feat: lokale Fernsteuerung per Named Pipe fuer das Stream Dock Plugin

Playback, Lautstaerke, Tab-Wechsel sowie list_playlists/play_playlist ueber
\.\pipe\Playtube.Remote.<Name>; Tests inklusive.

playtube/browser.py

@@ -21,8 +21,13 @@ from .audio_routing import SCRIPT_NAME as AUDIO_SCRIPT_NAME
 from .audio_routing import build_router_script
 from .chrome_shim import CHROME_FULL, CHROME_MAJOR, CHROME_SHIM_JS
 from .config import profile_dir
+from .media_control import LIST_PLAYLISTS_JS, MUSIC_PLAYLIST_URL, build_control_js
 from .media_probe import MEDIA_PROBE_JS, NEXT_TRACK_JS, PREV_TRACK_JS, TOGGLE_PLAYBACK_JS
 
+# Nach einem Fernsteuerungsbefehl den Status kurz darauf neu auslesen (Seite braucht einen
+# Moment, bis z.B. der neue Titel/Like-Status im DOM steht).
+_REFRESH_AFTER_COMMAND_MS = 300
+
 # Chrome-Versionsnummer, die exakt zur tatsaechlich in QtWebEngine eingebetteten
 # Chromium-Version passt (siehe QWebEngineCore.qWebEngineChromiumVersion()). Legacy-
 # User-Agent, die "Sec-CH-UA" Client-Hints (Header) UND navigator.userAgentData (JS,
@@ -180,6 +185,29 @@ class BrowserTab(QWebEngineView):
     def previous_track(self) -> None:
         self.page().runJavaScript(PREV_TRACK_JS)
 
+    def run_media_command(self, command: str, value: float = 0) -> None:
+        """Fuehrt einen Fernsteuerungsbefehl (siehe media_control.py) aus und liest den
+        Wiedergabestatus kurz danach neu aus, damit z.B. das Stream Dock den neuen Zustand
+        sofort statt erst beim naechsten 2-Sekunden-Poll sieht."""
+        self.page().runJavaScript(build_control_js(command, value))
+        QTimer.singleShot(_REFRESH_AFTER_COMMAND_MS, self._poll_media_state)
+
+    def list_playlists(self, callback) -> None:
+        """Ruft callback(list | None) mit den Playlists aus der Seitenleiste auf."""
+
+        def on_result(result) -> None:
+            try:
+                callback(json.loads(result) if isinstance(result, str) and result else None)
+            except json.JSONDecodeError:
+                callback(None)
+
+        self.page().runJavaScript(LIST_PLAYLISTS_JS, on_result)
+
+    def play_playlist(self, playlist_id: str) -> None:
+        """Oeffnet die Playlist (ID vorher in remote_control validiert); Autoplay startet
+        die Wiedergabe (PlaybackRequiresUserGesture ist aus)."""
+        self.load(QUrl(MUSIC_PLAYLIST_URL.format(playlist_id=playlist_id)))
+
     def _on_full_screen_requested(self, request) -> None:
         # Erlaubt echtes Fullscreen-Video (z.B. per YouTube-Fullscreen-Button).
         request.accept()

playtube/config.py

@@ -38,6 +38,9 @@ DEFAULT_CONFIG: dict[str, Any] = {
         "youtube_output": "",
         "music_output": "",
     },
+    # Lokale Fernsteuerung fuer das Stream-Dock-Plugin (Named Pipe, nur dieser Benutzer) -
+    # siehe playtube/remote_control.py.
+    "remote_control": {"enabled": True},
     "start_tab": "youtube",  # "youtube" oder "music"
     "home_youtube": "https://www.youtube.com/",
     "home_music": "https://music.youtube.com/",

playtube/mainwindow.py

@@ -24,6 +24,8 @@ from .audio_routing import sync_audio_permissions
 from .browser import BrowserTab, get_shared_profile
 from .config import APP_NAME
 from .discord_rpc import DiscordRPCWorker
+from .remote_control import build_state as build_remote_state
+from .remote_control import resolve_target as resolve_remote_target
 from .settings_tab import SettingsTab
 from .updater import UpdateChecker, UpdateInstaller
 
@@ -292,6 +294,43 @@ class MainWindow(QMainWindow):
         aus dem Tray, wenn Playtube ein zweites Mal gestartet wird."""
         self._show_and_raise()
 
+    # ------------------------------------------------- Fernsteuerung (remote_control.py)
+
+    def _browser_tabs_by_name(self) -> dict[str, BrowserTab]:
+        return {"youtube": self._youtube_tab, "music": self._music_tab}
+
+    def _visible_tab_name(self) -> str:
+        current = self._current_tab()
+        for name, tab in self._browser_tabs_by_name().items():
+            if current is tab:
+                return name
+        return "settings"
+
+    def _media_by_tab_name(self) -> dict[str, dict | None]:
+        return {name: self._latest_media.get(id(tab)) for name, tab in self._browser_tabs_by_name().items()}
+
+    def remote_state(self) -> dict:
+        return build_remote_state(APP_VERSION, self._visible_tab_name(), self._media_by_tab_name())
+
+    def remote_show(self) -> None:
+        self._show_and_raise()
+
+    def remote_switch_tab(self, target: str) -> None:
+        """"youtube"/"music" waehlt den Tab; "auto" wechselt zwischen beiden hin und her."""
+        if target == "auto":
+            target = "music" if self._visible_tab_name() == "youtube" else "youtube"
+        self._tabs.setCurrentWidget(self._browser_tabs_by_name()[target])
+
+    def remote_media_command(self, target: str, command: str, value: float) -> None:
+        name = resolve_remote_target(target, self._visible_tab_name(), self._media_by_tab_name())
+        self._browser_tabs_by_name()[name].run_media_command(command, value)
+
+    def remote_list_playlists(self, callback) -> None:
+        self._music_tab.list_playlists(callback)
+
+    def remote_play_playlist(self, playlist_id: str) -> None:
+        self._music_tab.play_playlist(playlist_id)
+
     def _quit(self) -> None:
         if self._rpc_worker is not None:
             self._rpc_worker.stop()

playtube/media_control.py

@@ -0,0 +1,156 @@
+"""JavaScript fuer die Fernsteuerung (siehe remote_control.py): baut pro Befehl ein kleines
+Skript, das im YouTube- bzw. YouTube-Music-Tab ausgefuehrt wird.
+
+Es werden ausschliesslich feste Skripte aus einer Whitelist erzeugt; der einzige
+variable Teil ist ein bereits validierter Zahlenwert (Sekunden/Lautstaerke), der als
+Zahl eingesetzt wird - fremder Text landet nie im Skript."""
+from __future__ import annotations
+
+import math
+
+# Gemeinsame Helfer: der YouTube-Player (#movie_player) bietet auf youtube.com UND
+# music.youtube.com eine API fuer Lautstaerke/Stummschaltung/Titelwechsel; das
+# <video>-Element dient als Fallback, falls die API (noch) nicht verfuegbar ist.
+_PRELUDE = r"""
+    var isMusic = location.hostname.indexOf('music.youtube.com') !== -1;
+    var video = document.querySelector('video');
+    var player = document.getElementById('movie_player');
+    function has(fn) { return player && typeof player[fn] === 'function'; }
+    function click(selectors) {
+        for (var i = 0; i < selectors.length; i++) {
+            var el = document.querySelector(selectors[i]);
+            if (el) { el.click(); return true; }
+        }
+        return false;
+    }
+    function clamp(v) { return Math.max(0, Math.min(100, Math.round(v))); }
+    function getVolume() {
+        if (has('getVolume')) { return player.getVolume(); }
+        return video ? video.volume * 100 : 0;
+    }
+    function unmute() {
+        if (has('unMute')) { player.unMute(); } else if (video) { video.muted = false; }
+    }
+    function mute() {
+        if (has('mute')) { player.mute(); } else if (video) { video.muted = true; }
+    }
+    function isMuted() {
+        if (has('isMuted')) { return player.isMuted(); }
+        return video ? video.muted : false;
+    }
+    function setVolume(v) {
+        v = clamp(v);
+        if (has('setVolume')) { player.setVolume(v); }
+        else if (video) { video.volume = v / 100; }
+        if (v > 0) { unmute(); }
+    }
+"""
+
+_NEXT_SELECTORS = (
+    "['ytmusic-player-bar .next-button', 'ytmusic-player-bar #next-button button', "
+    "'tp-yt-paper-icon-button.next-button', '.ytp-next-button']"
+)
+_PREV_SELECTORS = (
+    "['ytmusic-player-bar .previous-button', 'ytmusic-player-bar #previous-button button', "
+    "'tp-yt-paper-icon-button.previous-button', '.ytp-prev-button']"
+)
+_LIKE_SELECTORS = (
+    "['ytmusic-player-bar ytmusic-like-button-renderer #button-shape-like button', "
+    "'like-button-view-model button', '#segmented-like-button button']"
+)
+_DISLIKE_SELECTORS = (
+    "['ytmusic-player-bar ytmusic-like-button-renderer #button-shape-dislike button', "
+    "'dislike-button-view-model button', '#segmented-dislike-button button']"
+)
+
+# Befehl -> Skriptkoerper. "{value}" wird durch den validierten Zahlenwert ersetzt.
+_BODIES: dict[str, str] = {
+    "play_pause": "if (video) { video.paused ? video.play() : video.pause(); }",
+    "play": "if (video && video.paused) { video.play(); }",
+    "pause": "if (video && !video.paused) { video.pause(); }",
+    # YouTube (ohne Playlist) blendet den "Naechster"-Knopf teils aus -> Player-API.
+    "next": f"if (!click({_NEXT_SELECTORS}) && has('nextVideo')) {{ player.nextVideo(); }}",
+    # Ohne Vorgaenger springt "Zurueck" wie bei ueblichen Playern an den Anfang.
+    "previous": (
+        f"if (!click({_PREV_SELECTORS})) {{"
+        " if (video) { video.currentTime = 0; } }"
+    ),
+    "seek": (
+        "if (video && isFinite(video.currentTime)) {"
+        " var end = isFinite(video.duration) ? video.duration : video.currentTime + {value};"
+        " video.currentTime = Math.max(0, Math.min(end, video.currentTime + {value})); }"
+    ),
+    "volume_change": "setVolume(getVolume() + {value});",
+    "set_volume": "setVolume({value});",
+    "mute_toggle": "if (isMuted()) { unmute(); } else { mute(); }",
+    "like": f"click({_LIKE_SELECTORS});",
+    "dislike": f"click({_DISLIKE_SELECTORS});",
+    "shuffle": (
+        "if (isMusic) { click(['ytmusic-player-bar .shuffle', "
+        "'ytmusic-player-bar #shuffle-button', 'ytmusic-player-bar .shuffle-button']); }"
+    ),
+    # YouTube Music: Wiederholen-Modus durchschalten; YouTube: Video in Schleife an/aus.
+    "repeat": (
+        "if (isMusic) { click(['ytmusic-player-bar .repeat', "
+        "'ytmusic-player-bar #repeat-button', 'ytmusic-player-bar .repeat-button']); }"
+        " else if (video) { video.loop = !video.loop; }"
+    ),
+}
+
+MEDIA_COMMANDS = frozenset(_BODIES)
+
+# Liest die Playlists aus der Seitenleiste von YouTube Music. Die Eintraege sind keine
+# normalen Links: Ziel steht in den Polymer-Daten des Elements
+# (data.navigationEndpoint.browseEndpoint.browseId = "VL<Playlist-ID>"); Links
+# ("browse/VL<id>", "playlist?list=<id>") dienen nur als Fallback. Liefert einen
+# JSON-String (Objekte kommen ueber die runJavaScript()-Bruecke nicht zuverlaessig an,
+# siehe media_probe.py); die Daten gelten als fremd und werden in
+# remote_control.sanitize_playlists bereinigt.
+LIST_PLAYLISTS_JS = r"""
+(function() {
+    var out = [];
+    function idFromBrowseId(browseId) {
+        return (typeof browseId === 'string' && browseId.indexOf('VL') === 0) ? browseId.slice(2) : null;
+    }
+    function idFromHref(href) {
+        var m = /[?&]list=([A-Za-z0-9_-]+)/.exec(href || '') || /browse\/VL([A-Za-z0-9_-]+)/.exec(href || '');
+        return m ? m[1] : null;
+    }
+    function textOf(formatted) {
+        if (!formatted) { return ''; }
+        if (typeof formatted.simpleText === 'string') { return formatted.simpleText; }
+        return (formatted.runs || []).map(function(r) { return r.text || ''; }).join('');
+    }
+    var entries = document.querySelectorAll('ytmusic-guide-entry-renderer');
+    for (var i = 0; i < entries.length; i++) {
+        var el = entries[i];
+        var data = el.data || (el.__data && el.__data.data) || null;
+        var endpoint = data && data.navigationEndpoint;
+        var id = idFromBrowseId(endpoint && endpoint.browseEndpoint && endpoint.browseEndpoint.browseId);
+        if (!id) {
+            var link = el.querySelector('[href]');
+            id = idFromHref(link ? link.getAttribute('href') : '');
+        }
+        if (!id) { continue; }
+        var titleEl = el.querySelector('.title');
+        var title = textOf(data && data.formattedTitle) || (titleEl ? titleEl.textContent : '');
+        out.push({ id: id, title: (title || '').trim() });
+    }
+    return JSON.stringify(out);
+})();
+"""
+
+MUSIC_PLAYLIST_URL = "https://music.youtube.com/watch?list={playlist_id}"
+
+
+def build_control_js(command: str, value: float = 0) -> str:
+    """Liefert das Skript fuer `command`. Unbekannte Befehle oder nicht-endliche Werte
+    -> ValueError (die Wertebereiche prueft vorher remote_control.parse_request)."""
+    body = _BODIES.get(command)
+    if body is None:
+        raise ValueError(f"unbekannter Befehl: {command}")
+    number = float(value)
+    if not math.isfinite(number):
+        raise ValueError("value muss eine endliche Zahl sein")
+    # repr() einer endlichen float ist immer ein gueltiges JS-Zahlenliteral (z.B. -10.0).
+    return "(function() {" + _PRELUDE + body.replace("{value}", repr(number)) + "\n})();"

playtube/media_probe.py

@@ -105,6 +105,30 @@ MEDIA_PROBE_JS = r"""
         thumbnail = ytThumbnailUrl(videoId) || (imgY ? imgY.href : null);
     }
 
+    // Zusatzstatus fuer die Fernsteuerung (Stream-Dock-Plugin, siehe remote_control.py).
+    var player = document.getElementById('movie_player');
+    var volume = (player && typeof player.getVolume === 'function')
+        ? player.getVolume() : (video ? Math.round(video.volume * 100) : null);
+    var muted = (player && typeof player.isMuted === 'function')
+        ? player.isMuted() : (video ? video.muted : null);
+    function likeState() {
+        if (isMusic) {
+            var r = document.querySelector('ytmusic-player-bar ytmusic-like-button-renderer');
+            var s = r ? r.getAttribute('like-status') : null;
+            return s ? s.toLowerCase() : null;  // "like" | "dislike" | "indifferent"
+        }
+        var like = document.querySelector('like-button-view-model button, #segmented-like-button button');
+        var dislike = document.querySelector('dislike-button-view-model button, #segmented-dislike-button button');
+        if (like && like.getAttribute('aria-pressed') === 'true') { return 'like'; }
+        if (dislike && dislike.getAttribute('aria-pressed') === 'true') { return 'dislike'; }
+        return like ? 'indifferent' : null;
+    }
+    function repeatMode() {
+        if (!isMusic) { return video && video.loop ? 'ONE' : 'NONE'; }
+        var bar = document.querySelector('ytmusic-player-bar');
+        return bar ? (bar.getAttribute('repeat-mode') || bar.getAttribute('repeat-mode_') || null) : null;
+    }
+
     var timeInfo = isMusic ? musicTimeInfo() : youtubeTimeInfo();
     var currentTime = timeInfo ? timeInfo.current : (video ? video.currentTime : 0);
     var duration = timeInfo ? timeInfo.total : ((video && isFinite(video.duration)) ? video.duration : 0);
@@ -123,7 +147,11 @@ MEDIA_PROBE_JS = r"""
         playing: video ? (!video.paused && !video.ended && video.readyState > 2) : false,
         currentTime: currentTime,
         duration: duration,
-        hasVideo: !!video
+        hasVideo: !!video,
+        volume: volume,
+        muted: muted,
+        likeStatus: likeState(),
+        repeatMode: repeatMode()
     });
 })();
 """

playtube/remote_control.py

@@ -0,0 +1,300 @@
+"""Lokale Fernsteuerung fuer externe Tools - z.B. das Stream-Dock-Plugin
+(com.fojadrachi.playtube.sdPlugin).
+
+Transport: ein QLocalServer (Named Pipe unter Windows, z.B. \\\\.\\pipe\\Playtube.Remote.Playtube)
+- nur lokal erreichbar, kein offener Netzwerk-Port. Getrennt vom Einzelinstanz-Pipe
+(single_instance.py), damit ein Steuerbefehl nie das Fenster nach vorne holt und aeltere
+Playtube-Versionen nicht faelschlich reagieren.
+
+Protokoll (eine JSON-Nachricht pro Zeile, UTF-8, "\\n"-getrennt, Verbindung bleibt offen):
+
+    -> {"id": 1, "cmd": "play_pause", "target": "auto"}
+    <- {"id": 1, "ok": true}
+    -> {"id": 2, "cmd": "status"}
+    <- {"id": 2, "ok": true, "state": {...}}
+    <- {"id": 3, "ok": false, "error": "..."}
+
+Playlists (nur YouTube Music):
+
+    -> {"id": 4, "cmd": "list_playlists"}
+    <- {"id": 4, "ok": true, "playlists": [{"id": "LM", "title": "Titel, die ich mag"}, ...]}
+    -> {"id": 5, "cmd": "play_playlist", "playlist": "PL..."}
+
+`cmd` stammt aus einer festen Whitelist (APP_COMMANDS + media_control.MEDIA_COMMANDS),
+`target` ist "auto" | "youtube" | "music", `value` eine Zahl mit befehlsabhaengigem
+Wertebereich. Beliebiges JavaScript oder URLs lassen sich bewusst NICHT senden.
+"""
+from __future__ import annotations
+
+import json
+import math
+import re
+from dataclasses import dataclass
+from typing import Any, Callable, Protocol
+
+from PySide6.QtCore import QObject
+from PySide6.QtNetwork import QLocalServer, QLocalSocket
+
+from .debug_log import log_exception
+from .media_control import MEDIA_COMMANDS
+
+PROTOCOL_VERSION = 1
+PIPE_PREFIX = "Playtube.Remote."
+
+MAX_LINE_BYTES = 4096
+MAX_CLIENTS = 8
+
+TAB_NAMES = ("youtube", "music")
+TARGETS = frozenset({"auto", *TAB_NAMES})
+APP_COMMANDS = frozenset({"status", "show", "switch_tab", "list_playlists", "play_playlist"})
+
+# Playlist-IDs (z.B. "PL...", "OLAK5uy_...", "LM") - landen in einer URL, daher streng.
+PLAYLIST_ID_RE = re.compile(r"^[A-Za-z0-9_-]{2,64}$")
+LIKED_MUSIC = {"id": "LM", "title": "Titel, die ich mag"}
+MAX_PLAYLISTS = 100
+MAX_PLAYLIST_TITLE = 100
+
+# Befehl -> (min, max) fuer `value`; Befehle ohne Eintrag ignorieren `value`.
+_VALUE_RANGES: dict[str, tuple[float, float]] = {
+    "seek": (-3600, 3600),
+    "volume_change": (-100, 100),
+    "set_volume": (0, 100),
+}
+
+# Nur diese Felder des Media-Probes (media_probe.py) werden nach aussen gegeben.
+_STATE_FIELDS = (
+    "isMusic", "title", "subtitle", "thumbnail", "playing", "currentTime", "duration",
+    "hasVideo", "volume", "muted", "likeStatus", "repeatMode",
+)
+
+
+class ProtocolError(ValueError):
+    """Ungueltige Anfrage - wird dem Client als {"ok": false, "error": ...} gemeldet."""
+
+
+@dataclass(frozen=True)
+class Request:
+    id: Any
+    command: str
+    target: str = "auto"
+    value: float = 0
+    playlist: str | None = None
+
+
+class RemoteController(Protocol):
+    """Was der Server von der App braucht (implementiert von MainWindow)."""
+
+    def remote_state(self) -> dict: ...
+    def remote_show(self) -> None: ...
+    def remote_switch_tab(self, target: str) -> None: ...
+    def remote_media_command(self, target: str, command: str, value: float) -> None: ...
+    def remote_list_playlists(self, callback: Callable[[Any], None]) -> None: ...
+    def remote_play_playlist(self, playlist_id: str) -> None: ...
+
+
+def parse_request(line: str) -> Request:
+    """Parst und validiert eine Anfragezeile. Wirft ProtocolError bei jedem Fehler."""
+    try:
+        data = json.loads(line)
+    except json.JSONDecodeError as exc:
+        raise ProtocolError("ungueltiges JSON") from exc
+    if not isinstance(data, dict):
+        raise ProtocolError("Anfrage muss ein JSON-Objekt sein")
+
+    request_id = data.get("id")
+    if isinstance(request_id, bool) or (
+        request_id is not None and not isinstance(request_id, (int, str))
+    ):
+        raise ProtocolError("id muss Zahl oder Text sein")
+
+    command = data.get("cmd")
+    if not isinstance(command, str) or (
+        command not in APP_COMMANDS and command not in MEDIA_COMMANDS
+    ):
+        raise ProtocolError(f"unbekannter Befehl: {command!r}")
+
+    target = data.get("target", "auto")
+    if not isinstance(target, str) or target not in TARGETS:
+        raise ProtocolError(f"unbekanntes Ziel: {target!r}")
+
+    playlist = None
+    if command == "play_playlist":
+        playlist = data.get("playlist")
+        if not isinstance(playlist, str) or not PLAYLIST_ID_RE.fullmatch(playlist):
+            raise ProtocolError("play_playlist braucht eine gueltige Playlist-ID")
+
+    return Request(
+        id=request_id,
+        command=command,
+        target=target,
+        value=_parse_value(command, data),
+        playlist=playlist,
+    )
+
+
+def _parse_value(command: str, data: dict) -> float:
+    value_range = _VALUE_RANGES.get(command)
+    if value_range is None:
+        return 0
+    raw = data.get("value")
+    # bool ist in Python ein int - true/false sind hier aber kein sinnvoller Wert.
+    if isinstance(raw, bool) or not isinstance(raw, (int, float)) or not math.isfinite(raw):
+        raise ProtocolError(f"{command} braucht einen Zahlenwert")
+    low, high = value_range
+    if not low <= raw <= high:
+        raise ProtocolError(f"{command}: Wert muss zwischen {low:g} und {high:g} liegen")
+    return float(raw)
+
+
+Reply = Callable[[dict], None]
+
+
+def handle_request(request: Request, controller: RemoteController, reply: Reply) -> None:
+    """Fuehrt eine gueltige Anfrage aus und meldet die Antwort (ohne id) ueber `reply` -
+    sofort, oder bei list_playlists sobald die Seite geantwortet hat."""
+    if request.command == "status":
+        reply({"ok": True, "state": controller.remote_state()})
+        return
+    if request.command == "list_playlists":
+        controller.remote_list_playlists(
+            lambda raw: reply({"ok": True, "playlists": sanitize_playlists(raw)})
+        )
+        return
+    if request.command == "show":
+        controller.remote_show()
+    elif request.command == "switch_tab":
+        controller.remote_switch_tab(request.target)
+    elif request.command == "play_playlist":
+        controller.remote_play_playlist(request.playlist)
+    else:
+        controller.remote_media_command(request.target, request.command, request.value)
+    reply({"ok": True})
+
+
+def sanitize_playlists(raw: Any) -> list[dict]:
+    """Bereinigt die von der Seite gelieferte Liste (fremde Daten!): nur gueltige IDs,
+    Titel als gekuerzter Text, ohne Duplikate, "Titel, die ich mag" immer zuerst."""
+    result = [dict(LIKED_MUSIC)]
+    seen = {LIKED_MUSIC["id"]}
+    for item in raw if isinstance(raw, list) else []:
+        if len(result) >= MAX_PLAYLISTS:
+            break
+        if not isinstance(item, dict):
+            continue
+        playlist_id, title = item.get("id"), item.get("title")
+        if not isinstance(playlist_id, str) or not PLAYLIST_ID_RE.fullmatch(playlist_id):
+            continue
+        if playlist_id in seen:
+            continue
+        seen.add(playlist_id)
+        clean_title = " ".join(title.split())[:MAX_PLAYLIST_TITLE] if isinstance(title, str) else ""
+        result.append({"id": playlist_id, "title": clean_title or playlist_id})
+    return result
+
+
+def resolve_target(target: str, visible_tab: str | None, tabs: dict[str, dict | None]) -> str:
+    """Welcher Tab einen Medienbefehl bekommt. "auto": der Tab, der gerade abspielt
+    (spielen beide, der sichtbare), sonst der sichtbare Browser-Tab, sonst der mit einem
+    Video, sonst YouTube."""
+    if target in TAB_NAMES:
+        return target
+    playing = [name for name in TAB_NAMES if (tabs.get(name) or {}).get("playing")]
+    if len(playing) == 1:
+        return playing[0]
+    if visible_tab in TAB_NAMES:
+        return visible_tab
+    with_video = [name for name in TAB_NAMES if (tabs.get(name) or {}).get("hasVideo")]
+    return with_video[0] if with_video else TAB_NAMES[0]
+
+
+def build_state(version: str, visible_tab: str | None, tabs: dict[str, dict | None]) -> dict:
+    """Status-Antwort: pro Tab die oeffentlichen Probe-Felder plus der "auto"-Zieltab."""
+    public_tabs = {}
+    for name in TAB_NAMES:
+        info = tabs.get(name)
+        public_tabs[name] = {key: info.get(key) for key in _STATE_FIELDS} if info else None
+    return {
+        "protocol": PROTOCOL_VERSION,
+        "version": version,
+        "visibleTab": visible_tab,
+        "activeTab": resolve_target("auto", visible_tab, tabs),
+        "tabs": public_tabs,
+    }
+
+
+def encode_response(request_id: Any, response: dict) -> bytes:
+    return (json.dumps({"id": request_id, **response}, ensure_ascii=False) + "\n").encode("utf-8")
+
+
+def process_line(line: str, controller: RemoteController, write: Callable[[bytes], None]) -> None:
+    """Eine Anfragezeile -> genau eine kodierte Antwortzeile ueber `write`. Wirft nie."""
+    try:
+        request = parse_request(line)
+    except ProtocolError as exc:
+        write(encode_response(None, {"ok": False, "error": str(exc)}))
+        return
+    try:
+        handle_request(request, controller, lambda response: write(encode_response(request.id, response)))
+    except Exception as exc:  # noqa: BLE001 - ein Steuerbefehl darf die App nie abstuerzen lassen
+        log_exception(f"remote_control: {request.command}", exc)
+        write(encode_response(request.id, {"ok": False, "error": "interner Fehler"}))
+
+
+class RemoteControlServer(QObject):
+    """Lauscht auf der Named Pipe und beantwortet Anfragen im Qt-Hauptthread (die
+    Controller-Methoden fassen Widgets an und duerfen nur dort laufen)."""
+
+    def __init__(self, key: str, controller: RemoteController, parent: QObject | None = None) -> None:
+        super().__init__(parent)
+        self._key = key
+        self._controller = controller
+        self._server: QLocalServer | None = None
+        self._buffers: dict[QLocalSocket, bytearray] = {}
+
+    def start(self) -> bool:
+        server = QLocalServer(self)
+        # Nur der angemeldete Benutzer darf verbinden (Windows: Pipe-ACL).
+        server.setSocketOptions(QLocalServer.SocketOption.UserAccessOption)
+        if not server.listen(self._key):
+            log_exception("remote_control: listen", RuntimeError(server.errorString()))
+            return False
+        server.newConnection.connect(self._on_new_connection)
+        self._server = server
+        return True
+
+    def _on_new_connection(self) -> None:
+        while self._server is not None and self._server.hasPendingConnections():
+            socket = self._server.nextPendingConnection()
+            if len(self._buffers) >= MAX_CLIENTS:
+                socket.disconnectFromServer()
+                socket.deleteLater()
+                continue
+            self._buffers[socket] = bytearray()
+            socket.readyRead.connect(lambda s=socket: self._on_ready_read(s))
+            socket.disconnected.connect(lambda s=socket: self._on_disconnected(s))
+
+    def _on_ready_read(self, socket: QLocalSocket) -> None:
+        buffer = self._buffers.get(socket)
+        if buffer is None:
+            return
+        buffer.extend(bytes(socket.readAll().data()))
+        while (newline := buffer.find(b"\n")) >= 0:
+            raw = bytes(buffer[:newline])
+            del buffer[: newline + 1]
+            line = raw.decode("utf-8", errors="replace").strip()
+            if line:
+                process_line(line, self._controller, lambda data, s=socket: self._write(s, data))
+        if len(buffer) > MAX_LINE_BYTES:
+            # Kein Zeilenende in Sicht: Client verhaelt sich falsch -> trennen.
+            buffer.clear()
+            socket.write(encode_response(None, {"ok": False, "error": "Nachricht zu lang"}))
+            socket.disconnectFromServer()
+
+    def _write(self, socket: QLocalSocket, data: bytes) -> None:
+        # Asynchrone Antworten (list_playlists) koennen nach dem Trennen eintreffen.
+        if socket in self._buffers:
+            socket.write(data)
+
+    def _on_disconnected(self, socket: QLocalSocket) -> None:
+        self._buffers.pop(socket, None)
+        socket.deleteLater()