import re
from urllib.parse import urlparse
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from app.core.config import settings

def ensure_database_exists(db_url: str):
    """
    If using MySQL, automatically creates the target database if it does not exist
    (mirrors spring.datasource.url createDatabaseIfNotExist=true).
    """
    if db_url.startswith("mysql"):
        try:
            import pymysql
            # Parse connection URL safely
            clean_url = db_url.replace("mysql+pymysql://", "http://").replace("mysql://", "http://")
            parsed = urlparse(clean_url)
            db_name = parsed.path.lstrip("/").split("?")[0]
            if db_name:
                conn = pymysql.connect(
                    host=parsed.hostname,
                    port=parsed.port or 3306,
                    user=parsed.username,
                    password=parsed.password,
                    connect_timeout=5
                )
                with conn.cursor() as cur:
                    cur.execute(f"CREATE DATABASE IF NOT EXISTS `{db_name}`;")
                conn.close()
        except Exception as e:
            print(f"Note on DB creation: {e}")

ensure_database_exists(settings.DATABASE_URL)

connect_args = {}
if settings.DATABASE_URL.startswith("sqlite"):
    connect_args = {"check_same_thread": False}

engine = create_engine(
    settings.DATABASE_URL,
    connect_args=connect_args,
    pool_pre_ping=True
)

SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)

Base = declarative_base()

def get_db():
    """Dependency for obtaining database session per request."""
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()