from __future__ import annotations

from pathlib import Path
from typing import Generator

from dotenv import load_dotenv
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker

# Load environment variables from .env file if it exists
env_path = Path(__file__).parent.parent.parent.parent / ".env"
load_dotenv(dotenv_path=env_path)


def get_database_url() -> str:
    """Fetch database URL from environment or defaults."""
    import os
    # Check for environment variable first
    db_url = os.getenv("DATABASE_URL")
    if db_url:
        return db_url
    # Default to SQLite for development
    return "sqlite:///data/punimtag.db"


def get_auth_database_url() -> str:
    """Fetch auth database URL from environment."""
    import os
    db_url = os.getenv("DATABASE_URL_AUTH")
    if not db_url:
        raise ValueError("DATABASE_URL_AUTH environment variable not set")
    return db_url


database_url = get_database_url()
# SQLite-specific configuration
connect_args = {}
if database_url.startswith("sqlite"):
    connect_args = {"check_same_thread": False}

# PostgreSQL connection pool settings
pool_kwargs = {"pool_pre_ping": True}
if database_url.startswith("postgresql"):
    pool_kwargs.update({
        "pool_size": 10,
        "max_overflow": 20,
        "pool_recycle": 3600,
    })

engine = create_engine(
    database_url,
    future=True,
    connect_args=connect_args,
    **pool_kwargs
)
SessionLocal = sessionmaker(bind=engine, autoflush=False, autocommit=False, future=True)


def get_db() -> Generator:
    """Yield a DB session for request lifecycle."""
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


# Auth database setup
try:
    auth_database_url = get_auth_database_url()
    auth_connect_args = {}
    if auth_database_url.startswith("sqlite"):
        auth_connect_args = {"check_same_thread": False}
    
    auth_pool_kwargs = {"pool_pre_ping": True}
    if auth_database_url.startswith("postgresql"):
        auth_pool_kwargs.update({
            "pool_size": 10,
            "max_overflow": 20,
            "pool_recycle": 3600,
        })
    
    auth_engine = create_engine(
        auth_database_url,
        future=True,
        connect_args=auth_connect_args,
        **auth_pool_kwargs
    )
    AuthSessionLocal = sessionmaker(bind=auth_engine, autoflush=False, autocommit=False, future=True)
except ValueError:
    # DATABASE_URL_AUTH not set - auth database not available
    auth_engine = None
    AuthSessionLocal = None


def get_auth_db() -> Generator:
    """Yield a DB session for auth database request lifecycle."""
    if AuthSessionLocal is None:
        raise ValueError("Auth database not configured. Set DATABASE_URL_AUTH environment variable.")
    db = AuthSessionLocal()
    try:
        yield db
    finally:
        db.close()