"""Database connection — psycopg2 connection pool."""
import os
import psycopg2
import psycopg2.pool
import psycopg2.extras

_pool = None

DB_CONFIG = {
    "host": os.getenv("DB_HOST", "127.0.0.1"),
    "port": int(os.getenv("DB_PORT", "5432")),
    "dbname": os.getenv("DB_NAME", "baza"),
    "user": os.getenv("DB_USER", "super"),
    "password": os.getenv("DB_PASS", ""),
}


def get_pool():
    global _pool
    if _pool is None:
        _pool = psycopg2.pool.ThreadedConnectionPool(
            minconn=1, maxconn=10, **DB_CONFIG
        )
    return _pool


def query(sql, params=None):
    """SELECT → list of dicts (lowercase keys)."""
    pool = get_pool()
    conn = pool.getconn()
    try:
        with conn.cursor(cursor_factory=psycopg2.extras.RealDictCursor) as cur:
            cur.execute(sql, params)
            rows = cur.fetchall()
            return [{k.lower(): v for k, v in r.items()} for r in rows]
    finally:
        pool.putconn(conn)


def execute(sql, params=None):
    """INSERT/UPDATE/DELETE → rowcount."""
    pool = get_pool()
    conn = pool.getconn()
    try:
        with conn.cursor() as cur:
            cur.execute(sql, params)
            conn.commit()
            return cur.rowcount
    except Exception:
        conn.rollback()
        raise
    finally:
        pool.putconn(conn)


def execute_returning(sql, params=None):
    """INSERT/UPDATE/DELETE with RETURNING → first row dict."""
    pool = get_pool()
    conn = pool.getconn()
    try:
        with conn.cursor(cursor_factory=psycopg2.extras.RealDictCursor) as cur:
            cur.execute(sql, params)
            conn.commit()
            row = cur.fetchone()
            return {k.lower(): v for k, v in row.items()} if row else None
    except Exception:
        conn.rollback()
        raise
    finally:
        pool.putconn(conn)