from __future__ import annotations

import re
import shutil
import subprocess
import threading
import uuid
from pathlib import Path

from flask import (
    Blueprint,
    Response,
    current_app,
    flash,
    jsonify,
    redirect,
    render_template,
    request,
    send_file,
    session,
    url_for,
)
from werkzeug.utils import secure_filename

from .backend_client import BackendApiError, BackendClient, read_default_backend_url


ui = Blueprint("ui", __name__, template_folder="templates")

GPIO_PATTERN = re.compile(r"^GPIO\d+$")
ALLOWED_AUDIO_EXTENSIONS = {".mp3", ".wav", ".ogg", ".flac", ".aac", ".m4a"}
YOUTUBE_PROGRESS_PATTERN = re.compile(r"(\d+(?:\.\d+)?)%")
YOUTUBE_POSTPROCESS_HINTS = (
    "extractaudio",
    "ffmpeg",
    "postprocess",
    "post-process",
    "merging",
    "deleting original file",
    "destination",
)
INVALID_FILENAME_CHARS_PATTERN = re.compile(r"[<>:\"/\\|?*\x00-\x1f]")
_YOUTUBE_JOBS_LOCK = threading.Lock()
_YOUTUBE_JOBS: dict[str, dict[str, object]] = {}


def _backend_client() -> BackendClient | None:
    backend_url = session.get("backend_url")
    username = session.get("backend_username")
    password = session.get("backend_password")
    if not backend_url or not username or not password:
        return None
    return BackendClient(str(backend_url), str(username), str(password))


def _ensure_login() -> BackendClient | Response:
    client = _backend_client()
    if client is None:
        flash("Veuillez vous connecter d'abord.", "error")
        return redirect(url_for("ui.login"))
    return client


def _music_dir() -> Path:
    music_dir = current_app.config["MUSIC_DIR"]
    music_dir.mkdir(parents=True, exist_ok=True)
    return music_dir


def _list_audio_files() -> list[str]:
    files: list[str] = []
    for item in _music_dir().iterdir():
        if item.is_file() and item.suffix.lower() in ALLOWED_AUDIO_EXTENSIONS:
            files.append(item.name)
    return sorted(files, key=str.lower)


def _used_audio_files_from_triggers(triggers: dict[str, dict]) -> set[str]:
    used: set[str] = set()
    for trigger in triggers.values():
        if not isinstance(trigger, dict):
            continue
        music_file = str(trigger.get("music_file", "")).strip()
        if music_file:
            used.add(Path(music_file).name.lower())
    return used


def _parse_optional_float(value: str) -> float | None:
    clean = value.strip()
    if clean == "":
        return None
    return float(clean)


def _next_numeric_trigger_id(triggers: dict[str, dict]) -> str:
    max_id = 0
    for key in triggers:
        if key.isdigit():
            max_id = max(max_id, int(key))
    return str(max_id + 1)


def _normalize_key(value: str) -> str:
    return value.strip().lower()


def _audio_redirect_target() -> str:
    if request.form.get("return_to", "").strip() == "audio_storage":
        return url_for("ui.audio_storage")
    return url_for("ui.dashboard")


def _normalize_youtube_filename(raw_name: str) -> str | None:
    # Keep readable names (including spaces) but strip dangerous/path chars.
    candidate = Path(raw_name.strip()).name
    if candidate == "":
        return None

    stem = Path(candidate).stem
    stem = INVALID_FILENAME_CHARS_PATTERN.sub(" ", stem)
    stem = re.sub(r"\s+", " ", stem).strip(" .")
    if stem == "":
        return None
    return f"{stem}.mp3"


def _next_available_filename(filename: str, existing_names: set[str]) -> str:
    candidate = filename
    stem = Path(filename).stem
    suffix = Path(filename).suffix or ".mp3"
    index = 2
    while candidate.lower() in existing_names:
        candidate = f"{stem}_{index}{suffix}"
        index += 1
    return candidate


def _build_youtube_download_command(youtube_url: str, requested_name: str, music_dir: Path) -> tuple[list[str] | None, str | None]:
    yt_dlp_path = shutil.which("yt-dlp")
    if yt_dlp_path is None:
        return None, "yt-dlp est introuvable sur le système."

    if shutil.which("node") is None:
        return None, "node est requis pour l'option --js-runtimes node."

    command = [
        yt_dlp_path,
        "--js-runtimes",
        "node",
        "--remote-components",
        "ejs:github",
        "--newline",
        "-x",
        "--audio-format",
        "mp3",
    ]

    if requested_name:
        normalized_name = _normalize_youtube_filename(requested_name)
        if normalized_name is None:
            return None, "Nom de fichier YouTube invalide."

        existing_names = {item.name.lower() for item in music_dir.iterdir() if item.is_file()}
        if normalized_name.lower() in existing_names:
            return None, "Un fichier avec ce nom existe déjà."

        output_template = music_dir / f"{Path(normalized_name).stem}.%(ext)s"
        command.extend(["-o", str(output_template)])
    else:
        command.extend(["-P", str(music_dir)])

    command.append(youtube_url)
    return command, None


def _extract_progress_percent(line: str) -> float | None:
    match = YOUTUBE_PROGRESS_PATTERN.search(line)
    if match is None:
        return None
    try:
        value = float(match.group(1))
    except ValueError:
        return None
    return max(0.0, min(100.0, value))


def _set_youtube_job_state(job_id: str, **updates: object) -> None:
    with _YOUTUBE_JOBS_LOCK:
        current = _YOUTUBE_JOBS.get(job_id)
        if current is None:
            return
        current.update(updates)


def _create_youtube_job() -> str:
    job_id = uuid.uuid4().hex
    with _YOUTUBE_JOBS_LOCK:
        _YOUTUBE_JOBS[job_id] = {
            "status": "running",
            "percent": 0.0,
            "message": "Préparation du téléchargement...",
        }
    return job_id


def _run_youtube_download_job(job_id: str, command: list[str]) -> None:
    try:
        process = subprocess.Popen(
            command,
            stdout=subprocess.PIPE,
            stderr=subprocess.STDOUT,
            text=True,
            bufsize=1,
        )
    except OSError as exc:
        _set_youtube_job_state(job_id, status="error", message=f"Impossible d'exécuter yt-dlp: {exc}")
        return

    last_line = ""
    max_percent = 0.0
    in_postprocess = False
    output = process.stdout
    if output is not None:
        for raw_line in output:
            line = raw_line.strip()
            if line == "":
                continue
            last_line = line
            lower_line = line.lower()

            if any(hint in lower_line for hint in YOUTUBE_POSTPROCESS_HINTS):
                in_postprocess = True
                shown_percent = max(max_percent, 99.0)
                _set_youtube_job_state(
                    job_id,
                    status="running",
                    percent=shown_percent,
                    message="Conversion audio en cours...",
                )

            progress = _extract_progress_percent(line)
            if progress is None:
                continue
            if progress > max_percent:
                max_percent = progress

            shown_percent = min(max_percent, 99.0)
            if shown_percent >= 99.0:
                in_postprocess = True

            message = (
                "Conversion audio en cours..."
                if in_postprocess
                else f"Téléchargement en cours: {shown_percent:.1f}%"
            )
            _set_youtube_job_state(
                job_id,
                status="running",
                percent=shown_percent,
                message=message,
            )

    return_code = process.wait()
    if return_code == 0:
        _set_youtube_job_state(
            job_id,
            status="completed",
            percent=100.0,
            message="Audio YouTube extrait et ajouté au stockage.",
        )
        return

    detail = last_line if last_line else "Erreur inconnue"
    _set_youtube_job_state(job_id, status="error", message=f"Échec extraction YouTube: {detail}")


def _trigger_sort_key(item: tuple[str, dict]) -> tuple[int, int | str]:
    trigger_id = item[0]
    if trigger_id.isdigit():
        return (0, int(trigger_id))
    return (1, trigger_id.lower())


@ui.get("/")
def home() -> Response:
    if _backend_client() is None:
        return redirect(url_for("ui.login"))
    return redirect(url_for("ui.dashboard"))


@ui.route("/login", methods=["GET", "POST"])
def login() -> str | Response:
    project_root: Path = current_app.config["PROJECT_ROOT"]
    default_url = read_default_backend_url(project_root)

    if request.method == "POST":
        backend_url = default_url
        username = request.form.get("username", "").strip()
        password = request.form.get("password", "")

        session["backend_url"] = backend_url
        session["backend_username"] = username
        session["backend_password"] = password

        client = _backend_client()
        assert client is not None
        try:
            client.health()
            client.list_triggers()
        except BackendApiError:
            return render_template(
                "login.html",
                login_error="Impossible de se connecter au service pour le moment. Vérifiez que le backend est demarré puis réessayez.",
                attempted_username=username,
            )

        flash("Connexion au backend reussie.", "success")
        return redirect(url_for("ui.dashboard"))

    return render_template("login.html", login_error=None, attempted_username="")


@ui.get("/logout")
def logout() -> Response:
    session.clear()
    flash("Session fermee.", "info")
    return redirect(url_for("ui.login"))


@ui.get("/dashboard")
def dashboard() -> str | Response:
    client_or_redirect = _ensure_login()
    if isinstance(client_or_redirect, Response):
        return client_or_redirect

    client = client_or_redirect
    triggers: dict[str, dict] = {}
    used_audio_files: set[str] = set()
    try:
        raw = client.list_triggers()
        valid_triggers = {k: v for k, v in raw.items() if isinstance(v, dict)}
        triggers = dict(sorted(valid_triggers.items(), key=_trigger_sort_key))
        used_audio_files = _used_audio_files_from_triggers(valid_triggers)
    except BackendApiError as exc:
        flash(f"Impossible de charger les triggers: {exc}", "error")

    audio_files = _list_audio_files()

    return render_template(
        "dashboard.html",
        triggers=triggers,
        audio_files=audio_files,
        used_audio_files=used_audio_files,
        backend_url=session.get("backend_url", ""),
        username=session.get("backend_username", ""),
    )


@ui.get("/audio-storage")
def audio_storage() -> str | Response:
    client_or_redirect = _ensure_login()
    if isinstance(client_or_redirect, Response):
        return client_or_redirect

    client = client_or_redirect
    audio_files = _list_audio_files()
    used_audio_files: set[str] = set()
    try:
        raw = client.list_triggers()
        valid_triggers = {k: v for k, v in raw.items() if isinstance(v, dict)}
        used_audio_files = _used_audio_files_from_triggers(valid_triggers)
    except BackendApiError as exc:
        flash(f"Impossible de charger les triggers: {exc}", "error")
    return render_template("audio_storage.html", audio_files=audio_files, used_audio_files=used_audio_files)


@ui.post("/trigger/save")
def save_trigger() -> Response:
    client_or_redirect = _ensure_login()
    if isinstance(client_or_redirect, Response):
        if request.headers.get("X-Requested-With") == "fetch":
            return jsonify({"ok": False, "error": "Non connecte"}), 401
        return client_or_redirect
    client = client_or_redirect

    original_id = request.form.get("original_id", "").strip()
    trigger_type = request.form.get("type", "").strip()
    name = request.form.get("name", "").strip()
    music_file = request.form.get("music_file", "").strip()
    start_raw = request.form.get("start_seconds", "0")
    end_raw = request.form.get("end_seconds", "")
    volume_raw = request.form.get("volume", "80")
    fade_in_raw = request.form.get("fade_in_seconds", "0")
    fade_out_raw = request.form.get("fade_out_seconds", "0")
    repeat_count_raw = request.form.get("repeat_count", "0")
    normalize_audio = request.form.get("normalize_audio") in {"on", "true", "1"}

    def _err(msg: str) -> Response:
        if request.headers.get("X-Requested-With") == "fetch":
            return jsonify({"ok": False, "error": msg}), 400
        flash(msg, "error")
        return redirect(url_for("ui.dashboard"))

    if not GPIO_PATTERN.match(trigger_type):
        return _err("Le type doit respecter le format GPIO<number>.")

    if not name or not music_file:
        return _err("Le nom et le fichier audio sont obligatoires.")

    try:
        start_seconds = float(start_raw)
        end_seconds = _parse_optional_float(end_raw)
        volume = int(volume_raw)
        fade_in_seconds = float(fade_in_raw)
        fade_out_seconds = float(fade_out_raw)
        repeat_count = int(repeat_count_raw)
    except ValueError:
        return _err("Les temps de debut/fin, fondus, repetitions et le volume doivent être numériques.")

    if start_seconds < 0 or (end_seconds is not None and end_seconds <= start_seconds):
        return _err("Fenêtre temporelle invalide.")

    if not (0 <= volume <= 100):
        return _err("Le volume doit être compris entre 0 et 100.")

    if fade_in_seconds < 0 or fade_out_seconds < 0:
        return _err("Les durées de fondu doivent être supérieures ou égales à 0.")

    if repeat_count < 0:
        return _err("Le nombre de répétitions doit être supérieur ou égal à 0.")

    payload = {
        "name": name,
        "type": trigger_type,
        "music_file": music_file,
        "start_seconds": start_seconds,
        "end_seconds": end_seconds,
        "volume": volume,
        "fade_in_seconds": fade_in_seconds,
        "fade_out_seconds": fade_out_seconds,
        "repeat_count": repeat_count,
        "normalize_audio": normalize_audio,
    }

    try:
        existing_raw = client.list_triggers()
        existing_triggers = {k: v for k, v in existing_raw.items() if isinstance(v, dict)}

        if original_id and original_id in existing_triggers:
            trigger_id = original_id
        else:
            trigger_id = _next_numeric_trigger_id(existing_triggers)

        for existing_id, existing_trigger in existing_triggers.items():
            if existing_id == trigger_id:
                continue
            if existing_trigger.get("type") == trigger_type:
                return _err("Ce type de trigger est déjà utilisé.")
            if _normalize_key(str(existing_trigger.get("name", ""))) == _normalize_key(name):
                return _err("Ce nom de trigger est déjà utilisé.")

        client.upsert_trigger(trigger_id, payload)
    except BackendApiError as exc:
        if request.headers.get("X-Requested-With") == "fetch":
            return jsonify({"ok": False, "error": str(exc)}), 502
        flash(f"Echec d'enregistrement du trigger: {exc}", "error")
        return redirect(url_for("ui.dashboard"))

    if request.headers.get("X-Requested-With") == "fetch":
        return jsonify({
            "ok": True,
            "message": f"Trigger \"{name}\" enregistré.",
            "trigger_id": trigger_id,
            "original_id": original_id or trigger_id,
            "trigger": payload,
        })
    flash(f"Trigger \"{name}\" enregistré.", "success")
    return redirect(url_for("ui.dashboard"))


@ui.post("/trigger/delete")
def delete_trigger() -> Response:
    client_or_redirect = _ensure_login()
    if isinstance(client_or_redirect, Response):
        if request.headers.get("X-Requested-With") == "fetch":
            return jsonify({"ok": False, "error": "Non connecte"}), 401
        return client_or_redirect
    client = client_or_redirect

    trigger_id = request.form.get("trigger_id", "").strip()
    if not trigger_id:
        if request.headers.get("X-Requested-With") == "fetch":
            return jsonify({"ok": False, "error": "Identifiant du trigger manquant."}), 400
        flash("Identifiant du trigger manquant.", "error")
        return redirect(url_for("ui.dashboard"))

    try:
        client.delete_trigger(trigger_id)
        if request.headers.get("X-Requested-With") == "fetch":
            return jsonify({"ok": True, "message": "Trigger supprimé.", "trigger_id": trigger_id})
        flash("Trigger supprimé.", "success")
    except BackendApiError as exc:
        if request.headers.get("X-Requested-With") == "fetch":
            return jsonify({"ok": False, "error": f"Echec de suppression: {exc}"}), 500
        flash(f"Echec de suppression: {exc}", "error")
    return redirect(url_for("ui.dashboard"))


@ui.post("/trigger/play")
def play_trigger() -> Response:
    client_or_redirect = _ensure_login()
    if isinstance(client_or_redirect, Response):
        if request.headers.get("X-Requested-With") == "fetch":
            return jsonify({"ok": False, "error": "Non connecte"}), 401
        return client_or_redirect
    client = client_or_redirect

    trigger_id = request.form.get("trigger_id", "").strip()
    if not trigger_id:
        if request.headers.get("X-Requested-With") == "fetch":
            return jsonify({"ok": False, "error": "Identifiant du trigger manquant."}), 400
        flash("Identifiant du trigger manquant.", "error")
        return redirect(url_for("ui.dashboard"))

    try:
        client.play_trigger(trigger_id)
        if request.headers.get("X-Requested-With") == "fetch":
            return jsonify({"ok": True, "message": "Trigger démarré."})
        flash("Trigger démarré.", "success")
    except BackendApiError as exc:
        if request.headers.get("X-Requested-With") == "fetch":
            return jsonify({"ok": False, "error": str(exc)}), 502
        flash(f"Echec du lancement: {exc}", "error")
    return redirect(url_for("ui.dashboard"))


@ui.post("/audio/stop")
def stop_audio() -> Response:
    client_or_redirect = _ensure_login()
    if isinstance(client_or_redirect, Response):
        if request.headers.get("X-Requested-With") == "fetch":
            return jsonify({"ok": False, "error": "Non connecte"}), 401
        return client_or_redirect
    client = client_or_redirect

    try:
        client.stop_audio()
        if request.headers.get("X-Requested-With") == "fetch":
            return jsonify({"ok": True, "message": "Audio arrete."})
        flash("Audio arrete.", "info")
    except BackendApiError as exc:
        if request.headers.get("X-Requested-With") == "fetch":
            return jsonify({"ok": False, "error": str(exc)}), 502
        flash(f"Echec de l'arrêt audio: {exc}", "error")
    return redirect(url_for("ui.dashboard"))


@ui.post("/audio/upload")
def upload_audio() -> Response:
    client_or_redirect = _ensure_login()
    if isinstance(client_or_redirect, Response):
        return client_or_redirect

    youtube_url = request.form.get("youtube_url", "").strip()
    if youtube_url:
        requested_name = request.form.get("youtube_filename", "").strip()
        command, command_error = _build_youtube_download_command(youtube_url, requested_name, _music_dir())
        if command is None:
            flash(command_error or "Impossible de préparer la commande yt-dlp.", "error")
            return redirect(_audio_redirect_target())

        try:
            result = subprocess.run(command, check=False, capture_output=True, text=True)
        except OSError as exc:
            flash(f"Impossible d'exécuter yt-dlp: {exc}", "error")
            return redirect(_audio_redirect_target())

        if result.returncode != 0:
            detail = (result.stderr or result.stdout or "").strip().splitlines()
            message = detail[-1] if detail else "Erreur inconnue"
            flash(f"Échec extraction YouTube: {message}", "error")
            return redirect(_audio_redirect_target())

        flash("Audio YouTube extrait et ajouté au stockage.", "success")
        return redirect(_audio_redirect_target())

    audio = request.files.get("audio_file")
    if audio is None or audio.filename is None or audio.filename.strip() == "":
        flash("Sélectionnez d'abord un fichier.", "error")
        return redirect(_audio_redirect_target())

    filename = secure_filename(audio.filename)
    if filename == "":
        flash("Nom de fichier invalide.", "error")
        return redirect(_audio_redirect_target())

    ext = Path(filename).suffix.lower()
    if ext not in ALLOWED_AUDIO_EXTENSIONS:
        flash("Format audio non supporté.", "error")
        return redirect(_audio_redirect_target())

    existing_names = {item.name.lower() for item in _music_dir().iterdir() if item.is_file()}
    if filename.lower() in existing_names:
        flash("Un fichier avec ce nom existe déjà.", "error")
        return redirect(_audio_redirect_target())

    destination = _music_dir() / filename
    audio.save(destination)
    flash(f"Fichier {filename} téléversé.", "success")
    return redirect(_audio_redirect_target())


@ui.post("/audio/delete")
def delete_audio() -> Response:
    client_or_redirect = _ensure_login()
    if isinstance(client_or_redirect, Response):
        return client_or_redirect

    filename = request.form.get("filename", "").strip()
    if not filename:
        flash("Nom de fichier manquant.", "error")
        return redirect(_audio_redirect_target())

    target = _music_dir() / filename
    if not target.exists() or not target.is_file():
        flash("Fichier introuvable.", "error")
        return redirect(_audio_redirect_target())

    client = client_or_redirect
    try:
        raw = client.list_triggers()
        valid_triggers = {k: v for k, v in raw.items() if isinstance(v, dict)}
        used_audio_files = _used_audio_files_from_triggers(valid_triggers)
        if Path(filename).name.lower() in used_audio_files:
            flash("Ce fichier est associé à un trigger et ne peut pas être supprimé.", "error")
            return redirect(_audio_redirect_target())
    except BackendApiError as exc:
        flash(f"Impossible de vérifier les triggers: {exc}", "error")
        return redirect(_audio_redirect_target())

    target.unlink()
    flash(f"Fichier {filename} supprimé.", "success")
    return redirect(_audio_redirect_target())


@ui.post("/audio/youtube/proposed-name")
def youtube_proposed_name() -> Response:
    client_or_redirect = _ensure_login()
    if isinstance(client_or_redirect, Response):
        return jsonify({"ok": False, "error": "Non connecte"}), 401

    youtube_url = request.form.get("youtube_url", "").strip()
    if youtube_url == "":
        return jsonify({"ok": False, "error": "Lien YouTube manquant."}), 400

    yt_dlp_path = shutil.which("yt-dlp")
    if yt_dlp_path is None:
        return jsonify({"ok": False, "error": "yt-dlp est introuvable sur le système."}), 400
    if shutil.which("node") is None:
        return jsonify({"ok": False, "error": "node est requis pour l'option --js-runtimes node."}), 400

    command = [
        yt_dlp_path,
        "--js-runtimes",
        "node",
        "--remote-components",
        "ejs:github",
        "--no-playlist",
        "--skip-download",
        "--print",
        "%(title)s",
        youtube_url,
    ]

    try:
        result = subprocess.run(command, check=False, capture_output=True, text=True)
    except OSError as exc:
        return jsonify({"ok": False, "error": f"Impossible d'exécuter yt-dlp: {exc}"}), 500

    if result.returncode != 0:
        detail = (result.stderr or result.stdout or "").strip().splitlines()
        message = detail[-1] if detail else "Erreur inconnue"
        return jsonify({"ok": False, "error": f"Échec lecture metadonnées YouTube: {message}"}), 502

    title = next((line.strip() for line in result.stdout.splitlines() if line.strip()), "")
    proposed = _normalize_youtube_filename(title) or "audio_youtube.mp3"

    existing_names = {item.name.lower() for item in _music_dir().iterdir() if item.is_file()}
    available_name = _next_available_filename(proposed, existing_names)
    return jsonify({"ok": True, "filename": available_name})


@ui.post("/audio/youtube/start")
def youtube_download_start() -> Response:
    client_or_redirect = _ensure_login()
    if isinstance(client_or_redirect, Response):
        return jsonify({"ok": False, "error": "Non connecte"}), 401

    youtube_url = request.form.get("youtube_url", "").strip()
    if youtube_url == "":
        return jsonify({"ok": False, "error": "Lien YouTube manquant."}), 400

    requested_name = request.form.get("youtube_filename", "").strip()
    music_dir = _music_dir()
    command, command_error = _build_youtube_download_command(youtube_url, requested_name, music_dir)
    if command is None:
        return jsonify({"ok": False, "error": command_error or "Impossible de préparer la commande yt-dlp."}), 400

    job_id = _create_youtube_job()
    worker = threading.Thread(target=_run_youtube_download_job, args=(job_id, command), daemon=True)
    worker.start()
    return jsonify({"ok": True, "job_id": job_id})


@ui.get("/audio/youtube/status/<job_id>")
def youtube_download_status(job_id: str) -> Response:
    client_or_redirect = _ensure_login()
    if isinstance(client_or_redirect, Response):
        return jsonify({"ok": False, "error": "Non connecte"}), 401

    with _YOUTUBE_JOBS_LOCK:
        job = _YOUTUBE_JOBS.get(job_id)
        if job is None:
            return jsonify({"ok": False, "error": "Téléchargement introuvable."}), 404
        payload = {
            "ok": True,
            "status": str(job.get("status", "running")),
            "percent": float(job.get("percent", 0.0)),
            "message": str(job.get("message", "Téléchargement en cours...")),
        }
    return jsonify(payload)


@ui.get("/audio/download/<path:filename>")
def download_audio(filename: str) -> Response:
    client_or_redirect = _ensure_login()
    if isinstance(client_or_redirect, Response):
        return client_or_redirect

    safe_name = Path(filename).name
    target = _music_dir() / safe_name
    if not target.exists() or not target.is_file():
        flash("Fichier introuvable.", "error")
        return redirect(url_for("ui.dashboard"))
    return send_file(target, as_attachment=True)


@ui.get("/audio/stream/<path:filename>")
def stream_audio(filename: str) -> Response:
    client_or_redirect = _ensure_login()
    if isinstance(client_or_redirect, Response):
        return client_or_redirect

    safe_name = Path(filename).name
    target = _music_dir() / safe_name
    if not target.exists() or not target.is_file():
        flash("Fichier introuvable.", "error")
        return redirect(url_for("ui.dashboard"))
    return send_file(target, as_attachment=False)