# /home/Autopartes/pos/tenant_db.py
"""Tenant DB connection manager with pooling.

Uses psycopg2.pool.ThreadedConnectionPool for both master and tenant DBs.
Connections are returned to the pool on .close() via a thin wrapper —
this keeps the rest of the codebase unchanged.
"""

import psycopg2
from psycopg2 import pool
from config import MASTER_DB_URL, TENANT_DB_URL_TEMPLATE


# ─── Pools ─────────────────────────────────────
_master_pool = None
_tenant_pools = {}


def _get_master_pool():
    """Lazy-initialize master DB connection pool."""
    global _master_pool
    if _master_pool is None:
        _master_pool = pool.ThreadedConnectionPool(
            minconn=2, maxconn=10, dsn=MASTER_DB_URL
        )
    return _master_pool


def _get_tenant_pool(db_name):
    """Lazy-initialize tenant DB connection pool by db_name."""
    global _tenant_pools
    if db_name not in _tenant_pools:
        dsn = TENANT_DB_URL_TEMPLATE.format(db_name=db_name)
        _tenant_pools[db_name] = pool.ThreadedConnectionPool(
            minconn=2, maxconn=10, dsn=dsn
        )
    return _tenant_pools[db_name]


class _PooledConnection:
    """Thin wrapper that delegates all attribute access to the real
    psycopg2 connection, but returns it to the pool on .close().
    """
    __slots__ = ('_conn', '_pool')

    def __init__(self, conn, db_pool):
        self._conn = conn
        self._pool = db_pool

    def __getattr__(self, name):
        return getattr(self._conn, name)

    def close(self):
        try:
            self._pool.putconn(self._conn)
        except Exception:
            # If pool is already closed, fall back to real close
            self._conn.close()

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.close()


# ─── Public API ────────────────────────────────

def get_master_conn():
    """Get a pooled connection to the master DB."""
    p = _get_master_pool()
    return _PooledConnection(p.getconn(), p)


def get_tenant_conn(tenant_id):
    """Get a pooled connection to a tenant's DB."""
    master = get_master_conn()
    cur = master.cursor()
    cur.execute(
        "SELECT db_name FROM tenants WHERE id = %s AND is_active = true",
        (tenant_id,)
    )
    row = cur.fetchone()
    cur.close()
    master.close()

    if not row:
        raise ValueError(f"Tenant {tenant_id} not found or inactive")

    db_name = row[0]
    p = _get_tenant_pool(db_name)
    return _PooledConnection(p.getconn(), p)


def get_tenant_conn_by_dbname(db_name):
    """Get a pooled connection to a tenant DB directly by name."""
    p = _get_tenant_pool(db_name)
    return _PooledConnection(p.getconn(), p)