# Copyright 2026 Umbra Tools (umbratools.com)
# SPDX-License-Identifier: Apache-2.0

"""Local-first storage with transparent NAS fallback.

Primary store is the local SSD; the NAS mirror is secondary. When a file
has been pruned locally, resolve_path/fetch restores it from the mirror
before handing it back to callers.
"""

from __future__ import annotations

import logging
import shutil
import sys
from pathlib import Path

logger = logging.getLogger(__name__)

DEFAULT_LOCAL_ROOT = Path("/Volumes/1TB_APL_Storage/UmbraAudio")
DEFAULT_NAS_ROOT = Path("/Volumes/Umbra/UmbraAudio")


class NasUnavailableError(RuntimeError):
    pass


def nas_mirror_path(path: str | Path, local_root: Path = DEFAULT_LOCAL_ROOT,
                    nas_root: Path = DEFAULT_NAS_ROOT) -> Path:
    p = Path(path)
    rel = p.relative_to(local_root) if p.is_absolute() else p
    return nas_root / rel


def _restore_from_nas(mirror: Path, dest: Path) -> None:
    if not mirror.exists():
        raise FileNotFoundError(f"not on local SSD and no NAS copy: {dest}")
    dest.parent.mkdir(parents=True, exist_ok=True)
    shutil.copy2(mirror, dest)
    logger.info("restored %s from NAS mirror", dest)


def resolve_path(path: str | Path, *, local_root: Path = DEFAULT_LOCAL_ROOT,
                 nas_root: Path = DEFAULT_NAS_ROOT, restore: bool = True) -> Path:
    """Return a usable local path for `path`, pulling from NAS when pruned."""
    p = Path(path)
    if not p.is_absolute():
        p = local_root / p
    if p.exists() or not restore:
        return p
    mirror = nas_mirror_path(p, local_root, nas_root)
    if not mirror.exists():
        raise FileNotFoundError(f"not on local SSD and no NAS copy: {p}")
    try:
        _restore_from_nas(mirror, p)
    except OSError as e:
        raise NasUnavailableError(f"NAS not reachable while restoring {p}: {e}") from e
    return p


def fetch(*paths: str | Path, **kw) -> list[Path]:
    return [resolve_path(p, **kw) for p in paths]


def main(argv: list[str] | None = None) -> int:
    import argparse

    parser = argparse.ArgumentParser(description="Fetch files from local SSD or NAS fallback")
    parser.add_argument("paths", nargs="+", help="absolute or UmbraAudio-relative paths")
    args = parser.parse_args(argv)
    logging.basicConfig(level=logging.INFO, format="%(levelname)s %(message)s")
    try:
        for resolved in fetch(*args.paths):
            print(resolved)
    except (FileNotFoundError, NasUnavailableError) as e:
        print(f"error: {e}", file=sys.stderr)
        return 1
    return 0


if __name__ == "__main__":
    raise SystemExit(main())