import sqlite3
import os
import logging
import secrets
from datetime import datetime, timedelta
from typing import Optional, Dict, Any

logger = logging.getLogger(__name__)

# Locate db correctly in the same directory
DB_PATH = os.path.join(os.path.dirname(__file__), "localfood.db")

def get_db_connection():
    conn = sqlite3.connect(DB_PATH)
    conn.row_factory = sqlite3.Row
    return conn

def create_tables():
    """Initialize the SQLite database with required tables"""
    try:
        conn = get_db_connection()
        cursor = conn.cursor()
        
        # Create users table securely locally
        cursor.execute('''
        CREATE TABLE IF NOT EXISTS users (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            username TEXT UNIQUE NOT NULL,
            password_hash TEXT NOT NULL,
            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
        )
        ''')

        # Create sessions table for database-backed tokens
        cursor.execute('''
        CREATE TABLE IF NOT EXISTS sessions (
            token TEXT PRIMARY KEY,
            user_id INTEGER NOT NULL,
            expires_at TIMESTAMP NOT NULL,
            FOREIGN KEY (user_id) REFERENCES users (id)
        )
        ''')
        
        conn.commit()
        conn.close()
        logger.info("Database and tables initialized successfully.")
    except Exception as e:
        logger.error(f"Error initializing database: {e}")
        raise

def get_user_by_username(username: str) -> Optional[Dict[str, Any]]:
    """Retrieve user dictionary if they exist"""
    try:
        conn = get_db_connection()
        cursor = conn.cursor()
        cursor.execute("SELECT * FROM users WHERE username = ?", (username,))
        row = cursor.fetchone()
        conn.close()
        return dict(row) if row else None
    except Exception as e:
        logger.error(f"Database error fetching user: {e}")
        return None

def create_user(username: str, password_hash: str) -> Optional[int]:
    """Creates a user securely. Returns user_id if successful, None if username exists."""
    try:
        conn = get_db_connection()
        cursor = conn.cursor()
        cursor.execute(
            "INSERT INTO users (username, password_hash) VALUES (?, ?)",
            (username, password_hash)
        )
        user_id = cursor.lastrowid
        conn.commit()
        conn.close()
        return user_id
    except sqlite3.IntegrityError:
        return None
    except Exception as e:
        logger.error(f"Database error during user creation: {e}")
        raise

def create_session(user_id: int) -> str:
    """Create a secure 32-character session token in the DB valid for 24h"""
    token = secrets.token_urlsafe(32)
    expires_at = datetime.now() + timedelta(hours=24)
    
    try:
        conn = get_db_connection()
        cursor = conn.cursor()
        cursor.execute(
            "INSERT INTO sessions (token, user_id, expires_at) VALUES (?, ?, ?)",
            (token, user_id, expires_at)
        )
        conn.commit()
        conn.close()
        return token
    except Exception as e:
        logger.error(f"Error creating session: {e}")
        raise

def get_user_from_token(token: str) -> Optional[Dict[str, Any]]:
    """Verify a session token and return the associated user data if valid and not expired"""
    try:
        conn = get_db_connection()
        cursor = conn.cursor()
        # Find user if token exists and hasn't expired
        cursor.execute('''
            SELECT users.* FROM users
            JOIN sessions ON users.id = sessions.user_id
            WHERE sessions.token = ? AND sessions.expires_at > ?
        ''', (token, datetime.now()))
        row = cursor.fetchone()
        conn.close()
        return dict(row) if row else None
    except Exception as e:
        logger.error(f"Database error verifying token: {e}")
        return None

def delete_session(token: str):
    """Securely remove a session token when the user logs out"""
    try:
        conn = get_db_connection()
        cursor = conn.cursor()
        cursor.execute("DELETE FROM sessions WHERE token = ?", (token,))
        conn.commit()
        conn.close()
    except Exception as e:
        logger.error(f"Error deleting session: {e}")