"""Shared helpers for the album-bundle download flow.

The torrent and usenet download plugins both implement a
``download_album_to_staging`` method that searches Prowlarr for a
whole release, hands it to the active downloader, walks the
resulting audio files, and copies them into the staging folder. The
two implementations share the same release-picker heuristic and the
same staging-path collision logic.

Pulled out of ``core/download_plugins/torrent.py`` so the usenet
plugin doesn't have to import private helpers from a sibling
plugin (Cin's "no leaky module boundaries" standard).

Also exposes ``atomic_copy_to_staging`` — the audio file is copied
to a ``.tmp.<random>`` sidecar first and atomically renamed onto its
final extension. The Auto-Import worker filters by audio extension
so the in-flight ``.tmp`` file is never picked up mid-copy, closing
the race between the album-bundle copy loop and Auto-Import's
folder scan.
"""

from __future__ import annotations

import shutil
import time
import uuid
from pathlib import Path
from typing import Iterable, Optional

from config.settings import config_manager
from utils.logging_config import get_logger

logger = get_logger("download_plugins.album_bundle")


# Album-pick size floor / ceiling. Single-track torrents (~10 MB)
# are rejected when bigger candidates exist; anything past 3 GB is
# treated as suspicious (multi-disc box-set + scans + extras).
ALBUM_PICK_MIN_BYTES = 40 * 1024 * 1024
ALBUM_PICK_MAX_BYTES = 3 * 1024 * 1024 * 1024


# Quality-score weights for the album-pick heuristic. Mirrors the
# tier order in ``core/imports/file_ops.py``'s ``quality_tiers`` —
# higher number = preferred.
_QUALITY_SCORE = {'flac': 4, 'ogg': 3, 'aac': 2, 'mp3': 1}


# Default poll cadence + timeout for the album-download poll loop.
# Both are overridable through config so users with slow trackers
# / large box-sets can extend the deadline without editing code.
DEFAULT_POLL_INTERVAL_SECONDS = 2.0
DEFAULT_POLL_TIMEOUT_SECONDS = 6 * 60 * 60


def get_poll_interval() -> float:
    """Return the per-poll sleep duration (seconds). Configurable via
    ``download_source.album_bundle_poll_interval_seconds``."""
    raw = config_manager.get('download_source.album_bundle_poll_interval_seconds',
                             DEFAULT_POLL_INTERVAL_SECONDS)
    try:
        value = float(raw)
        if value > 0:
            return value
    except (TypeError, ValueError):
        pass
    return DEFAULT_POLL_INTERVAL_SECONDS


def get_poll_timeout() -> float:
    """Return the total deadline for an album-bundle download
    (seconds). Configurable via
    ``download_source.album_bundle_timeout_seconds``."""
    raw = config_manager.get('download_source.album_bundle_timeout_seconds',
                             DEFAULT_POLL_TIMEOUT_SECONDS)
    try:
        value = float(raw)
        if value > 0:
            return value
    except (TypeError, ValueError):
        pass
    return DEFAULT_POLL_TIMEOUT_SECONDS


def quality_score(title: str, quality_guess) -> int:
    """Map a release title's inferred quality to a sortable integer.

    ``quality_guess`` is the function from each plugin that maps a
    title string to a quality string ('flac' / 'mp3' / etc.) — passed
    in so this module doesn't have to import either plugin and risk
    a circular import."""
    return _QUALITY_SCORE.get(quality_guess(title) or '', 0)


def pick_best_album_release(candidates, quality_guess) -> Optional[object]:
    """Pick the single best torrent / NZB for an album-bundle download.

    Heuristic, in priority order:
    1. Reasonable album-ish size (40 MB – 3 GB) — drops single-track
       releases that snuck in and quarantines suspicious giants.
    2. Higher seeders > lower (dead torrents = dead downloads).
       Usenet releases use ``grabs`` as a popularity proxy when
       seeders is None.
    3. Higher quality (FLAC > AAC > MP3) inferred from title.
    4. Larger size as tiebreaker (often = higher bitrate).
    """
    if not candidates:
        return None
    sized = [c for c in candidates
             if ALBUM_PICK_MIN_BYTES <= (c.size or 0) <= ALBUM_PICK_MAX_BYTES]
    pool = sized or list(candidates)
    if not pool:
        return None

    def _score(c) -> tuple:
        seeders = c.seeders if c.seeders is not None else (c.grabs or 0)
        return (seeders, quality_score(c.title or '', quality_guess), c.size or 0)

    return max(pool, key=_score)


def unique_staging_path(staging_dir: Path, src: Path) -> Path:
    """Return a destination path inside ``staging_dir`` that doesn't
    collide with an existing file. Appends ``_1``, ``_2``, ... before
    the extension when needed; gives up after 1000 candidates and
    returns the unsuffixed path so the caller will overwrite (better
    than infinite loop or crash)."""
    dest = staging_dir / src.name
    if not dest.exists():
        return dest
    stem = dest.stem
    suffix = dest.suffix
    for i in range(1, 1000):
        candidate = staging_dir / f"{stem}_{i}{suffix}"
        if not candidate.exists():
            return candidate
    return dest


def atomic_copy_to_staging(src: Path, dest: Path) -> bool:
    """Copy ``src`` to ``dest`` without exposing a partial file to
    folder scanners.

    The Auto-Import worker filters by audio extension when scanning
    Staging — see ``AUDIO_EXTENSIONS`` in ``core/auto_import_worker.py``.
    Naming the in-flight file ``<dest>.tmp.<random>`` keeps it
    invisible until the rename atomically swings it to its final
    extension. ``os.replace`` (used by ``Path.rename`` on Python 3.x)
    is atomic on the same filesystem, so Auto-Import either sees the
    file at its final name (complete) or doesn't see it at all
    (in flight).

    Returns True on success, False on copy / rename failure. Caller
    is expected to log the failure case so we don't double-log here.
    """
    tmp = dest.with_name(f"{dest.name}.tmp.{uuid.uuid4().hex[:8]}")
    try:
        shutil.copy2(src, tmp)
    except Exception:
        # Best-effort cleanup of the partial file. If unlink fails
        # (locked, permissions) we leave it — Auto-Import ignores it
        # anyway because of the .tmp extension.
        try:
            if tmp.exists():
                tmp.unlink()
        except Exception as cleanup_exc:
            logger.debug("album_bundle tmp cleanup failed: %s", cleanup_exc)
        raise
    try:
        tmp.replace(dest)
        return True
    except Exception:
        try:
            tmp.unlink(missing_ok=True)
        except Exception as cleanup_exc:
            logger.debug("album_bundle tmp cleanup failed: %s", cleanup_exc)
        raise


def copy_audio_files_atomically(
    sources: Iterable[Path], staging_dir: Path,
) -> list:
    """Convenience wrapper: pick a non-colliding staging path for
    each source, copy via ``atomic_copy_to_staging``. Returns the
    list of final destination paths (as strings). Files that fail
    to copy are logged and skipped; the caller decides what to do
    with a partial result."""
    staging_dir.mkdir(parents=True, exist_ok=True)
    out: list = []
    for src in sources:
        dest = unique_staging_path(staging_dir, src)
        try:
            atomic_copy_to_staging(src, dest)
            out.append(str(dest))
        except Exception as e:
            logger.warning("[album_bundle] Failed to stage %s -> %s: %s", src, dest, e)
    return out


# Re-export so callers don't have to remember which module owns
# what. The ``time`` import is kept so plugins can ``from
# core.download_plugins.album_bundle import time`` if they want to,
# avoiding a second std-lib import line for a single use.
__all__ = [
    "ALBUM_PICK_MIN_BYTES",
    "ALBUM_PICK_MAX_BYTES",
    "DEFAULT_POLL_INTERVAL_SECONDS",
    "DEFAULT_POLL_TIMEOUT_SECONDS",
    "atomic_copy_to_staging",
    "copy_audio_files_atomically",
    "get_poll_interval",
    "get_poll_timeout",
    "pick_best_album_release",
    "quality_score",
    "time",
    "unique_staging_path",
]