"""Подключение к PostgreSQL — тот же паттерн, что в HR_TG_Bot/tgFlaskForm/db/session.py.

В Этапе 1 работаем с БД `clinic_tests` (схема не меняется). Опционально доступна
вторая БД `hr_bot_test` для HR-аутентификации (см. .env.example, флаг HR_AUTH).
"""
from __future__ import annotations

import os
import threading
from typing import Optional

from sqlalchemy import create_engine
from sqlalchemy.engine import Engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.pool import QueuePool

_lock = threading.Lock()
_engine: Optional[Engine] = None
_session_local: Optional[sessionmaker] = None
_hr_engine: Optional[Engine] = None
_hr_session_local: Optional[sessionmaker] = None


def get_database_url() -> str:
    """URL основной БД (`clinic_tests`).

    Приоритет: DATABASE_URL → отдельные DB_*-переменные.
    """
    if db_url := os.environ.get('DATABASE_URL'):
        return db_url.strip()

    db_host = os.environ.get('DB_HOST', 'localhost')
    db_port = os.environ.get('DB_PORT', '5432')
    db_name = os.environ.get('DB_NAME', 'clinic_tests')
    db_user = os.environ.get('DB_USER', 'hr_bot_user')
    db_password = os.environ.get('DB_PASSWORD', 'hrbot123')
    return f'postgresql://{db_user}:{db_password}@{db_host}:{db_port}/{db_name}'


def get_hr_database_url() -> Optional[str]:
    """URL БД HR (`hr_bot_test`) — только если включён HR_AUTH."""
    if not _hr_auth_enabled():
        return None
    if url := os.environ.get('HR_DATABASE_URL'):
        return url.strip()
    return None


def _hr_auth_enabled() -> bool:
    val = (os.environ.get('HR_AUTH') or '').strip().lower()
    return val in ('1', 'true', 'yes', 'on')


def get_engine() -> Engine:
    """Возвращает общий engine основной БД (singleton на процесс)."""
    global _engine
    if _engine is not None:
        return _engine
    with _lock:
        if _engine is not None:
            return _engine
        _engine = create_engine(
            get_database_url(),
            poolclass=QueuePool,
            pool_size=5,
            max_overflow=10,
            pool_pre_ping=True,
        )
    return _engine


def get_session():
    """Создаёт новую ORM-сессию поверх общего engine."""
    global _session_local
    if _session_local is None:
        with _lock:
            if _session_local is None:
                _session_local = sessionmaker(bind=get_engine())
    return _session_local()


def get_hr_engine() -> Optional[Engine]:
    """Engine для HR-БД. Возвращает None, если HR_AUTH не включён."""
    if not _hr_auth_enabled():
        return None
    global _hr_engine
    if _hr_engine is not None:
        return _hr_engine
    url = get_hr_database_url()
    if not url:
        return None
    with _lock:
        if _hr_engine is not None:
            return _hr_engine
        _hr_engine = create_engine(
            url,
            poolclass=QueuePool,
            pool_size=3,
            max_overflow=5,
            pool_pre_ping=True,
        )
    return _hr_engine


def get_hr_session():
    """Сессия для HR-БД (или None при выключенном HR_AUTH)."""
    eng = get_hr_engine()
    if eng is None:
        return None
    global _hr_session_local
    if _hr_session_local is None:
        with _lock:
            if _hr_session_local is None:
                _hr_session_local = sessionmaker(bind=eng)
    return _hr_session_local()


def ping() -> dict:
    """Smoke-проверка подключения к БД (используется в /health)."""
    out: dict = {'main': 'unknown'}
    try:
        with get_engine().connect() as conn:
            conn.exec_driver_sql('SELECT 1')
        out['main'] = 'ok'
    except Exception as e:
        out['main'] = f'error: {type(e).__name__}: {e}'

    if _hr_auth_enabled():
        out['hr'] = 'unknown'
        try:
            eng = get_hr_engine()
            if eng is None:
                out['hr'] = 'disabled (HR_DATABASE_URL not set)'
            else:
                with eng.connect() as conn:
                    conn.exec_driver_sql('SELECT 1')
                out['hr'] = 'ok'
        except Exception as e:
            out['hr'] = f'error: {type(e).__name__}: {e}'

    return out