"""Core nc-scan logic shared by the blocking and streaming endpoints."""

from __future__ import annotations

import logging
from collections.abc import AsyncGenerator
from pathlib import Path
from urllib.parse import unquote

from sqlalchemy.ext.asyncio import AsyncSession

from rehearsalhub.repositories.audio_version import AudioVersionRepository
from rehearsalhub.repositories.rehearsal_session import RehearsalSessionRepository
from rehearsalhub.repositories.song import SongRepository
from rehearsalhub.schemas.audio_version import AudioVersionCreate
from rehearsalhub.schemas.song import SongRead
from rehearsalhub.services.session import extract_session_folder, parse_rehearsal_date
from rehearsalhub.services.song import SongService
from rehearsalhub.storage.nextcloud import NextcloudClient

log = logging.getLogger(__name__)

AUDIO_EXTENSIONS = {".mp3", ".wav", ".flac", ".ogg", ".m4a", ".aac", ".opus"}

# Maximum folder depth to recurse into below the band root.
# Depth 0 = band root, 1 = YYMMDD folder, 2 = song subfolder, 3 = safety margin.
MAX_SCAN_DEPTH = 3


def _make_relative(dav_prefix: str):
    """Return a function that strips the WebDAV prefix and URL-decodes a href."""
    def relative(href: str) -> str:
        decoded = unquote(href)
        if decoded.startswith(dav_prefix):
            return decoded[len(dav_prefix):]
        # Strip any leading slash for robustness
        return decoded.lstrip("/")
    return relative


async def collect_audio_files(
    nc: NextcloudClient,
    relative: object,  # Callable[[str], str]
    folder_path: str,
    max_depth: int = MAX_SCAN_DEPTH,
    _depth: int = 0,
) -> AsyncGenerator[str, None]:
    """
    Recursively yield user-relative audio file paths under folder_path.

    Handles any depth:
      bands/slug/take.wav                       depth 0
      bands/slug/231015/take.wav                depth 1
      bands/slug/231015/groove/take.wav         depth 2  ← was broken before
    """
    if _depth > max_depth:
        log.debug("Max depth %d exceeded at '%s', stopping recursion", max_depth, folder_path)
        return

    try:
        items = await nc.list_folder(folder_path)
    except Exception as exc:
        log.warning("Could not list folder '%s': %s", folder_path, exc)
        return

    log.info(
        "scan depth=%d folder='%s' entries=%d",
        _depth, folder_path, len(items),
    )

    for item in items:
        rel = relative(item.path)  # type: ignore[operator]
        if rel.endswith("/"):
            # It's a subdirectory — recurse
            log.info("  → subdir: %s", rel)
            async for subpath in collect_audio_files(nc, relative, rel, max_depth, _depth + 1):
                yield subpath
        else:
            ext = Path(rel).suffix.lower()
            if ext in AUDIO_EXTENSIONS:
                log.info("  → audio file: %s", rel)
                yield rel
            elif ext:
                log.debug("  → skip (ext=%s): %s", ext, rel)


async def scan_band_folder(
    db_session: AsyncSession,
    nc: NextcloudClient,
    band_id,
    band_folder: str,
    member_id,
) -> AsyncGenerator[dict, None]:
    """
    Async generator that scans band_folder and yields event dicts:
      {"type": "progress", "message": str}
      {"type": "song",     "song": SongRead-dict, "is_new": bool}
      {"type": "session",  "session": {id, date, label}}
      {"type": "skipped",  "path": str, "reason": str}
      {"type": "done",     "stats": {found, imported, skipped}}
      {"type": "error",    "message": str}
    """
    dav_prefix = f"/remote.php/dav/files/{nc._auth[0]}/"
    relative = _make_relative(dav_prefix)

    version_repo = AudioVersionRepository(db_session)
    session_repo = RehearsalSessionRepository(db_session)
    song_repo = SongRepository(db_session)
    song_svc = SongService(db_session)

    found = 0
    imported = 0
    skipped = 0

    yield {"type": "progress", "message": f"Scanning {band_folder}…"}

    async for nc_file_path in collect_audio_files(nc, relative, band_folder):
        found += 1
        song_folder = str(Path(nc_file_path).parent).rstrip("/") + "/"
        song_title = Path(nc_file_path).stem

        # If the file sits directly inside a dated session folder (YYMMDD/file.wav),
        # give it a unique virtual folder so each file becomes its own song rather
        # than being merged as a new version of the first file in that folder.
        session_folder_path = extract_session_folder(nc_file_path)
        if session_folder_path and session_folder_path.rstrip("/") == song_folder.rstrip("/"):
            song_folder = song_folder + song_title + "/"

        yield {"type": "progress", "message": f"Checking {Path(nc_file_path).name}…"}

        # Fetch file metadata (etag + size) — one PROPFIND per file
        try:
            meta = await nc.get_file_metadata(nc_file_path)
            etag = meta.etag
        except Exception as exc:
            log.warning("Metadata error for '%s': %s", nc_file_path, exc)
            yield {"type": "skipped", "path": nc_file_path, "reason": f"metadata error: {exc}"}
            continue

        # Skip if this exact version is already indexed
        if etag and await version_repo.get_by_etag(etag):
            log.info("Already registered (etag match): %s", nc_file_path)
            skipped += 1
            yield {"type": "skipped", "path": nc_file_path, "reason": "already registered"}
            continue

        # Resolve or create a RehearsalSession from a YYMMDD folder segment
        rehearsal_date = parse_rehearsal_date(nc_file_path)
        rehearsal_session_id = None
        if rehearsal_date:
            session_folder = extract_session_folder(nc_file_path) or song_folder
            rs = await session_repo.get_or_create(band_id, rehearsal_date, session_folder)
            rehearsal_session_id = rs.id
            yield {
                "type": "session",
                "session": {
                    "id": str(rs.id),
                    "date": rs.date.isoformat(),
                    "label": rs.label,
                    "nc_folder_path": rs.nc_folder_path,
                },
            }

        # Find or create the Song record
        song = await song_repo.get_by_nc_folder_path(song_folder)
        if song is None:
            song = await song_repo.get_by_title_and_band(band_id, song_title)
        is_new = song is None
        if is_new:
            log.info("Creating song '%s' folder='%s'", song_title, song_folder)
            song = await song_repo.create(
                band_id=band_id,
                session_id=rehearsal_session_id,
                title=song_title,
                status="jam",
                notes=None,
                nc_folder_path=song_folder,
                created_by=member_id,
            )
        elif rehearsal_session_id and song.session_id is None:
            song = await song_repo.update(song, session_id=rehearsal_session_id)

        # Register the audio version
        await song_svc.register_version(
            song.id,
            AudioVersionCreate(
                nc_file_path=nc_file_path,
                nc_file_etag=etag,
                format=Path(nc_file_path).suffix.lstrip(".").lower(),
                file_size_bytes=meta.size,
            ),
            member_id,
        )

        imported += 1
        read = SongRead.model_validate(song).model_copy(update={"version_count": 1, "session_id": rehearsal_session_id})
        yield {"type": "song", "song": read.model_dump(mode="json"), "is_new": is_new}

    yield {
        "type": "done",
        "stats": {"found": found, "imported": imported, "skipped": skipped},
    }