"""Atomic environment persistence and the one-time WebSocket default migration."""

import os
from pathlib import Path
import tempfile

from dotenv import dotenv_values
from filelock import FileLock

TRANSPORT_DEFAULT_VERSION_KEY = "ARTEMIS_TRANSPORT_DEFAULT_VERSION"


def _lock(path: Path) -> FileLock:
    path.parent.mkdir(parents=True, exist_ok=True)
    return FileLock(str(path) + ".artemis.lock", timeout=5)


def _write(path: Path, values: dict[str, str]) -> None:
    original = path.read_text(encoding="utf-8") if path.exists() else ""
    kept = [
        line
        for line in original.splitlines()
        if line.strip().removeprefix("export ").split("=", 1)[0].strip() not in values
    ]
    for key, value in values.items():
        escaped = value.replace("\\", "\\\\").replace("'", "\\'")
        kept.append(f"{key}='{escaped}'")
    fd, temp_name = tempfile.mkstemp(prefix=".env-", dir=path.parent)
    try:
        with os.fdopen(fd, "w", encoding="utf-8", newline="\n") as stream:
            stream.write("\n".join(kept) + "\n")
            stream.flush()
            os.fsync(stream.fileno())
        os.replace(temp_name, path)
    finally:
        Path(temp_name).unlink(missing_ok=True)


def persist_environment(path: Path, values: dict[str, str]) -> None:
    with _lock(path):
        _write(path, values)
        os.environ.update(values)


def _transport_default_is_current(path: Path) -> bool:
    saved = dotenv_values(path, interpolate=False) if path.exists() else {}
    try:
        return int(saved.get(TRANSPORT_DEFAULT_VERSION_KEY) or "0") >= 1
    except ValueError:
        return False


def migrate_transport_default(path: Path) -> bool:
    """Migrate unversioned HTTP preferences once, preserving later opt-outs."""
    # Completed migrations need no write access, including read-only deployments.
    if _transport_default_is_current(path):
        return False
    with _lock(path):
        if _transport_default_is_current(path):
            return False
        values = {"OPENAI_TRANSPORT": "websocket", TRANSPORT_DEFAULT_VERSION_KEY: "1"}
        _write(path, values)
        os.environ.update(values)
        return True