"""
Tests for the tenant routing layer (app/tenancy/routing.py).

The crown-jewel invariant of the multi-tenant design is data isolation: a
request bound to tenant A must never touch tenant B's database. Full isolation
proof requires two live tenant DBs and belongs in an integration suite (see
tests/README.md). What we CAN verify cheaply and deterministically here is the
other half of the contract:

    "The routing layer is completely inert until a tenant is resolved."

If routing were NOT inert when MULTI_TENANT_ENABLED=false, the existing
single-tenant deployment would break. This test locks that guarantee in.
"""

from flask import g


def test_routing_is_inert_without_a_resolved_tenant(app):
    """With no g.tenant_engine set, db.session binds to the default engine."""
    from app import db
    with app.test_request_context('/'):
        # Multi-tenancy disabled → the resolver never sets g.tenant_engine.
        assert g.get('tenant_engine') is None
        # …so get_bind() must fall through to the app's default engine.
        assert db.session.get_bind() is db.engine


def test_resolved_tenant_engine_wins(app, monkeypatch):
    """When g.tenant_engine IS set, get_bind() returns it, not the default."""
    from app import db

    class _SentinelEngine:
        """Stand-in object; get_bind should return it verbatim when present."""

    sentinel = _SentinelEngine()

    with app.test_request_context('/'):
        g.tenant_engine = sentinel
        assert db.session.get_bind() is sentinel