"""Per-object export coordination and content-aware artifact reuse."""

from contextlib import contextmanager, ExitStack
import hashlib
import json
from pathlib import Path
import threading
from weakref import WeakValueDictionary

_guard = threading.Lock()
_locks: WeakValueDictionary = WeakValueDictionary()
TERMINAL = {"completed", "success", "failed", "cancelled", "interrupted", "skipped"}


@contextmanager
def export_lock(*keys: str):
    # Retain strong references until every lock is released. Unrelated exports
    # run concurrently; nested session exports can reacquire their own RLock.
    with _guard:
        locks = []
        for key in sorted(set(keys)):
            lock = _locks.get(key)
            if lock is None:
                lock = threading.RLock()
                _locks[key] = lock
            locks.append(lock)
    with ExitStack() as stack:
        for lock in locks:
            stack.enter_context(lock)
        yield


def fingerprint(report: dict, files=(), extra=None) -> str:
    metadata = []
    for path, name in files:
        stat = path.stat()
        metadata.append((name, str(path), stat.st_size, stat.st_mtime_ns))
    payload = json.dumps([2, report, metadata, extra], sort_keys=True, default=str)
    return hashlib.sha256(payload.encode()).hexdigest()


def reusable(path: Path, signature: str, status: str) -> bool:
    if status not in TERMINAL or not path.is_file():
        return False
    try:
        return path.with_suffix(path.suffix + ".fingerprint").read_text() == signature
    except OSError:
        return False


def remember(path: Path, signature: str) -> None:
    marker = path.with_suffix(path.suffix + ".fingerprint")
    temporary = marker.with_suffix(".tmp")
    temporary.write_text(signature, encoding="ascii")
    temporary.replace(marker)


def compression(path: Path) -> int:
    import zipfile

    return (
        zipfile.ZIP_STORED
        if path.suffix.lower()
        in {".mp4", ".mkv", ".webm", ".docx", ".xlsx", ".png", ".jpg", ".jpeg", ".zip"}
        else zipfile.ZIP_DEFLATED
    )