"""Test fixtures shared across unit + integration tests.

v0.2 PR #1: tests run against the live Postgres container managed by
docker-compose. Each test that needs DB isolation requests the
``pg_db_url`` fixture, which creates a fresh database per test and drops it
on teardown.

Prerequisites:
    docker compose up -d postgres      # devflow-postgres on 55432
"""

from __future__ import annotations

import os
import uuid
from collections.abc import AsyncIterator
from typing import Final

import psycopg
import pytest_asyncio

# Maintenance connection — used only to CREATE DATABASE / DROP DATABASE.
# `postgres` is the bootstrap DB present on every Postgres install.
_MAINTENANCE_DSN: Final[str] = os.environ.get(
    "MYDEEPAGENT_TEST_MAINTENANCE_DSN",
    "postgresql://devflow:devflow@localhost:55432/postgres",
)


def _async_url(db_name: str) -> str:
    """Return the SQLAlchemy + asyncpg URL for *db_name*."""
    return f"postgresql+asyncpg://devflow:devflow@localhost:55432/{db_name}"


def _create_test_database() -> str:
    """Create a fresh test database with a random suffix and return its name."""
    db_name = f"test_{uuid.uuid4().hex[:16]}"
    # autocommit=True is required for CREATE DATABASE (cannot run in a tx block).
    with psycopg.connect(_MAINTENANCE_DSN, autocommit=True) as conn:
        with conn.cursor() as cur:
            cur.execute(f'CREATE DATABASE "{db_name}"')
    return db_name


def _drop_test_database(db_name: str) -> None:
    """Forcefully terminate connections and drop *db_name*. Idempotent."""
    with psycopg.connect(_MAINTENANCE_DSN, autocommit=True) as conn:
        with conn.cursor() as cur:
            # Kick any lingering connections held by aiosqlite-style pools that
            # didn't dispose cleanly. WITH (FORCE) is Postgres 13+.
            cur.execute(
                """
                SELECT pg_terminate_backend(pid)
                FROM pg_stat_activity
                WHERE datname = %s AND pid <> pg_backend_pid()
                """,
                (db_name,),
            )
            cur.execute(f'DROP DATABASE IF EXISTS "{db_name}"')


@pytest_asyncio.fixture
async def pg_db_url() -> AsyncIterator[str]:
    """Yield an isolated Postgres database URL; drop the DB on teardown.

    Usage::

        async def test_something(pg_db_url: str) -> None:
            db = Database(pg_db_url)
            await db.init_schema()
            ...

    The returned URL uses the asyncpg driver. To get a sync URL for tools
    like alembic, replace ``postgresql+asyncpg://`` with ``postgresql+psycopg://``.
    """
    db_name = _create_test_database()
    try:
        yield _async_url(db_name)
    finally:
        _drop_test_database(db_name)