"""Migration 035 adds the untracked flag and stays reversible.

The downgrade matters more than usual here: dropping the column re-admits every
untracked symbol to the live path, and the rows survive either way. A migration
that could not roll back cleanly would make the prune change hard to undo on a
deploy that went wrong.
"""

from __future__ import annotations

import importlib.util
from pathlib import Path

import sqlalchemy as sa
from alembic.migration import MigrationContext
from alembic.operations import Operations


def _load_migration_module():
    path = (
        Path(__file__).resolve().parents[2]
        / "alembic"
        / "versions"
        / "035_ticker_untracked.py"
    )
    spec = importlib.util.spec_from_file_location("migration_035", path)
    assert spec is not None and spec.loader is not None
    module = importlib.util.module_from_spec(spec)
    spec.loader.exec_module(module)
    return module


def _tickers_table(connection: sa.Connection) -> None:
    connection.execute(sa.text(
        """
        CREATE TABLE tickers (
            id INTEGER PRIMARY KEY,
            symbol VARCHAR(10) NOT NULL,
            delisted_on DATE
        )
        """
    ))
    connection.execute(sa.text(
        "INSERT INTO tickers (id, symbol, delisted_on) VALUES (1, 'AAPL', NULL)"
    ))


def _columns(connection: sa.Connection) -> set[str]:
    return {row[1] for row in connection.execute(sa.text("PRAGMA table_info(tickers)"))}


def test_upgrade_adds_a_nullable_untracked_column_and_keeps_existing_rows():
    migration = _load_migration_module()
    engine = sa.create_engine("sqlite://")

    with engine.begin() as connection:
        _tickers_table(connection)
        with Operations.context(MigrationContext.configure(connection)):
            migration.upgrade()

        assert "untracked_on" in _columns(connection)
        # Existing rows default to NULL, i.e. still in the scanner — an upgrade
        # must not silently drop the whole universe out of the live path.
        rows = connection.execute(
            sa.text("SELECT symbol, untracked_on FROM tickers")
        ).all()
        assert rows == [("AAPL", None)]


def test_downgrade_removes_the_column_without_touching_the_rows():
    migration = _load_migration_module()
    engine = sa.create_engine("sqlite://")

    with engine.begin() as connection:
        _tickers_table(connection)
        with Operations.context(MigrationContext.configure(connection)):
            migration.upgrade()
        connection.execute(sa.text(
            "UPDATE tickers SET untracked_on = '2026-09-07' WHERE symbol = 'AAPL'"
        ))
        with Operations.context(MigrationContext.configure(connection)):
            migration.downgrade()

        assert "untracked_on" not in _columns(connection)
        # The ticker itself survives the rollback with its identity intact.
        assert connection.execute(sa.text("SELECT symbol FROM tickers")).all() == [("AAPL",)]