"""User-specific code and data structures."""
from uuid import UUID, uuid4
from typing import Any, Tuple, NamedTuple

from argon2 import PasswordHasher
from argon2.exceptions import VerifyMismatchError

from gn_auth.auth import db
from gn_auth.auth.authorisation.errors import NotFoundError

class User(NamedTuple):
    """Class representing a user."""
    user_id: UUID
    email: str
    name: str

    def get_user_id(self):
        """Return the user's UUID. Mostly for use with Authlib."""
        return self.user_id

    def dictify(self) -> dict[str, Any]:
        """Return a dict representation of `User` objects."""
        return {"user_id": self.user_id, "email": self.email, "name": self.name}

DUMMY_USER = User(user_id=UUID("a391cf60-e8b7-4294-bd22-ddbbda4b3530"),
                  email="gn3@dummy.user",
                  name="Dummy user to use as placeholder")

def user_by_email(conn: db.DbConnection, email: str) -> User:
    """Retrieve user from database by their email address"""
    with db.cursor(conn) as cursor:
        cursor.execute("SELECT * FROM users WHERE email=?", (email,))
        row = cursor.fetchone()

    if row:
        return User(UUID(row["user_id"]), row["email"], row["name"])

    raise NotFoundError(f"Could not find user with email {email}")

def user_by_id(conn: db.DbConnection, user_id: UUID) -> User:
    """Retrieve user from database by their user id"""
    with db.cursor(conn) as cursor:
        cursor.execute("SELECT * FROM users WHERE user_id=?", (str(user_id),))
        row = cursor.fetchone()

    if row:
        return User(UUID(row["user_id"]), row["email"], row["name"])

    raise NotFoundError(f"Could not find user with ID {user_id}")

def same_password(password: str, hashed: str) -> bool:
    """Check that `raw_password` is hashed to `hash`"""
    try:
        return hasher().verify(hashed, password)
    except VerifyMismatchError as _vme:
        return False

def valid_login(conn: db.DbConnection, user: User, password: str) -> bool:
    """Check the validity of the provided credentials for login."""
    with db.cursor(conn) as cursor:
        cursor.execute(
            ("SELECT * FROM users LEFT JOIN user_credentials "
             "ON users.user_id=user_credentials.user_id "
             "WHERE users.user_id=?"),
            (str(user.user_id),))
        row = cursor.fetchone()

    if row is None:
        return False

    return same_password(password, row["password"])

def save_user(cursor: db.DbCursor, email: str, name: str) -> User:
    """
    Create and persist a user.

    The user creation could be done during a transaction, therefore the function
    takes a cursor object rather than a connection.

    The newly created and persisted user is then returned.
    """
    user_id = uuid4()
    cursor.execute("INSERT INTO users VALUES (?, ?, ?)",
                   (str(user_id), email, name))
    return User(user_id, email, name)

def hasher():
    """Retrieve PasswordHasher object"""
    # TODO: Maybe tune the parameters here...
    # Tuneable Parameters:
    # - time_cost (default: 2)
    # - memory_cost (default: 102400)
    # - parallelism (default: 8)
    # - hash_len (default: 16)
    # - salt_len (default: 16)
    # - encoding (default: 'utf-8')
    # - type (default: <Type.ID: 2>)
    return PasswordHasher()

def hash_password(password):
    """Hash the password."""
    return hasher().hash(password)

def set_user_password(
        cursor: db.DbCursor, user: User, password: str) -> Tuple[User, bytes]:
    """Set the given user's password in the database."""
    hashed_password = hash_password(password)
    cursor.execute(
        ("INSERT INTO user_credentials VALUES (:user_id, :hash) "
         "ON CONFLICT (user_id) DO UPDATE SET password=:hash"),
        {"user_id": str(user.user_id), "hash": hashed_password})
    return user, hashed_password

def users(conn: db.DbConnection,
          ids: tuple[UUID, ...] = tuple()) -> tuple[User, ...]:
    """
    Fetch all users with the given `ids`. If `ids` is empty, return ALL users.
    """
    params = ", ".join(["?"] * len(ids))
    with db.cursor(conn) as cursor:
        query = "SELECT * FROM users" + (
            f" WHERE user_id IN ({params})"
            if len(ids) > 0 else "")
        print(query)
        cursor.execute(query, tuple(str(the_id) for the_id in ids))
        return tuple(User(UUID(row["user_id"]), row["email"], row["name"])
                     for row in cursor.fetchall())
    return tuple()