"""
Database connection management and initialization
Uses connection pooling to manage database connections efficiently
"""
import pymysql
import logging
from dbutils.pooled_db import PooledDB
from flask import g

logger = logging.getLogger(__name__)

# Global database pool
db_pool = None


def init_db(app):
    """Initialize database connection pool"""
    global db_pool
    
    try:
        db_pool = PooledDB(
            creator=pymysql,
            maxconnections=app.config.get('DB_POOL_SIZE', 10),
            mincached=2,
            maxcached=5,
            maxshared=3,
            blocking=True,
            maxusage=None,
            setsession=[],
            ping=1,
            # PyMySQL connection parameters
            user=app.config['DB_USER'],
            password=app.config['DB_PASSWORD'],
            host=app.config['DB_HOST'],
            port=app.config['DB_PORT'],
            database=app.config['DB_NAME'],
        )
        logger.info(f"Database pool initialized: {app.config['DB_HOST']}:{app.config['DB_PORT']}/{app.config['DB_NAME']}")
    except Exception as e:
        logger.error(f"Failed to initialize database pool: {e}")
        raise


def get_db():
    """Get database connection from pool"""
    if db_pool is None:
        raise RuntimeError("Database pool not initialized")
    
    if 'db' not in g:
        try:
            g.db = db_pool.connection()
            logger.debug("Database connection obtained from pool")
        except Exception as e:
            logger.error(f"Failed to get database connection: {e}")
            raise
    
    return g.db


def close_db(e=None):
    """Close database connection"""
    db = g.pop('db', None)
    if db is not None:
        try:
            db.close()
            logger.debug("Database connection closed")
        except Exception as e:
            logger.error(f"Error closing database connection: {e}")


def execute_query(query, params=None, fetch_one=False, fetch_all=True):
    """
    Execute a database query
    
    Args:
        query: SQL query string
        params: Query parameters (tuple or list)
        fetch_one: Fetch only one row
        fetch_all: Fetch all rows (if fetch_one is False)
    
    Returns:
        Query result or None
    """
    try:
        db = get_db()
        cursor = db.cursor()
        
        if params:
            cursor.execute(query, params)
        else:
            cursor.execute(query)
        
        if fetch_one:
            result = cursor.fetchone()
        elif fetch_all:
            result = cursor.fetchall()
        else:
            result = None
        
        cursor.close()
        return result
    except Exception as e:
        logger.error(f"Database query error: {e}\nQuery: {query}\nParams: {params}")
        raise


def execute_update(query, params=None):
    """
    Execute an UPDATE, INSERT, or DELETE query
    
    Args:
        query: SQL query string
        params: Query parameters (tuple or list)
    
    Returns:
        Number of affected rows
    """
    try:
        db = get_db()
        cursor = db.cursor()
        
        if params:
            cursor.execute(query, params)
        else:
            cursor.execute(query)
        
        affected_rows = cursor.rowcount
        db.commit()
        cursor.close()
        
        logger.debug(f"Query executed. Affected rows: {affected_rows}")
        return affected_rows
    except Exception as e:
        logger.error(f"Database update error: {e}\nQuery: {query}\nParams: {params}")
        raise


def init_app(app):
    """Initialize database with Flask app"""
    init_db(app)
    app.teardown_appcontext(close_db)