"""Apply huggingface/hnc-field/guard.py without keeping its directory change.

The Space module chdirs into the Space and may put the checkout on sys.path.
This loader reuses that module, restores the working directory, and prefers an
installed aureon distribution over the checkout when one is importable.

When that install is missing, imports fall back to the checkout. Callers must
read aureon_source() rather than assume the documented pin.
"""

from __future__ import annotations

import importlib.util
import json
import os
import subprocess
import sys
from pathlib import Path

from aureon_public.paths import repo_root, space_guard

_DONE = False
PINNED_COMMIT = "8aa6a2d971cc529484e2a5e261e28afafab4e4f4"
# git blob of the committed huggingface/hnc-field/guard.py.
# The check is these bytes. It is not a path lookup inside PINNED_COMMIT.
GUARD_BLOB = "b59a6ed8b82b98988e57c6897faba3eb9b98948d"
GUARD_MISMATCH = "checkout guard.py differs from pin 8aa6a2d9"


def _same(path: str, root: Path) -> bool:
    candidate = path or os.getcwd()
    try:
        return Path(candidate).resolve() == root.resolve()
    except OSError:
        return False


def apply_space_guard() -> None:
    """Install the Space environment and the trading-import blocker."""

    global _DONE
    if _DONE:
        return
    root = repo_root()
    guard_path = space_guard()
    cwd = Path.cwd()
    real_chdir = os.chdir
    os.chdir = lambda *_args, **_kwargs: None  # type: ignore[method-assign]
    try:
        from aureon_public.pin_blob import _SameBytesLoader, git_blob_sha1

        try:
            data = guard_path.read_bytes()
        except OSError as exc:
            raise ImportError(f"{guard_path.name} is not in this checkout") from exc
        if git_blob_sha1(data) != GUARD_BLOB:
            raise ImportError(GUARD_MISMATCH)
        from aureon_public.pin_blob import install_pinned_aureon_finder

        install_pinned_aureon_finder(root)
        loader = _SameBytesLoader(data, str(guard_path))
        spec = importlib.util.spec_from_loader(
            "aureon_hf_space_guard",
            loader,
            origin=str(guard_path),
        )
        if spec is None:
            raise ImportError(f"cannot load {guard_path}")
        spec.has_location = True
        module = importlib.util.module_from_spec(spec)
        module.__file__ = str(guard_path)
        sys.modules["aureon_hf_space_guard"] = module
        loader.exec_module(module)
    finally:
        os.chdir = real_chdir
    if Path.cwd() != cwd:
        real_chdir(cwd)
    os.environ.pop("AUREON_MCP_TRANSIT_KEY", None)
    _prefer_installed_aureon(root)
    _DONE = True


def _prefer_installed_aureon(root: Path) -> None:
    """Use the pinned install when it is present. Otherwise keep the checkout.

    The pinned finder is already on ``sys.meta_path``. It answers from the
    checkout without reading ``sys.path``, so this probe takes it off the path
    for the lookup. A direct_url.json that names the pin is what keeps the
    trimmed path. The blob check still decides which bytes run.
    """

    from aureon_public.pin_blob import PinnedAureonFinder

    saved = list(sys.path)
    trimmed = [entry for entry in saved if not _same(entry, root)]
    sys.path[:] = trimmed
    removed = [finder for finder in sys.meta_path if isinstance(finder, PinnedAureonFinder)]
    for finder in removed:
        sys.meta_path.remove(finder)
    try:
        found = importlib.util.find_spec("aureon")
    finally:
        for finder in reversed(removed):
            sys.meta_path.insert(0, finder)
        sys.path[:] = saved
    origin = getattr(found, "origin", None) if found is not None else None
    if not origin:
        return
    origin_path = Path(origin)
    if _outside_checkout(origin_path, root) and _direct_url_commit(origin_path) == PINNED_COMMIT:
        sys.path[:] = trimmed


def _outside_checkout(origin: Path, root: Path) -> bool:
    resolved = origin.resolve()
    root_resolved = root.resolve()
    return resolved != root_resolved and root_resolved not in resolved.parents


def _direct_url_commit(origin: Path) -> str | None:
    """Commit recorded beside an installed aureon, if direct_url.json has one."""

    site = origin.resolve().parent.parent
    for dist in sorted(site.glob("aureon-*.dist-info")):
        direct = dist / "direct_url.json"
        if not direct.is_file():
            continue
        try:
            payload = json.loads(direct.read_text(encoding="utf-8"))
        except (OSError, json.JSONDecodeError):
            continue
        vcs = payload.get("vcs_info") if isinstance(payload, dict) else None
        commit = vcs.get("commit_id") if isinstance(vcs, dict) else None
        if isinstance(commit, str) and commit.strip():
            return commit.strip()
    return None


def _git_commit(root: Path) -> str:
    try:
        result = subprocess.run(
            ["git", "rev-parse", "HEAD"],
            cwd=root,
            check=True,
            capture_output=True,
            text=True,
        )
    except (OSError, subprocess.CalledProcessError):
        return "unknown"
    commit = result.stdout.strip()
    if len(commit) == 40 and all(character in "0123456789abcdef" for character in commit):
        return commit
    return "unknown"


def describe_aureon_source(origin: Path | None, root: Path) -> dict[str, str]:
    """Say which tree answered. Pinned only when direct_url.json names the pin."""

    if origin is not None and _outside_checkout(origin, root):
        commit = _direct_url_commit(origin)
        if commit == PINNED_COMMIT:
            return {"kind": "pinned", "commit": commit}
        if commit:
            return {"kind": "installed", "commit": commit}
        return {"kind": "checkout", "commit": "unknown"}
    return {"kind": "checkout", "commit": _git_commit(root)}


def aureon_source() -> dict[str, str]:
    """The aureon import this process will use, after the guard has chosen a path.

    Raises FileNotFoundError, via repo_root(), when there is no checkout.
    There is no separate 'no checkout' status. The server needs the checkout.
    """

    apply_space_guard()
    root = repo_root()
    found = importlib.util.find_spec("aureon")
    origin_text = getattr(found, "origin", None) if found is not None else None
    origin = Path(origin_text) if origin_text else None
    return describe_aureon_source(origin, root)