/user/$(id -u)}"
    for _ in $(seq 60); do [ -e "$rt/pulse/native" ] && break; sleep 1; done
    [ -e "$rt/pulse/native" ] || exit 0

    is_dock() {
      printf '%s\n' "$1" | ${pkgs.gnugrep}/bin/grep -qE '^(${dockSinkRe})$'
    }

    switch_to() {  # $1 = sink node name, $2 = description
      [ "$($PACTL get-default-sink)" = "$1" ] && return 0
      $PACTL set-default-sink "$1" 2>/dev/null || return 0
      ${pkgs.libnotify}/bin/notify-send -a Nomarchy "Audio" \
        "Output → ''${2:-$1}" 2>/dev/null || true
    }

    # Startup sweep (login/relogin while already docked): adopt a dock
    # sink only when the current default is NOT one — a service restart
    # must not override a manual in-dock pick.
    if ! is_dock "$($PACTL get-default-sink)"; then
      $PACTL --format=json list sinks \
        | $JQ -r '.[] | "\(.name)\t\(.description)"' \
        | while IFS="$TAB" read -r name desc; do
            if is_dock "$name"; then switch_to "$name" "$desc"; break; fi
          done
    fi

    # Event loop: `pactl subscribe` prints "Event 'new' on sink #NN".
    LC_ALL=C $PACTL subscribe | while read -r _ ev _ kind id; do
      [ "$ev" = "'new'" ] && [ "$kind" = "sink" ] || continue
      id=''${id#\#}
      case "$id" in *[!0-9]*|"") continue ;; esac
      sleep 0.5   # let the node's description/routes settle
      line=$($PACTL --format=json list sinks | $JQ -r --argjson i "$id" \
               '.[] | select(.index == $i) | "\(.name)\t\(.description)"')
      [ -n "$line" ] || continue
      name=''${line%%"$TAB"*}; desc=''${line#*"$TAB"}
      if is_dock "$name"; then switch_to "$name" "$desc"; fi
    done
  '';
in
{
  config = lib.mkIf cfg.dockAudio.enable {
    systemd.user.services.nomarchy-dock-audio = {
      Unit = {
        Description = "Move the default audio sink to dock/monitor outputs on hotplug";
        After  = [ "graphical-session.target" ];
        PartOf = [ "graphical-session.target" ];
      };
      Service = {
        ExecStart  = "${watcher}";
        Restart    = "on-failure";
        RestartSec = 2;
      };
      Install.WantedBy = [ "graphical-session.target" ];
    };
  };
}