"""User CRUD and permission management for Vacuum Wall authentication.

All operations use DB query IDs through the Database abstract layer.
Password hashing uses Argon2id via lib.password.
"""

from __future__ import annotations

import logging
import re
import secrets
from typing import Any

from lib.auth import (
    blacklist_active_refresh_token,
    rotate_user_secret,
)
from lib.db import (
    Q_DELETE_PERMISSION_SUBSYSTEM,
    Q_DELETE_USER,
    Q_INSERT_USER,
    Q_SELECT_PERMISSIONS,
    Q_SELECT_USER_BY_NAME,
    Q_SELECT_USERS_WITH_PERMS,
    Q_UPDATE_PASSWORD,
    Q_UPSERT_PERMISSION,
    get_db,
)
from lib.password import hash_password, needs_rehash, verify_password

logger = logging.getLogger(__name__)

# Pre-computed dummy hash for constant-time verification on nonexistent users.
# Generated once at module load to avoid timing leaks from per-call hash generation.
_DUMMY_HASH = hash_password(secrets.token_hex(32))

# Builtin admin — hardcoded, full access, cannot be modified/deleted
BUILTIN_ADMIN_USERNAME = "admin"

# All subsystem names for default permission assignment
ALL_SUBSYSTEMS = [
    "firewall",
    "network",
    "dhcp",
    "proxy",
    "certs",
    "wireguard",
    "logs",
    "status",
    "auth",
]

_USERNAME_RE = re.compile(r"^[a-zA-Z0-9_-]{3,32}$")


def _get_permissions(username: str) -> dict[str, str]:
    """Load permissions for *username* from the database.

    Args:
        username: The username to load permissions for.

    Returns:
        Dict mapping subsystem names to permission levels.
    """
    db = get_db()
    rows = db.query(Q_SELECT_PERMISSIONS, (username,))
    return {row["subsystem"]: row["level"] for row in rows}


def get_user(username: str) -> dict[str, Any] | None:
    """Get a user by username (without password hash or JWT secret).

    Args:
        username: The username to look up.

    Returns:
        User dict with id, username, permissions, or None if not found.
    """
    user = find_user(username)
    if user is None:
        return None
    return {
        "id": user["id"],
        "username": user["username"],
        "permissions": _get_permissions(username),
    }


def find_user(username: str) -> dict[str, Any] | None:
    """Find a user by username, including password hash and JWT secret.

    Used for password verification and token operations. Not returned through APIs.

    Args:
        username: The username to look up.

    Returns:
        User dict from the database row, or None.
    """
    db = get_db()
    rows = db.query(Q_SELECT_USER_BY_NAME, (username,))
    if not rows:
        return None
    return rows[0]


def verify_user_password(username: str, password: str) -> dict[str, Any] | None:
    """Verify a user's password using Argon2id.

    Args:
        username: The username to verify.
        password: Plain-text password.

    Returns:
        User dict (without password hash) if the password is correct, None otherwise.
    """
    user = find_user(username)
    if user is None:
        # Run a dummy Argon2id verification against a pre-computed hash to
        # prevent timing-based user enumeration. Uses module-level hash
        # so both paths take ~1 verify call (~200ms) instead of ~400ms.
        verify_password(password, _DUMMY_HASH)
        return None
    if not verify_password(password, user["password_hash"]):
        return None
    if needs_rehash(user["password_hash"]):
        new_hash = hash_password(password)
        db = get_db()
        db.run(Q_UPDATE_PASSWORD, (new_hash, username))
        logger.info("Password hash rehashed for %r (param upgrade)", username)
    return {
        "id": user["id"],
        "username": user["username"],
        "permissions": _get_permissions(username),
    }


def create_user(
    username: str,
    password: str,
    permissions: dict[str, str] | None = None,
) -> dict[str, Any]:
    """Create a new user with the given password and permissions.

    Args:
        username: The new username (3-32 alphanumeric chars, dash, underscore).
        password: Plain-text password that will be hashed with Argon2id.
        permissions: Dict mapping subsystem names to "read" or "rw".

    Returns:
        The created user dict with id, username, permissions.

    Raises:
        ValueError: If username is invalid or already exists.
    """
    if not _USERNAME_RE.match(username):
        raise ValueError(
            "Username must be 3-32 characters: letters, digits, dash, underscore"
        )

    existing = find_user(username)
    if existing is not None:
        raise ValueError(f"User {username!r} already exists")

    password_hash = hash_password(password)
    jwt_secret = secrets.token_urlsafe(32)

    db = get_db()
    with db.in_transaction() as tx:
        user_id = tx.run_one(Q_INSERT_USER, (username, password_hash, jwt_secret))
        if permissions:
            for subsystem, level in permissions.items():
                tx.run(Q_UPSERT_PERMISSION, (username, subsystem, level))

    return {
        "id": user_id,
        "username": username,
        "permissions": _get_permissions(username),
    }


def update_password(username: str, old_password: str, new_password: str) -> bool:
    """Update a user's password and invalidate all active tokens.

    Rotates the user's JWT secret, immediately invalidating all existing
    access and refresh tokens.

    Args:
        username: The username.
        old_password: Current password.
        new_password: New plain-text password.

    Returns:
        True if password was updated.

    Raises:
        ValueError: If old password is incorrect.
    """
    if not verify_user_password(username, old_password):
        raise ValueError("Current password is incorrect")

    blacklist_active_refresh_token(username)
    new_hash = hash_password(new_password)
    rotate_user_secret(username)
    db = get_db()
    db.run(Q_UPDATE_PASSWORD, (new_hash, username))
    return True


def update_permissions(username: str, permissions: dict[str, str]) -> None:
    """Update a user's permissions and invalidate all existing tokens.

    Replaces all existing permissions with the provided mapping. Rotates the
    JWT secret so that permission changes take effect immediately — existing
    tokens with stale permissions are no longer valid.

    Args:
        username: The username.
        permissions: Dict mapping subsystem names to permission levels.

    Raises:
        ValueError: If attempting to modify builtin admin.
    """
    if username == BUILTIN_ADMIN_USERNAME:
        raise ValueError("Cannot modify permissions for builtin admin")

    user = find_user(username)
    if user is None:
        raise ValueError(f"User {username!r} not found")

    db = get_db()
    with db.in_transaction() as tx:
        # Upsert all new permissions first, then remove stale ones.
        # This order ensures that if an upsert fails mid-loop, the user's
        # permissions remain intact (transaction rolls back) rather than
        # being permanently wiped.
        existing = {
            row["subsystem"]: row["level"]
            for row in db.query(Q_SELECT_PERMISSIONS, (username,))
        }
        for subsystem, level in permissions.items():
            tx.run(Q_UPSERT_PERMISSION, (username, subsystem, level))
        for subsystem in existing:
            if subsystem not in permissions:
                tx.run(Q_DELETE_PERMISSION_SUBSYSTEM, (username, subsystem))
    blacklist_active_refresh_token(username)
    rotate_user_secret(username)


def list_users() -> list[dict[str, Any]]:
    """List all users with their permissions.

    Returns:
        List of user summary dicts.
    """
    db = get_db()
    rows = db.query(Q_SELECT_USERS_WITH_PERMS, ())

    users: dict[int, dict[str, Any]] = {}
    for row in rows:
        uid = row["id"]
        if uid not in users:
            users[uid] = {
                "id": uid,
                "username": row["username"],
                "permissions": {},
                "created_at": row["created_at"],
            }
        if row["subsystem"] is not None:
            users[uid]["permissions"][row["subsystem"]] = row["level"]

    return list(users.values())


def delete_user(username: str) -> bool:
    """Delete a user and all their associated data.

    Permissions and WebAuthn credentials are CASCADE-deleted by the schema.

    Args:
        username: The username to delete.

    Returns:
        True if the user was deleted.

    Raises:
        ValueError: If the user does not exist.
    """
    user = find_user(username)
    if user is None:
        raise ValueError(f"User {username!r} not found")

    blacklist_active_refresh_token(username)
    db = get_db()
    db.run(Q_DELETE_USER, (username,))
    return True