"""可信临时包扫描器；只解析 dist-info 元数据，不 import 用户代码。"""
from __future__ import annotations
import csv
import email.parser
import json
from pathlib import Path

BASE = Path("/sandbox/base-python-packages.json")
ROOT = Path("/tmp/.local/lib")


def safe_file(root: Path, path: Path) -> bool:
    try:
        path.relative_to(root)
    except ValueError:
        return False
    current = root
    for part in path.relative_to(root).parts:
        current = current / part
        if current.is_symlink():
            return False
    return path.is_file()


def safe_dir(root: Path, path: Path) -> bool:
    try:
        rel = path.relative_to(root)
    except ValueError:
        return False
    current = root
    for part in rel.parts:
        current = current / part
        if current.is_symlink():
            return False
    return path.is_dir()


def canonical(name: str) -> str:
    return name.lower().replace("_", "-").replace(".", "-")


def scan_packages(root: Path, base: dict) -> list[dict]:
    out = []
    if root.is_dir():
        for site in sorted(root.glob("python*/site-packages")):
            if not safe_dir(root, site):
                continue
            for dist in sorted(site.glob("*.dist-info")):
                if len(out) >= 5000:
                    return out
                meta_path = dist / "METADATA"
                if not safe_file(site, meta_path) or meta_path.stat().st_size > 1024 * 1024:
                    continue
                msg = email.parser.Parser().parsestr(meta_path.read_text(encoding="utf-8", errors="replace"), headersonly=True)
                name, version = msg.get("Name", "").strip(), msg.get("Version", "").strip()
                if not name:
                    continue
                total = 0
                record = dist / "RECORD"
                if safe_file(site, record) and record.stat().st_size <= 32 * 1024 * 1024:
                    for index, row in enumerate(csv.reader(record.read_text(encoding="utf-8", errors="replace").splitlines())):
                        if index >= 200_000:
                            break
                        if not row:
                            continue
                        candidate = site / row[0]
                        if safe_file(site, candidate):
                            try: total += candidate.stat().st_size
                            except OSError: pass
                key = canonical(name)
                old = base.get(key)
                change = "added" if old is None else ("reinstall" if old == version else "override")
                out.append({"name": name, "version": version, "base_version": old,
                            "change": change, "direct_requested": safe_file(site, dist / "REQUESTED") or safe_file(site, dist / "direct_url.json"),
                            "installed_bytes": total})
    return out


def main() -> None:
    base = json.loads(BASE.read_text(encoding="utf-8"))
    print(json.dumps(scan_packages(ROOT, base), ensure_ascii=False))

if __name__ == "__main__":
    main()