from contextlib import contextmanager
from typing import Any
from sqlalchemy import create_engine, text
from sqlalchemy.orm import Session, sessionmaker
from .config import get_settings

settings = get_settings()
engine = None
SessionLocal = None
database_url = settings.database_url

if database_url:
    if database_url.startswith("postgresql://"):
        database_url = database_url.replace("postgresql://", "postgresql+psycopg://", 1)
    
    engine = create_engine(
        database_url,
        future=True,
        pool_pre_ping=True,
    )
    SessionLocal = sessionmaker(bind=engine, autoflush=False, autocommit=False, future=True)
else:
    print("WARNING: DATABASE_URL is empty. Database features will be disabled.")

@contextmanager
def get_session() -> Session:
    if not SessionLocal:
        raise ValueError("Database connection not established. Please check your DATABASE_URL.")
    session = SessionLocal()
    try:
        yield session
    finally:
        session.close()

def run_sql(session: Session, sql: str, params: dict[str, Any] | None = None) -> list[dict[str, Any]]:
    result = session.execute(text(sql), params or {})
    return [dict(row) for row in result.mappings().all()]

def init_app_tables() -> None:
    if not engine:
        return
    create_chat_history_sql = """
    CREATE TABLE IF NOT EXISTS chat_messages (
        id BIGSERIAL PRIMARY KEY,
        session_id TEXT NOT NULL,
        role TEXT NOT NULL,
        content TEXT NOT NULL,
        created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
    );
    """
    with engine.begin() as conn:
        conn.execute(text(create_chat_history_sql))