# backend/auth/user_store.py
# CRUD operations on data/users.json with atomic writes.
# File is read on each auth request (no stale cache), written atomically
# via tmp+rename to prevent corruption on crash.

import json
import uuid
import logging
import shutil
from pathlib import Path
from datetime import datetime, timezone, timedelta
from typing import Optional, List

from .password import hash_password

logger = logging.getLogger("obsigate.auth.users")

USERS_FILE = Path("data/users.json")


def _read() -> dict:
    """Read users.json. Returns empty structure if file doesn't exist."""
    if not USERS_FILE.exists():
        return {"version": 1, "users": {}}
    try:
        return json.loads(USERS_FILE.read_text(encoding="utf-8"))
    except (json.JSONDecodeError, OSError) as e:
        logger.error(f"Failed to read users.json: {e}")
        return {"version": 1, "users": {}}


def _write(data: dict):
    """Atomic write: write to .tmp then rename to prevent corruption."""
    try:
        USERS_FILE.parent.mkdir(parents=True, exist_ok=True)
        tmp = USERS_FILE.with_suffix(".tmp")
        tmp.write_text(json.dumps(data, indent=2, default=str), encoding="utf-8")
        shutil.move(str(tmp), str(USERS_FILE))
        try:
            USERS_FILE.chmod(0o600)
        except OSError:
            pass  # Windows doesn't support Unix permissions
    except PermissionError as e:
        logger.critical("=" * 60)
        logger.critical(f"ERREUR DE PERMISSION : Impossible d'écrire dans {USERS_FILE.parent}")
        logger.critical("Le conteneur n'a pas les droits sur le volume monté dans /app/data.")
        logger.critical("FIX : Exécutez sur l'hôte (Linux) : sudo chown -R 1000:1000 /votre/chemin/data")
        logger.critical("=" * 60)
        raise e


def has_users() -> bool:
    """Check if any users exist."""
    return bool(_read()["users"])


def get_user(username: str) -> Optional[dict]:
    """Get a user by username. Returns None if not found."""
    return _read()["users"].get(username)


def get_all_users() -> List[dict]:
    """Get all users WITHOUT password_hash (safe for API responses)."""
    users = _read()["users"]
    return [
        {k: v for k, v in u.items() if k != "password_hash"}
        for u in users.values()
    ]


def create_user(
    username: str,
    password: str,
    role: str = "user",
    vaults: Optional[List[str]] = None,
    display_name: Optional[str] = None,
) -> dict:
    """Create a new user. Raises ValueError if username already taken."""
    data = _read()
    if username in data["users"]:
        raise ValueError(f"User '{username}' already exists")

    user = {
        "id": str(uuid.uuid4()),
        "username": username,
        "display_name": display_name or username,
        "password_hash": hash_password(password),
        "role": role,
        "vaults": vaults or [],
        "active": True,
        "created_at": datetime.now(timezone.utc).isoformat(),
        "last_login": None,
        "failed_attempts": 0,
        "locked_until": None,
    }
    data["users"][username] = user
    _write(data)
    logger.info(f"Created user '{username}' (role={role})")
    return {k: v for k, v in user.items() if k != "password_hash"}


def update_user(username: str, updates: dict) -> dict:
    """Update user fields. Raises ValueError if user not found.

    Forbidden fields (id, username, created_at) are silently ignored.
    If 'password' is in updates, it's hashed and stored as password_hash.
    """
    data = _read()
    if username not in data["users"]:
        raise ValueError(f"User '{username}' not found")

    forbidden = {"id", "username", "created_at"}
    safe_updates = {k: v for k, v in updates.items() if k not in forbidden}

    if "password" in safe_updates:
        safe_updates["password_hash"] = hash_password(safe_updates.pop("password"))

    data["users"][username].update(safe_updates)
    _write(data)
    return {k: v for k, v in data["users"][username].items() if k != "password_hash"}


def delete_user(username: str):
    """Delete a user. Raises ValueError if not found."""
    data = _read()
    if username not in data["users"]:
        raise ValueError(f"User '{username}' not found")
    del data["users"][username]
    _write(data)
    logger.info(f"Deleted user '{username}'")


def record_login_success(username: str):
    """Record a successful login: update last_login, reset failed attempts."""
    update_user(username, {
        "last_login": datetime.now(timezone.utc).isoformat(),
        "failed_attempts": 0,
        "locked_until": None,
    })


def record_login_failure(username: str) -> int:
    """Record a failed login. Returns the new attempt count.

    After 5 failures, locks the account for 15 minutes.
    """
    data = _read()
    user = data["users"].get(username)
    if not user:
        return 0

    attempts = user.get("failed_attempts", 0) + 1
    updates = {"failed_attempts": attempts}

    # Lock after 5 failed attempts (15 minutes)
    if attempts >= 5:
        locked_until = (
            datetime.now(timezone.utc) + timedelta(minutes=15)
        ).isoformat()
        updates["locked_until"] = locked_until
        logger.warning(f"Account '{username}' locked after {attempts} failed attempts")

    update_user(username, updates)
    return attempts


def is_locked(username: str) -> bool:
    """Check if an account is temporarily locked.

    Auto-unlocks if the lock period has expired.
    """
    user = get_user(username)
    if not user or not user.get("locked_until"):
        return False
    locked_until = datetime.fromisoformat(user["locked_until"])
    if datetime.now(timezone.utc) > locked_until:
        # Lock expired — unlock
        update_user(username, {"locked_until": None, "failed_attempts": 0})
        return False
    return True