"""
Python implementation of the security service pseudocode.
This module provides a simple CLI-like flow for registering,
logging in, restoring accounts, and managing credentials.
"""

import hashlib
import secrets
import sqlite3
from dataclasses import dataclass, field
from typing import List, Optional


DEFAULT_USERNAME = "default"


@dataclass
class SecurityService:
    """Service for managing user credentials in a SQLite database."""

    db_path: str = "security.db"
    username: str = field(default=DEFAULT_USERNAME, init=False)

    def __post_init__(self) -> None:
        self._conn = sqlite3.connect(self.db_path)
        self._conn.execute(
            """
            CREATE TABLE IF NOT EXISTS users (
                id INTEGER PRIMARY KEY AUTOINCREMENT,
                username TEXT UNIQUE NOT NULL,
                password_hash TEXT NOT NULL,
                security_code TEXT NOT NULL
            )
            """
        )
        self._conn.execute(
            """
            CREATE TABLE IF NOT EXISTS implants (
                id INTEGER PRIMARY KEY AUTOINCREMENT,
                name TEXT UNIQUE NOT NULL,
                info TEXT NOT NULL,
                ownername TEXT NOT NULL
            )
            """
        )
        self._conn.commit()

    # Utility helpers -----------------------------------------------------
    @staticmethod
    def _generate_random_char() -> str:
        return secrets.choice("abcdefghijklmnopqrstuvwxyz")

    @staticmethod
    def _generate_random_digit() -> str:
        return secrets.choice("0123456789")

    @staticmethod
    def make_unique_username(base_username: str) -> str:
        suffix = "".join(SecurityService._generate_random_char() for _ in range(8))
        return f"{base_username}_{suffix}"

    @staticmethod
    def make_new_password() -> str:
        return "".join(SecurityService._generate_random_char() for _ in range(8))

    @staticmethod
    def generate_code() -> str:
        return "".join(SecurityService._generate_random_digit() for _ in range(3))

    @staticmethod
    def hash_password(password: str) -> str:
        digest = hashlib.sha256(password.encode("utf-8")).hexdigest()
        return digest

    @staticmethod
    def print_system_data(message: str) -> None:
        print(message)

    # Database operations -------------------------------------------------
    def _user_exists(self, username: str) -> bool:
        row = self._conn.execute(
            "SELECT 1 FROM users WHERE username = ?", (username,)
        ).fetchone()
        return row is not None

    def _create_user(self, username: str, password: str, security_code: str) -> bool:
        password_hash = self.hash_password(password)
        try:
            self._conn.execute(
                "INSERT INTO users (username, password_hash, security_code) VALUES (?, ?, ?)",
                (username, password_hash, security_code),
            )
            self._conn.commit()
        except sqlite3.IntegrityError:
            return False
        return True

    def _check_user(self, username: str, password: str) -> bool:
        password_hash = self.hash_password(password)
        row = self._conn.execute(
            "SELECT 1 FROM users WHERE username = ? AND password_hash = ?",
            (username, password_hash),
        ).fetchone()
        return row is not None

    def _check_restore_user(self, username: str, code: str) -> bool:
        row = self._conn.execute(
            "SELECT 1 FROM users WHERE username = ? AND security_code = ?",
            (username, code),
        ).fetchone()
        return row is not None

    def _change_password(self, username: str, new_password: str) -> bool:
        password_hash = self.hash_password(new_password)
        cursor = self._conn.execute(
            "UPDATE users SET password_hash = ? WHERE username = ?",
            (password_hash, username),
        )
        self._conn.commit()
        return cursor.rowcount > 0

    def _get_security_code(self, username: str) -> Optional[str]:
        row = self._conn.execute(
            "SELECT security_code FROM users WHERE username = ?", (username,)
        ).fetchone()
        return row[0] if row else None

    def _user_implants(self, username: str) -> List[str]:
        rows = self._conn.execute(
            "SELECT name FROM implants WHERE ownername = ?", (username,)
        ).fetchall()
        return [row[0] for row in rows]

    def _implant_belongs_to(self, username: str, name: str) -> bool:
        row = self._conn.execute(
            "SELECT 1 FROM implants WHERE ownername = ? AND name = ?",
            (username, name),
        ).fetchone()
        return row is not None

    def _delete_implant(self, name: str) -> bool:
        cursor = self._conn.execute("DELETE FROM implants WHERE name = ?", (name,))
        self._conn.commit()
        return cursor.rowcount > 0

    def _add_implant(self, name: str, info: str, ownername: str) -> bool:
        try:
            self._conn.execute(
                "INSERT INTO implants (name, info, ownername) VALUES (?, ?, ?)",
                (name, info, ownername),
            )
            self._conn.commit()
        except sqlite3.IntegrityError:
            return False
        return True

    def _get_implant_info(self, name: str) -> Optional[str]:
        row = self._conn.execute(
            "SELECT info FROM implants WHERE name = ?", (name,)
        ).fetchone()
        return row[0] if row else None

    # User flows ----------------------------------------------------------
    def register_user(self) -> None:
        raw_username = input("\nEnter username: ").strip()
        password = input("Enter password: ").strip()
        self.print_system_data("Creating new account. Please wait...")

        candidate_username = self.make_unique_username(raw_username)
        security_code = self.generate_code()

        if self._user_exists(candidate_username):
            self.print_system_data("User already exists.")
            return

        if self._create_user(candidate_username, password, security_code):
            self.print_system_data("---Your credentials ---")
            print(f"Username: {candidate_username}")
            print(f"Password: {password}")
            print(f"Security code: {security_code}")
            self.print_system_data("Use these credentials to gain access to the system.")
        else:
            self.print_system_data("Failed to create user.")

    def login_user(self) -> None:
        username = input("\nEnter username: ").strip()
        password = input("Enter password: ").strip()
        self.print_system_data("Trying to log in...")

        if self._check_user(username, password):
            self.username = username
            self.print_system_data("Successfully logged in.")
        else:
            self.print_system_data("Failed to log in.")

    def restore_user(self) -> None:
        username = input("\nEnter username: ").strip()
        code = input("Enter security code: ").strip()
        self.print_system_data("Trying to find user...")

        if not self._check_restore_user(username, code):
            self.print_system_data("Failed to find user.")
            return

        self.print_system_data("Successfully found user.")
        new_password = self.make_new_password()
        if self._change_password(username, new_password):
            self.print_system_data("Changing password...")
            self.print_system_data("---Your new credentials ---")
            print(f"Username: {username}")
            print(f"Password: {new_password}")
            self.print_system_data(
                "Use these credentials to gain access to the system."
            )
        else:
            self.print_system_data("Unexpected error. Please try later.")

    def change_password(self) -> None:
        if self.username == DEFAULT_USERNAME:
            self.print_system_data("You need to log in first.")
            return

        new_password = input("Enter a new password: ").strip()
        if not new_password:
            self.print_system_data("Password cannot be empty.")
            return

        if self._change_password(self.username, new_password):
            self.print_system_data("Password changed successfully.")
        else:
            self.print_system_data("Failed to change password.")

    def show_security_code(self) -> None:
        if self.username == DEFAULT_USERNAME:
            self.print_system_data("You need to log in first.")
            return

        code = self._get_security_code(self.username)
        if code is None:
            self.print_system_data("Failed to retrieve security code.")
        else:
            print(f"Security code: {code}")

    def add_implant(self) -> None:
        if self.username == DEFAULT_USERNAME:
            self.print_system_data("You need to log in first.")
            return

        name = input("\nEnter implant name: ").strip()
        info = input("\nEnter implant info: ").strip()
        if not name or not info:
            self.print_system_data("Invalid option selected.")
            return

        if self._add_implant(name, info, self.username):
            self.print_system_data("Implant added successfully.")
        else:
            self.print_system_data("Unexpected error. Please try later.")

    def delete_implant(self) -> None:
        if self.username == DEFAULT_USERNAME:
            self.print_system_data("You need to log in first.")
            return

        self.print_system_data("Getting list of implants. Please wait...")
        implants = self._user_implants(self.username)
        if not implants:
            self.print_system_data("No implants found for this user.")
            return

        for idx, implant in enumerate(implants, start=1):
            print(f"{idx}. {implant}")

        name = input("\nEnter implant name: ").strip()
        if not name:
            self.print_system_data("Invalid option selected.")
            return

        if not self._implant_belongs_to(self.username, name):
            self.print_system_data("Invalid option selected.")
            return

        self.print_system_data("Deleting implant...")
        if self._delete_implant(name):
            self.print_system_data("Implant deleted successfully.")
        else:
            self.print_system_data("Unexpected error. Please try later.")

    def show_implant_info(self) -> None:
        if self.username == DEFAULT_USERNAME:
            self.print_system_data("You need to log in first.")
            return

        self.print_system_data("Getting list of implants. Please wait...")
        implants = self._user_implants(self.username)
        if not implants:
            self.print_system_data("No implants found for this user.")
            return

        for idx, implant in enumerate(implants, start=1):
            print(f"{idx}. {implant}")

        name = input("\nEnter implant name: ").strip()
        if not name:
            self.print_system_data("Invalid option selected.")
            return

        if not self._implant_belongs_to(self.username, name):
            self.print_system_data("Invalid option selected.")
            return

        self.print_system_data("Getting implant info...")
        info = self._get_implant_info(name)
        if info is None:
            self.print_system_data("Unexpected error. Please try later.")
            return

        print(f"Implant info: {info}")

    # Menus ---------------------------------------------------------------
    def settings_menu(self) -> None:
        while self.username != DEFAULT_USERNAME:
            self.print_system_data("--- Settings menu ---")
            self.print_system_data("1. Change password")
            self.print_system_data("2. Show security code")
            self.print_system_data("3. Return to previous menu")
            choice = input("Choose an option (1-3): ").strip()
            if choice == "1":
                self.change_password()
            elif choice == "2":
                self.show_security_code()
            elif choice == "3":
                return
            else:
                self.print_system_data("Invalid option selected.")

    def app_menu(self) -> None:
        while self.username != DEFAULT_USERNAME:
            self.print_system_data("--- Application menu ---")
            self.print_system_data("1. Implant menu")
            self.print_system_data("2. Settings menu")
            self.print_system_data("3. Log out")
            choice = input("Choose an option (1-3): ").strip()
            if choice == "1":
                self.implants_menu()
            elif choice == "2":
                self.settings_menu()
            elif choice == "3":
                self.username = DEFAULT_USERNAME
                self.print_system_data("Logged out.")
            else:
                self.print_system_data("Invalid option selected.")

    def implants_menu(self) -> None:
        while self.username != DEFAULT_USERNAME:
            self.print_system_data("--- Implants menu ---")
            self.print_system_data("1. Add new implant")
            self.print_system_data("2. Delete implant")
            self.print_system_data("3. Show info about implant")
            self.print_system_data("4. Return to previous menu")
            choice = input("Choose an option (1-4): ").strip()
            if choice == "1":
                self.add_implant()
            elif choice == "2":
                self.delete_implant()
            elif choice == "3":
                self.show_implant_info()
            elif choice == "4":
                return
            else:
                self.print_system_data("Invalid option selected.")

    def startup_menu(self) -> None:
        while True:
            if self.username != DEFAULT_USERNAME:
                self.app_menu()
                continue

            self.print_system_data("--- Startup menu ---")
            self.print_system_data("1. Register new account")
            self.print_system_data("2. Login to account")
            self.print_system_data("3. Restore an account")
            self.print_system_data("4. Exit from program")
            choice = input("Choose an option (1-4): ").strip()
            if choice == "1":
                self.register_user()
            elif choice == "2":
                self.login_user()
            elif choice == "3":
                self.restore_user()
            elif choice == "4":
                self.print_system_data("Goodbye!")
                break
            else:
                self.print_system_data("Invalid option selected.")


def main() -> None:
    service = SecurityService()
    service.print_system_data("Configuring network interfaces... done")
    service.print_system_data("Mounting /dev/sda1... done")
    service.print_system_data("Starting random number generator daemon... done")
    service.startup_menu()


if __name__ == "__main__":
    main()